Vestibular mapping in patients with unilateral peripheral-vestibular deficits.

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.

Hyperventilation-induced nystagmus in patients with vestibular schwannoma.

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.

[Vertigo due to neurovascular cross-compression: diagnosis and treatment].

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.

Cerebral venous thrombosis mimicking acute unilateral vestibulopathy.

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.

Evidence for a viral neuropathy in recurrent vertigo.

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%.

Opsoclonus-myoclonus syndrome: a clinicopathological confrontation.

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.

Distal effects in a model of proximal axonopathy: 3,3'-iminodipropionitrile causes specific loss of neurofilaments in rat vestibular afferent endings.

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.

Endoscopy in neuro-otologic surgery.

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.