HSC Section 8_April 2017

MIDDLE FOSSA APPROACH FOR TRAUMATIC FACIAL PARALYSIS

TABLE 2.

Location of the facial nerve injury diagnosed intraoperatively

linear regression analysis was performed to assess differences in outcome with timing of surgical intervention (37–38).

Peri-geniculate

66.7% 22.2% 11.1%

RESULTS

Tympanic segment Mastoid segment Labyrinthine segment

There were 18 patients who met inclusion criteria. The average patient age at the time of surgical decompression was 28 years and 72.2% of patients were men. Temporal bone CT scan demonstrated 94.4% of patients had otic capsule-sparing fractures and 5.6% had otic capsule- violating fractures. An isolated MF approach was per- formed on nine patients, whereas, nine patients had combined MF and transmastoid exposure. An anatomi- cally intact facial nerve was identified in 11 patients and an irreversible nerve injury, which required nerve graft- ing was identified in seven patients. The average duration of follow-up was 36 months. The mechanisms of injury are summarized in Table 1 and the location of facial nerve injury diagnosed intraoperatively in Table 2. For patients who underwent MF decompression and an intact facial nerve was identified (n ¼ 11), 72.7% regained normal or near normal facial function (HB I or II) within 1 year after surgery. Of these patients with intact nerves, 27.3% improved to normal (HB I), 45.5% improved to near normal (HB II), and all remaining patients, 27.3%, improved to a HB III (Fig. 1). At surgery, seven patients were found to have injuries that required nerve grafting, and all seven (100%) improved to HB III. For all patients, facial nerve function signifi- cantly improved after surgery ( p < 0.01). There was no difference in final facial nerve outcome depending on the patient’s sex, side of paralysis, ENoG degeneration, or type of temporal bone fracture. In the subset of patients with an intact facial nerve at decompression, the single patient older than 60 years had a HB III facial outcome. The average time from onset of traumatic facial para- lysis to MF decompression with or without nerve grafting was 12.4 days (range: 9–14 days; median: 12 days). Analyzing the final facial nerve grade for patients that did not require nerve grafting based on the number of days from the beginning of facial paralysis to surgical decom- pression demonstrated a moderate positive correlation ( R 2 ¼ 0.55; p < 0.01) (Fig. 2). Regression analysis with a best-fit linear line shows a statistically significant improvement in final HB grade the earlier the decom- pression was performed. Due to significant preoperative conductive hearing losses, the preoperative bone PTA was compared with the postoperative air PTA to illustrate their preoperative

5.6%

inner ear function and their postoperative hearing result. Results of patients’ hearing tests are summarized in Table 3. The average difference in pure tone average and word recognition after surgery was þ 2.9 dB and þ 3.3%, respectively ( p ¼ 0.44; p ¼ 0.74) and 1 of 18 patients experienced a significant change in final hearing results ( > 8 dB loss or > 8% decrease in WRS). According to a standardized classification of surgical complications (39), minor complications (Grade I) occurred in 16.7% of patients, including vertigo, autoph- ony, and tinnitus, and all resolved by 3 months after surgery. One patient developed a surgical wound infec- tion and abscess, 9 days postoperatively, which required an incision and drainage and IV antibiotics (Grade III). There were no other major complications. Most patients with traumatic facial paralysis can recover normal facial function with conservative treat- ments such as observation or steroids, however, a fraction of patients are at increased risk for permanent facial nerve dysfunction. Identifying these high-risk patients requires a clinical exam with complete facial paralysis (HB VI) identified immediately after the injury that is not recovering, electrodiagnostic testing with ENOG show- ing > 90% degeneration, and EMG with absent voluntary potentials. This subset of patients is at increased risk for a poor long-term outcome and benefit from decompression surgery to identify those with an irreversibly injured facial nerve. This procedure is also therapeutic to those patients with bony fragments and significant edema constricting the facial nerve because alleviating this impingement allows the facial nerve to recover. DISCUSSION

TABLE 1.

Mechanisms of injury of the temporal bone fracture

Motor vehicle

66.7% 11.1%

Falls

Water skiing

5.6% 5.6% 5.6% 5.6%

ATV

FIG. 1. Final facial nerve HB grade in patientswith an intact facial nerve after MF decompression compared with patients requiring nerve grafting.

Mining

Snowmobile

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