Auditory brain stem response--interwave measurements in acoustic neuromas

Area of Science:

• Neuroscience
• Audiology
• Neurosurgery

Background:

• Tumors of the VIIIth nerve or cerebellopontine angle can affect auditory pathways.
• Auditory brain stem responses (ABR) are a non-invasive electrophysiological test used to assess the integrity of the auditory pathway from the cochlea to the brainstem.

Purpose of the Study:

• To analyze auditory brain stem responses (ABR) in patients with VIIIth nerve or cerebellopontine angle tumors.
• To evaluate the diagnostic utility of interwave intervals (I-III, III-V, I-V) in identifying these tumors.

Main Methods:

• Analysis of ABR recordings from 61 patients with suspected VIIIth nerve or cerebellopontine angle tumors.
• Measurement of interwave latencies (I-III, III-V, I-V) in patients with identifiable waves I, III, and V.
• Comparison of ABR findings in tumor patients with a control group with cochlear lesions.

Main Results:

• In 16 out of 61 patients, measurable ABR waves I, III, and V were obtained.
• Abnormalities in the I-III interwave interval were common.
• The III-V interwave interval was extended in nearly 50% of the analyzed cases.
• ABR interwave measurements demonstrated higher specificity than sensitivity for detecting VIIIth nerve tumors.

Conclusions:

• Auditory brain stem response interwave interval analysis can aid in the diagnosis of VIIIth nerve and cerebellopontine angle tumors.
• Extended III-V intervals are a significant finding in these tumor cases.
• ABR interwave measurements are more valuable for confirming the presence of a tumor (specificity) than for ruling it out (sensitivity).