Longitudinal and transverse fractures of the temporal bone may disrupt the facial nerve. Longitudinal fractures are more external, occurring in the plane of the external auditory canal (EAC). They are apt to disrupt the ossicles in the middle ear. They cause facial nerve problems about 20 % of the time and are the much more prevalent type. Transverse fractures are rarer, traversing the petrous apex from anterior to posterior. These have a much higher incidence of facial paralysis, as well as vesti-bulocochlear damage. Immediate facial paralysis warrants surgical exploration and decompression. Delayed onset with incomplete paralysis will probably recover spontaneously.
Middle ear and mastoid surgery are the dreaded causes of facial injury in the ENT specialty. Mastoidectomy is the most common cause, usually
86 6 Disorders of the Facial Nerve from an injury to the second turn, posterior to the stapes. This can be done in an effort to remove cholesteatoma or chronically infected tissue that closely involves the nerve. Re-approximation or grafting of the damaged ends can result in a recovery of function, although the result may take 6 months or more to show up; regeneration occurs at roughly 1 cm a month. Stapedectomy can also result in facial nerve injury. The fallopian canal is immediately superior to the oval window and can be dehiscent here, rendering it susceptible to damage. Distal to the ear, parotid tumors, or their surgical removal, can endanger the nerve. Adenoid cystic carcinoma is a major culprit in that it is malignantly invasive and tends to grow along perineurium, the lining of nerves.
Finally, traumatic forceps deliveries have caused neonatal facial paralysis, either by temporal bone fracture or by direct compression beneath the ear. These are also associated with hearing damage and are extremely rare. We might group penetrating injuries together with this; these may occur through the ear canal or beneath it at the stylomastoid foramen and posterior parotid gland.
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