This study employed a randomized, controlled, open-label crossover design, adhering to the Consolidated Standards of Reporting Trials (CONSORT) statement for crossover trials (41) and incorporating relevant elements from the Standards for the Reporting of Diagnostic Accuracy Studies (STARD) (42). This research formed a part of a broader umbrella study overall investigating BPPV diagnostics and, therefore, sharing participant data with two previously published studies: one comparing diagnostic modalities (TMD and MRC diagnostics) (34) and another quantifying the head orientation and - movement during TMDs (31). Due to the exploratory nature of this specific study and the absence of comparable prior research, an independent power calculation was not performed. Instead, the sample size was determined based on the a priori power calculation of the comparative diagnostic study (34).

All participants underwent BPPV diagnostics using both TMD and MRC diagnostics, with the order of the diagnostic methods randomized in a 1:1 ratio. The randomization was achieved using permuted blocks 4, 6, and 8 (made with Sealed Envelope Ltd. 2022). To minimize potential carryover effects, such as fatigue of the positional nystagmus and vertigo, participants were seated for a minimum of 30 min between the two diagnostic methods (43). While blinding of the examiner and participants was not feasible due to the nature of the interventions, the examiner was kept blinded [no feedback of the output of the head-mounted sensors (inertial measurement unit), see 2.3.2 materials] to the specific head orientation that were imposed in the TMDs.

The study was conducted between April 12, 2023, and January 11, 2024, at a university hospital-based tertiary outpatient clinic specializing in vestibular Disorders (the Balance and Dizziness Centre, Department of Otorhinolaryngology, Head and Neck Surgery and Audiology, Aalborg University Hospital, Denmark). Participants were referred by general practitioners within the North Denmark Region and private ENT practices in the North and Central Denmark Regions. The general practitioners were instructed to refer patients with a typical BPPV case history without performing any canalith repositioning maneuvers before referral. In contrast, participants referred by the private ENT practices had undergone one or several unsuccessful canalith repositioning maneuvers at the time of referral.

The same examiner screened all referred patients for eligibility at their initial visit. Inclusion criteria included an age of 18 years or above, a typical BPPV case history, including short-lived positional vertigo (typically lasting less than 1 min, with a maximum duration of a few minutes), and sufficient Danish proficiency (both written and spoken) to understand the informed consent. Exclusion criteria included spontaneous- and/or gaze-evoked nystagmus, ejection fraction < 40%, known cerebral aneurysm, recent cerebrovascular event (< 3 months), arterial dissection disease, pregnancy, neck and/or spine immobility impeding the TMDs, physical limitations excluding MRC diagnostics (weight ≥ 150 kilograms and/or height ≥ 2 meters), insufficient cooperation during the diagnostic testing (TMDs and/or MRC diagnostics), and intake of sedative antihistamines within the past 7 days. Eligible participants received oral and written information and provided written consent before enrollment.

All diagnostic tests were performed by the same (right-handed) examiner, who had prior experience with conducting and interpreting TMD tests equivalent to that of a basic junior ENT resident. Prior to participant enrollment, the examiner received additional BPPV management training, which was in accordance with the level of training for the health professionals managing BPPV at the study site (a tertiary center for Dizziness and Balance). This training encompassed the use of the equipment (including operation of the MRC), identification and interpretation of nystagmus, and training in doing TMDs. Supervision was provided by two neurotology experts throughout the study period (DDH and HK), with scheduled sessions at the beginning and end of the study period. Ad hoc supervision was provided upon request by the examiner.

Prior to the BPPV diagnostics, participants were screened for spontaneous- and gaze-evoked nystagmus and for the presence of a vestibulo-ocular reflex, including a fixation-suppression test (manual to the left and right yaw-axis rotation in the MRC with and without visual fixation). Participants with abnormal results were excluded and referred for further evaluation following local clinical guidelines. Neither additional vestibular (no video head impulse test was performed to avoid potential displacements of otoliths) nor neurological examination was performed. The TMD and MRC diagnostics were conducted in the same standardized sequence of positions: (1) upright position with the head in neutral position, (2) supine position (30 s), (3) right SRT, followed by (4) left SRT (right and left SRT were held until nystagmus was observed and interpreted, or for a maximum of 30 s if no nystagmus appeared), (5) upright position with the head in neutral position, (6) upright position with the head rotated 45° to the right, (7) right DHT position (60 s), (8) upright position with the head in neutral position, (9) upright position with the head rotated 45° to the left, (10) left DHT position (60 s), and (11) upright position with the head in neutral position. Based on recommendations from simulation tests, the sequence of diagnostic tests was chosen to minimize the risk of displacement of otoconia debris in the lateral SCC during the DHT (45).

The target head angles were based on the Bárány Society diagnostic criteria for BPPV (1) and were consistent for both TMDs (Figure 2) and MRC diagnostics (Figure 3). The SRT preceded the DHT to minimize the potential unintended displacement of otoconia in the lateral SCC during DHT (46). The intended duration of the movement to the primary diagnostic positions (positions 2, 3, 4, 7, and 10) was set to be within 2 seconds. With the MRC diagnostics, the transition between positions 3 and 4 was ideally performed as one single smooth movement. However, in obese participants, this movement was divided into two steps for safety. During diagnostic procedures with the MRC, target positions were ensured by using fixed position markers of the MRC. No visual feedback was provided during the TMDs, thereby allowing only the examiner’s subjective bedside assessment of the participant’s head orientation. To optimize participant cooperation, all participants received detailed pre-test instructions, including the importance of maintaining a straightforward gaze eye position and minimizing blinking (incorporating required reminders). To prevent any eye movement artifacts, the participants were instructed to close their eyes during the head movement preceded by a three-second countdown. For the TMDs, participants were instructed to sit upright on the examination bed (with the legs straight if possible) and with a neutral head orientation (guided by the examiner). Participants were informed that the examiner should perform and determine all head orientation and -movements.

The 6DOF IMU sensor was calibrated at positions 1, 5, and 8 (upright position with neutral head position). Throughout the TMDs, the examiner maintained a firm grip on the VNG goggle headband to prevent it from displacing. The examiner reviewed eye movements in real-time during all diagnostic tests. The recorded eye videos could be reviewed subsequently (with a supervising neurotologist if needed) to support the diagnostic conclusion. All recorded eye movement files were reviewed post-data collection by a blinded neurotology expert to ensure high standards of diagnostic accuracy (34).

The examiner placed the BPPV diagnosis and further specified (1) laterality, (2) affected SCC(s), and subtype (canalolithiasis or cupulolithiasis) on-site in accordance with the Bárány Society diagnostic criteria (1). A BPPV-characteristic positional nystagmus (BPPV-CPN) was defined as a positional nystagmus with characteristics compatible with having BPPV (specified in Table 1), an average slow-phase velocity of a minimum of 3 °/second, and at least five consecutive beats (47).

The diagnostic outcome was defined as the observation of BPPV-CPN in each side of the SRT and DHTs rather than the BPPV diagnosis itself. The reason for choosing this approach was that previous results from simulation models have shown that the nystagmus patterns with lateral canal BPPV are highly dependent on both the position of the otoconia (the ampullary or non-ampullary arm of the lateral SCC) as well as the initial side of the SRT performed (46). If the BPPV diagnosis (bilateral geotropic or apogeotropic nystagmus) was exclusively used as the study’s outcome measure for lateral canal BPPV, we could theoretically exclude those cases with lateral canal BPPV, where only unilateral BPPV-CPN was observed during the SRT, e.g., due to accidental liberation. However, when displaying the combined result of the positional nystagmus on both the right and left SRT, the term ‘BPPV diagnosis’ will be used.

The BPPV was classified as either primary or secondary BPPV. Secondary BPPV was defined when the participant had a previous or present ipsilateral inner ear disease (excluding presbycusis), previous ipsilateral middle- or inner ear surgery, or recent head trauma (< 6 months prior to the debut of symptoms). Primary BPPV (idiopathic) was defined when no clear etiology was identified. Participants diagnosed with BPPV were offered subsequent treatment with MRC following local clinical guidelines.

Data collection was conducted during the participants’ first visit, where the examiner gathered information through electronic patient record review, history taking, and physical examination(s). This information was entered into a secure REDCap® database (version 13.1.37) hosted by the North Denmark Region (48, 49). The 6DOF IMU data were recorded in real-time during the TMDs and saved immediately after the participants’ visit. The processed head orientation data from the 6DOF IMU software was exported as a compound CSV file and subsequently merged with the main REDCap export file within the statistical software (StataNow/MP 18.5), which was used for all data analyses.

The baseline characteristics of the randomized groups were summarized using descriptive statistics. Continuous variables were presented with means and standard deviations, with normality assessed visually (using histograms and Q-Q plots) and using the Shapiro–Wilk test. Categorical data were reported using absolute and relative frequencies. The head orientation was displayed using the imposed head angles, and the head movement variables (angular velocity and duration of movement) were displayed as absolute numbers. For clarity, only the relevant head orientations of the SRT and DHT were presented in the tables and figures. The BPPV-CPN observed during the MRC diagnostics was used as the gold standard, based on prior studies showing that the MRC diagnostics appear to be more sensitive than TMDs in detecting BPPV (33, 34). The association between the BPPV-CPN and the head orientation, as well as the head movement variables, was tested by comparing the true positives (cases where the BPPV-CPN observed during the MRC diagnostics was reproduced during the TMD) and false negatives (cases where the BPPV-CPN observed during the MRC diagnostics was not reproduced during the TMD).

Comparison between all groups was performed using an unpaired Student’s t-test (with Welch’s t-test for unequal variances) for continuous data and a Chi-square test (with Fisher’s exact test used for expected cell counts less than 5) for categorical data. In the case of non-normal distribution, bootstrapping was used to obtain reported results for continuous variables. The head orientation during the TMDs was visualized with scatterplots and a head orientation-time graph. The head movement variables during the TMDs were visualized with scatterplots.

All data analyses included only participants who completed the trial and for whom the 6DOF IMU data were of sufficient quality (per protocol analyses). The analysis was not performed blinded to the randomization, and no interim analyses were conducted during the study period. The data analyses and visualization were selected in collaboration with an independently certified biostatistician who also provided consultation throughout the study period. An alpha significance level of 0.05 was used for all statistical tests. All data analyses were performed using StataNow/MP 18.5.

With TMDs, all head angles deviated significantly from the target head angles (the confidence interval did not include the target head angle) (Table 3). This inaccuracy was greatest for the yaw-axis head angles of the SRTs, which were considerably undershot. During TMDs, BPPV-CPN was observed in 8.9% (n = 17/192) of the right SRTs, 10.9% (n = 21/192) of the left SRTs, 24.1% (n = 47/195) of the right DHTs, and 15.5% (n = 30/193) of the left DHTs. The left SRT yaw-axis head angle was significantly more accurate in the group with observed BPPV-CPN than in the group without BPPV-CPN. No other significant differences in SRT and DHT yaw- and pitch axes were found between groups with and without observed BPPV-CPN (Table 3).

The TMDs yielded a substantial number of false negatives (cases where the BPPV-CPN observed during the MRC diagnostics was not reproduced during the TMD) (right SRT: n = 19; left SRT: n = 24; right DHT: n = 13; left DHT: n = 13) (Table 4). Conversely, a smaller number of participants exhibited BPPV-CPN during the TMD that was not reproduced during the MRC diagnostics (right SRT: n = 6; left SRT: n = 6; right DHT: n = 6; left DHT: n = 3).

Except for the left SRT yaw-axis head angle, no significant difference in the head angles was observed between the true positives and false negatives (Table 4). The left SRT yaw-axis head angle was significantly more accurate (closer to the target head angle: −90°) in the true positives [−69.8° (95% CI: −77.6°, −61.9°)] compared to the false negatives [−60.5° (95% CI: −65.5°, −55.5)].

The manual SRT and DHT head orientation (including the roll-axis head angle) are visualized in a head orientation-time graph in relation to the BPPV diagnosis, differentiating between the true positives and false negatives in the manual SRT and DHT when compared to the corresponding MRC diagnostic test (Figure 5). Please note that the right and left SRTs are combined (to demonstrate the entire sequence of head orientation during the SRT). Hence, the groups of true positives and false negatives in Figure 5 refer to the BPPV diagnosis combining the observed nystagmus in the right and left SRT (requiring bilateral geotropic or apogeotropic nystagmus for a positive BPPV diagnosis). When using BPPV diagnosis as the outcome for the manual SRT and DHT, there was no significant difference between the yaw, pitch, and roll axes between groups with true positive and false negative BPPV diagnoses. All head orientation-time graphs (Figure 5) revealed a bias in the roll-axis head angle (differing from the target head angle of 0°) for the majority of the SRT and DHT head orientations.

Figure 6 displays the head orientation in the manual SRT and DHT in relation to the true positive and false negative BPPV-CPN when compared to the corresponding MRC diagnostic tests. The manual SRT head orientation, particularly the left SRT yaw axis, showed an overall broader range and greater inaccuracy of the applied head angles in the false negative group compared to the true positive group. For the SRT pitch axis, the true positives appeared to be clustered between −60° (the target head angle) and −75°. The manual DHT tended to have a more pronounced right DHT yaw-axis head rotation (applied head angle above the target +45°) and pitch-axis head angles clustered between −100° and −120° (right and left DHT) for the true positive BPPV-CPN group compared to the false negative group.

Figure 7 visualizes the yaw and pitch head orientation of the manual SRTs and DHTs relative to all four categorization groups of the BPPV-CPN (true positive, false positive, true negative, and false negative). For all four categories, the general distribution seemed to be randomly scattered with no apparent pattern, except for the more accurate left SRT yaw-axis head angle in the true positive BPPV-CPN group (in line with the described findings in Table 4). This indicates no clear relationship between the applied yaw- and pitch head angles and the BPPV-CPN categories.

The TMDs duration of movements were for the SRTs performed within the targeted 2-s [supine position to the right SRT: 1.4 s (95% CI: 1.4–1.4); the right SRT to the left SRT: 1.8 s (95% CI: 1.8–1.9). The duration of movement with the DHTs was slightly above 2 sec upright to the right DHT supine position: 2.1 (95% CI: 2.0–2.1); upright to the left DHT supine position: 2.1 (95% CI: 2.0–2.2)] (Table 5).

A trend of a higher mean and peak angular velocity (except for the left DHT peak velocity) was observed in the group with detected BPPV-CPN during TMDs (Table 5). However, no significant difference in the angular velocities or duration of movement was found between the true positive and false negative groups (Table 6). Figure 8 illustrates this observation, displaying a random distribution of the angular velocity and duration of movement according to the categorization of the BPPV-CPN (true positive, false positive, true negative, and false negative). The majority of the SRTs and DHTs were performed within a narrow range of mean velocity and duration of movement (with few outliers), making it challenging to determine their individual or combined impact on the diagnostic test’s ability to reproduce the BPPV-CPN observed with MRC diagnostics.

With this study, we aimed to investigate whether head orientation and -movement (angular velocity and duration of movement), measured during the TMD (SRT and DHT), might affect the outcome of BPPV diagnostics when compared to MRC diagnostics with fixed positions (the gold standard).

To the best of our knowledge, this study is the first to analyze the impact of the head orientation and -movement on the outcome of TMD. Therefore, direct comparison with other studies is not possible. Instead, we discuss our findings in relation to existing theories and research dealing with BPPV diagnostics.

The main finding of this study was unexpected, as we found no significant difference in imposed head orientation and -movements between the groups that successfully identified BPPV-CPN (true positive) and those who did not (false negative). This finding could partly be explained by the inherent challenges associated with BPPV diagnostics, particularly the assumed heterogeneity of BPPV pathophysiology (otoconia size, quantity, localization, etc.) (36, 37). This heterogeneity might, at least theoretically, explain why the importance of the specific head orientation and -movement is subject to various degrees of inter-individual variability. Precise head orientation and minimum angular velocities might be critical when the otoconia are clustered within the SCC, with different optimal values depending on individual otoconia characteristics (36, 37). Conversely, with very dispersed otoconia, otoconial movement may occur as long as the head moves in a way that aligns the affected SCC with the gravity vector, regardless of the precise angulation of the head orientation. The latter assumption aligns with the minimum stimulus theory as proposed by Libonati et al. (52), which uses the upright BPPV protocol to elicit BPPV-CPN with minimal SCC stimulus (by minimal angulation in the head orientation), aiming to increase patient cooperation by minimizing the induced discomfort. This protocol includes a 30° lateral head bend bilaterally (rotation around the roll axis) for examination of the lateral SCCs. The vertical SCCs are examined in pairs (left anterior and right posterior; right anterior and left posterior) by rotating the patient’s head 45° to the right and left side, respectively, followed by a slow cervical flexion (30°) and extension (60°). If no nystagmus occurs in these minimum stimulus positions, the examination is followed by a TMD (52). The upright BPPV protocol was reported to show high BPPV identification rates in previous studies [lateral canal BPPV: 95.5% (compared to a diagnostic protocol including the upright BPPV protocol, supine position, and SRT); posterior canal BPPV: 87.2% (compared to DHT)] (53, 54). However, the observation that minimal head orientation is sufficient to identify the majority of lateral canal BPPV is contradicted by our findings. We observed the opposite: the manual SRT, failing to reach the target −90° yaw-axis rotation, was unable to identify 63% of the BPPV-CPN detected during the SRT with an MRC (reaching the target ±90° rotation). It might be that this comparison does not hold due to a difference in orientation of the lateral SCCs in the SRT and the upright BPPV protocol (46, 52).

BPPV diagnostic outcomes are likely not solely determined by the accuracy of head orientation. Some participants showed BPPV-CPN during the TMDs but not with the MRC diagnostics (classified as false positives) (right SRT: n = 6; left SRT: n = 6; right DHT: n = 3; left DHT: n = 6) (Supplementary Table C1). This raises the hypothesis that the SRT’s and DHT’s reproducibility of the BPPV-CPN cannot reach 100%. This could, theoretically, be explained by the fact that free-floating displaced otoconia move with every diagnostic test procedure. It is doubtful that these otoconia will return to their exact initial position, and this will, per se, limit the reproducibility of the BPPV diagnostics. If it is true that BPPV may be overlooked despite accurate head orientation, it might turn out advantageous to repeat the BPPV diagnostic procedures in case you encounter a patient with a typical BPPV case history but with a negative diagnostic outcome (55).

With the head movements (angular velocity and duration of movement), we found no difference between the true positive and false negative BPPV-CPN with the TMDs.

In general, there exists a sparse amount of literature on the head movements in BPPV diagnostics. One biomechanical model suggests that inertial forces only play a minimal role in the movement of otoconia, potentially only disrupting the otoconia-wall interaction (37). A clinical study by Anurin et al. (56) found that DHT angular velocities between 100 and 200°/second triggered a more intense BPPV-CPN (higher average slow-phase velocity), suggesting that a high angular velocity increased the possibility of identifying a BPPV-CPN response. However, they did not report the same association with the SRT.

Given the fact that the MRC has a different angular velocity profile (the head is more excentric, resulting in stronger linear accelerations and a longer duration of movement) compared to the profile seen with TMDs, we cannot rule out that head movement variables might have caused, or at least to some extent contributed, to the higher sensitivity of BPPV-CPN identification as seen with the MRC diagnostics compared to the TMD. Anyway, the head movement profiles of TMD and MRC diagnostics differ.

Finally, the identification of BPPV-CPN and, hence, the diagnostic outcome (of both TMD and MRC diagnostics) is also highly dependent on the examiner’s identification and interpretation of the positional nystagmus. With many commercially available eye-tracking systems, accurate 3D detection and quantification of eye movements remains a significant challenge. Therefore, identification and interpretation of positional nystagmus remain subjective and, as a direct consequence thereof, highly dependent on the examiner’s level of experience. Accurate nystagmus observation with BPPV diagnostics requires specific and unambiguous patient instructions (eye position with a straightforward gaze and minimal blinking). Gaze direction affects the intensity and direction of nystagmus, especially in posterior canal BPPV. With posterior canal BPPV, the amplitude of the torsional component increases when the gaze is directed toward the affected ear, while the amplitude of the vertical component increases with the gaze directed toward the unaffected ear (57). With the interpretation of nystagmus, the risk of BPPV overdiagnosis is also possible, as positional nystagmus during BPPV diagnostics is commonly encountered (71–88%) in individuals without vertigo (38, 39). However, this type of asymptomatic positional nystagmus typically differs from BPPV-CPN by lacking a torsional component, having prolonged duration, and exhibiting a low average slow-phase velocity (38, 39). Assisted diagnostic tools, like deep learning models, have been suggested to improve the objectivity of the nystagmus interpretation and, thereby, reduce over- and/or misdiagnosis of BPPV (58, 59).

A randomized controlled crossover design was chosen to minimize bias. A key strength was the focus on conducting the study in the same clinical context where the results are to be interpreted, with a study population carefully selected to reflect this context. However, despite the relatively large overall sample size (n = 198), some of the subgroups were inevitably rather small.

For all BPPV diagnostics (TMD and MRC diagnostics), we opted to execute this study with only one examiner, ensuring consistency in the performance of the diagnostic tests and the identification and interpretation of positional nystagmus. To validate the examiner’s performance in nystagmus identification and interpretation, a blinded expert reviewed all recorded eye videos. The agreement between these interpretations was overall satisfying, with no difference between the interpretation of posterior and non-posterior canal BPPV. However, the agreement tended to improve in the second study period, suggesting either bias from a learning effect (in nystagmus interpretation) or improved quality of the eye video recordings as the examiner gained more experience (34). We found, however, no indication that this potential learning effect influenced the imposed head orientation (Supplementary Table E). Conversely, the head movement of the TMDs did differ between the study periods, with significantly shorter duration of movements and higher angular velocities for the majority of the head movements in the second study period (Supplementary Table F). The risk of a learning effect was further reinforced by the nature of the intervention of this study, where total blinding of the examiner was not possible. The impact of the lack of blinding was attempted to be minimized by allowing the examiner to assess head orientation by eye measure only (with no feedback). Additionally, the head orientation and -movement may have been influenced by physical constraints of the participants (e.g., neck mobility or high BMI) and should be acknowledged as a possible limitation to this study.

The analysis of the association between the diagnostic outcome and the performance of the TMDs (head orientation and -movement) was restricted to the intra-examiner variability seen with that one examiner, introducing a risk of operator bias. Using several different examiners might have revealed a more nuanced pattern with the results. Another limitation in relation to the imposed head orientation and -movement is the 6DOF IMU’s attachment on top of the VNG goggles, making the VNG goggles’ position a proxy measure of the orientation of the head. The risk of measurement error by slippage of the VNG goggles was minimized by careful manual fixation throughout the procedure. Data with movement artifacts was excluded. Ideally, the 6DOF IMU-related uncertainty could be avoided by fixating it on the skull, i.e., with a bite board, which, however, is often not well tolerated by patients and less applicable in routine clinical practice.

Crossover studies are generally susceptible to carryover effects, and this study is no exception. Specifically, when considering the study protocol, the displaced otoconia were unlikely to remain in the exact location in the SCC(s) after the initial diagnostic test procedures (46). Therefore, the two diagnostic modalities did, most likely, not have identical starting points, introducing a potential carryover effect. This fundamental challenge was mitigated by (1) a washout period of a minimum of 30 min minimizing fatigue-related influence on the vertigo and the nystagmus (43) and (2) randomization of the order of the TMDs and MRC diagnostics. Furthermore, the randomization also reduced and minimized any confirmation bias identification and interpretation of positional nystagmus in the second test modality was influenced by the interpretation of positional nystagmus in the first test modality. The distribution between the observed BPPV-CPN with TMDs and MRC diagnostics seemed to be comparable between the two randomized groups, indicating that the positional nystagmus interpretation was not influenced by confirmation bias (Supplementary Tables C2, C3).

The results of this study are applicable to adults undergoing TMD (with VNG goggles) when performed by a trained examiner. The generalizability of this study may be reduced, when applied to less experienced clinicians. This study showed that the inaccuracy of the manual DHT did not seem to influence its ability to identify most of the BPPVs. In contrast, the manual SRT with only head rotation often failed to achieve sufficient yaw head angles and simultaneously failed to identify the majority of the BPPV-CPN seen with lateral canal BPPV. This may lead to missed, incorrect, or delayed diagnosis in real-world clinical settings with the risk of psychosocial consequences and expanded healthcare costs. This challenge in diagnosing lateral canal BPPV might be overcome by modifying either the examiner training or the standard manual diagnostic procedure. A simple solution might be to apply head and upper trunk rotation, or a full-body roll to replace the head-only rotation in the SRT. An alternative approach to improving head orientation in the TMD is to utilize a guidance system.

As this study focused on the performance of TMDs in a clinical context, future research should employ a more rigorous and systematic approach to define the minimum head angles of head orientation and the optimal head movement profile (angular velocity and duration of movement) to identify BPPV-CPN during the SRT and DHT. Ideally, such a study would include patients diagnosed with BPPV and systematic rotation of their heads until BPPV-CPN is elicited.

Finally, this study used the BáránySociety diagnostic criteria (1) and did not address the presence of both positional vertigo and BPPV-CPN during the TMD. We highly recommend that future studies explore the relationship between positional vertigo and head orientation, as well as -movement. This information might add significant scientific information to internationally standardized BPPV diagnostic criteria.