Ipsilateral and Contralateral Acoustic Brainstem Response Abnormalities in Patients With Vestibular Schwannoma

[Association between the inter-aural latency difference of brainstem auditory evoked potential wave V and neonatal hyperbilirubinemia]

OBJECTIVE

To study brainstem auditory evoked potential (BAEP) in neonates with hyperbilirubinemia using short auditory stimuli (60 dBnHL), and to investigate the differences in the inter-aural latency difference (ILD) of wave V between neonates with different total serum bilirubin (TSB) levels.

METHODS

A prospective study was conducted in neonates with hyperbilirubinemia who were admitted to the Department of Neonatology, Yuhuan People's Hospital of Zhejiang Province, from May 2019 to October 2020. The neonates were divided into a severe group (n=50) and a mild group (n=50) according to their TSB levels. The mild group was divided into two subgroups: 7-10 days (n=20) and 11-14 days (n=20) according to their age. ILD was compared between the neonates with different TSB levels, and its diagnostic value was analyzed.

RESULTS

Compared with the mild group, the severe group had significantly higher proportions of neonates with abnormal hearing threshold and abnormal ILD (P < 0.05) and a significantly larger ILD of wave V (P < 0.05). The latency of wave V (left ear) in the 7-10 days subgroup was significantly longer than that in the 11-14 days subgroup (P < 0.05), but there was no significant difference in the ILD of wave V between the two groups (P > 0.05). The receiver operating characteristic (ROC) analysis showed that ILD had predictive value for hearing impairment caused by neonatal hyperbilirubinemia (P < 0.05), with an area under the ROC curve of 0.727 as well as a sensitivity of 52.4% and a specificity of 90.9% at the optimal cut-off value of 0.365 ms.

CONCLUSIONS

Serum bilirubin in neonates affects the ILD of BAEP wave V, especially in those with severe hyperbilirubinemia. ILD at the optimal cut-off value of ≥0.4 ms shows potential value in the diagnosis of hearing impairment caused by neonatal hyperbilirubinemia.

Audiological Evaluation of Vestibular Schwannoma Patients with Normal Hearing

Objective: To evaluate the audiological aspects of vestibular schwannoma (VS) patients with normal hearing. Study Design: Retrospective study. Setting: Quaternary referral center for skull base pathologies. Patients: The records on 4,000 patients who had been diagnosed with VS between 1986 and December 2017 were retrospectively reviewed. The patients included in the study were the ones who complied with the strict audiological normality criteria, as follows: a pure tone hearing threshold (at the 6-octave-spaced frequencies from 250 to 8,000 Hz) ≤25 dBHL; a word recognition score >90%; and interaural differences ≤10 dB at each frequency. Interventions: Auditory brainstem response (ABR) testing and radiological imaging. Main Outcome Measures: The incidence of normal objective hearing among VS patients, and the diagnostic utility of the ABR and the effect of tumor size and site on the response. Results: The incidence of normal hearing among VS patients was 4.2%. Tinnitus and vertigo were the most common symptoms across tumor grades; 5.6% of the tumors were large and giant tumors. The ABR yielded a sensitivity of 73.6%, with a false negative rate of 26.3% using a cutoff point of 0.2 ms for interaural latency differences. Conclusions: The diagnosis of VS should not be based on audiometric thresholds alone. Alarming signs of VS should be clear to the physician in order not to miss or delay the diagnosis of the disease. The ABR is useful in the diagnosis of VS, but normal results do not exclude the occurrence of the disease in patients with normal hearing.

Predictors of hearing outcomes following low-dose stereotactic radiosurgery in patients with vestibular schwannomas: A retrospective cohort review

OBJECTIVES

Hearing deterioration is a major concern for hearing-preserved patients with vestibular schwannomas who are treated with stereotactic radiosurgery (SRS). Thus, determining which patients are more likely to have worse hearing outcomes following SRS may facilitate clinicians in deciding whether conservative policy should be applied in the interest of hearing preservation. This study aimed to define the predictors of hearing outcomes following SRS.

PATIENTS AND METHODS

This retrospective study included 100 patients who underwent low-dose SRS (12- to 13-Gy marginal dose) for vestibular schwannomas between January 2004 and January 2014. Clinical factors and hearing outcomes following radiosurgery were reviewed.

RESULTS

All patients had serviceable hearing at diagnosis and prior to SRS. The median follow-up period was 6.5years (range, 3-10years). The hearing preservation rate in the first, third, and fifth year after radiosurgery was 89%, 68%, and 63%, respectively. A mean cochlear dose lower than 4Gy was a favorable predictor of hearing outcome. Maximal cochlear dose, patient age, pre-treatment pure-tone average, and imaging characteristics were not associated with post-treatment hearing preservation. Our study showed an accelerated rate of deterioration of serial pure-tone average in the first 3years, followed by a more gradual decline after radiosurgery.

CONCLUSION

Our results suggest that cochlear dose constraint is the most crucial factor for hearing preservation. This study provides insight into the rate of hearing preservation and the pattern of hearing deterioration following radiosurgery and can help clinicians advise patients of hearing outcomes following SRS.

Role of cervical vestibular evoked myogenic potentials (cVEMP) and auditory brainstem response (ABR) in the evaluation of vestibular schwannoma

INTRODUCTION

Cervical vestibular evoked myogenic potentials (cVEMP) can assess the integrity of the inferior vestibular nerve thereby promising to be a useful tool in the audiological test battery to diagnose vestibular schwannoma.

OBJECTIVE

To ascertain the utility of cVEMP in diagnosis of vestibular schwannoma in conjunction with the ABR and to evaluate whether the size of lesion has any effect on the cVEMP measures.

METHODS

Case-files of 15 known cases of vestibular schwannoma whose pure tone audiometry, auditory brainstem response (ABR), cVEMP and radiological investigation findings were available, were included in the study. Patients were categorised as large or small tumours based on the size. The absolute and inter-peak latencies of ABR, amplitudes of waves V and I, and inter-aural latency difference of wave V of ABR; and latency of P1 and N1 of cVEMP and amplitude of P1-N1 complex were considered in the study.

RESULTS

There were eight large and nine small tumours. All the patients with large tumours showed significant severity of hearing loss whereas only three out of nine patients with small tumours showed severe to profound deafness in the affected ear. The rest showed hearing status ranging from normal hearing sensitivity to moderate hearing loss. Most of the patients with large tumours showed complete absence of ABR in the affected ears with no identifiable wave-peaks. ABR in small tumours exhibited delayed III-I and delayed V-I interpeak latency interval (IPL). Four out of five patients with large unilateral tumours revealed contralateral effects of reduced amplitude or absence of cVEMP. On the contrary, six out of eight unilateral small tumours showed a normal cVEMP response in the contralateral ear. Both the patients with NF2 in the present study demonstrated cVEMP abnormalities.

CONCLUSION

ABR and cVEMP, when used in combination, can be of immense use in identification of neuro-otologic conditions such as vestibular schwannoma and bilateral tumours in NF2. In the evaluation of unilateral vestibular schwannoma, abnormal contralateral findings of cVEMP and ABR are strongly indicative of the tumour size >2.5cm. In unilateral severe to profound loss wherein ABR in poorer ear cannot give information of site-of-lesion, cVEMP can help in the differentiation.

Otologic manifestations of acoustic neuroma

CONCLUSION

Many patients with acoustic neuroma (AN) experience hearing loss and tinnitus. Time from first symptoms to diagnosis can be considerable. AN should be suspected, and MRI scans performed, in patients with hearing loss accompanied by asymmetry, tinnitus, low speech discrimination score (SDS), and abnormal auditory brainstem response (ABR).

OBJECTIVES

To determine the otorhinolaryngological factors associated with AN by analyzing the clinical manifestations and diagnostic test results of patients with AN before MRI scanning.

METHODS

This study enrolled 114 patients definitively diagnosed with AN after visiting the Ear-Nose-and-Throat and Neurosurgery Departments of Kyung Hee University Medical Center from 2001 to 2013. Factors retrospectively analyzed included patient age, gender, major symptoms, accompanying symptoms, symptom duration, pure-tone audiometry, SDS, asymmetry, tinnitogram, ABR, and MRI scan results.

RESULTS

The main symptom of AN was hearing loss, and the most frequent accompanying symptom was tinnitus. More severe deafness correlated significantly with lower SDS (p < 0.05). Asymmetric hearing was observed in 75 of 116 patients (64.6%), and mean SDS was 73.1 ± 34.1%. Of patients with latencies of waves I, III, and V on ABR tests, 56.1%, 92.4%, and 92.4%, had interaural latency differences ≥0.2 ms. However, audiometry results did not correlate with lesion site or tumor size (p > 0.05).

Ipsilateral and contralateral auditory brainstem response reorganization in hemispherectomized patients

Background. Cortical hemispherectomy leads to degeneration of ipsilateral subcortical structures, which can be observed long term after the operation. Therefore, reorganization of the brainstem auditory pathway might occur. The aim of this study was to assess reorganization of brainstem auditory pathways by measuring the auditory brainstem response (ABR) in long-term hemispherectomized patients. Methods. We performed bilateral monaural stimulation and measured bilateral ABR in 8 patients ~20 years after hemispherectomy and 10 control subjects. Magnetic resonance imaging (MRI) was performed in patients to assess structural degeneration. Results. All patients showed degenerated ipsilateral brainstem structures by MRI but no significant differences in bilateral recording ABR wave latencies. However, nonsurgical-side stimulation elicited significantly longer wave V latencies compared to surgical-side stimulation. Differences in bilateral ABR were observed between hemispherectomized patients and control subjects. Waves III and V latencies elicited by nonsurgical-side stimulation were significantly longer than those in control subjects; surgical-side stimulation showed no significant differences. Conclusions. (1) Differences in ABR latency elicited by unilateral stimulation are predominantly due to bilateral brainstem auditory pathway activity rather than to changes in brainstem volume; (2) ABR Waves III and V originate predominantly in the contralateral brainstem; and (3) subcortical auditory pathways appear to reorganize after long term hemispherectomy.

ABR in the diagnosis of vestibular schwannomas: a meta-analysis

PURPOSE

The aim of this study is to rigorously evaluate the role of auditory brainstem response (ABR) testing in the diagnosis of vestibular schwannomas (VS).

MATERIALS AND METHODS

Searches were conducted in multiple online databases, supplemented by hand searches. From the studies chosen for final inclusion, relevant data were extracted and meta-analysis of pooled data was performed.

RESULTS

623 studies were identified from which 43 met inclusion criteria for analysis (1978 to 2009) including 3314 patients. Pooled sensitivity for ABR detection of vestibular schwannomas was 93.4% (95% CI 92.6-94.3, P=0.0000). For tumors less than 1cm (8 studies, 176 patients) sensitivity was 85.8% (95% CI 80.6-90.1, P=0.0116). For tumors greater than 1cm (6 studies, 251 patients) pooled sensitivity was 95.6% (95% CI 93.1-98.2, P=0.0660). Sensitivity of ABR to detect extracanalicular tumors was higher than for intracanalicular tumors, though pooled data were not statistically valid. Pooled specificity (8 studies, 2432 patients) was 82.0% (95% CI 80.5-83.6, P=0.0000).

CONCLUSIONS

Although MRI remains the gold standard, emerging trends towards more conservative management coupled with limited financial resources may prompt many clinicians to review the role of ABR testing in screening for retrocochlear pathology. In light of the high sensitivity and specificity of ABR testing for VS, we strongly urge its reconsideration as a useful diagnostic tool for patients with clinically suspected VS.