Comparison of ocular motor effects of unilateral stereotactic midbrain lesions in man

Abstract

A series of 22 patients with stereotactic lesions in the rostral dorsolateral mesencephalon are presented. Lesion I was larger than Lesion II. more irregular in size. and extended further laterally and dorsally at the level of the superior colliculus. Lesion II was maller and placed within 5 mm of the midline aqueduct and 5 mni caudally from the posterior commissure. Lesion I created paralysis of elevation. depression. and convergence and induced pupillary miosis in all patients. Lesion II appeared to spare elevation in all patients but one, and it tended to produce skew deviation in conjunction with divergence pnralysis in three patients and an associated convergence paralysis in only one patient. Three patients suffered a paralysis of convergence. Pupils were symmetrically miotic in three patients out of the six with Lesion II. Conclusions from this indicate that perhaps Lesion I at the posterior commissure was interfering with the crossing fibers subserving vertical gaze, convergence and pupillary reaction and thus by moving the lesion caudally below the posierior commissure and nearer the midline, these functions were less likely to be involved. The caudal Lesion II altered the function of divergence and produced a concurrent skew deviation. It should be emphasized that the stereotactic Lesions I and II were smaller in comparison to the destructive lesions found in disease states and therefore are valuable in [dying the neural pathways subserving ocular motility in the midbrain.