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3 Head and Neck

structions of multiplanar data or dedicated temporal bone CT can provide more de-tailed anatomic assessment.

Longitudinal fractures do not typicallyinvolve the otic capsule. Hemorrhage with-in the mastoid air cells and tympanic cavitycauses an immediate conductive hearingloss that resolves over time. Some patientswill have more complicated injuries withossicular dislocation and/or tympanicmembrane disruption. In the case of os-sicular dislocation, conductive hearing lossmay not resolve without surgical repair. Incontrast, fractures that involve the otic cap-sule are usually transversely oriented andare more likely to result in immediate andirreversible sensorineural hearing loss, CSFotorrhea, and facial nerve injury (Fig. 3.10).

◆Temporal Bone Fracture

High-energy impact to the lateral skull can result in fractures through the mas-toid and temporal bone. They are best de-scribed by the fracture orientation relative to the axis of the petrous temporal bone and by involvement of the otic capsule or labyrinth. Patients may have conductive or sensorineural hearing loss, facial paralysis (peripheral seventh-nerve palsy), bruising about the mastoid eminence (Battle sign), or periorbital ecchymosis (raccoon eyes).

Indirect findings are usually evident on noncontrast head CT and include mastoid air cell opacification, fluid within the ex-ternal auditory canal and middle ear, air in the temporomandibular fossa, and in-tracranial air adjacent to the petrous bone. High-resolution axial and coronal recon-

Fig. 3.10a–da,b Otic capsule–violating (transverse) fracture. The fracture is oriented perpendicular to the axis of the petrous temporal bone and crosses the vestibule, the posterior semicircular canal, and the lateral semicir-cular canal. The tympanic cavity and epitympanum are completely opacied.

c,d Otic capsule–sparing (longitudinal) fracture. This fracture is parallel to the axis of the temporal bone and results in incudomalleolar dislocation and intratympanic hematoma. The otic capsule is intact.