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<front>
<journal-meta>
<journal-id journal-id-type="publisher-id">Front. Neurosci.</journal-id>
<journal-title>Frontiers in Neuroscience</journal-title>
<abbrev-journal-title abbrev-type="pubmed">Front. Neurosci.</abbrev-journal-title>
<issn pub-type="epub">1662-453X</issn>
<publisher>
<publisher-name>Frontiers Media S.A.</publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id pub-id-type="doi">10.3389/fnins.2020.574713</article-id>
<article-categories>
<subj-group subj-group-type="heading">
<subject>Neuroscience</subject>
<subj-group>
<subject>Original Research</subject>
</subj-group>
</subj-group>
</article-categories>
<title-group>
<article-title>Clinical Efficacy of Short-Term Peripheral Nerve Stimulation in Management of Facial Pain Associated With Herpes Zoster Ophthalmicus</article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name><surname>Han</surname> <given-names>Rui</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/1023130/overview"/>
</contrib>
<contrib contrib-type="author">
<name><surname>Guo</surname> <given-names>Gangwen</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Ni</surname> <given-names>Yuncheng</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Wang</surname> <given-names>Ziyang</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Yang</surname> <given-names>Liuqing</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Zhang</surname> <given-names>Jianping</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Li</surname> <given-names>Xuelian</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author">
<name><surname>Hu</surname> <given-names>Rong</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Huang</surname> <given-names>Dong</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
<xref ref-type="corresp" rid="c001"><sup>&#x002A;</sup></xref>
</contrib>
<contrib contrib-type="author" corresp="yes">
<name><surname>Zhou</surname> <given-names>Haocheng</given-names></name>
<xref ref-type="aff" rid="aff1"><sup>1</sup></xref>
<xref ref-type="aff" rid="aff2"><sup>2</sup></xref>
<xref ref-type="corresp" rid="c002"><sup>&#x002A;</sup></xref>
<uri xlink:href="http://loop.frontiersin.org/people/428099/overview"/>
</contrib>
</contrib-group>
<aff id="aff1"><sup>1</sup><institution>Department of Pain, The Third Xiangya Hospital and Institute of Pain Medicine, Central South University</institution>, <addr-line>Changsha</addr-line>, <country>China</country></aff>
<aff id="aff2"><sup>2</sup><institution>Hunan Key Laboratory of Brain Homeostasis, Central South University</institution>, <addr-line>Changsha</addr-line>, <country>China</country></aff>
<author-notes>
<fn fn-type="edited-by"><p>Edited by: Hari S. Sharma, Uppsala University, Sweden</p></fn>
<fn fn-type="edited-by"><p>Reviewed by: Aritra Kundu, University of Texas at Austin, United States; Victor Manuel Pulgar, Wake Forest School of Medicine, United States</p></fn>
<corresp id="c001">&#x002A;Correspondence: Dong Huang, <email>Huangdong6619@vip.163.com</email></corresp>
<corresp id="c002">Haocheng Zhou, <email>Haocheng.Zhou@csu.edu.cn</email></corresp>
<fn fn-type="other" id="fn004"><p>This article was submitted to Neural Technology, a section of the journal Frontiers in Neuroscience</p></fn>
</author-notes>
<pub-date pub-type="epub">
<day>23</day>
<month>09</month>
<year>2020</year>
</pub-date>
<pub-date pub-type="collection">
<year>2020</year>
</pub-date>
<volume>14</volume>
<elocation-id>574713</elocation-id>
<history>
<date date-type="received">
<day>21</day>
<month>06</month>
<year>2020</year>
</date>
<date date-type="accepted">
<day>19</day>
<month>08</month>
<year>2020</year>
</date>
</history>
<permissions>
<copyright-statement>Copyright &#x00A9; 2020 Han, Guo, Ni, Wang, Yang, Zhang, Li, Hu, Huang and Zhou.</copyright-statement>
<copyright-year>2020</copyright-year>
<copyright-holder>Han, Guo, Ni, Wang, Yang, Zhang, Li, Hu, Huang and Zhou</copyright-holder>
<license xlink:href="http://creativecommons.org/licenses/by/4.0/"><p>This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.</p></license>
</permissions>
<abstract>
<sec><title>Objective</title><p>Peripheral nerve stimulation may be an alternative option to treat severe facial pain. We assessed the application of peripheral nerve stimulation for pain management in patients with herpes zoster ophthalmicus.</p></sec>
<sec><title>Method</title><p>A retrospective analysis was conducted in patients suffering severe facial pain caused by ophthalmic herpetic lesions. We identified the change in pain severity before and after peripheral nerve stimulation for up to 12 months.</p></sec>
<sec><title>Results</title><p>Eighteen patients were enrolled. Their mean age was 70.8 &#x00B1; 9.5 years. Fifteen patients presented with subacute pain for 1&#x2013;3 months, and three patients suffered postherpetic neuralgia. Dramatic relief from pain was achieved in 83% of patients (15 out of 18) upon initial removal of the stimulator, with pain reduction of &#x003E; 50%. The long-term analgesic effect was reported at the 6- and 12-month follow-ups, with reductions in the visual analog scale of 4.8 &#x00B1; 1.2 (<italic>n</italic> = 18) and 5.4 &#x00B1; 1.4 (<italic>n</italic> = 11), respectively. The prevalence of postherpetic neuralgia was 7% (1 out of 15) in the subacute pain group. No obvious adverse effect was observed.</p></sec>
<sec><title>Conclusion</title><p>Peripheral nerve stimulation may be an efficacious and safe approach for pain control in patients with herpes zoster ophthalmicus.</p></sec>
</abstract>
<kwd-group>
<kwd>neuromodulation</kwd>
<kwd>peripheral nerve stimulation</kwd>
<kwd>facial pain</kwd>
<kwd>herpes zoster ophthalmicus</kwd>
<kwd>postherpetic neuralgia</kwd>
</kwd-group>
<contract-num rid="cn001">81901146</contract-num>
<contract-num rid="cn001">81771101</contract-num>
<contract-sponsor id="cn001">National Natural Science Foundation of China<named-content content-type="fundref-id">10.13039/501100001809</named-content></contract-sponsor>
<counts>
<fig-count count="3"/>
<table-count count="2"/>
<equation-count count="0"/>
<ref-count count="33"/>
<page-count count="7"/>
<word-count count="0"/>
</counts>
</article-meta>
</front>
<body>
<sec id="S1">
<title>Introduction</title>
<p>Herpes zoster ophthalmicus (HZO) is a viral disease associated with the first branch of the trigeminal nerve [i.e., ophthalmic nerve (V1)]. It has been estimated that about 10&#x2013;20% of herpetic infections affect V1 (<xref ref-type="bibr" rid="B21">Liesegang, 2008</xref>). HZO prevalence has increased 3.6% per year in the last two decades in the United States (<xref ref-type="bibr" rid="B18">Kong et al., 2020</xref>). Patients suffer severe facial pain in the distribution of the ophthalmic division. In addition, the incidence of postherpetic neuralgia (PHN, which is defined as a persistent neuropathic pain condition) is much higher with ophthalmic involvement (<xref ref-type="bibr" rid="B5">Coen et al., 2006</xref>). The chronicity of the disease results in ongoing treatment in &#x223C;20% of HZO patients (<xref ref-type="bibr" rid="B30">Tran et al., 2016</xref>).</p>
<p>Routine medical therapy for HZO comprises antiviral drugs, topical corticosteroids, and analgesics (<xref ref-type="bibr" rid="B15">Johnson et al., 2015</xref>). Early antiviral treatment is essential to reduce acute pain and prevent PHN development (<xref ref-type="bibr" rid="B32">Wood et al., 1996</xref>; <xref ref-type="bibr" rid="B3">Chang et al., 2019</xref>). However, conventional medications may not provide satisfactory relief from pain. Pain severity and PHN risk also increases with advancing age and immunosuppressive status, which significantly reduces the quality of life (<xref ref-type="bibr" rid="B21">Liesegang, 2008</xref>; <xref ref-type="bibr" rid="B16">Johnson and Rice, 2014</xref>; <xref ref-type="bibr" rid="B33">Zhou et al., 2018</xref>). Thus, it is necessary to improve pain management for HZO patients.</p>
<p>Recently, peripheral nerve stimulation (PNS) has increasingly been used to treat intractable headache disorders such as migraine and cluster headache through the stimulation of the occipital nerve (<xref ref-type="bibr" rid="B28">Saper et al., 2011</xref>; <xref ref-type="bibr" rid="B8">Dodick et al., 2015</xref>). Additional indications for PNS include classical trigeminal neuralgia, trigeminal neuropathic pain, complex regional pain syndrome, and fibromyalgia (<xref ref-type="bibr" rid="B12">Hassenbusch et al., 1996</xref>; <xref ref-type="bibr" rid="B14">Johnson and Burchiel, 2004</xref>; <xref ref-type="bibr" rid="B29">Thimineur and De Ridder, 2007</xref>; <xref ref-type="bibr" rid="B13">Jeon et al., 2009</xref>; <xref ref-type="bibr" rid="B17">Klein et al., 2016</xref>). However, the evidence for using PNS against HZO is limited. Other neuromodulation approaches, such as pulsed radiofrequency, have been widely used to treat herpetic pain (<xref ref-type="bibr" rid="B31">Wan et al., 2019</xref>; <xref ref-type="bibr" rid="B7">Ding et al., 2019</xref>). Compared with pulsed radiofrequency, PNS provides enduring pain relief for the prolonged duration of stimulation (<xref ref-type="bibr" rid="B22">McMahon et al., 2019</xref>). Thus, PNS may be promising treatment for HZO patients who have not responded successfully to conventional therapy.</p>
<p>The branches of the trigeminal nerve as well as the Gasserian ganglion are considered the targets of PNS therapy for facial pain (<xref ref-type="bibr" rid="B19">Kustermans et al., 2017</xref>). Specifically, by placing electrodes close to the nerves, current flow is generated between the cathode and anode to interrupt the processing of pain signals. Patients may suffer paralysis in the pain-related region instead of pain. PHN is observed in &#x003E; 50% of HZO patients, mostly with involvement of the ophthalmic branch (<xref ref-type="bibr" rid="B21">Liesegang, 2008</xref>). The stimulation of the supraorbital and supratrochlear nerves may be an alternative pain management option for HZO patients. Here, we analyzed the effect of PNS on pain management for patients with HZO.</p>
</sec>
<sec id="S2" sec-type="materials|methods">
<title>Materials and Methods</title>
<sec id="S2.SS1">
<title>Ethical Approval of the Study Protocol</title>
<p>The evaluation of patient medical records was approved by the ethics board of the Third Xiangya Hospital of Central South University (Changsha, China).</p>
</sec>
<sec id="S2.SS2">
<title>Participants</title>
<p>Patients&#x2019; medical records were reviewed to identify those who were diagnosed with HZO and who subsequently underwent PNS between 2018 and 2019. The diagnosis of HZO was made according to the characteristic vesicular rash and dermatomal pain associated with the distribution of V1. One brief questionnaire was given to the patients to evaluate general information, duration of preoperative pain, medication use, and postoperative pain relief.</p>
</sec>
<sec id="S2.SS3">
<title>Implantation</title>
<p>A detailed description of the PNS procedure has been described by <xref ref-type="bibr" rid="B20">Lerman et al. (2015)</xref>. Briefly, patients were placed supine with the head turned to the contralateral side of the surgical approach. Local anesthesia was induced with 1% lidocaine in a total volume of 10 mL by infiltration 2 cm lateral to the orbit at the level of the supraorbital ridge and superficial temporal fascia. A 14-G Tuohy needle was inserted 2 cm posterolateral to the junction of the frontal and zygomatic portion of the orbital rim. The Tuohy needle was advanced through the tissue and aimed at a supra-periosteal tissue plane over the eyebrow in a semilunar path, cephalad to the orbicularis oculi, terminating slightly in the cranial midline. A test stimulation lead with eight electrodes (Model 3873; Medtronic, Minneapolis, MN, United States) was inserted through the Tuohy needle. Fluoroscopic imaging was used to identify the eight-contact lead overlying the supraorbital ridge (<xref ref-type="fig" rid="F1">Figure 1</xref>), and the guiding needle was removed after the lead had been placed in the desired location. The distal ends of the inserted electrodes were connected to an extension multi-lead cable (Model: 355531; Medtronic). To program the implantable electrodes, the external cable was plugged into a neurostimulator (Model 37022; Medtronic).</p>
<fig id="F1" position="float">
<label>FIGURE 1</label>
<caption><p>Placement of an implantable stimulation tetrode identified by fluoroscopic imaging.</p></caption>
<graphic xlink:href="fnins-14-574713-g001.tif"/>
</fig>
</sec>
<sec id="S2.SS4">
<title>Stimulation Parameter</title>
<p>The PNS electrodes were retained for &#x2264; 14 days to avoid potential infection. The duration of electrode implantation for each patient is shown in <xref ref-type="table" rid="T1">Table 1</xref>. The stimulation parameters were adjusted twice a day on the ward according to the pain assessment and tolerance of stimulation. The stimulation amplitude was set at 0.5&#x2013;3.0 mV, with the painful area covered completely. The stimulation frequency was set at 40 Hz and the pulse width was 450&#x2013;500 &#x03BC;S. The lead was programed with its own bipolar configuration. The first four tetrodes were set as the anode and the last four as the cathode. Using this stimulation strategy, we could adjust the parameter of stimulation to achieve optimal coverage of the pain region.</p>
<table-wrap position="float" id="T1">
<label>TABLE 1</label>
<caption><p>General characteristics of patients.</p></caption>
<table cellspacing="5" cellpadding="5" frame="hsides" rules="groups">
<thead>
<tr>
<td valign="top" align="left" colspan="11">Sub-acute pain</td>
</tr>
<tr>
<td valign="top" align="left" colspan="11"><hr/></td>
</tr>
<tr>
<td valign="top" align="left">Age<hr/></td>
<td valign="top" align="center">Sex</td>
<td valign="top" align="center">Area</td>
<td valign="top" align="center">Duration<hr/></td>
<td valign="top" align="center">FU<hr/></td>
<td valign="top" align="center">Hospitalization<hr/></td>
<td valign="top" align="center">Stimulation<hr/></td>
<td valign="top" align="center">VAS<hr/></td>
<td valign="top" align="center">Pre Anti-virus</td>
<td valign="top" align="center" colspan="2">Pain management<hr/></td>
</tr>
<tr>
<td valign="top" align="left">(Years)</td>
<td/>
<td/>
<td valign="top" align="center">(Months)</td>
<td valign="top" align="center">(Months)</td>
<td valign="top" align="center">(Days)</td>
<td valign="top" align="center">(Days)</td>
<td valign="top" align="center">Pre/last FU</td>
<td/>
<td valign="top" align="center">Pre PNS</td>
<td valign="top" align="center">Last FU</td>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left">63</td>
<td valign="top" align="center">M</td>
<td valign="top" align="center">Rt V1</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">22</td>
<td valign="top" align="center">10</td>
<td valign="top" align="center">8/1</td>
<td valign="top" align="center">ACY</td>
<td valign="top" align="center">GBP, Ops, NB</td>
<td valign="top" align="center">Herb, acupuncture</td>
</tr>
<tr>
<td valign="top" align="left">67</td>
<td valign="top" align="center">F</td>
<td valign="top" align="center">Rt V1</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">17</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">8/1</td>
<td valign="top" align="center">ACY</td>
<td valign="top" align="center">GBP, Ops, NB</td>
<td valign="top" align="center">Herb</td>
</tr>
<tr>
<td valign="top" align="left">64</td>
<td valign="top" align="center">M</td>
<td valign="top" align="center">Lt V1</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">18</td>
<td valign="top" align="center">15</td>
<td valign="top" align="center">6/1</td>
<td valign="top" align="center">N/A</td>
<td valign="top" align="center">GBP, Ops, NB</td>
<td valign="top" align="center">GBP</td>
</tr>
<tr>
<td valign="top" align="left">71</td>
<td valign="top" align="center">M</td>
<td valign="top" align="center">Rt V1</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">19</td>
<td valign="top" align="center">10</td>
<td valign="top" align="center">6/2</td>
<td valign="top" align="center">ACY</td>
<td valign="top" align="center">PGB, Ops</td>
<td valign="top" align="center">N/A</td>
</tr>
<tr>
<td valign="top" align="left">76</td>
<td valign="top" align="center">M</td>
<td valign="top" align="center">Rt V1</td>
<td valign="top" align="center">3</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">24</td>
<td valign="top" align="center">13</td>
<td valign="top" align="center">8/2</td>
<td valign="top" align="center">ACY</td>
<td valign="top" align="center">PGB, Ops, NB</td>
<td valign="top" align="center">N/A</td>
</tr>
<tr>
<td valign="top" align="left">50</td>
<td valign="top" align="center">F</td>
<td valign="top" align="center">Rt V1</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">17</td>
<td valign="top" align="center">14</td>
<td valign="top" align="center">8/3</td>
<td valign="top" align="center">ACY</td>
<td valign="top" align="center">GBP, Ops, NSAIDs</td>
<td valign="top" align="center">None</td>
</tr>
<tr>
<td valign="top" align="left">65</td>
<td valign="top" align="center">M</td>
<td valign="top" align="center">Rt V1</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">17</td>
<td valign="top" align="center">10</td>
<td valign="top" align="center">8/2</td>
<td valign="top" align="center">ACY</td>
<td valign="top" align="center">GBP, Ops, NB</td>
<td valign="top" align="center">None</td>
</tr>
<tr>
<td valign="top" align="left">73</td>
<td valign="top" align="center">M</td>
<td valign="top" align="center">Lt V1</td>
<td valign="top" align="center">0.5</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">20</td>
<td valign="top" align="center">14</td>
<td valign="top" align="center">8/3</td>
<td valign="top" align="center">VAL</td>
<td valign="top" align="center">GBP, Ops, NB</td>
<td valign="top" align="center">None</td>
</tr>
<tr>
<td valign="top" align="left">75</td>
<td valign="top" align="center">F</td>
<td valign="top" align="center">Lt V1</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">21</td>
<td valign="top" align="center">16</td>
<td valign="top" align="center">6/4</td>
<td valign="top" align="center">ACY</td>
<td valign="top" align="center">GBP, Ops, NSAIDs, NB</td>
<td valign="top" align="center">None</td>
</tr>
<tr>
<td valign="top" align="left">57</td>
<td valign="top" align="center">F</td>
<td valign="top" align="center">Lt V1,2</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">6</td>
<td valign="top" align="center">15</td>
<td valign="top" align="center">9</td>
<td valign="top" align="center">6/2</td>
<td valign="top" align="center">ACY</td>
<td valign="top" align="center">PGB, Ops</td>
<td valign="top" align="center">PGB, Herb</td>
</tr>
<tr>
<td valign="top" align="left">62</td>
<td valign="top" align="center">F</td>
<td valign="top" align="center">Lt V1,2</td>
<td valign="top" align="center">1.5</td>
<td valign="top" align="center">6</td>
<td valign="top" align="center">7</td>
<td valign="top" align="center">14</td>
<td valign="top" align="center">6/2</td>
<td valign="top" align="center">ACY</td>
<td valign="top" align="center">GBP, NSAIDs</td>
<td valign="top" align="center">None</td>
</tr>
<tr>
<td valign="top" align="left">82</td>
<td valign="top" align="center">M</td>
<td valign="top" align="center">Lt V1</td>
<td valign="top" align="center">0.5</td>
<td valign="top" align="center">6</td>
<td valign="top" align="center">19</td>
<td valign="top" align="center">14</td>
<td valign="top" align="center">8/2</td>
<td valign="top" align="center">ACY</td>
<td valign="top" align="center">PGB, LP, NB</td>
<td valign="top" align="center">None</td>
</tr>
<tr>
<td valign="top" align="left">72</td>
<td valign="top" align="center">M</td>
<td valign="top" align="center">Lt V1,2</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">15</td>
<td valign="top" align="center">14</td>
<td valign="top" align="center">8/2</td>
<td valign="top" align="center">VAL</td>
<td valign="top" align="center">PGB, NSAIDs, NB</td>
<td valign="top" align="center">None</td>
</tr>
<tr>
<td valign="top" align="left">76</td>
<td valign="top" align="center">M</td>
<td valign="top" align="center">Rt V1</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">6</td>
<td valign="top" align="center">13</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">8/2</td>
<td valign="top" align="center">ACY</td>
<td valign="top" align="center">PGB, Ops, NB</td>
<td valign="top" align="center">PGB</td>
</tr>
<tr>
<td valign="top" align="left">80</td>
<td valign="top" align="center">F</td>
<td valign="top" align="center">Rt V1</td>
<td valign="top" align="center">1</td>
<td valign="top" align="center">6</td>
<td valign="top" align="center">11</td>
<td valign="top" align="center">10</td>
<td valign="top" align="center">7/1</td>
<td valign="top" align="center">GAN</td>
<td valign="top" align="center">PGB, NSAIDs, NB</td>
<td valign="top" align="center">None</td>
</tr>
<tr>
<td valign="top" align="left" colspan="11"><bold>Postherpetic neuralgia</bold></td>
</tr>
<tr>
<td valign="top" align="left">86</td>
<td valign="top" align="center">M</td>
<td valign="top" align="center">Lt V1,2</td>
<td valign="top" align="center">96</td>
<td valign="top" align="center">6</td>
<td valign="top" align="center">14</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">8/5</td>
<td valign="top" align="center">N/A</td>
<td valign="top" align="center">PGB, LP</td>
<td valign="top" align="center">None</td>
</tr>
<tr>
<td valign="top" align="left">71</td>
<td valign="top" align="center">F</td>
<td valign="top" align="center">Lt V1</td>
<td valign="top" align="center">72</td>
<td valign="top" align="center">6</td>
<td valign="top" align="center">6</td>
<td valign="top" align="center">14</td>
<td valign="top" align="center">8/3</td>
<td valign="top" align="center">N/A</td>
<td valign="top" align="center">GBP, NSAIDs</td>
<td valign="top" align="center">None</td>
</tr>
<tr>
<td valign="top" align="left">84</td>
<td valign="top" align="center">M</td>
<td valign="top" align="center">Rt V1</td>
<td valign="top" align="center">4</td>
<td valign="top" align="center">12</td>
<td valign="top" align="center">13</td>
<td valign="top" align="center">10</td>
<td valign="top" align="center">8/2</td>
<td valign="top" align="center">None</td>
<td valign="top" align="center">PGB, NSAIDs</td>
<td valign="top" align="center">N/A</td>
</tr>
</tbody>
</table>
<table-wrap-foot>
<attrib><italic><italic>ACY, Acyclovir; GBP, Gabapentin; GAN, Ganciclovir; FU, Follow-up; Lt, Left; LP, Lidocaine Path; NSAIDs, Non-steroidal Anti-inflammatory Drugs; NB, Nerve Block; Rt, Right; Ops, Opsioids; PGB, Pregabalin; VAL, Valaciclovir.</italic></italic></attrib>
</table-wrap-foot>
</table-wrap>
</sec>
<sec id="S2.SS5">
<title>Measurement and Follow-Up</title>
<p>The primary outcome was the change in pain intensity after PNS. This was evaluated by a visual analog scale (VAS) ranging from 0 (&#x201C;pain free&#x201D;) to 10 (&#x201C;worst pain imaginable&#x201D;). The postoperative VAS score was compared with that at baseline before implantation, and a decrease in the VAS score indicated pain relief. Patients who had pain relief &#x2265; 50% on the VAS after PNS were classified as &#x201C;responders.&#x201D; To identify the long-term analgesic effect of PNS, a telephone interview was conducted 1, 3, 6, and 12 months after discharge from hospital. &#x201C;PHN&#x201D; was defined as chronic neuropathic pain with a VAS score &#x003E; 3 and symptom duration &#x003E; 3 months, as described previously (<xref ref-type="bibr" rid="B16">Johnson and Rice, 2014</xref>).</p>
</sec>
<sec id="S2.SS6">
<title>Statistical Analyses</title>
<p>Descriptive analysis was used to capture the general characteristics of patients. Variables are presented as the mean &#x00B1; standard deviation. Paired comparisons of pain scores before and after PNS were made using the Wilcoxon signed-rank test. <italic>P</italic> &#x003C; 0.05 was considered significant. Data were analyzed using Prism v8 (GraphPad, San Diego, CA, United States).</p>
</sec>
</sec>
<sec id="S3">
<title>Results</title>
<sec id="S3.SS1">
<title>Demographic Features</title>
<p>Eighteen patients (11 male and seven female) who received PNS therapy were identified. The mean age of patients was 70.8 &#x00B1; 9.5 (range, 50&#x2013;86) years. All patients presented with severe pain associated with the ophthalmic nerve after an initial herpetic skin rash, characterized by a burning, throbbing, stabbing, shocking pain. Most (15 out of 18) cases had suffered subacute facial pain for 1&#x2013;3 months. Three patients developed chronic postherpetic neuralgia over 3 months. Thus, we divided the cohort into two subgroups according to symptom duration (<xref ref-type="table" rid="T1">Table 1</xref>). Fifteen of 18 participants had received antiviral treatment. One or more medications, or nerve block, was administrated before PNS. Patients were insensitive to conventional therapy, with a mean baseline VAS of 7.4 &#x00B1; 0.9 (<xref ref-type="table" rid="T2">Table 2</xref>).</p>
<table-wrap position="float" id="T2">
<label>TABLE 2</label>
<caption><p>Pain scores collected at each follow-up visit.</p></caption>
<table cellspacing="5" cellpadding="5" frame="hsides" rules="groups">
<thead>
<tr>
<td valign="top" align="left"></td>
<td valign="top" align="center">Baseline</td>
<td valign="top" align="center">Discharge</td>
<td valign="top" align="center">1 month</td>
<td valign="top" align="center">3-month</td>
<td valign="top" align="center">6-month</td>
<td valign="top" align="center">12-month</td>
</tr>
</thead>
<tbody>
<tr>
<td valign="top" align="left">VAS</td>
<td valign="top" align="center">7.3 &#x00B1; 0.9</td>
<td valign="top" align="center">3.3 &#x00B1; 0.8</td>
<td valign="top" align="center">3.3 &#x00B1; 0.9</td>
<td valign="top" align="center">2.9 &#x00B1; 1.0</td>
<td valign="top" align="center">2.6 &#x00B1; 0.9</td>
<td valign="top" align="center">2.1 &#x00B1; 0.9</td>
</tr>
<tr>
<td valign="top" align="left"><italic>n</italic></td>
<td valign="top" align="center">18</td>
<td valign="top" align="center">18</td>
<td valign="top" align="center">18</td>
<td valign="top" align="center">18</td>
<td valign="top" align="center">18</td>
<td valign="top" align="center">11</td>
</tr>
</tbody>
</table></table-wrap>
</sec>
<sec id="S3.SS2">
<title>Follow-Up</title>
<p>All patients were followed up on at 1, 3, and 6 months after their hospital discharge. A final follow-up was accomplished for 11 out of 18 patients, at 12 months after PNS. The pain scores collected at each follow-up are given in <xref ref-type="table" rid="T2">Table 2</xref>.</p>
</sec>
<sec id="S3.SS3">
<title>Therapeutic Efficacy</title>
<sec id="S3.SS3.SSS1">
<title>Initial Relief From Pain</title>
<p>The overall response rate was 83% (15 out of 18) upon initial removal of the stimulator (<xref ref-type="fig" rid="F2">Figure 2B</xref>). The response rate was 100% (<italic>n</italic> = 3) in the PHN group and 80% (12 out of 15) for the subacute-pain cohort. PNS provided instant and significant pain relief compared with the pain measured at the baseline (<xref ref-type="fig" rid="F3">Figure 3A</xref>). Two patients with subacute pain due to HZO continued to present moderate facial pain upon discharge, with the VAS score decreasing from 8 to 5. PNS treatment provided dramatic relief from pain in all PHN patients, and the mean reduction in pain severity was 4.8 points. The initial relief from pain of PNS is shown in <xref ref-type="fig" rid="F2">Figures 2</xref>, <xref ref-type="fig" rid="F3">3A</xref>.</p>
<fig id="F2" position="float">
<label>FIGURE 2</label>
<caption><p>Initial relief from pain provided by PNS upon discharge. <bold>(A)</bold> The distribution of pain change for the subacute pain group and PHN group. <bold>(B)</bold> Ratio of patients having pain reduction &#x003E; 50%.</p></caption>
<graphic xlink:href="fnins-14-574713-g002.tif"/>
</fig>
<fig id="F3" position="float">
<label>FIGURE 3</label>
<caption><p>Long-term analgesic effect of PNS. <bold>(A)</bold> Comparison of initial and long-term pain relief. <bold>(B)</bold> Response rate at final follow-up. <bold>(C)</bold> Percentage of PHN in the subacute-pain group at a 6-month follow-up. <bold>(D)</bold> Detail of analgesic medication before and after PNS. GBP, Gabapentin; NSAIDs, Non-steroidal Anti-inflammatory Drugs; Ops, Opsioids; PGB, Pregabalin.</p></caption>
<graphic xlink:href="fnins-14-574713-g003.tif"/>
</fig>
</sec>
<sec id="S3.SS3.SSS2">
<title>Long-Term Analgesic Effect</title>
<p>PNS provided enduring relief from pain for 6&#x2013;12 months, with an average decrease in the pain score of 5.1 (<xref ref-type="fig" rid="F3">Figure 3A</xref>). The average reduction in pain was 4.8 &#x00B1; 1.2 points (<italic>n</italic> = 18) at the 6-month follow-up and 5.4 &#x00B1; 1.4 points (<italic>n</italic> = 11) at 12-month follow-up, respectively (<xref ref-type="table" rid="T2">Table 2</xref>). One patient who had PHN for &#x003E; 8 years had recurrent moderate-to-severe facial pain 1 month after PNS. The long-term response rate was 93% (14 out of 15) and 67% (2 out of 3) for the subacute pain group and PHN group, respectively (<xref ref-type="fig" rid="F3">Figure 3B</xref>). The prevalence of PHN (defined as persistent moderate or severe pain for &#x003E; 3 months) was 7% in the subacute pain group (<xref ref-type="fig" rid="F3">Figure 3C</xref>). Only one of 15 patients with subacute pain continued to feel mild-to-moderate pain (VAS score = 4) at the final follow-up. Use of analgesic medication was reduced after PNS (<xref ref-type="fig" rid="F3">Figure 3D</xref>). Use of neither opiates nor non-steroidal anti-inflammatory drugs (NSAIDs) was reported at the final interview. Two patients continued to take pregabalin, and one was taking gabapentin with tolerable pain. Other interventions included acupuncture and treatment using herbal formulations.</p>
</sec>
<sec id="S3.SS3.SSS3">
<title>Complications</title>
<p>No obvious adverse effects (e.g., infection, hemorrhage, or tetrode migration) were observed in this study.</p>
</sec>
</sec>
</sec>
<sec id="S4">
<title>Discussion</title>
<p>Patients suffer severe and long-lasting facial pain with HZO. The high risk of PHN is associated with ophthalmic involvement (especially for older people). Conventional intervention remains insufficient to control HZO pain. Thus, improving the pain management of HZO patients and preventing PHN development are important tasks.</p>
<p>Early antiviral therapy can attenuate acute herpetic pain and reduce the risk of PHN (<xref ref-type="bibr" rid="B4">Cobo et al., 1986</xref>; <xref ref-type="bibr" rid="B32">Wood et al., 1996</xref>). However, many patients continue to suffer intolerable pain after conventional treatment. In the present study, 14 out of 15 patients took routine antiviral drugs in the initial phase of herpetic infection, and all of them continued to suffer severe facial pain 1&#x2013;3 months later. To control pain, anticonvulsants, tricyclic antidepressants, corticosteroids, opioid analgesics, or topical lidocaine paths are recommended (<xref ref-type="bibr" rid="B10">Gintautas et al., 2002</xref>; <xref ref-type="bibr" rid="B9">Gan et al., 2013</xref>). Along with side effects (e.g., gastrointestinal and psychiatric dysfunction, addiction, and tolerance), current medications for HZO-related pain remain unsatisfactory. The blockade of the stellate ganglion may be an easy and safe option to relieve HZO-related pain, but the long-term analgesic effect is controversial (<xref ref-type="bibr" rid="B25">Opstelten et al., 2004</xref>).</p>
<p>Multimodal analgesia plays an important role in solving the undertreatment of pain. Neuromodulation therapy is a key component of a multimodal-analgesia strategy, and has been used to alleviate intractable neuropathic pain, such as &#x201C;phantom limb pain&#x201D; (<xref ref-type="bibr" rid="B2">Campbell and Long, 1976</xref>). Meanwhile, functional electrical stimulation (FES) has also been applied widely for: treatment of bladder, bowel, and sexual dysfunctions; respiration problems; restoration of hand grasping and release; and standing and stepping (<xref ref-type="bibr" rid="B27">Ragnarsson, 2008</xref>; <xref ref-type="bibr" rid="B6">Creasey and Craggs, 2012</xref>). The other clinical indications for FES include bladder prostheses, cochlear implants, retinal and visual prostheses, and vagus-nerve stimulation for the treatment of epilepsy and depression (<xref ref-type="bibr" rid="B26">Peckham and Creasey, 1992</xref>; <xref ref-type="bibr" rid="B23">Milby et al., 2008</xref>; <xref ref-type="bibr" rid="B11">Goetz and Palanker, 2016</xref>).</p>
<p>Recent innovations in PNS have indicated its potential role in the treatment of intractable facial pain (<xref ref-type="bibr" rid="B24">Nayak and Banik, 2018</xref>). However, few studies have used PNS specifically for the management of HZO-related pain. The effect of PNS on facial-pain control may vary based on the etiology. <xref ref-type="bibr" rid="B14">Johnson and Burchiel (2004)</xref> reported that patients with posttraumatic trigeminal neuropathy responded better than a cohort with trigeminal PHN. The response (pain relief &#x2265; 50%) was 100% in the posttraumatic neuropathy subgroup, and 50% in the PHN cohort, respectively. Likewise, we found that 2 out of 3 PHN (67%) patients with ophthalmic involvement had pain reduction &#x003E; 50% at the final follow-up. Given that permanent implantation increases the risk of adverse effects (e.g., infection, electrode migration, inadequate pain relief), our data suggest that temporary PNS therapy may be an alternative option for patients with ophthalmic PHN who refuse permanent implantation of tetrodes.</p>
<p>Timely management of pain is crucial to prevent the chronicity of HZO. Our study focused, for the first time, on a population of patients with subacute HZO-related pain who received PNS. We demonstrated that 80% (12 out of 15) of patients with subacute HZO-related pain experienced &#x003E; 50% pain relief when discharged. Only one out of 15 patients (7%) developed PHN in the subacute group 3 months after the initial skin rash. <xref ref-type="bibr" rid="B1">Borkar et al. (2013)</xref> found that 21% of HZO patients developed PHN eventually. The risk of PHN was 2.5-fold higher for those aged &#x003E; 65 years, and only 3.6% of HZO patients aged &#x003C; 45 years suffered PHN. Other risk factors of PHN associated with HZO were keratitis, conjunctivitis, and/or uveitis. Considering the advanced age of patients enrolled in our study, early PNS intervention in the subacute phase may be the key to improving the long-term outcome of HZO patients (especially for the older population).</p>
<p>Our study had three main limitations. First, it was retrospective. Second, it had an uncontrolled design. Third, the details of analgesic use were not recorded systematically. Randomized controlled trials are needed to confirm our findings of the superiority of PNS compared with conventional treatments for HZO-related pain.</p>
</sec>
<sec id="S5">
<title>Conclusion</title>
<p>PNS was demonstrated to achieve instant and effective pain control for HZO patients. The long-term effect of PNS was enduring, with a low prevalence of PHN. For HZO patients who suffer severe pain with conventional therapy, PNS may be a promising option.</p>
</sec>
<sec id="S6">
<title>Data Availability Statement</title>
<p>The original contributions generated for this study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s.</p>
</sec>
<sec id="S7">
<title>Ethics Statement</title>
<p>The studies involving human participants were reviewed and approved by the ethics board of the Third Xiangya Hospital, Central South University. Written informed consent was signed before PNS therapy. The procedures and data analysis in this study were conducted in accordance with the research guideline of Third Xiangya Hospital Institutional Review Board.</p>
</sec>
<sec id="S8">
<title>Author Contributions</title>
<p>HZ and DH designed the study. RuH, GG, YN, JZ, and DH carried out the procedures. XL, ZW, LY, and RoH conducted the follow-ups. XL and HZ conducted the data analyses. HZ wrote the manuscript. All authors contributed to the article and approved the submitted version.</p>
</sec>
<sec id="conf1">
<title>Conflict of Interest</title>
<p>The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p>
</sec>
</body>
<back>
<fn-group>
<fn fn-type="financial-disclosure">
<p><bold>Funding.</bold> This study was supported by the National Natural Science Foundation of China (81901146 to HZ and 81771101 to HZ and DH) and the Key Laboratory of Hunan Province grants (2018TP1009 to HZ and DH).</p>
</fn>
</fn-group>
<ref-list>
<title>References</title>
<ref id="B1"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Borkar</surname> <given-names>D. S.</given-names></name> <name><surname>Tham</surname> <given-names>V. M.</given-names></name> <name><surname>Esterberg</surname> <given-names>E.</given-names></name> <name><surname>Ray</surname> <given-names>K. J.</given-names></name> <name><surname>Vinoya</surname> <given-names>A. C.</given-names></name> <name><surname>Parker</surname> <given-names>J. V.</given-names></name><etal/></person-group> (<year>2013</year>). <article-title>Incidence of herpes zoster ophthalmicus: results from the Pacific Ocular Inflammation Study.</article-title> <source><italic>Ophthalmology</italic></source> <volume>120</volume> <fpage>451</fpage>&#x2013;<lpage>456</lpage>. <pub-id pub-id-type="doi">10.1016/j.ophtha.2012.09.007</pub-id> <pub-id pub-id-type="pmid">23207173</pub-id></citation></ref>
<ref id="B2"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Campbell</surname> <given-names>J. N.</given-names></name> <name><surname>Long</surname> <given-names>D. M.</given-names></name></person-group> (<year>1976</year>). <article-title>Peripheral nerve stimulation in the treatment of intractable pain.</article-title> <source><italic>J. Neurosurg.</italic></source> <volume>45</volume> <fpage>692</fpage>&#x2013;<lpage>699</lpage>. <pub-id pub-id-type="doi">10.3171/jns.1976.45.6.0692</pub-id> <pub-id pub-id-type="pmid">1086348</pub-id></citation></ref>
<ref id="B3"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Chang</surname> <given-names>H. C.</given-names></name> <name><surname>Sung</surname> <given-names>C. W.</given-names></name> <name><surname>Lin</surname> <given-names>M. H.</given-names></name></person-group> (<year>2019</year>). <article-title>The efficacy of oral acyclovir during early course of pityriasis rosea: a systematic review and meta-analysis.</article-title> <source><italic>J. Dermatolog. Treat.</italic></source> <volume>30</volume> <fpage>288</fpage>&#x2013;<lpage>293</lpage>. <pub-id pub-id-type="doi">10.1080/09546634.2018.1508820</pub-id> <pub-id pub-id-type="pmid">30109959</pub-id></citation></ref>
<ref id="B4"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Cobo</surname> <given-names>L. M.</given-names></name> <name><surname>Foulks</surname> <given-names>G. N.</given-names></name> <name><surname>Liesegang</surname> <given-names>T.</given-names></name> <name><surname>Lass</surname> <given-names>J.</given-names></name> <name><surname>Sutphin</surname> <given-names>J. E.</given-names></name> <name><surname>Wilhelmus</surname> <given-names>K.</given-names></name><etal/></person-group> (<year>1986</year>). <article-title>Oral acyclovir in the treatment of acute herpes zoster ophthalmicus.</article-title> <source><italic>Ophthalmology</italic></source> <volume>93</volume> <fpage>763</fpage>&#x2013;<lpage>770</lpage>.</citation></ref>
<ref id="B5"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Coen</surname> <given-names>P. G.</given-names></name> <name><surname>Scott</surname> <given-names>F.</given-names></name> <name><surname>Leedham-Green</surname> <given-names>M.</given-names></name> <name><surname>Nia</surname> <given-names>T.</given-names></name> <name><surname>Jamil</surname> <given-names>A.</given-names></name> <name><surname>Johnson</surname> <given-names>R. W.</given-names></name><etal/></person-group> (<year>2006</year>). <article-title>Predicting and preventing post-herpetic neuralgia: are current risk factors useful in clinical practice?</article-title> <source><italic>Eur. J. Pain.</italic></source> <volume>10</volume> <fpage>695</fpage>&#x2013;<lpage>700</lpage>. <pub-id pub-id-type="doi">10.1016/j.ejpain.2005.11.002</pub-id> <pub-id pub-id-type="pmid">16427792</pub-id></citation></ref>
<ref id="B6"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Creasey</surname> <given-names>G. H.</given-names></name> <name><surname>Craggs</surname> <given-names>M. D.</given-names></name></person-group> (<year>2012</year>). <article-title>Functional electrical stimulation for bladder, bowel, and sexual function.</article-title> <source><italic>Handb. Clin. Neurol.</italic></source> <volume>109</volume> <fpage>247</fpage>&#x2013;<lpage>257</lpage>. <pub-id pub-id-type="doi">10.1016/b978-0-444-52137-8.00015-2</pub-id> <pub-id pub-id-type="pmid">23098717</pub-id></citation></ref>
<ref id="B7"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Ding</surname> <given-names>Y.</given-names></name> <name><surname>Hong</surname> <given-names>T.</given-names></name> <name><surname>Li</surname> <given-names>H.</given-names></name> <name><surname>Yao</surname> <given-names>P.</given-names></name> <name><surname>Zhao</surname> <given-names>G.</given-names></name></person-group> (<year>2019</year>). <article-title>Efficacy of CT guided pulsed radiofrequency treatment for trigeminal postherpetic neuralgia.</article-title> <source><italic>Front. Neurosci.</italic></source> <volume>13</volume>:<issue>708</issue>. <pub-id pub-id-type="doi">10.3389/fnins.2019.00708</pub-id> <pub-id pub-id-type="pmid">31354417</pub-id></citation></ref>
<ref id="B8"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Dodick</surname> <given-names>D. W.</given-names></name> <name><surname>Silberstein</surname> <given-names>S. D.</given-names></name> <name><surname>Reed</surname> <given-names>K. L.</given-names></name> <name><surname>Deer</surname> <given-names>T. R.</given-names></name> <name><surname>Slavin</surname> <given-names>K. V.</given-names></name> <name><surname>Huh</surname> <given-names>B.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>Safety and efficacy of peripheral nerve stimulation of the occipital nerves for the management of chronic migraine: long-term results from a randomized, multicenter, double-blinded, controlled study.</article-title> <source><italic>Cephalalgia</italic></source> <volume>35</volume> <fpage>344</fpage>&#x2013;<lpage>358</lpage>. <pub-id pub-id-type="doi">10.1177/0333102414543331</pub-id> <pub-id pub-id-type="pmid">25078718</pub-id></citation></ref>
<ref id="B9"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Gan</surname> <given-names>E. Y.</given-names></name> <name><surname>Tian</surname> <given-names>E. A.</given-names></name> <name><surname>Tey</surname> <given-names>H. L.</given-names></name></person-group> (<year>2013</year>). <article-title>Management of herpes zoster and post-herpetic neuralgia.</article-title> <source><italic>Am. J. Clin. Dermatol.</italic></source> <volume>14</volume> <fpage>77</fpage>&#x2013;<lpage>85</lpage>.</citation></ref>
<ref id="B10"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Gintautas</surname> <given-names>J.</given-names></name> <name><surname>Abraham</surname> <given-names>Y.</given-names></name> <name><surname>Doss</surname> <given-names>N. W.</given-names></name> <name><surname>Ghobriel</surname> <given-names>A.</given-names></name> <name><surname>Kashem</surname> <given-names>A.</given-names></name> <name><surname>Fogler</surname> <given-names>R. J.</given-names></name></person-group> (<year>2002</year>). <article-title>Lidocaine and methylprednisolone in management of herpes zoster and post-herpetic neuralgia.</article-title> <source><italic>Proc. West Pharmacol. Soc.</italic></source> <volume>45</volume>:<issue>73</issue>.</citation></ref>
<ref id="B11"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Goetz</surname> <given-names>G. A.</given-names></name> <name><surname>Palanker</surname> <given-names>D. V.</given-names></name></person-group> (<year>2016</year>). <article-title>Electronic approaches to restoration of sight.</article-title> <source><italic>Rep. Prog. Phys.</italic></source> <volume>79</volume>:<issue>096701</issue>. <pub-id pub-id-type="doi">10.1088/0034-4885/79/9/096701</pub-id></citation></ref>
<ref id="B12"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Hassenbusch</surname> <given-names>S. J.</given-names></name> <name><surname>Stanton-Hicks</surname> <given-names>M.</given-names></name> <name><surname>Schoppa</surname> <given-names>D.</given-names></name> <name><surname>Walsh</surname> <given-names>J. G.</given-names></name> <name><surname>Covington</surname> <given-names>E. C.</given-names></name></person-group> (<year>1996</year>). <article-title>Long-term results of peripheral nerve stimulation for reflex sympathetic dystrophy.</article-title> <source><italic>J. Neurosurg.</italic></source> <volume>84</volume> <fpage>415</fpage>&#x2013;<lpage>423</lpage>. <pub-id pub-id-type="doi">10.3171/jns.1996.84.3.0415</pub-id> <pub-id pub-id-type="pmid">8609552</pub-id></citation></ref>
<ref id="B13"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Jeon</surname> <given-names>I. C.</given-names></name> <name><surname>Kim</surname> <given-names>M. S.</given-names></name> <name><surname>Kim</surname> <given-names>S. H.</given-names></name></person-group> (<year>2009</year>). <article-title>Median nerve stimulation in a patient with complex regional pain syndrome type II.</article-title> <source><italic>J. Korea. Neurosurg. Soc.</italic></source> <volume>46</volume> <fpage>273</fpage>&#x2013;<lpage>276</lpage>. <pub-id pub-id-type="doi">10.3340/jkns.2009.46.3.273</pub-id> <pub-id pub-id-type="pmid">19844632</pub-id></citation></ref>
<ref id="B14"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Johnson</surname> <given-names>M. D.</given-names></name> <name><surname>Burchiel</surname> <given-names>K. J.</given-names></name></person-group> (<year>2004</year>). <article-title>Peripheral stimulation for treatment of trigeminal postherpetic neuralgia and trigeminal posttraumatic neuropathic pain: a pilot study.</article-title> <source><italic>Neurosurgery</italic></source> <volume>55</volume> <fpage>135</fpage>&#x2013;<lpage>141</lpage>. <pub-id pub-id-type="doi">10.1227/01.neu.0000126874.08468.89</pub-id></citation></ref>
<ref id="B15"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Johnson</surname> <given-names>R. W.</given-names></name> <name><surname>Alvarez-Pasquin</surname> <given-names>M. J.</given-names></name> <name><surname>Bijl</surname> <given-names>M.</given-names></name> <name><surname>Franco</surname> <given-names>E.</given-names></name> <name><surname>Gaillat</surname> <given-names>J.</given-names></name> <name><surname>Clara</surname> <given-names>J. G.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>Herpes zoster epidemiology, management, and disease and economic burden in Europe: a multidisciplinary perspective.</article-title> <source><italic>Ther. Adv. Vaccines</italic></source> <volume>3</volume> <fpage>109</fpage>&#x2013;<lpage>120</lpage>. <pub-id pub-id-type="doi">10.1177/2051013615599151</pub-id> <pub-id pub-id-type="pmid">26478818</pub-id></citation></ref>
<ref id="B16"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Johnson</surname> <given-names>R. W.</given-names></name> <name><surname>Rice</surname> <given-names>A. S.</given-names></name></person-group> (<year>2014</year>). <article-title>Clinical practice <italic>Postherpetic neuralgia</italic>.</article-title> <source><italic>N. Engl. J. Med.</italic></source> <volume>371</volume> <fpage>1526</fpage>&#x2013;<lpage>1533</lpage>.</citation></ref>
<ref id="B17"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Klein</surname> <given-names>J.</given-names></name> <name><surname>Sandi-Gahun</surname> <given-names>S.</given-names></name> <name><surname>Schackert</surname> <given-names>G.</given-names></name> <name><surname>Juratli</surname> <given-names>T. A.</given-names></name></person-group> (<year>2016</year>). <article-title>Peripheral nerve field stimulation for trigeminal neuralgia, trigeminal neuropathic pain, and persistent idiopathic facial pain.</article-title> <source><italic>Cephalalgia</italic></source> <volume>36</volume> <fpage>445</fpage>&#x2013;<lpage>453</lpage>. <pub-id pub-id-type="doi">10.1177/0333102415597526</pub-id> <pub-id pub-id-type="pmid">26209705</pub-id></citation></ref>
<ref id="B18"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Kong</surname> <given-names>C. L.</given-names></name> <name><surname>Thompson</surname> <given-names>R. R.</given-names></name> <name><surname>Porco</surname> <given-names>T. C.</given-names></name> <name><surname>Kim</surname> <given-names>E.</given-names></name> <name><surname>Acharya</surname> <given-names>N. R.</given-names></name></person-group> (<year>2020</year>). <article-title>Incidence rate of herpes zoster ophthalmicus: a retrospective cohort study from 1994 through 2018.</article-title> <source><italic>Ophthalmology</italic></source> <volume>127</volume> <fpage>324</fpage>&#x2013;<lpage>330</lpage>.</citation></ref>
<ref id="B19"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Kustermans</surname> <given-names>L.</given-names></name> <name><surname>Van Buyten</surname> <given-names>J. P.</given-names></name> <name><surname>Smet</surname> <given-names>I.</given-names></name> <name><surname>Coucke</surname> <given-names>W.</given-names></name> <name><surname>Politis</surname> <given-names>C.</given-names></name></person-group> (<year>2017</year>). <article-title>Stimulation of the Gasserian ganglion in the treatment of refractory trigeminal neuropathy.</article-title> <source><italic>J. Craniomaxillofac. Surg.</italic></source> <volume>45</volume> <fpage>39</fpage>&#x2013;<lpage>46</lpage>. <pub-id pub-id-type="doi">10.1016/j.jcms.2016.10.014</pub-id> <pub-id pub-id-type="pmid">27919593</pub-id></citation></ref>
<ref id="B20"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Lerman</surname> <given-names>I. R.</given-names></name> <name><surname>Chen</surname> <given-names>J. L.</given-names></name> <name><surname>Hiller</surname> <given-names>D.</given-names></name> <name><surname>Souzdalnitski</surname> <given-names>D.</given-names></name> <name><surname>Sheean</surname> <given-names>G.</given-names></name> <name><surname>Wallace</surname> <given-names>M.</given-names></name><etal/></person-group> (<year>2015</year>). <article-title>Novel high-frequency peripheral nerve stimulator treatment of refractory postherpetic neuralgia: a brief technical note.</article-title> <source><italic>Neuromodulation</italic></source> <volume>18</volume> <fpage>487</fpage>&#x2013;<lpage>493</lpage>. <pub-id pub-id-type="doi">10.1111/ner.12281</pub-id> <pub-id pub-id-type="pmid">25832898</pub-id></citation></ref>
<ref id="B21"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Liesegang</surname> <given-names>T. J.</given-names></name></person-group> (<year>2008</year>). <article-title>Herpes zoster ophthalmicus natural history, risk factors, clinical presentation, and morbidity.</article-title> <source><italic>Ophthalmology</italic></source> <volume>115</volume>(<issue>2 Suppl</issue>.), <fpage>S3</fpage>&#x2013;<lpage>S12</lpage>.</citation></ref>
<ref id="B22"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>McMahon</surname> <given-names>J. T.</given-names></name> <name><surname>Tora</surname> <given-names>M. S.</given-names></name> <name><surname>Bentley</surname> <given-names>J. N.</given-names></name> <name><surname>Texakalidis</surname> <given-names>P.</given-names></name> <name><surname>Campbell</surname> <given-names>M. A.</given-names></name> <name><surname>Keifer</surname> <given-names>U.</given-names> <suffix>Jr.</suffix></name><etal/></person-group> (<year>2019</year>). <article-title>Percutaneous trigeminal nerve stimulation for persistent idiopathic facial pain: a case series.</article-title> <source><italic>World Neurosurg.</italic></source> <volume>126</volume> <fpage>e1379</fpage>&#x2013;<lpage>e1386</lpage>.</citation></ref>
<ref id="B23"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Milby</surname> <given-names>A. H.</given-names></name> <name><surname>Halpern</surname> <given-names>C. H.</given-names></name> <name><surname>Baltuch</surname> <given-names>G. H.</given-names></name></person-group> (<year>2008</year>). <article-title>Vagus nerve stimulation for epilepsy and depression.</article-title> <source><italic>Neurotherapeutics</italic></source> <volume>5</volume> <fpage>75</fpage>&#x2013;<lpage>85</lpage>. <pub-id pub-id-type="doi">10.1016/j.nurt.2007.10.071</pub-id> <pub-id pub-id-type="pmid">18164486</pub-id></citation></ref>
<ref id="B24"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Nayak</surname> <given-names>R.</given-names></name> <name><surname>Banik</surname> <given-names>R. K.</given-names></name></person-group> (<year>2018</year>). <article-title>Current innovations in peripheral nerve stimulation.</article-title> <source><italic>Pain Res. Treat.</italic></source> <volume>2018</volume>:<issue>9091216</issue>.</citation></ref>
<ref id="B25"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Opstelten</surname> <given-names>W.</given-names></name> <name><surname>van Wijck</surname> <given-names>A. J.</given-names></name> <name><surname>Stolker</surname> <given-names>R. J.</given-names></name></person-group> (<year>2004</year>). <article-title>Interventions to prevent postherpetic neuralgia: cutaneous and percutaneous techniques.</article-title> <source><italic>Pain</italic></source> <volume>107</volume> <fpage>202</fpage>&#x2013;<lpage>206</lpage>. <pub-id pub-id-type="doi">10.1016/j.pain.2003.10.021</pub-id> <pub-id pub-id-type="pmid">14736581</pub-id></citation></ref>
<ref id="B26"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Peckham</surname> <given-names>P.</given-names></name> <name><surname>Creasey</surname> <given-names>G.</given-names></name></person-group> (<year>1992</year>). <article-title>Neural prostheses: clinical applications of functional electrical stimulation in spinal cord injury.</article-title> <source><italic>Spinal Cord</italic></source> <volume>30</volume> <fpage>96</fpage>&#x2013;<lpage>101</lpage>. <pub-id pub-id-type="doi">10.1038/sc.1992.33</pub-id> <pub-id pub-id-type="pmid">1589297</pub-id></citation></ref>
<ref id="B27"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Ragnarsson</surname> <given-names>K.</given-names></name></person-group> (<year>2008</year>). <article-title>Functional electrical stimulation after spinal cord injury: current use, therapeutic effects and future directions.</article-title> <source><italic>Spinal Cord</italic></source> <volume>46</volume> <fpage>255</fpage>&#x2013;<lpage>274</lpage>. <pub-id pub-id-type="doi">10.1038/sj.sc.3102091</pub-id> <pub-id pub-id-type="pmid">17846639</pub-id></citation></ref>
<ref id="B28"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Saper</surname> <given-names>J. R.</given-names></name> <name><surname>Dodick</surname> <given-names>D. W.</given-names></name> <name><surname>Silberstein</surname> <given-names>S. D.</given-names></name> <name><surname>McCarville</surname> <given-names>S.</given-names></name> <name><surname>Sun</surname> <given-names>M.</given-names></name> <name><surname>Goadsby</surname> <given-names>P. J.</given-names></name><etal/></person-group> (<year>2011</year>). <article-title>Occipital nerve stimulation for the treatment of intractable chronic migraine headache: ONSTIM feasibility study.</article-title> <source><italic>Cephalalgia</italic></source> <volume>31</volume> <fpage>271</fpage>&#x2013;<lpage>285</lpage>. <pub-id pub-id-type="doi">10.1177/0333102410381142</pub-id> <pub-id pub-id-type="pmid">20861241</pub-id></citation></ref>
<ref id="B29"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Thimineur</surname> <given-names>M.</given-names></name> <name><surname>De Ridder</surname> <given-names>D.</given-names></name></person-group> (<year>2007</year>). <article-title>C2 area neurostimulation: a surgical treatment for fibromyalgia.</article-title> <source><italic>Pain Med.</italic></source> <volume>8</volume> <fpage>639</fpage>&#x2013;<lpage>646</lpage>. <pub-id pub-id-type="doi">10.1111/j.1526-4637.2007.00365.x</pub-id> <pub-id pub-id-type="pmid">18028042</pub-id></citation></ref>
<ref id="B30"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Tran</surname> <given-names>K. D.</given-names></name> <name><surname>Falcone</surname> <given-names>M. M.</given-names></name> <name><surname>Choi</surname> <given-names>D. S.</given-names></name> <name><surname>Goldhardt</surname> <given-names>R.</given-names></name> <name><surname>Karp</surname> <given-names>C. L.</given-names></name> <name><surname>Davis</surname> <given-names>J. L.</given-names></name><etal/></person-group> (<year>2016</year>). <article-title>Epidemiology of herpes zoster ophthalmicus: recurrence and chronicity.</article-title> <source><italic>Ophthalmology</italic></source> <volume>123</volume> <fpage>1469</fpage>&#x2013;<lpage>1475</lpage>.</citation></ref>
<ref id="B31"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Wan</surname> <given-names>C.</given-names></name> <name><surname>Dong</surname> <given-names>D. S.</given-names></name> <name><surname>Song</surname> <given-names>T.</given-names></name></person-group> (<year>2019</year>). <article-title>High-voltage, long-duration pulsed radiofrequency on gasserian ganglion improves acute/subacute zoster-related trigeminal neuralgia: a randomized, double-blinded, controlled trial.</article-title> <source><italic>Pain Phys.</italic></source> <volume>22</volume> <fpage>361</fpage>&#x2013;<lpage>368</lpage>.</citation></ref>
<ref id="B32"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Wood</surname> <given-names>M. J.</given-names></name> <name><surname>Kay</surname> <given-names>R.</given-names></name> <name><surname>Dworkin</surname> <given-names>R. H.</given-names></name> <name><surname>Soong</surname> <given-names>S. J.</given-names></name> <name><surname>Whitley</surname> <given-names>R. J.</given-names></name></person-group> (<year>1996</year>). <article-title>Oral acyclovir therapy accelerates pain resolution in patients with herpes zoster: a meta-analysis of placebo-controlled trials.</article-title> <source><italic>Clin. Infect. Dis.</italic></source> <volume>22</volume> <fpage>341</fpage>&#x2013;<lpage>347</lpage>. <pub-id pub-id-type="doi">10.1093/clinids/22.2.341</pub-id></citation></ref>
<ref id="B33"><citation citation-type="journal"><person-group person-group-type="author"><name><surname>Zhou</surname> <given-names>R.</given-names></name> <name><surname>Wang</surname> <given-names>J.</given-names></name> <name><surname>Qi</surname> <given-names>W.</given-names></name> <name><surname>Liu</surname> <given-names>F. Y.</given-names></name> <name><surname>Yi</surname> <given-names>M.</given-names></name> <name><surname>Guo</surname> <given-names>H.</given-names></name><etal/></person-group> (<year>2018</year>). <article-title>Elevated resting state gamma oscillatory activities in electroencephalogram of patients with post-herpetic neuralgia.</article-title> <source><italic>Front. Neurosci.</italic></source> <volume>12</volume>:<issue>750</issue>. <pub-id pub-id-type="doi">10.3389/fnins.2019.00750</pub-id> <pub-id pub-id-type="pmid">31379495</pub-id></citation></ref>
</ref-list>
</back>
</article>