Language and speech correlates of anatomically verified lesions in thalamic surgery for parkinsonism.

Abstract

The brains of 27 deceased parkinsonian patients who had undergone stereotaxic thalamic surgery were examined anatomically to define the exact location of the surgical lesion in each case. A correlative study was then carried out between the site of these lesions and any language or speech deficits which might have resulted from the thalamic surgery. The following conclusions were drawn: A lesion strictly confined to the ventrolateral nucleus (VL) of the thalamus may be followed by language and/or speech deficits. No definite relationship existed between postoperative language or speech deficits and partial involvement of thalamic nuclei surrounding VL nucleus; H fields of Forel; subthalamic nucleus or red nucleus. Also, mild encroachment on the internal capsule could be tolerated without language or speech deficits, so long as the pyramidal tract remained intact. The size of the lesion was not related to postoperative language and/or speech deficits. Postoperative language deficits were mild and improved in time; whereas speech disturbances could be either mild, moderate, or severe. When language deficits did occur, they followed surgery on the left dominant hemisphere in most instances. In contradistinction, no definite relationship was found between the side of surgery and speech deficits. Language and speech disturbances are most frequently associated with bilateral rather than with unilateral surgery, regardless of the cerebral hemisphere involved in the second operation.