Facial nerve neuroma
A facial nerve neuroma is a rare tumour of the facial nerve. If all tumours in the temporal bone are to be considered facial nerve neuromas will occur in less than 1% of cases.
They can occur in any part of the facial nerve but only those in the temporal bone would be considered here. There are no age predisposition and patients of all ages can be affected. They most often occur in more than one segment of the facial nerve. In cases where they occur with other central nervous system tumours, Neurofibromatosis type 2 should be considered. Although usually benign (non-cancerous) they often cause facial nerve paralysis. Facial nerve neuromas occur far less frequently than vestibular schwannomas (acoustic neuromas).
Whereas patients with vestibular schwannomas rarely present with facial nerve weakness facial nerve neuromas often cause facial nerve spasm, weakness and paralysis. When they originate inside the internal auditory meatus they may present with hearing loss, dizziness, vertigo and disequilibrium before the onset of facial nerve weakness.
It should be emphasized that when a patient present with facial nerve weakness and a magnetic resonance image (MRI) suggest an intratemporal bone tumour, a facial nerve neuroma should be considered.
Less than 5% of all facial nerve paralysis are caused by tumours. Patients who are diagnosed with Bell’s palsy and do not regain function or who re-paralyze after improvement should be investigated for a facial nerve neuroma. Patients with slow onset facial nerve weakness should also be investigated.
The examination of choice is a MRI with gadolinium contrast enhancement but a computed tomography (CT scan) will aid in demonstarting the bony involvement.
Facial nerve neuromas may not grow and those that do usually do so at a very slow rate. Management include observation, surgical removal and in rare cases radiation. Most often the patient will end up with a permanent facial paralysis necessitating facial nerve grafting or other reparative plastic surgical procedures.