Front. Rehabil. Sci. Frontiers in Rehabilitation Sciences Front. Rehabil. Sci. 2673-6861 Frontiers Media S.A. 10.3389/fresc.2026.1766757 Mini Review Transcranial stimulation as a possible therapeutic proposal in long COVID dos SantosLidiane Palheta Miranda 1 2 Writing – original draftWriting – review & editing LeãoJulliana Vieira 2Writing – original draftWriting – review & editing SilvaKetelen Yasmim Braga de Moraes 1Writing – original draftWriting – review & editing dos SantosDanilo Lameira 1Writing – original draftWriting – review & editing BatistaChrisllane Nascimento 1Writing – original draftWriting – review & editing BarrosJonna Almeida 1Writing – original draftWriting – review & editing ParanhosAlna Carolina Mendes 1ValidationVisualizationWriting – original draftWriting – review & editing DiasÁpio Ricardo Nazareth 1 *ValidationVisualizationWriting – original draftWriting – review & editing FalcãoLuiz Fábio Magno 1 2 3ValidationVisualizationWriting – original draftWriting – review & editing Centro de Ciências Biológicas e da Saúde, Universidade do Estado do Pará, Belém, Brazil Programa de Pós Graduação em Biologia Parasitária na Amazônia, Universidade do Estado do Pará, Belém, Brazil Faculdade de Medicina, Universidade de São Paulo, Belém, Brazil Correspondence: Ápio Ricardo Nazareth Dias apio.dias@uepa.br 27022026 2026 71766757 12122025 02022026 09022026 © 2026 dos Santos, Leão, Silva, dos Santos, Batista, Barros, Paranhos, Dias and Falcão. 2026dos Santos, Leão, Silva, dos Santos, Batista, Barros, Paranhos, Dias and Falcãohttps://creativecommons.org/licenses/by/4.0/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.

The COVID-19 pandemic triggered an unprecedented global health crisis, with significant repercussions on the mental and neurological health of millions of individuals. Long COVID, characterized by persistent and debilitating symptoms, including chronic fatigue, pain, cognitive impairment, and mood swings, represents a substantial therapeutic challenge. In this context, neuromodulation emerges as a promising therapeutic strategy, offering new perspectives for the management of refractory neurological symptoms. This article aims to critically review the current evidence on the use of neuromodulation in patients with long COVID.

 long COVID neurological rehabilitation neuromodulation therapeutic interventions transcranial stimulation The author(s) declared that financial support was received for this work and/or its publication. This work was supported by the Pará Secretariat for Science, Technology and Higher, Professional and Technological Education (SECTET) [grant number 09/2021], and Coordination for the Improvement of Higher Education Personnel—Brazil (CAPES) [Financial code 001, grant number 13/2020], the National Council for Scientific and Technological Development -Brazil (CNPq), [INCT:406360/2022]. section-at-acceptanceInterventions for Rehabilitation Introduction

According to the World Health Organization (WHO), the COVID-19 virus (SARS-CoV-2) has infected more than 765 million people worldwide (1, 2). SARS-CoV-2 is considered neuroinvasive, capable of reaching the nervous system through multiple pathways, including the olfactory nerve, bloodstream, and brainstem, resulting in neurological disorders (3). Although COVID-19 is primarily a respiratory infection, it may generate prolonged sequelae known as Long COVID, affecting both severely ill and non-hospitalized individuals (4, 5). This may be attributed to impairment of the blood–brain barrier, leading to increased glutamate levels, which in turn promote oxidative stress, endothelial dysfunction, and hypercoagulability. Additionally, reduced activity of the angiotensin-converting enzyme (ACE) caused by infection contributes to a hyperinflammatory state (6).

Persistent symptoms include fatigue, pulmonary dysfunction, anosmia, cognitive alterations, among more than 50 long-term effects (4), Long COVID is a multifaceted clinical entity affecting a substantial proportion of individuals following SARS-CoV-2 infection (4, 5). Neurological manifestations include headache, chronic fatigue, neuropathic pain, cognitive impairment, anosmia, ageusia, and mood changes, which interfere with occupational performance, memory, concentration, and overall quality of life (6, 7).

Neuromodulation has been proposed as a therapeutic option to manage neurological symptoms (6, 8, 9). Recent evidence indicates that non-invasive neuromodulation may contribute to improvements by modulating inflammatory processes and neuroplasticity (10–19). tDCS may reduce persistent neuroinflammation by modulating microglial activation and cytokine levels. By attenuating the inflammatory milieu, this technique creates more favourable conditions for neural plasticity, while the active promotion of new synaptic connections contributes to the functional compensation of deficits. Thus, tDCS emerges as an adjuvant intervention targeting the core pathophysiological mechanisms of long COVID (18, 19, 21).

Thus, neuromodulation, a rapidly expanding field aimed at modulating neural activity through non-invasive or minimally invasive techniques, emerges as an innovative therapeutic approach to mitigate persistent neurological symptoms.

 Current evidence on neuromodulation in long-term COVID

Neuromodulation is an expanding field that modulates neural activity through non-invasive or minimally invasive techniques and has emerged as a promising therapeutic option to mitigate persistent neurological symptoms (23, 25, 26). Therapeutic modalities include: Transcranial Magnetic Stimulation (TMS): uses magnetic fields to induce electrical currents in the brain, modulating cortical excitability; Transcranial Direct Current Stimulation (tDCS): Applies direct electrical current to the scalp, altering neuronal polarity and cortical excitability (18, 19).

Although literature is still limited, preliminary studies suggest that neuromodulation may reduce neurological symptoms in long COVID patients (Table 1). For instance, TMS and tDCS have demonstrated improvements in fatigue, pain, and cognitive function. Studies highlight the importance of integrating immunology, neurology, psychiatry, and engineering to develop clinical strategies using non-invasive neuromodulation for treating COVID-19 sequelae, offering a safe and accessible treatment option (15, 20). Recent evidence indicates significant advances in long-term COVID rehabilitation. A meta-analysis of 51 randomized clinical trials with 4,026 participants showed that interventions such as physical training, respiratory muscle strengthening, and telerehabilitation improve functional capacity, cardiorespiratory performance, reduce dyspnea and fatigue, and enhance quality of life. However, no consistent effects were observed on spirometric parameters (FEV1, FVC, FEV1/FVC), global fatigue (MFIS), or anxiety and depression symptoms (8).

Primary studies cited in manuscript.

Author Year Type of study Study population Method Primary outcome
Santana et al. (21) 2023 Randomized, double-blind, placebo-controlled clinical trial Patients aged 18–80 years with a diagnosis of PASC-related fatigue. HD-tDCS 4 × 1 with a central electrode over M1; 30-s ramp-up and ramp-down; 3 mA intensity; 10 sessions of 30 min; rehabilitation program conducted in parallel with the stimulation. Significant reduction in fatigue assessed by the MFIS was found when the active group was compared with the sham group.
Andrade et al. (22) 2022 Randomized, double-blind, placebo-controlled clinical trial Patients aged 18 years or older, diagnosed with SARS-CoV-2 by PCR, and undergoing weaning after receiving at least 48 h of mechanical ventilation. HD-tDCS 4 × 1 with a central electrode over M1; 30-s ramp-up and ramp-down; 3 mA intensity; two sessions per day for 10 consecutive working days; 30-min duration per session; pulmonary rehabilitation conducted in parallel with the stimulation. The active group showed more ventilator-free days during the first 28 days compared with the sham group.
Oliver-Mas et al. (29) 2023 Randomized, double-blind, placebo-controlled pilot study Patients diagnosed with SARS-CoV-2 by PCR and reporting fatigue symptoms. tDCS with the anode over the left DLPFC and the cathode over the contralateral supraorbital region; 15-s ramp-up and ramp-down; 2 mA intensity; 8 consecutive sessions, one per day on weekdays; 20-min duration per session. The active tDCS group was associated with improvement of fatigue symptoms at the end of treatment and at 1-month follow-up compared with the sham group.
Oliver-Mas et al. (30) 2025 Randomized controlled trial Post-COVID patients with PCR-confirmed COVID-19 at least 6 months before study inclusion and self-reported fatigue symptoms. tDCS with the anode over the left M1 or DLPFC and the cathode over the contralateral supraorbital region; 10-s ramp-up and ramp-down; 2 mA intensity; 15 sessions, one per day on weekdays; 20-min duration per session; use of CT in parallel with the sessions. The M1 + CT group showed a slight improvement in fatigue symptoms and sleep quality compared with the DLPFC + CT group. Overall, both groups showed improvements in cognition and sleep quality with reduction of anxiety, depression, pain,
Vidal et al. (19) 2025 Randomized, double-blind, placebo-controlled clinical trial Patients aged 18–75 years with a diagnosis of COVID-19 within the last 6 months and incident cognitive symptoms persisting for 4 weeks or more after infection. tDCS with the anode over the left side (F3) and the cathode over the right side (F4) over the prefrontal cortex; 30-s ramp-up and 45-s ramp-down, respectively; 2 mA intensity for the active protocol and 1 mA for the sham protocol; 20 consecutive sessions on weekdays; 20-min duration per session; use of CT in parallel with the sessions. The tDCS + CT group showed significant improvements in inhibitory control, processing speed, and divided attention assessment tests compared with the sham group.
Souza et al. (11) 2024 Case Series Six patients with COVID-19 infection confirmed by a nasal swab test, with an acute infection duration of 2–6 months. Patients reported dyspnea, cough, odynophagia, and rhinorrhea. HD-tDCS 4 × 1 with a central electrode over M1; 30-s ramp-up and ramp-down; 3 mA intensity; 10 sessions; 20-min duration per session; IMT conducted in parallel with the sessions. Patients improved their SMIP at the end of treatment, as well as respiratory muscle function, inspiratory muscle power, and pulmonary function.
Gómez et al. (14) 2021 Case Report A 58-year-old patient with PCR-confirmed COVID-19 and signs of fatigue and anxiety. tDCS with the anode over the left side (F3) and the cathode over the right side (F4) over the prefrontal cortex; 3 mA intensity; 20 sessions, one per day, each lasting 20 min. A clinically significant reduction in HARS, HDRS, and MFIS scores.
Klírová et al. (20) 2024 Randomized, double-blind, placebo-controlled study Patients aged 18–75 years; symptom duration longer than 1 month after infection; a score ≥ 40 on the FIS questionnaire; presence of PASC-related neuropsychiatric symptoms. tDCS with the anode over the left side (F3) and the cathode over the right side (F4) over the prefrontal cortex; 30-s ramp-up and ramp-down; 2 mA intensity; 20 sessions, one per day on weekdays; 30-min duration per session. Change in FIS score at the end of treatment in both groups, being higher in the sham group, but with no statistically significant difference.

MFIS, modified fatigue impact scale; PASC, post-acute sequelae of SARS-CoV-2 infection; PCR, polymerase chain reaction; MV, mechanical ventilation; M1, primary motor cortex; DLPFC, dorsolateral prefrontal cortex; CT, cognitive training; IMT, inspiratory muscle training; SMIP, sustained maximal inspiratory pressure; HARS, Hamilton anxiety rating scale; HDRS, Hamilton depression rating scale; FIS, fatigue impact scale.

Combining rehabilitation with neuromodulation has shown promise (19). Adding tDCS has been associated with a significant reduction in the physical component of fatigue in individuals with long COVID (21). Similarly, a case report demonstrated that tDCS contributed to reducing anxiety and depression symptoms in post-COVID patients, supporting the potential role of neuromodulation as an adjunctive therapy in rehabilitation (15, 17).

Transcranial direct current stimulation and fatigue

A randomized, double-blind clinical trial conducted in Paraíba involving 70 patients with fatigue related to chronic post-COVID syndrome demonstrated that high-definition tDCS (HD-tDCS), applied over the left motor cortex (M1) for 10 sessions over 5 weeks, significantly reduced fatigue as measured by the Modified Fatigue Impact Scale (MFIS) (19, 21), including cognitive and psychosocial dimensions, compared to the sham group. Active stimulation involved 3 mA for 30 min, while the placebo group received only ramp-up and ramp-down currents without sustained stimulation. Both groups also participated in individualized rehabilitation programs based on post-COVID guidelines, including breathing exercises, gradual stretching, and submaximal resistance training, with progression guided by the Borg scale and fatigue symptoms (19, 20).

Similarly, a randomized clinical trial with 56 adults who had undergone mechanical ventilation for at least 48 h and presented moderate to severe acute respiratory distress syndrome (ARDS) demonstrated that HD-tDCS applied over the left diaphragmatic primary motor cortex in a 4 × 1 montage significantly increased ventilator-free days within the first 28 days compared to controls. The protocol consisted of 3 mA for 30 min, twice daily for 10 weekdays, with systematic electrode repositioning (22, 23). Both groups received concurrent pulmonary rehabilitation, including inspiratory muscle training starting at 30% of maximal inspiratory pressure with 10% daily progression, physiotherapy support, and supplemental oxygen as needed (22).

Additional evidence from a study involving 47 post-COVID patients with persistent fatigue (>6 months), mostly middle-aged women, investigated the effects of eight sessions of tDCS over the left dorsolateral prefrontal cortex (2 mA for 20 min) in a double-blind, placebo-controlled design over 2 weeks. Active stimulation significantly reduced physical fatigue both immediately post-treatment and at 1-month follow-up, alongside a reduction in depressive symptoms. Cognitive fatigue and quality of life did not show significant improvements. Adverse effects were mild, confirming good tolerability (23). Furthermore, a case series of six patients with persistent respiratory sequelae post-COVID investigated the combination of HD-tDCS with inspiratory muscle training (IMT). The integrated intervention enhanced respiratory muscle strength and efficiency, increased inspiratory capacity, ventilation, lung volumes, and maximal inspiratory pressure (SMIP). Although preliminary, this approach demonstrated potential as a safe and effective strategy for long COVID respiratory rehabilitation, with the need for larger studies to validate findings (25).

Overall, these studies converge on the central point that neuromodulation, particularly HD-tDCS, is a promising adjunct in rehabilitating persistent post-COVID symptoms, including fatigue and respiratory performance. While populations, protocols, and objectives differed, the combination of brain stimulation with structured rehabilitation consistently produced superior outcomes compared to conventional therapies alone. HD-tDCS shows good tolerability, with adverse events limited to mild and transient skin discomfort, positioning it as a non-pharmacological, scalable therapeutic option in post-COVID rehabilitation (20, 23–25) (Figure 1).

Effects of brain stimulation in neurological disorders.

Infographic comparing TMS and tDCS findings, showing key outcomes in a circular diagram. TMS findings include overall improvement in fatigue, pain, cognitive function, and some neurological benefits, with superior results when combined with rehabilitation. tDCS findings detail improved cognitive performance, reduced fatigue, reduced anxiety and depressive symptoms with better sleep quality, and increased cardiorespiratory outcomes. Illustrations of brain stimulation devices are shown beside each modality. Transcranial direct current stimulation and cognition

A randomized study evaluated the efficacy of tDCS combined with cognitive training in individuals with persistent post-COVID symptoms, including fatigue and cognitive impairments persisting on average for almost 3 years after infection (26, 27). Participants, predominantly middle-aged women, were randomly assigned to two groups: one received tDCS applied to the primary motor cortex (M1) and the other to the dorsolateral prefrontal cortex (DLPFC). Both groups underwent 15 sessions accompanied by structured cognitive training. Pre-intervention, immediate post-intervention, and 1-month follow-up assessments showed consistent improvements across multiple domains, including fatigue, cognitive performance, anxiety, depression, pain, and sleep quality. Stimulation of M1 showed slight superiority in reducing fatigue and improving sleep, suggesting the potential of combining neuromodulation with cognitive training as a safe and promising approach for persistent post-COVID symptoms (27).

In a pilot study, tDCS applied to the prefrontal cortex combined with structured cognitive training was investigated in adults with persistent cognitive complaints post-COVID. Participants, mostly women with an average age of 43 years, were randomized to 20 sessions of active or sham tDCS, both paired with the same cognitive training. Neuropsychological assessments demonstrated modest but significant improvements in inhibitory control, processing speed, and divided attention. Both groups also showed reduced anxiety and depressive symptoms, highlighting an emotional benefit associated with cognitive training. The authors emphasized the need for larger, methodologically robust studies to confirm these effects and define the role of tDCS in managing cognitive sequelae of long COVID (28).

A randomized, double-blind, placebo-controlled study evaluated tDCS targeting the medial prefrontal cortex for neuropsychiatric symptoms in long COVID. Participants were assigned to active tDCS or sham groups, receiving 20 sessions of 30 min each. The study did not find significant improvements in cognitive function, suggesting that tDCS monotherapy may be insufficient. Limitations included small sample size and possible suboptimal stimulation protocol (29).

Another study investigated non-invasive neurostimulation for persistent anosmia post-COVID in two phases. In the first phase, 25 participants underwent olfactory assessment and EEG recordings to identify target regions. In the second phase, 15 participants continued with neurostimulation divided into active and sham groups. Stimulation targeted olfactory structures (olfactory bulb, tract, and piriform cortex) across five 20-minute sessions. Participants with more severe initial olfactory deficits showed better outcomes, though statistical significance was limited due to small sample size (30). Across these four studies, populations were predominantly female, with mean ages between 43 and 47 years and persistent symptoms approximately 32 months post-infection. Results were heterogeneous. Studies combining tDCS with cognitive training (27, 28) showed significant improvements in fatigue, cognition, anxiety, depression, and sleep quality, whereas tDCS monotherapy or olfactory stimulation alone (29, 30) had limited or selective effects. Methodological limitations included small sample sizes, heterogeneity in protocols, and variable stimulation targets, which hindered direct comparison and generalizability.

Overall, tDCS paired with cognitive training emerges as a promising approach for managing cognitive deficits in post-COVID-19 patients. However, larger, rigorously designed clinical trials with standardized protocols are required to determine optimal parameters and validate clinical efficacy (27–30) (Figure 1).

 Challenges and limitations

The application of neuromodulation in long COVID faces substantial challenges, including the heterogeneity of symptoms, the lack of complete understanding of the underlying pathophysiological mechanisms, and the need for personalized treatment protocols. Furthermore, the accessibility and cost of neuromodulation techniques may limit their widespread use.

Future directions

To advance the use of neuromodulation for long COVID, well-designed clinical studies are needed to assess efficacy, safety, and best treatment protocols. Furthermore, it is crucial to investigate the mechanisms underlying long COVID and how neuromodulation can influence these processes. Neuromodulation presents itself as an innovative and promising therapeutic approach to alleviate the debilitating neurological symptoms of long COVID. While current data are encouraging, there is an urgent need for more research to establish efficacy, safety, and best treatment protocols. With increased understanding of long COVID and advancements in neuromodulation techniques, there is hope that these approaches can offer significant relief to the millions of patients affected by this condition.

 Author contributions

LS: Writing – original draft, Writing – review & editing. JL: Writing – original draft, Writing – review & editing. KS: Writing – original draft, Writing – review & editing. DS: Writing – original draft, Writing – review & editing. CB: Writing – original draft, Writing – review & editing. JB: Writing – original draft, Writing – review & editing. AP: Validation, Visualization, Writing – original draft, Writing – review & editing. AD: Validation, Visualization, Writing – original draft, Writing – review & editing. LF: Validation, Visualization, Writing – original draft, Writing – review & editing.

 Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

 Generative AI statement

The author(s) declared that generative AI was not used in the creation of this manuscript.

Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.

 Publisher's note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

 References Carfì A Bernabei R Landi F, Gemelli Against COVID-19 Post-Acute Care Study Group. Persistent symptoms in patients after acute COVID-19. J Am Med Assoc. (2020) 324(6):603–5. 10.1001/jama.2020.12603 Hayes LD Ingram J Sculthorpe NF. More than 100 persistent symptoms of SARS-CoV-2 (long COVID): a scoping review. Front Med. (2021) 8:750378. 10.3389/fmed.2021.750378 Altuna M Sánchez-Saudinós MB Lleó A. Cognitive symptoms after COVID-19. Neurol Perspect. (2021) 1:S16–24. 10.1016/j.neurop.2021.03.00138620975 Lopez-Leon S Wegman-Ostrosky T Perelman C Sepulveda R Rebolledo PA Cuapio A More than 50 long-term effects of COVID-19: a systematic review and meta-analysis. Sci Rep. (2021) 11:16144. 10.1038/s41598-021-95565-834373540 Fernández-de-Las-Peñas C Palacios-Ceña D Gómez-Mayordomo V Florencio LL Cuadrado ML Plaza-Manzano G Prevalence of post-COVID-19 symptoms in hospitalized and non-hospitalized COVID-19 survivors: a systematic review and meta-analysis. Eur J Intern Med. (2021) 92:55–70. 10.1016/j.ejim.2021.06.009 Engin AB Engin ED Engin A. Current opinion in neurological manifestations of SARS-CoV-2 infection. Curr Opin Toxicol. (2021) 25:49–56. 10.1016/j.cotox.2021.03.00433817451 Premraj L Kannapadi NV Briggs J Seal SM Battaglini D Fanning J Mid and long-term neurological and neuropsychiatric manifestations of post-COVID-19 syndrome: a meta-analysis. J Neurol Sci. (2022) 434:120162. 10.1016/j.jns.2022.12016235121209 Hsu WY Cheng CH Zanto TP Gazzaley A Bove RM. Effects of transcranial direct current stimulation on cognition, mood, pain, and fatigue in multiple sclerosis: a systematic review and meta-analysis. Front Neurol. (2021) 12:626113. 10.3389/fneur.2021.62611333763014 Bikson M Grossman P Thomas C Zannou AL Jiang J Adnan T Safety of transcranial direct current stimulation: evidence based update 2016. Brain Stimul. (2016) 9(5):641–61. 10.1016/j.brs.2016.06.00427372845 Baptista AF Baltar A Okano AH Moreira A Campos ACP Fernandes AM Applications of non-invasive neuromodulation for the management of disorders related to COVID-19. Front Neurol. (2020) 11:573718. 10.3389/fneur.2020.57371833324324 de Souza ITC Dos Santos EGG da Costa RVA Ferreira WDN Santana KJ Felix JVS Effects of high-definition transcranial direct current stimulation combined with inspiratory muscle training for treating respiratory sequelae of long COVID: a case series. Physiother Res Int. (2024) 29(3):e2109. 10.1002/pri.210938961771 Delgado-Alonso C Cuevas C Oliver-Mas S Díez-Cirarda M Delgado-Álvarez A Gil-Moreno MJ Fatigue and cognitive dysfunction are associated with occupational status in post-COVID syndrome. Int J Environ Res Public Health. (2022) 19(20):13368. 10.3390/ijerph19201336836293950 Delgado-Alonso C Díez-Cirarda M Pagán J Pérez-Izquierdo C Oliver-Mas S Fernández-Romero L Unraveling brain fog in post-COVID syndrome: relationship between subjective cognitive complaints and cognitive function, fatigue, and neuropsychiatric symptoms. Eur J Neurol. (2025) 32(1):e16084. 10.1111/ene.1608437797297 Gómez L Vidal B Cabrera Y Hernández L Rondón Y. Successful treatment of post-COVID symptoms with transcranial direct current stimulation. Prim Care Companion CNS Disord. (2021) 23(6):21cr03059. 10.4088/PCC.21cr03059 Herrera JE Niehaus WN Whiteson J Azola A Baratta JM Fleming TK Multidisciplinary collaborative consensus guidance statement on the assessment and treatment of fatigue in postacute sequelae of SARS-CoV-2 infection (PASC) patients. PM R. (2021) 13(9):1027–43. 10.1002/pmrj.12684; Erratum in: PM R. 2022 Jan;14(1):164. doi: 10.1002/pmrj.12748.34346558 Azabou E Bao G Heming N Bounab R Moine P Chevallier S Randomized controlled study evaluating efficiency of low intensity transcranial direct current stimulation (tDCS) for dyspnea relief in mechanically ventilated COVID-19 patients in ICU: the tDCS-DYSP-COVID protocol. Front Med. (2020) 7:372. 10.3389/fmed.2020.00372 Ke Y Liu S Chen L Wang X Ming D. Lasting enhancements in neural efficiency by multi-session transcranial direct current stimulation during working memory training. NPJ Sci Learn. (2023) 8(1):48. 10.1038/s41539-023-00200-y37919371 Gracia DI Ortiz M Candela T Iáñez E Sánchez RM Díaz C Design and evaluation of a potential non-invasive neurostimulation strategy for treating persistent anosmia in post-COVID-19 patients. Sensors. (2023) 23(13):5880. 10.3390/s2313588037447728 Vidal KS Cavendish BA Goerigk S Pita Batista M Oliveira Lima AR Pinto BS Transcranial direct current stimulation plus cognitive training for cognitive symptoms in patients with post-acute sequelae of SARS-CoV-2 infection: a randomized, double-blind, sham-controlled trial. Brain Stimul. (2025) 18(5):1608–16. 10.1016/j.brs.2025.08.01840848897 Klírová M Adamová A Biačková N Laskov O Renková V Stuchlíková Z Transcranial direct current stimulation (tDCS) in the treatment of neuropsychiatric symptoms of long COVID. Sci Rep. (2024) 14(1):2193. 10.1038/s41598-024-52763-4 Santana K França E Sato J Silva A Queiroz M de Farias J Non-invasive brain stimulation for fatigue in post-acute sequelae of SARS-CoV-2 (PASC). Brain Stimul. (2023) 16(1):100–7. 10.1016/j.brs.2023.01.167236693536 Andrade SM Cecília de Araújo Silvestre M Tenório de França EÉ Bezerra Sales Queiroz MH de Jesus Santana K Lima Holmes Madruga ML Efficacy and safety of HD-tDCS and respiratory rehabilitation for critically ill patients with COVID-19 the HD-RECOVERY randomized clinical trial. Brain Stimul. (2022) 15(3):780–8. 10.1016/j.brs.2022.05.00635568312 Lefaucheur JP Antal A Ayache SS Benninger DH Brunelin J Cogiamanian F Evidence-based guidelines on the therapeutic use of transcranial direct current stimulation (tDCS). Clin Neurophysiol. (2017) 128(1):56–92. 10.1016/j.clinph.2016.10.08727866120 Khatoon F Prasad K Kumar V. Neurological manifestations of COVID-19: available evidences and a new paradigm. J Neurovirol. (2020) 26(5):619–30. 10.1007/s13365-020-00908-932839951 Lefaucheur JP Chalah MA Mhalla A Palm U Ayache SS Mylius V. The treatment of fatigue by non-invasive brain stimulation. Neurophysiol Clin. (2017) 47(2):173–84. 10.1016/j.neucli.2017.03.00328410876 Pilloni G Bikson M Badran BW George MS Kautz SA Okano AH Update on the use of transcranial electrical brain stimulation to manage acute and chronic COVID-19 symptoms. Front Hum Neurosci. (2020) 14:595567. 10.3389/fnhum.2020.59556733281589 Markser A Vöckel J Schneider A Baumeister-Lingens L Sigrist C Koenig J. Non-invasive brain stimulation for post-COVID-19 conditions: a systematic review. Am J Med. (2025) 138(4):681–97. 10.1016/j.amjmed.2024.07.00739089436 Martin DM Liu R Alonzo A Green M Loo CK. Use of transcranial direct current stimulation (tDCS) to enhance cognitive training: effect of timing of stimulation. Exp Brain Res. (2014) 232(10):3345–51. 10.1007/s00221-014-4022-x24992897 Oliver-Mas S Delgado-Alonso C Delgado-Álvarez A Díez-Cirarda M Cuevas C Fernández-Romero L Transcranial direct current stimulation for post-COVID fatigue: a randomized, double-blind, controlled pilot study. Brain Commun. (2023) 5(2):fcad117. 10.1093/braincomms/fcad11737091591 Oliver-Mas S Matias-Guiu JA Delgado-Alonso C Gil-Martínez L Cuevas C Polidura C A randomized comparative feasibility study of neuromodulation and cognitive training for post-COVID fatigue. Sci Rep. (2025) 15(1):26818. 10.1038/s41598-025-09772-840702022

Edited by: David Putrino, Icahn School of Medicine at Mount Sinai, United States

Reviewed by: Marwa Ghanmi, University of Sousse, Tunisia