Visual hemi-inattention after ventrolateral thalamotomy.

Ten patients undergoing left ventrolateral thalamotomy (LVLT) and 11 patients undergoing right ventrolateral thalamotomy (RVLT) for Parkinsonian or essential tremor performed a test of visual searching for parallel lines before and after surgery. On average RVLT caused impairment of searching only on the left side. LVLT affected searching on both sides, with the impairment being slightly more marked on the right side, The tendency to initiate searching from the side ipsilateral to the lesion increased after VLT. The results indicated that unilateral VLT caused hemi-inattention in visual searching, which deficit is possibly related to the transient motor neglect usually observed in the extremities contralateral to VLT.