HSC Section 3 - Trauma, Critical Care and Sleep Medicine

Surgical Management of Acute Facial Palsy

crush or penetrating injury to the nerve caused by displaced bone fragments, and sometimes even transection of the nerve. Radiologic studies (temporal bone computed tomography [CT] scans: fine-cut, axial, and coronal planes; bone win- dow) therefore become important in assessing the likely sites of facial nerve injury ( Figs. 3–5 ). Facial paresis or paralysis can present either acutely after injury or in a delayed fashion. For patients with complete facial paralysis and radiographic evidence of fracture extending to the perigeniculate region, the electrophysiologic testing algo- rithm is commenced much like in Bell palsy. Electrophysiologic testing may be abbre- viated if imaging reveals obvious nerve displacement and transection, which represents a clear indication for surgical exploration and repair. For patients without obvious nerve transection or impingement, our institution uses the same criteria for surgical intervention as in Bell palsy. However, it should be noted that these criteria have not been studied in a specific cohort of patients who lack evidence of nerve tran- section or impingement on imaging. All patients undergo bone and air conduction audiometry as well as electrophysiologic testing before surgical intervention. MRI or temporal bone CT imaging may be ob- tained but is not necessary. A preoperative Stenver view plain radiograph may aid in determining the depth of the semicircular canal from the MCF floor. 42 The anes- thesia team should be informed that long-acting paralytic agents may not be used. Endotracheal intubation is performed and the bed is rotated 180 . An arterial line, tem- perature probe, and urinary catheter are placed. Intraoperative hearing monitoring us- ing auditory brainstem response is an option but is not routinely used at our institution for this procedure. Facial nerve monitoring leads are applied. Prophylactic antibiotics, corticosteroids, and mannitol (0.5 g/kg ideal weight) are given. The end-tidal carbon dioxide level is decreased to less than 30 mm Hg by hyperventilation. The head may be positioned via pinning, a horseshoe, or a circular gel headrest. At our institu- tion, the head is rested on a circular gel headrest with the ear of the affected side fac- ing the ceiling. If necessary, the incision site is shaved. The planned incision site is injected with local anesthetic and epinephrine. The operative site is prepared and draped. DESCRIPTION OF SURGERY FOR ACUTE FACIAL PARALYSIS Facial Nerve Decompression via Middle Cranial Fossa Approach

Fig. 3. Coronal-section temporal bone CT scan showing comminuted fracture ( red arrow ) of the middle fossa floor causing crush injury to the perigeniculate section ( white arrow ) of the facial nerve. This patient developed delayed facial paralysis. MCF approach was used for facial nerve decompression.

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