Assessment of Balance and Vestibular Functions in Patients with Idiopathic Sudden Sensorineural Hearing Loss

This study investigated the relationship among the severity of hearing impairment,vestibular function and balance function in patients with idiopathic sudden sensorineural hearing loss（ISSNHL）.A total of 35 ISSNHL patients（including 21 patients with vertigo） were enrolled.All of the patients underwent audiometry,sensory organization test（SOT）,caloric test,cervical vestibular-evoked myogenic potential（cV EMP） test and ocular vestibular-evoked myogenic potential（o VEMP） test.Significant relationship was found between vertigo and hearing loss grade（P=0.009）,and between SOT VEST grade and hearing loss grade（P=0.001）.The abnormal rate of o VEMP test was the highest,followed by the abnormal rates of caloric and c VEMP tests,not only in patients with vertigo but also in those without vertigo.The vestibular end organs were more susceptible to damage in patients with vertigo（compared with patients without vertigo）.Significant relationship was found between presence of vertigo and SOT VEST grade（P=0.010）.We demonstrated that vestibular end organs may be impaired not only in patients with vertigo but also in patients without vertigo.The cochlear and vestibular impairment could be more serious in patients with vertigo than in those without vertigo.Vertigo does not necessarily bear a causal relationship with the impairment of the vestibular end organs.SOT VEST grade could be used to reflect the presence of vertigo state in the ISSNHL patients.Apart from audiometry,the function of peripheral vestibular end organs and balance function should be evaluated to comprehensively understand ISSNHL.Better assessment of the condition will help us in clinical diagnosis,treatment and prognosis evaluation of ISSNHL.

Prophylactic effect of Ca^(2+)-deficient artificial perilymph perfusion on noise-induced hearing loss

Objective To investigate the prophylactic effect of low calcium concentration perilymph on noise-induced hearing loss. Methods Forty guinea pigs with normal hearing weighing 250-350 g were assigned to five groups (8 in each group): (1) Ca2+-deficient perilymph perfusion (CDP) for 2 h; (2) white noise (120 dB SPL) exposure (WNE) only for 1 h, (3) combination of calcium-deficient perilymph perfusion and white noise (120 dB SPL) exposure (WNE+CDP); (4) normal artificial perilymph (NAP) perfusion for 2 h; and (5) white noise exposure + normal artificial perilymph perfusion (WNE+NAP) for 2 h. Compound action potentials (CAP) evoked by click was recorded from round window every 15 min. The cochleae from 5 animals in each group were examined with scanning electron microscope. Results The CAP for group 1 experienced a threshold shift (TS) of 15-26 dB, while group 2 yielded a 46-59 dB TS and group 3 a 37-45 dB TS; no threshold shift occurred in group 4. The CAP TS in group 5 was 33-64 dB. The CAP TS of group 3 was less than that of group 2. After one hour of noise exposure, the CAP TS of group 3 were 45.92±2.90 dB and 59.30±3.95dB in group 2. There were significant differences (P<0.05) between groups 3 and 2. The CAP TS of group 3 was less than that of group 5 at the points of 1, 1.5 and 2 h after noise exposure. There was a significant difference between groups 3 and 5 (P<0.01). Stereocilia of 89 OHC3 were in disarray in five cochleae after noise exposure in group 2. The cuticular plates of 8 OHC2,3 sank and the stereocilia became fused in only one animal cochlea after noise exposure in group 3 combined with low calcium perilymph perfusion. Conclusions Low calcium concentration appears to participate in preventing noise-induced hearing loss and the rising of calcium concentrations in inner hair cells after noise exposure, which may have been due to the opening of calcium channels in inner hair cells during noise exposure. The mechanism of the prophylactic effect might be caused by a lower calcium concentration in inner hair cells in the cochlea attenuating the influence of noise exposure on hearing loss; calcium deficient perilymph perfusion prevented calcium accumulation in inner hair cells of the cochlea. The motility of the OHCs might be partially inhibited by low calcium concentration that reduced noise-induced hearing loss in turn.