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.