Patterns of music agnosia associated with middle cerebral artery infarcts

The objective of the study is to evaluate if the rupture of an aneurysm loc ated on the middle cerebral artery (MCA) results in disorders of music reco gnition. To this aim, 20 patients having undergone brain surgery for the cl ipping of a unilateral left (LBS), right (RBS) or bilateral (BBS) aneurysm( s) of the MCA and 20 neurologically intact control subjects (NC) were evalu ated with a series of tests assessing most of the abilities involved in mus ic recognition. In general, the study shows that a ruptured aneurysm on the MCA that is repaired by brain surgery is very likely to produce deficits i n the auditory processing of music. The incidence of such a deficit was not only very high but also selective. The results show that the LBS group was more impaired than the NC group in all three tasks involving musical long- term memory, The study also uncovered two new cases of apperceptive agnosia for music. These two patients (N.R. and R.C.) were diagnosed as such becau se both exhibit a clear deficit in each of the three music memory tasks and both are impaired in all discrimination tests involving musical perception . Interestingly, the lesions overlap in the right superior temporal lobe an d in the right insula, making the two new cases very similar to an earlier case report. Altogether, the results are also consistent with the view that apperceptive agnosia results from damage to right hemispheric structures w hile associative agnosia results from damage to the left hemisphere.