An analysis of facial nerve function in irradiated and unirradiated facialnerve grafts

Purpose: The effect of high-dose radiation therapy on facial nerve grafts i s controversial. Some authors believe radiotherapy is so detrimental to the outcome of facial nerve graft function that dynamic or static slings shoul d be performed instead of facial nerve grafts in all patients who are to re ceive postoperative radiation therapy. Unfortunately, the facial function a chieved with dynamic and static slings is almost always inferior to that af ter facial nerve grafts. In this retrospective study, we compared facial ne rve function in irradiated and unirradiated nerve grafts. Methods and Materials: The medical records of 818 patients with neoplasms i nvolving the parotid gland who received treatment between 1974 and 1997 wer e reviewed, of whom 66 underwent facial nerve grafting. Fourteen patients w ho died or had a recurrence less than a year after their facial nerve graft were excluded. The median follow-up for the remaining 52 patients was 10.6 years. Cable nerve grafts were performed in 50 patients and direct anastom oses of the facial nerve in two. Facial nerve function was scored by means of the House-Brackmann (H-B) facial grading system. Twenty-eight of the 52 patients received postoperative radiotherapy. The median time from nerve gr afting to start of radiotherapy was 5.1 weeks. The median and mean doses of radiation were 6000 and 6033 cGy, respectively, for the irradiated grafts. One patient received preoperative radiotherapy to a total dose of 5000 cGy in 25 fractions and underwent surgery 1 month after the completion of radi otherapy. This patient was placed, by convention, in the irradiated facial nerve graft cohort. Results: Potential prognostic factors for facial nerve function such as age , gender, extent of surgery at the time of nerve grafting, preoperative fac ial nerve palsy, duration of preoperative palsy if present, or number of pr evious operations in the parotid bed were relatively well balanced between irradiated and unirradiated patients. However, the irradiated graft group h ad a greater proportion of patients with pathologic evidence of nerve invas ion (p = 0.007) and unfavorable type of nerve graft (p = 0.04). Although th e irradiated graft cohort had more potentially negative prognostic factors, there was no difference in functional outcome (H-B Grade III or TV) betwee n irradiated and unirradiated graft patients. H-B Grades III, IV, V, and VI were the best postoperative facial nerve functions achieved in 35%, 39%, 1 3%, and 13% of patients, respectively. The patient with preoperative radiot herapy never recovered any facial nerve function (H-B Grade VI). Median tim e to best facial nerve function after surgery was longer in the irradiated patients (13.1 vs. 10.8 months), but this was not statistically significant (p = 0.10). Presence of preoperative facial nerve palsy (p = 0.005), durat ion of preoperative palsy (p = 0.003), and age greater than 60 years at the time of grafting (p = 0.04) were all negative prognostic factors for achie ving a functional facial nerve on univariate analysis. Analysis of age as a continuous variable (p = 0.12) and pathologic evidence of nerve invasion ( p = 0.1) revealed a trend toward negative prognostic factors. Gender, numbe r of previous operations in the parotid bed, extent of surgery at the time of nerve grafting, and type of grafting procedure were not significant prog nostic factors. Whether radiotherapy was delivered less than 6 weeks after nerve grafting or more than 6 weeks had no impact on achievement of a funct ional facial nerve. Conclusion: Negative prognostic factors for achieving a functional facial n erve in our series include the presence of preoperative facial nerve palsy, duration of preoperative palsy, and age greater than 60 years. Radiotherap y was not a negative prognostic factor. Comparing irradiated and unirradiat ed grafts revealed no difference in best facial nerve function achieved, de spite the presence of a greater proportion of negative prognostic factors i n the irradiated group. Therefore, planned postoperative radiation therapy is not a contraindication to facial nerve grafting. Consideration for regen eration of the facial nerve should not influence the timing of postoperativ e radiotherapy, because early initiation of radiotherapy after facial nerve grafting did not have a deleterious effect on facial nerve function. Howev er, the time required to attain best facial nerve function postoperatively may be slightly longer in irradiated patients. (C) 2000 Elsevier Science In c.