Pneumolabyrinth after temporal bone fracture: documentation by high-resolution CT.

The incidence and clinical features of temporal bone fractures have been well documented in the medical literature. Characteristically, longitudinal fractures account for 80% of the total [1, 2] and result from trauma to the parietal and temporal regions of the skull [3]. The fracture line starts at the tympanic annulus and runs parallel to the petrous pyramid, traversing the external auditory canal, mastoid air cells, tympanic membrane, and ossicles before it extends across the floor of the middle cranial fossa to the area of the trigeminal ganglion. Facial weakness occurs in about 25% of the cases and is usually temporary [4]. Hearing loss is generally of the conductive type, although often there is some degree of neurosensory deafness [5]. Transverse fractures make up 10%-20% of the total and classically result from trauma to the occiput. The fracture line starts at the floor of the middle fossa and runs perpendicular to the petrous pyramid, traversing the vestibule, cochlea, and the labyrinthine part of the facial nerve near the geniculate ganglion. There is usually complete loss of cochlear and vestibular function on the side of the injury. The facial nerve is involved in almost half of the cases, often requiring surgical decompression. Plain films of the temporal bone often do not reveal the site of fracture [6], although the evolution of hypocycloidal polytomography has tremendously aided in anatomic localization [7]. The advent of high-resolution computed tomography (CT) of the temporal bone [8, 9] has added a new dimension of accuracy to diagnosis.