Adverse effects of topical papaverine on auditory nerve function.

Background: Papaverine hydrochloride is a direct-acting vasodilator used to manage vasospasm during various neurosurgical operations. Transient cranial nerve dysfunction has been described in a few cases with topical papaverine. This study supports previous reports and provides neurophysiological evidence of an adverse effect on the auditory nerve.

Methods: We conducted a retrospective review of 70 consecutive microvascular decompression operations and studied those patients who received topical papaverine for vasospasm. Topical papaverine was used as a direct therapeutic action to manage vasospasm in a total of 11 patients. The timing of papaverine application and ongoing operative events was reviewed relative to changes in neurophysiological recordings. Brainstem auditory evoked potentials (BAEPs) were routinely used to monitor cochlear nerve function during these operations.

Findings: A temporal relationship was found between topical papaverine and BAEP changes leading to complete waveform loss. The average temporal delay between papaverine and the onset of an adverse BAEP change was 5 min. In 10 of 11 patients, BAEP waves II/III-V completely disappeared within 2 to 25 min after papaverine. Eight of these 10 patients had complete loss of BAEP waveforms within 10 min. One patient showed no recovery of later waves and a delayed profound sensorineural hearing loss. The average recovery time of BAEP waveforms to pre-papaverine baseline values was 39 min.

Conclusions: Topical papaverine for the treatment of vasospasm was associated with the onset of a transient disturbance in neurophysiological function of the ascending auditory brainstem pathway. The complete disappearance of BAEP waveforms with a consistent temporal delay suggests a possible adverse effect on the proximal eighth nerve. Recommendations to avoid potential cranial nerve deficits from papaverine are provided.