Intratemporal Bone Trauma Workup

Updated: May 31, 2018
  • Author: Noah Massa, MD, FRCSC; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Workup

Imaging Studies

See the list below:

  • CT scanning

    • A high-resolution CT scan of the temporal bone can reveal findings diagnostic of temporal bone fracture, as depicted in the images below.

      High-resolution CT scan of the temporal bone demon High-resolution CT scan of the temporal bone demonstrates a longitudinal temporal bone fracture. Number sign marks the lateral extent of the fracture.
      High-resolution CT scan of the temporal bone demon High-resolution CT scan of the temporal bone demonstrates a transverse temporal bone fracture. Number sign marks the lateral extent of the fracture.
    • Scans reveal multiple fracture lines in most cases, and they may reveal bony impingement of the facial canal.

    • Whenever possible, direct axial and coronal scanning should be performed with 0.6 mm sections and with bone-algorithm views.

    • The integrity of the ossicular chain may also be evaluated with an optimal CT scan.

  • Magnetic resonance imaging

    • Gadolinium-enhanced MRI has been used to study facial nerve injuries after trauma.

    • MRI is often warranted to evaluate concomitant intracranial injuries.

    • The usefulness of MRI is limited because global signal enhancement makes interpretation of images difficult.

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Other Tests

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  • Audiometric testing: When the patient's condition permits, formal audiologic testing should be performed to characterize the extent of hearing loss. The findings help in determining the surgical approach if and when surgery is necessary.

  • Electrophysiologic assessment of the facial nerve: The most common electrodiagnostic tests used are ENoG and EMG.

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Histologic Findings

On a histopathologic level, most injuries to the facial nerve occur in the labyrinthine segment and perigeniculate region, resulting in anterograde and retrograde axonal degeneration. This area includes the narrowest portion of the facial canal, or the meatal foramen, which measures 0.68 mm in diameter. Edema or hematoma in this confined space may result in ischemic injury to the facial nerve secondary to compression of its vascular supply. In some patients, formation of intraneural fibrosis at the site of injury impedes distal regeneration of axons, resulting in poor functional recovery though proximal regeneration seems to occur.

Ulug et al described surgical findings in 11 patients with complete facial paralysis after temporal bone fracture treated with surgical exploration. [8] Fibrosis at the geniculate ganglion was seen in 5 fractures, impingement of the facial nerve by bone spicules at the geniculate ganglion in 2 fractures, disruption or laceration at the origin of the greater superficial petrosal nerve in 2 fractures, and perigeniculate ganglion edema in the remaining 2 fractures.

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