Resident Manual of Trauma to the Face, Head and Neck

Chapter 6: Temporal Bone Fractures

EMG is a volitional test performed by intramuscular recording elec- trodes to assess for voluntary action potentials, which correlate with a good prognosis. The EMG patterns can also include fibrillation poten- tials, indicating degeneration and polyphasic potentials, which in turn indicate recovery. ENOG is an evoked test that compares the compound action potential of the two sides of the face to determine the percent- age of degeneration on the affected side. Wallerian degeneration, progressive nerve degeneration distal to the site of injury, occurs over 3–5 days post-injury. Early testing may produce erroneous results if Wallerian degeneration is not complete. This is why serial electrophysi- ologic testing is performed. Controversy exists regarding the indications for facial nerve exploration and decompression. Data regarding prognostic ENOG use in traumatic facial nerve injury are limited. Data on ENOG use, steroids, and decom- pression in Bell’s palsy are more extensive, and traumatic facial nerve management principles have been partly extrapolated from the data. It is generally accepted that patients with >95 percent severe degenera- tion have a poor prognosis and should be considered for surgery. Figure 6.5 presents an algorithm for evaluating and managing patients with facial nerve injury.

Figure 6.5 Algorithm for evaluating and managing patients with facial nerve injury.

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Resident Manual of Trauma to the Face, Head, and Neck