Abstract
The stapedial reflexes were measured in cases of acoustic neuromas, brainstem lesions and unilateral hearing loss, and their diagnostic significance for retrocochlear lesions were investigated.
1. The following findings could strongly suggest retrocochlear lesions or acoustic neuroma: a) when stapedial reflexes are absent in cases with hearing loss below 60dB in speech frequencies, b) when the reflex threshold in the diseased side is more than 15dB that in the normal side.
2. In small acoustic neuroma confined to the internal auditory meatus, reflex decay is frequently seen, even though the stapeidial reflex is within normal limits.
3. With the measurement of stapedial reflex threshold and reflex decay, the findings suggesting acoustic tumor or retrocochlear lesions were found in 78% of cases with hearing loss below 60dB in speech frequencies and in 86% of cases in which hearing could in any way be obtained within the measurable areas.
4. -Both the measurement of crossed and uncrossed stapedial reflex is useful in the diagnosis of brainstem lesions. The stapedial reflex was found to be normal in the central auditory pathways, such as cortical or subcortical lesions.
5. In intramedullary lesions, especially in lower pontine lesions, there are some cases with normal pure tone and speech audiogram, but with abnormal findings in directional hearing and with reflex decay.
6. The measurement of the stapedial reflex, together with the other audiometric tests could be applied as a diagnostic tool in central auditory disorders.
