DOI: 10.1097/TA.0b013e3181e9c14d

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PMID: 21610382

Issn Print: 0022-5282

Publication Date: 2011/04/01


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Air in Temporomandibular Joint: An Indirect, Specific CT Sign of Temporal Bone Fracture in the Setting of Head Trauma

Anoosh Montaser; Manish Goyal; Mark A. Weiner

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Excerpt

Fractures of the temporal bone can be difficult to detect both clinically and radiographically but can have serious potential complications including middle ear ossicle disruption, facial nerve damage, dural tear with cerebrospinal fluid leak, and rarely, injury to the carotid artery or jugular vein.1 Computed tomography (CT) is the optimal modality for detection of temporal bone fractures. However, because most emergent CT studies of head are done with wide, often 2.5 mm to 5 mm, collimation, not all acute temporal bone fractures are detected unless narrow collimation, high-resolution temporal bone CT is performed.2,3 When routine CT scan disclose no obvious fracture, indirect signs can indicate the likelihood of an occult temporal bone fracture. Finding air in the temporomandibular joint (TMJ) on a head CT, in a patient with trauma, is a previously described but infrequently documented indirect sign of a temporal bone fracture.1,4
A previously healthy 23-year-old man was brought to the emergency department with chief complaint of seizure of ∼6 minutes duration after assault and head trauma. He was also experiencing severe left-sided headache. Patient was awake, alert, and oriented. His vital signs were stable. There was left temporal soft-tissue swelling without laceration or ecchymosis. Neurologic examination was within normal limits.
Routine head CT (wide collimation; 3.8-mm slice thickness) at admission demonstrated no intracranial findings or calvarial fracture. A small amount of air was observed in the left TMJ but no temporal fracture was seen (Fig. 1). The mastoid air cells and middle air cavity were clear. As a result of the reported strong association of TMJ air and temporal bone skull base fracture, a dedicated temporal bone CT was recommended by the radiologist. A high-resolution (narrow collimation; 0.6-mm slice thickness; with coronal reformatting) temporal bone CT was performed about 2 hours, which later demonstrated a linear fracture of the left temporal bone, opacification of few mastoid air cells, and small air-fluid (air-blood) level in the left middle air cavity (Fig. 2).
The temporal bone is involved in ∼20% of all skull fractures.1 Two-thirds of all fractures involving the temporal bone extend through its tympanic portion.4 The close proximity of this part of the temporal bone to the TMJ results in passage of air from the auditory canal into the joint.1,4 In a study by Betz and Wiener,1 all 26 patients with TMJ air on routine head CT had clinical and/or CT findings of temporal bone fractures. In the setting of trauma, finding air in the TMJ on a head CT is specific, although indirect sign of a temporal bone fracture that may otherwise be inconspicuous.
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