Quantitative Assessment of Cochlear Histopathologic Findings in Patients With Suppurative Labyrinthitis

Better understanding of the effects of suppurative labyrinthitis (SL) on cochlear elements will aid the development of new approaches to treat its sequelae and complications in the ear.

To quantitatively evaluate the effects of SL on cochlear elements in humans.

A comparative study was conducted at a tertiary academic medical center from October 20, 2014, to January 3, 2015, of the histopathologic characteristics of 28 archived human temporal bone samples from 19 deceased patients with SL and 20 temporal bone samples from 14 deceased, age-matched controls.

Evaluation of archived human temporal bone samples.

The locations of SL in the inner ear and the degree of endolymphatic hydrops were noted; the area of the stria vascularis and the spiral ligament in all turns of the cochlea at the midmodiolar level and in the adjacent 2 sections were measured; and the number of remaining outer and inner hair cells of the cochlea were counted to calculate the loss of both types of cells. To evaluate the loss of fibrocytes in the spiral ligament, a rating scale in each cochlear turn was used. For each segment of the cochlea, the number of spiral ganglion cells was determined. Outcomes between the group with SL and the control group were compared.

Of the 28 temporal bone samples from the 19 deceased patients (16 men and 3 women; mean [SD] age, 23.1 [24.6] years) with SL, all showed SL in the scala tympani of the basal turn. In the group with SL vs the control group, the mean (SD) loss of outer hair cells was significantly higher in the lower (28.6% [11.4%] vs 12.4% [6.2%]; P = .02) and upper (22.3% [9.7%] vs 8.8% [3.2%]; P = .01) basal cochlear turn, the mean (SD) loss of inner hair cells was significantly higher in the lower (15.4% [6.7%] vs 2.6% [1.1%]; P = .02) and upper (10.6% [4.6%] vs 2.2% [0.7%]; P = .03) basal cochlear turn, the mean (SD) total number of spiral ganglion cells (28,132 [2068] vs 30,358 [2036]; P = .001) and the mean (SD) number of spiral ganglion cells in segment I (3554 [847] vs 4223 [649]; P = .003) was significantly decreased, the mean (SD) degree of atrophy of the stria vascularis in the lower (8455 [924] vs 9368 [1049] μm2; P = .003) and upper (7911 [837] vs 8474 [813] μm2; P = .02) basal cochlear turn was significantly greater, and the degree of endolymphatic hydrops was significantly greater (10 bone samples [36%] vs 1 [5%]; P = .006). No significant differences were found between the 2 groups in the number of fibrocytes and in the presence of atrophy of the spiral ligament in any cochlear turn.

This study demonstrates that SL can lead to cochlear damage, especially in the basal turn of the cochlea. These pathological observations have formed the basis for clinical findings of hearing loss and tinnitus detected in those patients with SL.