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Herpesvirus is a prevalent pathogen that primarily infects human epithelial cells and has the ability to reside in neurons. In the field of otolaryngology, herpesvirus infection primarily leads to hearing loss and vestibular neuritis and is considered the primary hypothesis regarding the pathogenesis of vestibular neuritis. In this review, we provide a summary of the effects of the herpes virus on cellular processes in both host cells and immune cells, with a focus on HSV-1 as illustrative examples.

Unilateral vestibular lesions induce a vestibular syndrome, which recovers over time due to vestibular compensation. The therapeutic effect of L-Thyroxine (L-T4) on vestibular compensation was investigated by behavioral testing and immunohistochemical analysis in a rat model of unilateral vestibular neurectomy (UVN). We demonstrated that a short-term L-T4 treatment reduced the vestibular syndrome and significantly promoted vestibular compensation. Thyroid hormone receptors (TRα and TRβ) and type II iodothyronine deiodinase (DIO2) were present in the vestibular nuclei (VN), supporting a local action of L-T4. We confirmed the T4-induced metabolic effects by demonstrating an increase in the number of cytochrome oxidase-labeled neurons in the VN three days after the lesion. L-T4 treatment modulated glial reaction by decreasing both microglia and oligodendrocytes in the deafferented VN three days after UVN and increased cell proliferation. Survival of newly generated cells in the deafferented vestibular nuclei was not affected, but microglial rather than neuronal differentiation was favored by L-T4 treatment.

Objective: To test the hypothesis that patterns of semicircular canal (SCC) and otolith impairment in unilateral vestibular loss depend on the underlying disorders, we analyzed peripheral-vestibular function of all 5 vestibular sensors., Methods: For this retrospective case series, we screened the hospital video-head-impulse test database (n = 4,983) for patients with unilaterally impaired SCC function who also received ocular vestibular-evoked myogenic potentials and cervical vestibular-evoked myogenic potentials (n = 302). Frequency of impairment of vestibular end organs (horizontal/anterior/posterior SCC, utriculus/sacculus) was analyzed with hierarchical cluster analysis and correlated with the underlying etiology., Results: Acute vestibular neuropathy (AVN) (37.4%, 113 of 302), vestibular schwannoma (18.2%, 55 of 302), and acute cochleovestibular neuropathy (6.6%, 20 of 302) were most frequent. Horizontal SCC impairment (87.4%, 264 of 302) was more frequent ( p < 0.001) than posterior (47.4%, 143 of 302) and anterior (37.8%, 114 of 302) SCC impairment. Utricular damage (58%, 175 of 302) was noted more often ( p = 0.003) than saccular impairment (32%, 98 of 302). On average, 2.6 (95% confidence interval 2.48-2.78) vestibular sensors were deficient, with higher numbers ( p ≤ 0.017) for acute cochleovestibular neuropathy and vestibular schwannoma than for AVN, Menière disease, and episodic vestibular syndrome. In hierarchical cluster analysis, early mergers (posterior SCC/sacculus; anterior SCC/utriculus) pointed to closer pathophysiologic association of these sensors, whereas the late merger of the horizontal canal indicated a more distinct state., Conclusions: While the extent and pattern of vestibular impairment critically depended on the underlying disorder, more limited damage in AVN and Menière disease was noted, emphasizing the individual range of loss of function and the value of vestibular mapping. Likely, both the anatomic properties of the different vestibular end organs and their vulnerability to external factors contribute to the relative sparing of the vertical canals and the sacculus., (© 2020 American Academy of Neurology.)

: We report a case of a 62-year-old woman who was found to have bilateral atrophy of the inferior vestibular nerves on magnetic resonance imaging (MRI) after presenting to our clinic with 6 years of intermittent vertigo and residual unsteadiness. The nerve atrophy may be associated with an episode of vestibular neuritis, a common cause of vertigo that exclusively involves the inferior vestibular nerve in less than 3% of cases. While MRI may demonstrate vestibular nerve enhancement in cases of acute vestibular neuritis, no single MRI finding has been demonstrated consistently among cases of acute or chronic vestibular neuritis. Physical therapy is likely an effective long-term treatment for this patient to achieve central compensation for symptomatic relief.

Vestibular neuritis (VN) is characterised by acute vertigo due to a sudden loss of unilateral vestibular function. A considerable proportion of VN patients proceed to develop chronic symptoms of dizziness, including visually induced dizziness, specifically during head turns. Here we investigated whether the development of such poor clinical outcomes following VN, is associated with abnormal visuo-vestibular cortical processing. Accordingly, we applied functional magnetic resonance imaging to assess brain responses of chronic VN patients and compared these to controls during both congruent (co-directional) and incongruent (opposite directions) visuo-vestibular stimulation (i.e. emulating situations that provoke symptoms in patients). We observed a focal significant difference in BOLD signal in the primary visual cortex V1 between patients and controls in the congruent condition (small volume corrected level of p < .05 FWE). Importantly, this reduced BOLD signal in V1 was negatively correlated with functional status measured with validated clinical questionnaires. Our findings suggest that central compensation and in turn clinical outcomes in VN are partly mediated by adaptive mechanisms associated with the early visual cortex., (Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.)

Controversy still surrounds both the etiology and pathophysiology of vestibular neuritis (VN). Especially uncertain is why the superior vestibular nerve (SVN) is more frequently affected than the inferior vestibular nerve (IVN), which is partially or totally spared. To address this question, we developed an improved method for preparing human vestibular ganglia (VG) and nerve. Subsequently, macro- and microanatomical as well as PCR studies were performed on 38 human ganglia from 38 individuals. The SVN was 2.4 mm longer than the IVN, and in 65% of the cases, the IVN ran in two separate bony canals, which was not the case for the SVN. Anastomoses between the facial and cochlear nerves were more common for the SVN (14/38 and 9/38, respectively) than for the IVN (7/38 and 2/38, respectively). Using reverse transcription-quantitative PCR (RT-qPCR), we found only a few latently herpes simplex virus 1 (HSV-1)-infected VG (18.4%). In cases of two separate neuronal fields, infected neurons were located in the superior part only. In summary, these PCR and micro- and macroanatomical studies provide possible explanations for the high frequency of SVN infection in vestibular neuritis. IMPORTANCE Vestibular neuritis is known to affect the superior part of the vestibular nerve more frequently than the inferior part. The reason for this clinical phenomenon remains unclear. Anatomical differences may play a role, or if latent HSV-1 infection is assumed, the etiology may be due to the different distribution of the infection. To shed further light on this subject, we conducted different macro- and microanatomical studies. We also assessed the presence of HSV-1 in VG and in different sections of the VG. Our findings add new information on the macro- and microanatomy of the VG as well as the pathophysiology of vestibular neuritis. We also show that latent HSV-1 infection of VG neurons is less frequent than previously reported., (Copyright © 2017 American Society for Microbiology.)

Objective: To investigate the clinical significance of cardiovascular factors, including arterial stiffness and metabolic syndrome scores, in the development of vestibular neuritis., Study Design: A prospective, case-control study., Setting: Tertiary referral center., Patients: Fifty-eight adult patients with vestibular neuritis (VN) and 58 age- and sex-matched controls were evaluated between January 2015 and January 2016., Intervention: Measurement of arterial stiffness., Main Outcome Measures: Arterial stiffness was assessed from brachial-ankle pulse wave velocity (baPWV), and cardiovascular markers including blood pressure, body mass index and lipid profiles, and metabolic syndrome scores were determined. The dizziness handicap inventory (DHI) and vestibular function tests, including the caloric test and video head impulse test were evaluated. The correlations between cardiovascular factors and clinical parameters of VN were assessed., Results: Blood pressure, baPWV, and metabolic syndrome scores were higher in the VN group than in the control group (p = 0.002, p = 0.001, and p = 0.001, respectively), whereas comorbidity, anthropometric characteristics, and lipid profiles did not differ significantly. baPWV and metabolic syndrome scores were not correlated with the clinical parameters of the DHI scores, canal paresis, and spontaneous nystagmus duration. In addition, cardiovascular factors did not associate with the vestibular compensation., Conclusions: Higher baPWV, representative of arterial stiffness, and higher metabolic syndrome scores, are associated with the development of VN. This supports the hypothesis of a vascular etiology of the disease. However, cardiovascular risk factors had limited value in predicting the clinical course of VN.

Objectives: The aim of this study was to describe the signalment, clinical presentation, diagnostic findings and long-term follow-up in dogs with concomitant facial and vestibular neuropathy of unknown origin., Methods: Appropriate cases were located through medical record searches. Inclusion criteria comprised dogs that had: clinical signs of facial paralysis with concomitant peripheral vestibular syndrome, thyroid function tests, no abnormalities on magnetic resonance imaging of the brain and tympanic bullae, and cerebrospinal fluid analysis., Results: Sixteen dogs met the inclusion criteria. Facial paralysis had acute onset (<24 hours) in all dogs, thyroid function was within normal limits. There was albuminocytologic dissociation in cerebrospinal fluid of 69% of the dogs. There was complete resolution of clinical signs in 31% of the dogs but 38% showed long-term vestibular deficits, 46% developed hemifacial contracture, 15% had permanent facial paralysis and 15% relapsed., Clinical Significance: Facial and vestibular neuropathy of unknown origin shares similarities with idiopathic facial paralysis. The prognosis for return of normal facial and vestibular function is guarded and there may be relapse after recovery., (© 2016 British Small Animal Veterinary Association.)

Hypothesis: Intrinsic differences in neurons of the vestibular ganglia result in the increased likelihood of superior vestibular ganglion involvement in vestibular neuritis., Background: Vestibular neuritis is hypothesized to result from herpes simplex type I (HSV1) infection or reactivation in vestibular ganglia. Involvement of the inferior vestibular ganglion is extremely rare in patients with vestibular neuritis., Methods: Primary cultures of rat superior and inferior vestibular ganglion neurons (VGNs) were cultivated separately. Neurons were lytically and latently infected with HSV1 with a US11-green fluorescent protein (GFP) chimera. Percentage lytic infection and baseline reactivation was assessed by microscopy for GFP fluorescence. Trichostatin-A (TSA) was used to stimulate HSV1 reactivation. Virion production was assessed by viral titers. Relative numbers of latency-associated (LAT) transcripts were determined by real-time reverse-transcription polymerase chain reaction (real-time RT-PCR)., Results: Lytic infection rates were equivalent between the two ganglia (p > 0.05). Lytic infections yielded similar amounts of plaque-forming units (p > 0.05). Relative amounts of LAT transcripts did not differ between latently infected superior and inferior VGNs. Latently infected cultures showed no differences in rates of baseline and TSA-induced HSV1 reactivation (p > 0.05). Production of virions was not significantly different between reactivated, latently infected superior versus inferior VGNs (p = 0.45)., Conclusion: Differences in prevalence of superior and inferior vestibular neuritis do not result from intrinsic differences in HSV1 infection or virion production of these neurons. Other factors, such as the length and width of the bony canal containing the ganglia and nerves, account for the greater involvement of the superior vestibular ganglion in vestibular neuritis.

Main Objective: To determine the utility of the hyperventilation test (HVT) in the diagnosis of vestibular schwannoma (VS)., Study Design: A retrospective analysis of hyperventilation-induced nystagmus (HVIN) in 45 patients with unilateral VS., Setting: A tertiary referral center., Patients: Forty-five patients with VS; 30 patients with chronic vestibular neuritis; 20 healthy subjects with normal hearing and without symptoms or a history of vertigo, migraine, or neurological diseases (control group)., Interventions: Audiological and vestibular examination; "side-stream" measurement of end-tidal CO2 pressure (P(EtCO2)) to standardize the procedure; magnetic resonance imaging (MRI) centered on the cerebellopontine angle., Main Outcome Measures: An analysis of HVIN, its patterns, and its appearance threshold via the measurement of P(EtCO2) correlations with the tumor size., Results: HVIN was observed in 40 of 45 cases (88.9%) in the schwannoma group and in 12 of 30 cases (40%) in the chronic vestibular neuritis group; HVIN was not observed in the control group (0/20 cases) (p < 0.001). In the schwannoma group, HVIN was evoked at a mean P(EtCO2) value of 16.5 ± 1.15 mm Hg. The hypofunctional labyrinth was identified with high sensibility and specificity through caloric test, head shaking test, and head thrust test. The excitatory pattern, which included HVIN with slow phases that beat toward the hypofunctional side, and the paretic pattern, which included HVIN with slow phases that beat toward the hypofunctional side, were not significantly associated with VS size (19.04 ± 10.56 mm for the excitatory pattern and 19.06 ± 11.01 mm for the paretic pattern). The difference in the VS size in HVIN+ (19.05 ± 10.60 mm) and HVIN- (8.40 ± 2.19 mm) cases was significant (p = 0.009)., Conclusions: A 60-second hyperventilation event causes metabolic changes in the vestibular system and reveals a latent vestibular asymmetry. The presence of an excitatory pattern is the major criterion that suggests VS in patients with signs of unilateral vestibular deficit.

Purpose: Peripheral vestibular dysfunction following vestibular neuritis (VN) often persists but functional recovery of balance can be variable. The authors compared structural changes in the brain before and after post-VN compensation and related it to the functional recovery., Methods: Nine patients diagnosed with unilateral VN were included. Brain MRI and clinical observation were performed within 2 days of acute VN diagnosis and were repeated 3 months after the first exam. Voxel-based morphometry (VBM) analysis for longitudinal data was performed using VBM8 toolbox running within SPM8. Changes in local grey matter volume (GMV) were examined using a paired t-test and clinical relevance was tested using correlation analyses with functional improvement., Results: Significant increases in GMV were observed in the vestibular cortex, bilateral hippocampus, visual cortices and the cerebellum. GMV decreased in cerebellar regions, including the vermis, and in the prefrontal cortex. Increases in GMV in visual cortices and cerebellum were associated with the poorest recovery of balance, which might be explained by functional substitution., Conclusions: The structural layout of vestibular compensation suggests that memory and motor planning are closely related to this process. Vision seems to be a major source of functional substitution, as has been previously demonstrated. This study, however, is the first longitudinal analysis of brain structural changes associated with recovery of balance following unilateral VN.

The recurrent nature of the 3 most common vestibulopathies suggests a recurrent cause. Histopathology in temporal bones from patients with these syndromes - vestibular neuronitis (VN, n = 7), Ménière's disease (MD, n = 8) and benign paroxysmal positional vertigo (BPPV, n = 5) - shows focal degeneration of vestibular nerve axons and degenerated nearby facial nerve meatal ganglion cells. Transmission electron microscopic confirmation of intracytoplasmic viral particles in surgically excised vestibular nerves from patients with VN and MD support a viral etiology in these vestibulopathies. Antiviral treatment of these syndromes in a series of 211 patients with a 3- to 8-year follow-up resulted in complete control of vertigo in VN (88%), MD (90%) and BPPV (60%)., (Copyright © 2013 S. Karger AG, Basel.)

Objectives: We examined the association between the size and cross-sectional area of the superior vestibular nerve as measured on constructive interference in steady-state (CISS) parasagittal magnetic resonance imaging (MRI) and the vestibular nerve function as measured by electronystagmography., Methods: The retrospective observational cohort study took place at an academic tertiary referral center. Twenty-six patients who met established clinical and electronystagmographic criteria for vestibular neuritis and who underwent parasagittal CISS MRI were identified. Two blinded investigators measured vestibular nerve height and width bilaterally at the level of the fundus of the internal auditory canal and calculated the cross-sectional nerve areas. The inter-rater reliability and agreement were analyzed. Symptom duration, age, and gender were also examined., Results: A statistically significant decrease was observed in both vestibular nerve cross-sectional area and height as compared to the contralateral vestibular nerve. A non-statistically significant trend was observed for a relative decreased cross-sectional nerve area with increased age, as well as a decrease in nerve area with an increase in symptom duration., Conclusions: Decreases in both vestibular nerve cross-sectional area and height are observed in patients with unilateral vestibular neuritis as measured on parasagittal CISS MRI.

Objectives: To test the hypothesis that vertebral artery hypoplasia (VAH) may affect the lateralisation of vestibular neuropathy (VN), probably through haemodynamic effect on the vestibular labyrinth., Methods: 69 patients with unilateral VN were examined with a magnetic resonance angiographic (MRA) and caloric test. 50 healthy subjects served as controls. The diagnosis of intracranial VAH was based on MRA if <0.22 cm in VA diameter and a diameter asymmetry index >40%. The authors then correlated the canal paretic side with the VAH side., Results: MRA study revealed 29 VAH (right/left: 23/6) in VN subjects and six VAH in controls (right/left: 5/1). The RR of VAH in VN subjects compared with controls was elevated (RR=2.2; 95% CI 1.8 to 2.8). There was a high accordance rate between the side of VAH and VN. Among 29 patients with unilateral VAH, 65.5% (N=19) had an ipsilateral VN, in which left VAH showed a higher accordance rate (83.3%) than the right side (60.9%). VN subjects with vascular risk factors also had a higher VAH accordance rate (81%) than those without (25%)., Conclusions: VAH may serve as a regional haemodynamic negative contributor and impede blood supply to the ipsilateral vestibular labyrinth, contributing to the development of VN, which could be enhanced by atherosclerotic risk factors and the left-sided location.

Objective: To explore the clinical characteristics, pathological mechanism, diagnose, differential diagnosis and the treatment of vascular compressive vestibular neuropathy., Method: The authors retrospectively studied 2 cases of vascular compressive vestibular neuropathy about clinical characteristics, auditory tests, vestibular tests and imaging examine results, pharmacotherapy results and reviewed the related documents., Result: There were some common clinical characteristics: (1) Vertigo and disequilibrium could be elicited by any physical activity and head movement and abated with complete bed rest; (2) Symptoms and signs can't be improved by vestibular suppressant medications; (3) When taken Dix-Hallpike test, true vertigo or a spinning sensation appeared during head movement, when head skilled at any position,the symptoms disappeared; (4) The suffering lateral often showed high frequency sensorineural hearing loss ,the ABR of the suffering lateral showed prolonged inter wave latency of I-III wave; (5) Vestibular tests showed central lesion; (6) Occupying lesion can be ruled out by CT and MRI, MRI showed neurovascular compression of vestibular nerve; (7) Taking carbamazepine plus baclofen or only Tegretol orally can alleviate symptoms. A great deal of surgeries confirmed neurovascular compression of cranial nerve U as a disease entity, the offending artery mainly anterior inferior cerebellar artery. Microvascular decompression of cranial nerve VIII can successfully relieve vertigo., Conclusion: Neurovascular compression of cranial nerve VIII is a disease entity beyond question. It's major characters were vertigo and disequilibrium which elicited by any physical activity and head movement, magnetic resonance tomographic angiography can give valuable information for diagnosis and treatment. Microvascular decompression can effectively relieve vertigo.

Objective: Patients who have had vestibular neuritis (VN) show a remarkable clinical improvement especially in gait and posture >6 months after disease onset., Methods: Voxel-based morphometry was used to detect the VN-induced changes in gray and white matter by means of structural magnetic resonance imaging. Twenty-two patients were compared an average 2.5 years after onset of VN to a healthy sex-and age-matched control group., Results: Our analysis revealed that all patients had signal intensity increases for gray matter in the medial vestibular nuclei and the right gracile nucleus and for white matter in the area of the pontine commissural vestibular fibers. A relative atrophy was observed in the left posterior hippocampus and the right superior temporal gyrus. Patients with a residual canal paresis also showed an increase of gray matter in middle temporal (MT)/V5 bilaterally., Interpretation: These findings indicate that the processes of central compensation after VN seem to occur in 3 different sensory systems. First of all, the vestibular system itself showed a white matter increase in the commissural fibers as a direct consequence of an increased internuclei vestibular crosstalk of the medial vestibular nuclei. Second, to regain postural stability, there was a shift to the somatosensory system due to an elevated processing of proprioceptive information in the right gracile nucleus. Third, there was a bilateral increase in the area of MT/V5 in VN patients with a residual peripheral vestibular hypofunction. This seems to be the result of an increased importance of visual motion processing.

Morphological and clinical evidence supports a viral neuropathy in Ménière's disease (MD). Quantitative examination of 11 sectioned temporal bones (TBs) from 8 patients with a history of MD revealed a significant loss of vestibular ganglion cells in both the endolymph hydropic (EH) and non-EH ears. Transmission electron microscopy of vestibular ganglion cells excised from a patient with MD revealed viral particles enclosed in transport vesicles. Antiviral treatment controlled vertigo in 73 of 86 patients with vestibular neuronitis (85%) and 32 of 35 patients with MD (91%)., (Copyright 2009 S. Karger AG, Basel.)

We report a patient with cerebral venous thrombosis who presented with acute onset of severe prolonged vertigo, nausea, vomiting, unilateral decreased caloric response and occipital headache, simultaneously with acute venous cerebral infarcts on brain MRI. Although the patient had occipital headache, overall symptoms and signs closely mimicked those of acute unilateral vestibulopathy. Cerebral venous thrombosis should be considered in the differential diagnosis of acute unilateral vestibular syndrome.

The concept that reactivation of latent neurotropic viruses (i.e. Herpesviridae group) in the vestibular ganglion is responsible for recurrent vestibulopathies is presented. A similar histopathologic degeneration of vestibular ganglion cells in vestibular neuronitis (VN), Ménière's disease and benign paroxysmal positional vertigo is presented to support this concept. The clinical response (relief of vertigo) to the administration of antiviral medication in these syndromes provides practical evidence of a viral neuropathy in patients with recurrent vertigo. Relief of vertigo after this treatment was 90% in VN, Ménière's disease and VN. The relief of positional vertigo (benign paroxysmal positional vertigo) was 66%., ((c) 2008 S. Karger AG, Basel)

Objective: To determine the frequency of cerebellar infarction mimicking vestibular neuritis (VN), the pattern of clinical presentation, and the territory of the cerebellar infarction when it simulates VN., Methods: We studied 240 consecutive cases of isolated cerebellar infarction in the territories of the cerebellar arteries diagnosed by brain MRI from the acute stroke registry at the Keimyung University Dongsan Medical Center., Results: We identified 25 patients (10.4%) with isolated cerebellar infarction who had clinical features suggesting VN. Two types of cerebellar infarction simulating VN were found: isolated spontaneous prolonged vertigo with imbalance as a sole manifestation of cerebellar infarction (n = 24) and isolated spontaneous prolonged vertigo with imbalance as an initial manifestation of cerebellar infarction (n = 1) followed by delayed neurologic deficits 2 days after the onset. The cerebellar infarction territory most commonly involved was the medial branch of the posterior inferior cerebellar artery territory (24/25: 96%), followed by the anterior inferior cerebellar artery territory (1/25: 4%). None of patients with infarcts in the territory of the superior cerebellar artery or multiple cerebellar arteries showed isolated spontaneous prolonged vertigo., Conclusions: Cerebellar infarction simulating vestibular neuritis is more common than previously thought. Early recognition of the pseudo-vestibular neuritis of vascular cause may allow specific management.

Opsoclonus-myoclonus syndrome (OMS), a movement disorder characterised by chaotic eye movements and myoclonus, is a rare clinical entity. We present two cases of opsoclonus-myoclonus syndrome of paraneoplastic origin. In the first patient the syndrome was associated with a breast carcinoma and in the second patient with a non small cell lung carcinoma. However none of the commonly associated antibodies were found in these cases. From the neuropathological findings from the first patient we find arguments that support the current hypothesis on the pathophysiology of OMS namely a dysfunction in brainstem and cerebellum. We conclude that in adults with OMS one has to be very suspicious of a possible neoplastic origin of the syndrome. The antibodies associated with some cases of OMS are thought to play a role in the pathophysiology of the syndrome although the exact immunologic mechanism remains unknown. Research into the neuropathological substrate of OMS yields a broad range of abnormalities in brain stem and cerebellum. However none of these findings seem to be pathognomonic. As for the possible therapy of OMS, several immunomodulating strategies can be used with varying success. At present there is no established standard therapy.

Ramsay Hunt syndrome (RHS) is characterized by vestibulocochlear dysfunction in addition to facial paralysis and auricular vesicles. The present study investigated the lesion site of vestibular dysfunction in a group of 10 RHS patients. Caloric testing, vestibular evoked myogenic potentials by click sound (cVEMP) and by galvanic stimulation (gVEMP) were used to assess the function of the lateral semicircular canal, saccule, and their afferents. The results of caloric testing (all 10 cases showed canal paresis) mean the existence of lesion sites in lateral semicircular canal and/or superior vestibular nerve (SVN). Abnormal cVEMPs in 7 patients mean the existence of lesions in saccule and/or inferior vestibular nerve (IVN). Four of the 6 patients with absent cVEMP also underwent gVEMP. The results of gVEMP (2 absent and 2 normal) mean that the former 2 have lesions of the vestibular nerve, and the latter 2 have only saccular lesions concerning the pathway of VEMPs. Thus, our study suggested that lesion sites of vestibular symptoms in RHS could be in the vestibular nerve and/or labyrinth, and in SVN and/or IVN. In other words, in the light of vestibular symptoms, there is the diversity of lesion sites.

The author describes the pathology, the symptoms and the treatment of these vertigo.

Sense organ deposits have been described in temporal bones from patients with vestibular neuronitis, Meniere's disease, and benign paroxysmal positional vertigo that are not found in a comparable series of temporal bones without vestibulopathy. Because the recurrent vestibulopathies are caused by vestibular ganglionitis and the vestibulocochlear anastomosis was degenerated in these temporal bones, the deposits may represent the end buds of regenerating efferent axons injured in passage through the vestibular ganglion. Such neural buds have been described with transmission electron microscopy in animals after vestibular nerve transection and in a human temporal bone with endolymphatic hydrops. The buds may be visible by light microscopy, because their size is comparable to that of hair cell nuclei and they stain blue with hematoxylin because of their nucleic acid content. The variable location and size of these deposits (buds) in the labyrinthine sense organs is described to aid in the recognition of efferent system injury in human temporal bones.

3,3'-Iminodipropionitrile (IDPN) is a neurotoxic compound that causes both a proximal neurofilamentous axonopathy and loss of the vestibular sensory hair cells. We used immunocytochemistry to examine changes in the expression of heavy, medium and light neurofilament (NF-H, NF-M, NF-L) proteins in the afferent terminals of vestibular sensory epithelia after IDPN exposure in rats. Acute, repeated and subchronic IDPN exposure induced a marked loss of NFs in the nerve terminals. The effect of subchronic IDPN was specific, as demonstrated by comparison with the synaptic membrane protein SNAP-25. In addition, Western blot analysis indicated specific loss of NFs in the vestibular receptors. Ultrastructural analysis revealed that afferent endings in the vestibular receptors were significantly preserved in animals exposed to subchronic IDPN, but that these endings showed NF segregation from microtubules followed by NF loss. These effects were closely paralleled by ultrastructural changes in the nerve terminals, particularly in the afferent contacts with the hair cells, and preceded hair cell loss. Thus, distal NF loss and nerve terminal pathology occur in the IDPN model of proximal neurofilamentous axonopathy. Similar distal pathology could also occur in human diseases characterized by proximal axonal swellings, particularly in amyotrophic lateral sclerosis.

Background: Experimental work indicates that the vestibular system participates in autonomic reflexes during body movement and postural changes. However, there are no studies of cardiovascular reflexes during vertigo due to human acute vestibular lesions., Methods: We assessed the response to active change of posture and hand immersion in cold water in seven patients with unilateral peripheral vestibular failure (vestibular neuritis) and seven age/sex-matched healthy subjects in acute phase (72 h from vertigo onset) and at 2 weeks of follow-up., Results: During acute phase, patients showed decreased blood pressure response during cold hand test (p < 0.05). Upright stance induced deficient decrease of the respiratory component of heart rate variability (p < 0.05) with lack of increase in low frequency/high frequency (LF/HF) ratio. At 2 weeks of follow-up, these abnormalities improved., Conclusions: Results suggest that acute vestibular lesions can interfere with cardiovascular autonomic responses in humans. This may reflect disruption of normal vestibulo-autonomic reflexes.

The authors investigated the central projection of excitement in acute stage vestibular neuronitis using positron emission tomography. The changes in the pattern of regional cerebral blood flow caused by the disease were compared with the effect of cold caloric stimulation known to provoke similar signs. It was concluded that the involved brain regions overlapped each other only partially. The mismatch could be explained by the compensatory processes developing during the disease. These processes do not normally develop during the caloric vestibular stimulation because of its short duration.

Endoscopy offers several distinct advantages over the operating microscope during neuro-otologic surgery that make it an excellent adjunctive tool to the microscope or independent modality during cranial base surgery. The high magnification gives excellent definition of perforating blood vessels, cranial nerves, and neural structures, which in many cases is superior to that achieved with the microscope. Furthermore, the use of angled or flexible endoscopes allows one to look around corners and behind anatomic structures blocking the view seen via a 0 degree microscope. Endoscopy also has the theoretical advantage that a less invasive operative procedure is required, which should reduce the operative morbidity. Several notable disadvantages of endoscopy include the problems associated with blood soiling the endoscope, making visualization difficult or impossible, the lack of readily available instrumentation designed specifically for endoscopic neuro-otology, and the poor overview of the operative field. This last point is an important one because the endoscope is placed adjacent to the lesion and does not allow one to look backward to prevent [figure: see text] injury to structures next to the shaft of the telescope. Furthermore, the surgeon must be cognizant of potential thermal injury to structures caused by the heat generated by the light source. The present endoscopic technology limits the image that the surgeon sees to two dimensions, which results in certain unique problems when operating in a three-dimensional milieu. Because of this, there is a steep learning curve to acquire endoscopic dexterity and three-dimensional orientation. Finally, bimanual operation requires the use of an articulated endoscope holder or the commitment of the co-surgeon to hold the endoscope. One of the limitations of the operative microscope is that the angle of view is determined by the distance of the lens to the skull, retractor, or obstructing tissue, which is a function of the lens focal length; the longer the focal length, the narrower the viewing angle. During most microsurgical procedures, the focal distance varies between 200 and 400 mm. Using a previous analogy, if one looks through a door's keyhole at close range, nearly the entire room on the opposite side of the door can be seen, although nothing can be seen when the hole is viewed from a long distance. This is similar to what happens when using the endoscope with focal lengths ranging from 5 to 20 mm: a wider angle of view can be achieved. Based on their, experience the authors believe that endoscopes can be used safely during neuro-otologic surgery. As an adjunct to or substitution for the operative microscope, this modality does improve visualization of bony, neural, and vascular structures while minimizing cerebellar retraction.

We present temporal bone and clinical evidence that common syndromes of recurrent vertigo are caused by a viral infection of the vestibular ganglion. In the present series, histopathologic and radiologic changes in the vestibular ganglion and meatal ganglion were consistent with a viral inflammation of ganglion cells in cases of Meniere's disease, benign paroxysmal positional vertigo, and vestibular neuronitis. Clinical observations of multiple neuropathies involving cranial nerves V, VII, and VIII on the same side in patients with recurrent vertigo are best explained by a cranial polyganglionitis caused by a neurotrophic virus, which is reactivated by a stressful event later in life. The reactivation of the latent virus may manifest as one of the above vertigo syndromes, depending on the part of the vestibular ganglion that is inflamed, the type and strain of the virus, and host resistance.

Eight patients diagnosed with vestibular neuritis received the newly developed three-dimensional videonystagmography (3D VNG) and vestibular evoked myogenic potential (VEMP) examination in order to localize the lesion site. Two (25%) of the 8 patients exhibited spontaneous nystagmus with 3 components, indicating that both the horizontal semicircular canal (HSCC) and anterior semicircular canal (ASCC) were affected. The remaining 6 patients (75%) displayed only horizontal nystagmus, meaning that only the HSCC was involved. Seven (88%) of the 8 patients had bilateral normal VEMPs, revealing sparing of the posterior semicircular canal (PSCC). In a comparative study, another seven patients with vestibular neuritis 1 year post-treatment also received the caloric test, 3D VNG and VEMP examination. Only one patient exhibited spontaneous nystagmus. An absent caloric response of the lesioned side persisted in 5 (71%) of the 7 patients. However, all patients showed normal VEMPs bilaterally. 3D VNG and VEMP examination indicates that vestibular neuritis mainly affects the superior division of the vestibular nerve, which innervates the HSCC and ASCC. Meanwhile, the function of the PSCC and saccule, innervated by the inferior vestibular nerve, is preserved.