[Frequency characteristics of utricular damage and pathological ultrastructural analysis in patients with unilateral...

Objective: To investigate the frequency characteristics of utricular damage and pathological ultrastructural features in patients with unilateral Ménière's disease (MD). Methods: This cross-sectional study included 104 patients with unilateral MD admitted to Shandong Provincial ENT Hospital between July 2019 and September 2021. There were 50 males and 54 females, aged 21-72 years (mean 46.4 years). Disease duration ranged from 1 month to 40 years (median duration 4.5 years). All patients underwent pure-tone audiometry and vestibular function tests, including caloric test, video head impulse test (v-HIT), vestibular evoked myogenic potentials (VEMP), and unilateral centrifugation subjective visual vertical (UC-SVV). Utricular maculae from 4 patients who underwent labyrinthectomy for intractable vertigo were observed under light microscopy and transmission electron microscopy (TEM). Type Ⅰ and Type Ⅱ hair cells were counted and compared, and common pathological changes of the utricular macula were observed. SPSS 19.0 software was used for statistical analysis. Results: According to pure-tone average, patients were clinically staged as follows: stage Ⅰ, 26 cases; stage Ⅱ, 26 cases; stage Ⅲ, 39 cases; and stage Ⅳ, 13 cases. The abnormality rates of vestibular function tests were as follows: 63.5% by caloric test (66/104), 32.7% by v-HIT (34/104), 65.4% by cervical VEMP (cVEMP) (68/104), 68.3% by ocular VEMP (oVEMP) (71/104), and 58.7% by UC-SVV (61/104). There was a statistically significant difference in the abnormality rates between the caloric test and v-HIT, which assessed low-frequency and high-frequency semicircular canal function, respectively (χ²=7.775, P=0.005). However, there was no statistically significant difference in the abnormality rates between oVEMP and UC-SVV, which assessed high-frequency and low-frequency utricular function, respectively (χ²=0.495, P=0.482). Pathological examination under light microscopy revealed monolayer degeneration of the sensory epithelium in the utricular macula, with varying degrees of reduction in the number of both Type Ⅰ and Type Ⅱ hair cells and absence of cilia. No significant difference was observed in the quantity between Type Ⅰ and Type Ⅱ hair cells. TEM examination showed numerous vacuoles formed by swollen endoplasmic reticulum in the hair cells, dilated perinuclear cisternae, edema, scattered lipid droplets, and lysosome distribution within the cells. Occasional mitochondrial swelling was also observed. Conclusions: No frequency-specific characteristics were found in the oVEMP and UC-SVV test results of patients with unilateral MD. Damage was commonly observed in both Type Ⅰ and Type Ⅱ hair cells of the utricular macula, with no significant differences noted in cell count or the degree of damage between the two types.