Glycerol test is used for diagnosis of ?
Ans. is 'a' i.e., Meniere's disease Investigations in Meniere's disease 1) Tuning fork tests Tuning fork tests show sensorineural hearing loss :- Rinne test - Positive Weber test - Lateralized to better ear ABC test - Reduced in affected ear 2) Pure tone audiometry There is sensorineural hearing loss with affection of lower frequencies in early stages and the curve is of rising type. When higher frequencies are involved, curve becomes flat or a falling type. 3) Speech audiometry Discrimnation score is usually 55-85%. 4) Special audiometry tests Indicate cochlear lesion :- Recruitment test is positive SISI (sho increment sensitivity index) score is better than 70% Tone decay test shows decay of less than 20 dB. 5) Electrocochleography Normally, ratio of summating potential (SP) to action potential (AP) is 30%. In Meniere's disease, SP/AP ratio is greater than 30% and is diagnostic of Meniere's disease. 6) Caloric test It shows reduced response on the affected side. Often, it reveals a canal paresis on the affected side (most common) but sometimes there is directional preponderance to healthy side or a combination of both canal paresis on the affected side and directional preponderance to opposite side. 7) Glycerol test Glycerol reduces endolymphatic pressure due to its dehydrating propey and thus causes an improvement in hearing. 8) Reverse glycerol test Performed by using acetazolamide. Shows deterioration in the pure tone threshold and speech discrimination score.
Meniere's disease
Otosclerosis
ASOM
Malignant otitis externa