Auditory brainstem and middle-latency responses in Bell's palsy

Area of Science:

• Neurology
• Neurophysiology
• Audiology

Background:

• Bell's palsy is acute peripheral facial palsy of unknown cause.
• Brainstem involvement is sometimes suspected in Bell's palsy.
• Evoked potentials like ABR and MLR can assess neural pathway function.

Purpose of the Study:

• To investigate potential brainstem involvement in Bell's palsy patients using auditory brainstem response (ABR) and middle-latency response (MLR).
• To determine if evoked potential abnormalities are consistently found in Bell's palsy.

Main Methods:

• Auditory brainstem response (ABR) was performed on 30 patients with acute peripheral facial palsy.
• Middle-latency response (MLR) was performed on 14 of these patients.
• Analysis focused on wave V latencies in ABR and overall MLR responses.

Main Results:

• ABR showed abnormal wave V latencies ( > 3 SD) in only 2 out of 30 patients.
• Reducing the abnormality criterion to 2 SD identified only 3 patients with abnormal ABR wave V latencies.
• All 14 patients tested with MLR exhibited normal responses.

Conclusions:

• Evoked potential measures, specifically ABR and MLR, show limited evidence of brainstem involvement in most Bell's palsy cases.
• Brainstem involvement, as assessed by these evoked potentials, may not be a pathognomonic feature of Bell's palsy.
• Further research may be needed to clarify the role of central pathways in Bell's palsy.