Audiogram

Abstract: We characterised the clinical and neuro-otological characteristics of patients with Susac syndrome. The medical records of 30 patients with Susac syndrome were reviewed for details of their clinical presentation and course, neuro-otological symptoms, investigation results including audiology and vestibular function tests, treatment and outcomes. Our findings demonstrate that 29 of our 30 patients with Susac syndrome developed neuro-otological symptoms such as hearing loss, disequilibrium, tinnitus or vertigo during their disease course. Hearing loss was the most common neuro-otological symptom occurring in 93% of patients. A rising configuration of low-frequency greater than the high-frequency sensorineural hearing loss was the most characteristic finding on audiological testing (37% of reviewed audiograms). Disproportionately poor speech discrimination was identified in 20% of cases, and one case demonstrated a retrocochlear pattern on electrophysiological testing. Four patients required hearing aids and a further two patients required a cochlear implant due to severe hearing loss. Two out of two treated patients had improvements in hearing after the prompt administration of corticosteroids, indicating the potential for recoverable hearing loss if relapses are treated early. Effects on vestibular function were variable in ten patients who were tested, with most showing preservation of function despite significant hearing loss. Neuro-otological symptoms in Susac syndrome are almost universal. In the correct clinical context, a rising configuration of low to high-frequency sensorineural hearing loss should prompt consideration of Susac syndrome. Treatment of inner ear symptoms in Susac syndrome requires further research as early immunotherapy may be beneficial.

Abstract: Four new approaches to the diagnostic problem of differentiating cochlear and retrocochlear disorders are described. The four procedures are: 1) the forward-backward discrepancy in the Bekesy audiogram; 2) the Bekesy Comfortable Loudness (BCL) test; 3) the rollover of the performance-intensity function for PB words; and 4) the acoustic reflex. Findings on these new auditory test procedures were contrasted in three groups of patients having either confirmed cochlear, VIII nerve or brain stem disorders. Results suggest that suprathreshold levels are a more fruitful area in which to explore VIII nerve symptomatology than threshold levels.

Abstract: The possible effects of ultrasonic scaling of all maxillary teeth for a total of 5 min on the inner ears of 20 healthy young adults, 22-36 years of age, were investigated by means of pure tone audiometry. Audiograms were obtained just before and immediatley after scaling. Temporary shifts in hearing threshold (TTS) of 10-20 dB, mostly at 7--8 kHz, ersisting for up to 30 min, were recorded in eight of the individuals. Three patients reported high-pitched tinnitus lasting for 20-30 min after ultrasonic scaling. When audiograms were obtained 3--5 weeks later in the same 20 individuals before and immediatley after they had kept their mouths open for 5 min, but with no scaling performed, TTS was recorded in three of the individuals. TTS after opening only was less pronounced than TTS after ultrasonic scaling, both with regard to severity and duration.

Abstract: We measured the auditory sensitivity of the barn owl ( Tyto alba ), using a behavioural Go/NoGo paradigm in two different age groups, one younger than 2 years ( n = 4) and another more than 13 years of age ( n = 3). In addition, we obtained thresholds from one individual aged 23 years, three times during its lifetime. For computing audiograms, we presented test frequencies of between 0.5 and 12 kHz, covering the hearing range of the barn owl. Average thresholds in quiet were below 0 dB sound pressure level (SPL) for frequencies between 1 and 10 kHz. The lowest mean threshold was –12.6 dB SPL at 8 kHz. Thresholds were the highest at 12 kHz, with a mean of 31.7 dB SPL. Test frequency had a significant effect on auditory threshold but age group had no significant effect. There was no significant interaction between age group and test frequency. Repeated threshold estimates over 21 years from a single individual showed only a slight increase in thresholds. We discuss the auditory sensitivity of barn owls with respect to other species and suggest that birds, which generally show a remarkable capacity for regeneration of hair cells in the basilar papilla, are naturally protected from presbycusis.