الفهرس 
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Abstract
SUMMARY
Sudden hearing loss (SHL) means a sensorineural hearing loss of sudden onset or one that happens in minutes, hours or even in a few days. The hearing impairment varies as far as intensity and sound frequency are concerned, and in general, it is unilateral (98-99% of the cases).
Sudden hearing loss is still a controversial and obscure issue in several aspects. Several factors have been postulated to elicit the etiology of ISSNHL. These include vascular abnormalities, rupture of the inner ear membrane and autoimmune diseases. However, later on viral infection had have received more attention in the etiopathogenesis. The exact mechanism involving viral infection in hearing loss is well documented. Acute viral infection can cause sudden hearing loss. Also, the latent viral infection with reactivation may be considered as explanations of the cochlear injury mechanism. Even though hearing loss can be explained by a blood viscosity change, no evidence of labyrinthine fibrosis and new bone formation, or labyrinthine membrane breaks. Autoimmunity is suggested etiology because of the presence of antibodies against the inner ear. However, there is difficulty to establish a correlation of morphological and clinical aspects of autoimmunity to the hearing loss (Lazarini and Camargo 2006).
In this study, we aimed to provide insight into the relationship between ABR latencies and the level of serum thyroid hormones with the prognosis of ISSNHL. The current study included thirty patients with ISSNHL that developed within the last 72 hours with 30 dB hearing loss at three consecutive frequencies from both sexes admitted from October 2020 to October 2021, attending the Audio-vestibular medicine Outpatient clinic, Beni-Suef University Hospital. The audiological assessment was performed at the Unit of Audio-Vestibular Medicine in Beni-Suef University Hospital.
The main findings of the study revealed that
● A total of 30 patients with newly coded SSNHL met the criteria for inclusion in our study, among which majorities were 20 males (66.67%) and 10 females (33.33%).
● The mean age of the 30 study individuals was 52.40 years, with a standard deviation of 6.07 years. Regarding comorbidities, DM was noted in 9 (30%) patients, in contrast to HTN, which was present in 10 (33.33 %) patients.
● The right ear was involved in 12 (40%) cases and the left ear in 18 (60%) cases; but the affected ear had no side predominance.
● The average time from onset to treatment was 2.23 ± 0.77 days, 6 (20%) patients had one day, 11(36.7%) patients had two days, and 13 (43.3%) had three days.
● According to the initial PTA, patients were divided according to hearing loss degree to mild, moderate, moderately severe, and severe groups, that consisted of 5 (16.7 %), 12 (40%), 4 (13.3%), and 9 (30%) patients, respectively.
● pure tone threshold was statistically significant higher in the affected ear than the unaffected ear, and SDS% was statistically significant lower in the affected ear than the unaffected ear
● Comparison of ABR parameters between the affected and unaffected ears in ISSNHL patients. The absolute latencies of wave I, wave III, and wave V were significantly longer in the affected ears compared with the unaffected ears. The inter-peak latencies of wave I, wave III, and wave V were no significant in the affected ears compared with the unaffected ear.
● The mean latencies of the wave I increased with hearing loss initial severity with statistical significance
● The mean SDS and threshold in dBHL increased with hearing loss initial severity hearing loss with statistical significance
● The SDS and threshold in dBHL were significantly prolonged in the affected ears before treatment compared with after treatment.
● The absolute latencies of wave I, wave III, and wave V were significantly delayed in the affected ears before treatment compared with after treatment.
● Among cases, one patient (3.3%) had preexisting hypothyroidism, and 4 patients (13.33 %) had preexisting hyperthyroidism while 25 patients had normal thyroid functions
● pure tone threshold of the affected ears in patients with ISSNHL before treatment was statistically significant higher in the normal thyroid function patients than the abnormal thyroid function patients, and SDS% was statistically significant lower in in the normal thyroid function patients than the abnormal thyroid function patients
● Wave I, wave III, and wave V absolute latencies showed non-significant differences in the affected ears of patients on treatments for hypothyroidism or hyperthyroidism and the normal patients developing SSNHL.
● Wave I, wave III, and wave V inter-peak latencies showed non-significant differences in the affected ears of patients on treatments for hypothyroidism or hyperthyroidism and the normal patients developing SSNHL.
● Based on hearing recovery, subjects were divided into 3 groups; complete recovery, partial recovery, and non-recovery group. According to pure tone audiometry results before and after treatment respectively, every frequency in patients was calculated with PTA, including the average threshold of hearing level before treatment (PTA-BT, initial hearing) and after treatment (PTA-AT, final hearing), then divided all patients into recovery group and non-recovery group. Hearing recovery was showed in 21 (70%) of 30 cases, including complete recovery in 15(50%) cases, partial recovery in 6 (20 %) cases, and no recovery in 9 (30 %) cases
● There were statistically significant differences between Initial PTA average, and SDS of affected ears of patients.
● In complete recovery group, the mean absolute latency wave I was (1.71±0.16SD), the mean absolute latency wave III was (3.79±0.12SD), the mean absolute latency wave V was (5.78±0.24SD).
● In partial recovery group, the mean absolute latency wave I was (1.72±0.38SD), the mean absolute latency wave III was (3.81±0.91SD), the mean absolute latency wave V was (5.65±0.31SD).
● In no recovery group, the mean absolute latency wave I was (1.43±0.17SD), the mean absolute latency wave III was (3.85±0.31SD), the mean absolute latency wave V was (5.67±0.21SD).
● There was significant correlation between absolute latency wave I and hearing outcomes in all patients with ISSNHL.
● There was non-significant correlation between other ABR parameters and hearing results in all patients with ISSNHL.
● According to Person’s rank correlation coefficient analysis, the ABR parameters; wave I latency and IPI I–III were statistically significantly negatively correlated with initial PTA average, and SDS.
● According to Person’s rank correlation coefficient analysis, initial PTA average at 500Hz was statistically significantly positively correlated with free T3, and at 1kHz, 2kHz, 4kHz, and 8kHz was statistically significantly positively correlated with free T3 and free T4.
● According to Person’s rank correlation coefficient analysis, the ABR parameters; wave V latency was statistically significantly negatively correlated with free T4.
Based on our findings, we recommend further studies on larger sample size and on a large geographical scale to emphasize our conclusion.