Facial Nerve Palsy

multiple myeloma

This 59 year-old patient presented with a left facial droop and a known history of multiple myeloma. A CT brain was performed looking for a cerebral cause. The brain appeared normal. Close inspection revealed a lytic lesion in the left temporal bone, and focused reconstructions of the petrous temporal bones confirmed a lytic lesion involving the mastoid segment of the facial nerve canal. Click image for arrows (green – lesion, red – normal contralateral facial nerve canal). The lytic lesion was one of many in the skull and is consistent with a myeloma deposit.

The facial nerve has five named segments: the meatal segment (brainstem to lateral end of internal auditory canal); the labyrinthine segment (IAC to geniculate ganglion); the typanic segment (from geniculate ganglion to pyramidal eminence); the mastoid segment (from pyramidal eminence to stylomastoid foramen); and the extratemporal segment (from stylomastoid foramen to division into major branches). A lesion above the origin of the chorda tympani (mastoid segment) will lead to unilateral loss of taste to the anterior 2/3 of the tongue. A lesion above the pyramidal eminence (at junction of tympanic and mastoid segments) will lead to hyperacusis due to involvement of the branch to stapedius.

Reference: eMedicine.com

Credit: Dr Laughlin Dawes