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Background Focal seizures may encompass vestibular sensations in their symptomatology. When these manifestations occur in isolation or constitute the predominant symptom, they prompt consideration for diagnosing recurrent paroxysmal vertigo. However, the characterization of “vestibular epilepsy” remains debated and underexplored. Our objective is to characterize the clinical and electrophysiological criteria of vestibular epilepsy. Methods We retrospectively analyzed data from a cohort of outpatients treated in the epileptology department of Marseille University Hospital. The study focused on patients presenting with vestibular symptoms without focal abnormalities on brain MRI, and with interictal epileptic abnormalities on wake or sleep EEG. Results 31 patients (15 men and 16 women) were included in the study. Visual, auditory, and dysautonomic symptoms were frequently associated with vestibular symptoms. The mean time to diagnosis was 3 years. The duration of attacks was generally short, ranging from a few seconds to a few minutes, with variable frequency. Most patients responded well to antiseizure medication. Some patients showed interictal phenomena, such as permanent instability, raising the possibility of inter/postictal disturbances. Seizures could be triggered by peripheral vestibular stimuli. Interictal EEG abnormalities were observed only during sleep in 25% of patients and predominated in the posterior temporoparietal regions. Discussion We propose clinical–electro-radiological criteria for defining vestibular epilepsy. These diagnostic criteria overlap with the criteria for vestibular paroxysmia, suggesting the possibility of a single nosological entity.

Background Vestibular migraine (VM) is a relatively recently acknowledged vestibular syndrome with a very relevant prevalence of about 10% among patients complaining of vertigo. The diagnostic criteria for VM have been recently published by the Bárány Society, and they are now included in the latest version of the International Classification of Headache Disorders, yet there is no instrumental test that supports the diagnosis of VM. Objective In the hypothesis that the integration of different vestibular stimuli is functionally impaired in VM, we tested whether the combination of abrupt vestibular stimuli and full-field, moving visual stimuli would challenge vestibular migraine patients more than controls and other non-vestibular migraineurs. Methods In three clinical centers, we compared the performance in the functional head impulse test (fHIT) without and with an optokinetic stimulus rotating in the frontal plane in a group of 44 controls (Ctrl), a group of 42 patients with migraine (not vestibular migraine, MnoV), a group of 39 patients with vestibular migraine (VM) and a group of 15 patients with vestibular neuritis (VN). Results The optokinetic stimulation reduced the percentage of correct answers (%CA) in all groups, and in about 33% of the patients with migraine, in as many as 87% of VM patients and 60% of VN patients, this reduction was larger than expected from controls’ data. Conclusions The comparison of the fHIT results without and with optokinetic stimulation unveils a functional vestibular impairment in VM that is not as large as the one detectable in VN, and that, in contrast with all the other patient groups, mainly impairs the capability to integrate different vestibular stimuli.

ObjectivesThe thalamus plays an important role in the mediation and integration of various stimuli (e.g., somatosensory, pain, and vestibular). Whether a stimulus-specific and topographic organization of the thalamic nuclei exists is still unknown. The aim of our study was to define a functional, in vivo map of multimodal sensory processing within the human thalamus.MethodsTwenty healthy individuals (10 women, 21–34 years old) participated. Defined sensory stimuli were applied to both hands (innocuous touch, mechanical pain, and heat pain) and the vestibular organ (galvanic stimulation) during 3 T functional MRI.ResultsBilateral thalamic activations could be detected for touch, mechanical pain, and vestibular stimulation within the left medio-dorsal and right anterior thalamus. Heat pain did not lead to thalamic activation at all. Stimuli applied to the left body side resulted in stronger activation patterns. Comparing an early with a late stimulation interval, the mentioned activation patterns were far more pronounced within the early stimulation interval.ConclusionsThe right anterior and ventral-anterior nucleus and the left medio-dorsal nucleus appear to be important for the processing of multimodal sensory information. In addition, galvanic stimulation is processed more laterally compared to mechanical pain. The observed changes in activity within the thalamic nuclei depending on the stimulation interval suggest that the stimuli are processed in a thalamic network rather than a distinct nucleus. In particular, the vestibular network within the thalamus recruits bilateral nuclei, rendering the thalamus an important integrative structure for vestibular function.

Persistent postural-perceptual dizziness (PPPD) is often preceded by vestibular disorders. We applied galvanic vestibular stimulation (GVS) and related stimulus-evoked activity to individual ratings of perceived motion for each stimulus and to perceived egomotion thresholds by GVS and behavioural parameters outside the scanner: levels of functional disability by standardized questionnaires, visual motion coherence, passive egomotion perception by chair rotation and quantitative postural stability. We hypothesized that the preceding vestibular disorder predisposes to abnormal brain excitability by vestibular stimulation. All participants showed normal vestibular function tests on quantitative testing. GVS with different intensities was applied to 28 patients and 28 age- and gender-matched healthy participants (HC) in the scanner. After each stimulus, participants rated their perceived level of egomotion. GVS perception threshold was significantly lower in PPPD patients. Contrasting stimulus-identical GVS against a sham stimulus, group comparison revealed a stronger activation in the patient’s supramarginal gyrus, insular cortex (operculum 3), and vermis. This stronger excitability was not related to the individual threshold of perceived egomotion by GVS. Patients rated GVS-evoked egomotion intensity by identical GVS intensities larger than HC but neural activity did not correlate with individual ratings of perceived egomotion by GVS. As GVS evoked larger egomotion and larger brain activation in patients, the ratio of brain activity to egomotion perception was not different between groups. GVS-evoked insular activity increased with the level of PPPD-related disability and postural imbalance. The larger activation in multisensory cortical vestibular network indicates a sensitization to vestibular stimuli eliciting egomotion perception which increases with levels of PPPD disability. It seems to reflect a sensory-neural amplification rather than an abnormal sensory-perceptual scaling.

ObjectivesTo examine the mechanism underlying previously reported ameliorating effects of noisy galvanic vestibular stimulation (GVS) on balance performance in patients with bilateral vestibulopathy (BVP) and determine those patients (incomplete versus complete vestibular loss) that might benefit from this intervention.MethodsVestibulospinal reflex thresholds were determined in 12 patients with BVP [2 with complete loss (cBVP) and 10 with residual function (rBVP)]. Patients were stimulated with 1 Hz sinusoidal GVS of increasing amplitudes (0–1.9 mA). Coherence between GVS input and stimulation-induced body motion was determined and psychometric function fits were subsequently used to determine individual vestibulospinal reflex thresholds. The procedure was repeated with an additional application of imperceptible white noise GVS (nGVS).ResultsAll patients with rBVP but none with cBVP exhibited stimulation-induced vestibulospinal reflex responses with a mean threshold level of 1.26 ± 0.08 mA. Additional nGVS resulted in improved processing of weak subthreshold vestibular stimuli (p = 0.015) and thereby effectively decreased the vestibulospinal threshold in 90% of patients with rBVP (mean reduction 17.3 ± 3.9%; p < 0.001).ConclusionThe present findings allow to identify the mechanism by which nGVS appears to stabilize stance and gait performance in patients with BVP. Accordingly, nGVS effectively lowers the vestibular threshold to elicit balance-related reflexes that are required to adequately regulate postural equilibrium. This intervention is only effective in the presence of a residual vestibular functionality, which, however, applies for the majority of patients with BVP. Low-intensity noise stimulation thereby provides a non-invasive treatment option to optimize residual vestibular resources in BVP.

The integration of visual and vestibular input is crucial for self-motion. Information from both sensory systems merges early in the central nervous system. Among the numerous cortical areas involved in processing this information, some (V6 and the ventral intraparietal area –VIP) respond specifically to vestibular anteroposterior information. A series of experiments were carried out to further understand the involvement of these and other areas in self-motion processing when vestibular and visual information are combined with varying congruence and direction parameters. Fifteen subjects underwent an MRI session while receiving visual (optic flow patterns) and galvanic vestibular stimuli, mimicking six conditions: (1) visual forward, (2) visual backward, visual forward with (3) congruent or (4) incongruent vestibular information, visual backward with (5) congruent or (6) incongruent vestibular information. At the voxel-wise level, adding vestibular stimulation to optic flow stimulation activated several bilateral areas located predominantly in the insular cortex. However, the region of interest (ROI) analysis of these areas indicated that none of them exhibits any specificity for the forward/backward direction or for the visuo-vestibular congruency. By extending the ROI approach to other well-known visuo-vestibular areas, we found that the parieto-occipital area V6 is unique in showing not only an increased level of activation for concurrent visual and vestibular stimulation, but also a marked preference when these signals are congruent and specify forward motion. Since area V6 is the only region more active when both visual and vestibular signals specify the most common self-motion direction (i.e. forward self-motion), our results support the view that this area plays a crucial role in visuo-vestibular integration during locomotion. This could be the first step towards the construction of a conscious perception of self-motion, possibly involving other areas.

Objective To examine how concussion may impair sensory processing for control of upright stance. Methods Participants were recruited from a single university into 3 groups: 13 participants (8 women, 21 ± 3 years) between 2 weeks and 6 months post-injury who initiated a return-to-play progression (under physician management) by the time of testing (recent concussion group), 12 participants (7 women, 21 ± 1 years) with a history of concussion (concussion history group, > 1 year post-injury), and 26 participants (8 women, 22 ± 3 years) with no concussion history (control group). We assessed sensory reweighting by simultaneously perturbing participants’ visual, vestibular, and proprioceptive systems and computed center of mass gain relative to each modality. The visual stimulus was a sinusoidal translation of the visual scene at 0.2 Hz, the vestibular stimulus was ± 1 mA binaural monopolar galvanic vestibular stimulation (GVS) at 0.36 Hz, the proprioceptive stimulus was Achilles’ tendon vibration at 0.28 Hz. Results The recent concussion (95% confidence interval 0.078–0.115, p  = 0.001) and the concussion history (95% confidence interval 0.056–0.094, p  = 0.038) groups had higher gains to the vestibular stimulus than the control group (95% confidence interval 0.040–0.066). The recent concussion (95% confidence interval 0.795–1.159, p  = 0.002) and the concussion history (95% confidence interval 0.633–1.012, p  = 0.018) groups had higher gains to the visual stimulus than the control group (95% confidence interval 0.494–0.752). There were no group differences in gains to the proprioceptive stimulus or in sensory reweighting. Conclusion Following concussion, participants responded more strongly to visual and vestibular stimuli during upright stance, suggesting they may have abnormal dependence on visual and vestibular feedback. These findings may indicate an area for targeted rehabilitation interventions.

Recordings from over the posterior fossa following impulsive acceleration stimuli have shown short latency evoked potentials of presumed cerebellar origin. In this study, we investigated the effect of posture on these cerebellar evoked potentials (CEPs) and their relationship to postural reflexes recorded from the leg muscles evoked by the same stimuli. Nine healthy subjects were tested during lying (supine and prone), sitting and standing. Impulsive accelerations were applied at the mastoid and to truncal (both C7 and sternal) stimulation sites. The effect of vision, eyes open or closed, was investigated for all three stimuli. For the truncal stimuli, the effect of differing leaning conditions during standing was also recorded. CEP amplitudes were correlated for the three stimuli. For C7 stimulation during standing, both CEPs and postural reflexes scaled as the threat to postural stability increased. However, CEPs for all stimuli were present during lying, sitting and standing with amplitude and latency parameters mainly unaffected by posture or vision. In contrast, postural reflexes from the leg muscles were attenuated when not standing, with the effect being more marked for truncal stimuli. We conclude that CEPs evoked by axial and vestibular stimuli are not systematically gated by posture, in contrast to the reflex responses evoked by the same stimuli.

Introduction Postural balance impairment can affect the quality of life of patients with Parkinson’s disease. Previous studies have described connections of the vestibular system with postural functions, suggesting a potential participation of the basal ganglia in receiving vestibular stimuli. This systematic review aims to summarize the evidence on the effectiveness of vestibular rehabilitation on postural balance in patients with Parkinson’s disease. Methods A systematic review was conducted using the electronic databases: PubMed, Embase, Scopus and PEDro. The study selection was independently conducted by two reviewers, and disagreements were evaluated by a third reviewer. The included studies had no restrictions on publication dates or languages and the last update occurred in July 2023. Results From the 485 studies found in the searches, only 3 studies were deemed eligible for the systematic review involving a total of 130 participants. The Berg Balance Scale was described as the tool for evaluation of postural balance in all studies. The meta-analysis showed statistically significant results in favor of vestibular rehabilitation (MD = 5.35; 95% CI = 2.39, 8.31; P  < 0.001), regardless of the stage of Parkinson’s disease. Although the effect size was suggested as a useful functional gain, the analysis was done with caution, as it only included 3 randomized controlled trials. The risk of bias using the RoB-2 was considered as being of “some concern” in all studies. Furthermore, the quality of the evidence based on the Grading of Recommendations Assessment Development and Evaluation system, produced by pooling the included studies was considered very low. Conclusion Compared to other interventions, vestibular rehabilitation has potential to assist the postural balance of patients with Parkinson’s disease. However, the very low quality of the evidence demonstrates uncertainty about the impact of this clinical practice. More robust studies are needed to confirm the benefits of this therapy in patients with Parkinson’s disease. This study was prospectively registered in PROSPERO: CRD42020210185.

The vestibular system, which detects gravity and motion, is crucial to survival, but the neural circuits processing vestibular information remain incompletely characterised. In part, this is because the movement needed to stimulate the vestibular system hampers traditional neuroscientific methods. Optical trapping uses focussed light to apply forces to targeted objects, typically ranging from nanometres to a few microns across. In principle, optical trapping of the otoliths (ear stones) could produce fictive vestibular stimuli in a stationary animal. Here we use optical trapping in vivo to manipulate 55-micron otoliths in larval zebrafish. Medial and lateral forces on the otoliths result in complementary corrective tail movements, and lateral forces on either otolith are sufficient to cause a rolling correction in both eyes. This confirms that optical trapping is sufficiently powerful and precise to move large objects in vivo, and sets the stage for the functional mapping of the resulting vestibular processing. The neural circuits of the vestibular system, which detects gravity and motion, remain incompletely characterised. Here the authors use an optical trap to manipulate otoliths (ear stones) in zebrafish larvae, and elicit corrective tail movements and eye rolling, thus establishing a method for mapping vestibular processing.