Pattern of localisation error in patients with stroke to sound processed by a binaural sound space processor

Objective-The ability of 46 patients with supratentorial stroke and 15 heal thy subjects to localise sounds was tested using an apparatus with headphon e and sound space processor. Methods-With a binaural sound space processor, sounds were randomly present ed from seven directions in the 180 degree frontal area of the subject at i ntervals of 30 degrees. The subject was asked to imagine a clock face throu gh the horizontal plane passing through the subject's ears with 12 o'clock denoting a sound from directly in front of the subject. After each sound, t he subject indicated the direction from which he or she thought the sound c ame by mentioning the corresponding hour hand on the clock face; therefore, the answer directions were also separated by 30 degrees. A total of 21 sou nds with three sounds from each direction, were presented in random order. The error between the presented direction and the answered direction of eac h sound was calculated. Results-The mean absolute error which does not distinguish whether an error was in the counterclockwise or clockwise direction, was larger in the pati ents with stroke than in the healthy subjects. Overall, the patients with s troke who had right brain damage (n=29) had a larger mean absolute error th an those who had left brain damage (n=17). The patients with right brain da mage did not show any systematic deviation such as a rightward error or lef tward error. Conclusion-A right brain lesion or left brain lesion can cause a patient to have error in sound localisation, and patients with right brain damage gen erally have a larger mean absolute error of sound localisation. The differe nce in the mean absolute error of sound localisation between patients with stroke with right brain damage and those with stroke with left brain damage may be explained by the inattention theory of hemispatial neglect.