Vestibular investigations in acoustic neuroma

A Preliminary Data Visualization Approach to Vestibulocochlear Diseases Based on Multiple Scalar Dimensions

For vestibulocochlear diseases, traditional clinical history-taking, and the terminology of widely taught nosologic taxonomy, have misleading implications that can lead to errors in diagnosis and therefore in treatment. In the interest of facilitating differential diagnosis while simultaneously recognizing that many of these diseases may not be as discrete as textbooks suggest, we propose a data visualization approach focusing on several continuous scalar dimensions in the domains of anatomy, physiology, and chronology. We illustrate the application of this approach to several categories of clinical presentation.

Pre- and post-operative semicircular canal function evaluated by video head impulse test in patients with vestibular schwannoma

OBJECTIVES

To evaluate pre- and post-operative semicircular canal function in patients with vestibular schwannoma (VS) by the video Head Impulse Test (vHIT).

METHODS

Nineteen patients with VS who underwent surgery were enrolled in this study. The gain in vestibulo-ocular reflex (VOR) and the degree of scatter in catch-up saccades were examined pre- and post-operatively for the semicircular canals in VS patients.

RESULTS

Ten of 19 cases (52.6 %) with VS were defined as demonstrating both superior vestibular nerve (SVN) and inferior vestibular nerve (IVN) impairment from the results of pre-operative vHIT. Hearing level and subjective vestibular symptoms showed significant correlations with pre-operative semicircular canal function. Compared to pre-operative vHIT results, VOR gains within 1 month after surgery were significantly reduced in all three canals; however, significant differences had disappeared in the anterior and posterior semicircular canals at 6 months after surgery. Cases of unknown origin had a significantly greater reduction in posterior semicircular canal function after surgery compared with those with disease of IVN origin.

CONCLUSIONS

As vHIT could evaluate pre-operative vestibular nerve impairment, post-operative VOR gain reduction and the degree of vestibular compensation, semicircular canal function evaluated by vHIT provides a good deal of useful information regarding VS patients undergoing surgery compared to caloric testing, and vHIT should be performed pre- and post-operatively for patients with VS.

Electronystagmography in 166 patients with acoustic neuroma before and after surgery

OBJECTIVE

To analyze the preoperative patterns of caloric test, eye tracking test (ETT), and optokinetic pattern (OKP) in patients with acoustic neuroma (AN) and compare them with the postoperative patterns of ETT and OKP results METHODS: A total of 166 patients with AN (102 women; mean age: 41 years, range: 11-79 years) who were being treated at our hospital between 2013 and 2016 were enrolled. Preoperatively, a detailed history was taken regarding the presence of subjective symptoms of equilibrium dysfunction, and the patients underwent caloric test, ETT, and OKP. They were classified into three groups based on the preoperative ETT and OKP results as follows: Group A, normal ETT and OKP; Group B, either ETT or OKP was abnormal; and Group C, both ETT and OKP were abnormal. All patients were evaluated for subjective symptoms of vestibular dysfunction and were also grouped based on the tumor size on imaging. All surgeries were performed by a neurosurgeon using the lateral suboccipital retrosigmoid approach. About one month later after surgery, postoperatively ETT was performed on 150 patients and OKP was performed on 148 patients. The preoperative and postoperative ETT and OKP results were compared. The same two specialists analyzed the postoperative ETT and OKP findings as improved, unchanged, or worse. Student t-test was used for statistical analysis and a P-value of <0.05 was considered to indicate a statistically significant difference.

RESULTS

The average canal paresis(CP) % was 65.8%. No correlation was found between tumor size and CP%. The other side, the average tumor size in each group was 26.6 mm, 28.7 mm, and 37.8 mm in the Group A, B, and C, respectively. The average tumor size in Group C was significantly greater than those of Group A and B (P<0.01). The presence of gait disturbance in Group C was significantly higher than the other groups (P<0.01). The other side, abnormal ETT and OKP were seen in 32.5% and 31.9% of all patients, respectively. ETT and OKP results improved postoperatively in 67.4% and 68.9% of these patients.

CONCLUSIONS

Abnormal ETT and OKP results showed positive correlations with the tumor size and presence of subjective symptoms. Further, dysfunction of cerebellum and brain stem owing to tumor compression was observed to recover in many cases after surgery.

Bilateral multicanal benign paroxysmal positional vertigo coexisting with a vestibular schwannoma: case report

We describe a rarely encountered case of coexisting bilateral multicanal benign paroxysmal positional vertigo (BPPV) and vestibular schwannoma in a 56-year-old woman. The patient had presented with a 10-year history of dizziness and imbalance, and her vestibular findings were perplexing. We decided on a working diagnosis of BPPV and began treatment. After several months of canalith repositioning maneuvers had failed to resolve her symptoms, we obtained magnetic resonance imaging, which revealed the presence of the vestibular schwannoma. This case serves as a reminder of the importance of differentiating between central and peripheral vestibular disorders, as well as central and anterior canal BPPV-induced down-beating nystagmus in order to establish the correct diagnosis and initiate appropriate treatment.

The diagnostic value of vestibular-evoked myogenic potential in patients with vestibular schwannoma

OBJECTIVE

This study examined the diagnostic value of the vestibular-evoked myogenic potential (VEMP) in comparison with the caloric test in patients with vestibular schwannoma (VS).

METHODS

Data were retrospectively collected from 803 consecutive patients who visited our vertigo clinic and underwent vestibular tests. Amongst them, 78 patients were diagnosed as having untreated unilateral VS. VEMP was performed using click and short-tone burst stimulation. The caloric test was performed using ice water. The sensitivity and specificity of each test were evaluated.

RESULTS

Of the 78 patients with VS, 63 had abnormal VEMPs as well as abnormal caloric responses. Of the 725 patients without VS, 382 had normal VEMPs and 416 had normal caloric responses. The sensitivity and specificity of VEMP were 80.8% (95% CI: 72.0-89.5%) and 52.7% (95% CI: 49.1-56.3%), respectively; those of the caloric test were 80.8% (95% CI: 72.0-89.5%) and 57.4% (95% CI: 53.8-61.0%), respectively.

CONCLUSIONS

The sensitivity and specificity of VEMP and the caloric test showed no significant differences.

SIGNIFICANCE

In patients with VS, although the specificity of VEMP was not very high, its sensitivity was high and comparable to that of the caloric test.

Prediction of the origin of intracanalicular neoplasms with high-resolution MR imaging

Correct diagnosis of intracanalicular neoplasms is important to avoid unnecessary operations or an unsuitable surgical approach. We investigated the capability of high-resolution three-dimensional MR imaging in predicting the origin of intracanalicular neoplasms. Twenty cases underwent three-dimensional Fourier-transformation (3DFT) constructive interference in steady state and contrast-enhanced 3DFT-fast low angled shot MR imaging and surgery. Seventeen cases underwent caloric test. MR diagnosis on the origin of intracanalicular neoplasms was compared with surgical results. For MR diagnosis, the origin of intracanalicular neoplasms was predicted according to the location of the tumor in the internal auditory canal (IAC) in two ways, i.e., determining (1) a single specific nerve of origin and (2) whether the tumor originated from the superior or inferior aspect of the IAC. Surgery could determine the nerve of origin in 16 cases (14 inferior and 2 superior vestibular schwannomas), but it was indeterminate in 4. Comparison between MR prediction and surgical results on a single nerve origin revealed exact agreement in five, but inconsistent in three. Regarding whether the tumor was derived from superior or inferior aspect of the IAC, agreement was found in 10 of the 16 cases (62.5%). Caloric test was abnormal in all patients examined but one with superior vestibular schwannoma. 3DFT-MR imaging was not particularly useful in predicting a precise nerve of origin of intracanalicular neoplasms. The prediction on whether the tumor originated in the superior or inferior aspect of the IAC was superior to caloric test, which might have clinical significance in treatment planning especially for hearing preservation surgery.

Galvanic-induced body sway in vestibular schwannoma patients: evidence for stimulation of the central vestibular system

OBJECTIVE

To investigate the various possible sites of excitation by galvanic stimulation by comparing the galvanic-induced body sway (GBS) in vestibular schwannoma (VS) patients with that in healthy subjects.

MATERIAL AND METHODS

This was a prospective experimental study conducted in a tertiary referral centre. In a previous study we developed a standardized procedure for reproducible quantification of GBS using a monaural continuous 1-cosinusoidal stimulus (0.5 Hz; 2 mA). In this study, 23 VS patients were tested before and 12 VS patients were also tested after surgical intervention (extirpation of tumour with concomitant vestibular neurectomy) and the results were compared with those obtained in 47 healthy subjects.

RESULTS

There were no significant differences in mean total GBS gain between VS patients and healthy subjects (p>0.05) before surgical intervention. After vestibular neurectomy a significant difference in the mean total GBS gain was observed, but GBS was still present after surgery.

CONCLUSION

These results prove that galvanic vestibular stimulation excites the central vestibular system even when conduction via the vestibular nerve is hampered.

[Nystagmographic findings in pontocerebellar angle tumors]

OBJECTIVE

To determine the diagnostic and prognostic value of vestibular function tests in cerebellopontine angle tumors

METHODS

Analysis of preoperative nystagmographic findings in 29 patients affected of cerebellopontine angle tumors and its possible correlation with anatomical and progressive patterns

RESULTS

Tumor size and growth pattern were statistically significantly related to auditory and vestibular functions and to central findings on nystagmography. Age, gender, tumor size and central findings on nystagmography did not show influence upon postoperative dysbalance. However, alterations related with adaptation of the vestibular system (positional nystagmus and asymmetry on rotational tests) correlated significantly with postsurgical dysbalance.

CONCLUSIONS

The tests for vestibular function reflect a the characteristics of growth of the cerebellopontine angle tumors and can help to identify the patients susceptible of prolonged postoperative dysbalance.

Acoustic neuroma: correlations between morphology and otoneurological manifestations

Forty-two patients with acoustic neuroma (AN) were studied to determine whether different types of neuroma could be correlated with specific signs and symptoms of the disease. Based on gadolinium-enhanced TI-weighted MRI sequences, the 42 cases of AN could be divided into three groups, either by size (small: 11.9%, medium: 50%, and large: 38.1%) or by site of origin of the tumour (lateral: 16.7%, intermediate: 69%, and medial: 14.3%). Relations were found between the size and the site of origin of the neuromas and certain clinical, audiological and vestibular findings. The clinical presentation seemed to vary with the site of origin and the size of the tumour: patients with lateral neuromas generally had small tumours, sometimes only located in the internal auditory canal (IAC), and presented early subjective hearing loss while patients with medial neuromas had larger tumours which grew without causing significant audiological symptoms. Normal hearing function was seen only in the patients with medial ANs; however, a significant relation between the size or the site of origin of the AN and the average hearing threshold was not demonstrated. The sensitivity of the stapedial reflex test (SR) was higher for lateral ANs. Anomalies in the brainstem auditory evoked potentials (BAEPs) did not seem to be related to either the size or the site of origin of the AN. The vestibular tests demonstrated a higher frequency of central vestibular involvement in the large tumours, while normal function was more frequent in the lateral tumours. In the group studied the combination of BAEPs and vestibular tests allowed us to identify all the ANs with an optimal level of sensitivity.

Evaluation of patients with acoustic neuroma with dynamic posturography

The purpose of the present work was to consider the use of posture tests in patients who had known acoustic tumors. The results suggest that it might be possible to determine whether the tumor is on the inferior or superior branch of the vestibular nerve. This would have clinical significance for planning a surgical approach to the tumor.

Electronystagmographic findings in 147 patients with acoustic neuroma

We report on the preoperative findings in 147 patients with surgically confirmed acoustic neuroma (AN). Gaze nystagmus, spontaneous nystagmus and positional nystagmus were present in 23.1%, 47.5% and 63.0% of the patient, respectively. Pathological findings in ETT, OKP and bithermal caloric test were found in 44.3%, 45.3% and 77.0%, respectively. The ratio of pathological findings in ETT and OKP was larger in the large tumor group than in the small tumor group. Gaze nystagmus to both directions and direction-changing positional nystagmus were also found in the large tumor group. While the correlation between tumor size and CP% in caloric test was slightly significant (correlation coefficient, 0.52) in all 122 patients, it was more significant (correlation coefficient, 0.65) in 16 patients whose tumor origin was surgically confirmed to be the inferior vestibular nerve. These findings suggest that reduced caloric response is caused by compression of the nerve by tumor mass. On the other hand, 6 patients whose tumor originated from the superior vestibular nerve showed no significant correlation between CP% and tumor size.