Effects of type 2 diabetes mellitus on cochlear structure in humans.
OBJECTIVE
To evaluate the effects of type 2 diabetes mellitus on cochlear elements in humans.


METHODS
Comparative study of the histopathologic characteristics of human temporal bones.


METHODS
Otopathology laboratory in a tertiary academic medical center.


METHODS
Temporal bones from 18 patients with type 2 diabetes mellitus were divided into 2 groups according to the method of management of diabetes: insulin in 11 patients (mean age, 51.9 years; age range, 44-65 years) and oral hypoglycemic agents in 7 patients (mean age, 54.4 years; age range, 45-64 years). The diabetic groups and 26 age-matched controls (mean age, 52.9 years) were examined using light microscopy, and the cochlear changes were compared between groups.


METHODS
Morphometric measurements of vessel wall thickness in the basilar membrane and stria vascularis were made in all turns of the cochlea at the midmodiolar level. Area measurements of the stria vascularis were made in all turns of the cochlea at the midmodiolar level. Cochlear reconstructions and standard cytocochleograms were prepared using an oil immersion objective. The number of spiral ganglion cells was determined for each segment of the cochlea. Comparisons were made in each segment between diabetic and control groups.


RESULTS
In the insulin group, walls of the vessels of the basilar membrane and stria vascularis in all turns were significantly thicker than those of controls. Walls of the vessels of the stria vascularis in the basal turn were also significantly thicker in the oral hypoglycemic group than in controls. Atrophy of the stria vascularis in most turns of the insulin group and the lower middle turn of the oral hypoglycemic group was significantly greater than in the controls. Loss of cochlear outer hair cells was significantly greater in the lower and upper basal turns in both diabetic groups. No significant difference was found in the number of spiral ganglion cells or inner hair cells between groups.


CONCLUSIONS
This study demonstrates that cochlear microangiopathy and degeneration of the stria vascularis and cochlear outer hair cells are found in patients with type 2 diabetes mellitus.
Fukushima
Hisaki
H
International Hearing Foundation, Department of Otolaryngology, Otitis Media Research Center, University of Minnesota, and Minnesota Ear, Head and Neck Clinic, Minneapolis, USA.
Cureoglu
Sebahattin
S
Schachern
Patricia A
PA
Paparella
Michael M
MM
Harada
Tamotsu
T
Oktay
Mehmet F
MF
D000284:Administration, Oral; D000328:Adult; D000368:Aged; D001489:Basilar Membrane / Q000473:pathology; D003051:Cochlea / Q000473:pathology*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000473:pathology*; D005260:Female; D018072:Hair Cells, Auditory, Outer / Q000473:pathology; D006801:Humans; D007004:Hypoglycemic Agents / Q000008:administration & dosage; D007328:Insulin / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D013136:Spiral Ganglion / Q000473:pathology; D013316:Stria Vascularis / Q000473:pathology; D013701:Temporal Bone / Q000473:pathology
D007004:Hypoglycemic Agents; D007328:Insulin