Defective auditory recognition after small hemorrhage in the inferior colliculi

We report the case of a male patient with a traumatic small hemorrhage part ially involving the bilateral inferior colliculi without evidence of a temp oral lobe lesion. He was unable to comprehend spoken words although he had intact speech production, reading and writing abilities. Comprehension of e nvironmental sounds was also affected. Among the receptive musical abilitie s, discrimination of intensity, tone and rhythm were preserved, while recog nition of melody was impaired. Audiometry showed normal thresholds for pure tone. Waves I-IV of brainstem auditory evokedpotentials were elicited norm ally, whereas the wave V was elicited with reduced amplitude and prolonged latencies on both sides. The main component of middle latency auditory evok edpotentials, which is evoked over both hemispheres by monaural stimulation to either side in normal subjects, was elicited only over the hemisphere c ontralateral to the ear receiving stimulation. Our patient's auditory findi ngs were similar to those usually found in generalized auditory agnosia. Au ditory agnosia is usually considered as a sign of a bitemporal cortical or subcortical disorder, but, in our patient, a brainstem disorder caused a di sturbance of auditory recognition similar to auditory agnosia due to a bite mporal lesion. Our patient's auditory findings may belong to the category o f a brainstem auditory-processing disorder brought on by a small hemorrhage in the inferior colliculi. In addition, the impairment in our patient impl ies that, in the neural processing of musical parameters, the decoding of i ntensity, tone and rhythm is accomplished at the level of inferior collicul us, whereas further cortical processing is necessary for the appropriate re cognition of melody. (C) 1998 Elsevier Science BN. All rights reserved.