Aetiology of delayed facial palsy after vestibular schwannoma surgery: clinical data and hypothesis.

A patient developed delayed facial nerve palsy at the level of House-Brackmann grade I to grade III 10 days after vestibular schwannoma surgery by the suboccipital transmeatal approach. The palsy had completely recovered after one month. Immunological study showed reactivation of herpes simplex and magnetic resonance (MR) imaging demonstrated an abnormal enhancement pattern of the facial nerve; intense enhancement of the distal intracanalicular segment and labyrinthine segment, similar to the MR findings for Bell's palsy. A prospective control study on the enhancement pattern of the functionally preserved facial nerve after vestibular schwannoma surgery in six cases showed a similar pattern to that of the normal facial nerve. Based on these findings, we propose the hypothesis that herpes simplex reactivation is an underlying cause of delayed facial palsy after vestibular schwannoma surgery.