Vascular findings in the facial nerve canal in human temporal bones with diabetes mellitus.

OBJECTIVE: To identify pathological changes to vessels in the facial nerve canal among patients with diabetes mellitus.
DESIGN: Histopathologic human temporal bone study. SUBJECT: This study examined 26 temporal bones from 13 patients with type 1 diabetes mellitus and 40 temporal bones from 20 patients with type 2 diabetes mellitus. Temporal bones from patients with type 2 diabetes mellitus were divided into 2 groups according to the method of diabetes management: insulin (n = 11) and oral hypoglycemic agents (n = 9). For the control groups, 16 age-matched normal temporal bones from 11 subjects were recruited for type 1 diabetes mellitus and 11 age-matched normal temporal bones from 8 subjects were recruited for type 2 diabetes mellitus. MAIN OUTCOME MEASURES: Thicknesses of vessel walls in the labyrinthine, tympanic, and mastoid portions of the facial nerve canal were examined under light microscopy.
RESULTS: Vessel walls for all portions of the facial nerve canal were significantly thicker in diabetic patients than in normal controls for both types 1 and 2 diabetes. In type 2 diabetic patients, vessel wall thickness was significantly greater in patients treated with insulin therapy than in patients treated via oral hypoglycemic agents.
CONCLUSION: The facial nerve in patients with diabetes mellitus is ischemic compared with normal controls. These findings suggest a histologic basis for the high incidence and difficulty in achieving improvement of facial nerve palsy in patients with diabetes mellitus.