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This report concerns the effects on ocular movements from stimulation of the paramedian region of the depths of the cerebellum and the dentate nucleus. Stimulation in the region of the dentate nucleus of the cerebellum resulted in ipsilateral eye movements. Activation of the cerebellum also resulted in nystagmoid movements and a subjective feeling of dizziness. After a lesion in the same region, the head and eyes were deviated contralaterally and the patient was unable to look toward the side of the lesion. The ocular defects resulting from stereotactic lesions in the depths of the cerebellum were transient.

This is a report of the occurrence of nystagmus retractorius, inferior quadrantanopia of optic tract or geniculate origin, and paresis of conjugate gaze, following localized stereotactic lesions in the central nervous system of man. These ocular phenomena were observed after the lesions were placed in the region of the pallidum or thalamus for the relief of tremor and rigidity in extrapyramidal diseases and for the relief of intractable pain. Report of Cases Case 1. —This 72-year-old white woman developed intractable postherpetic neuralgia following herpes zoster ophthalmicus on the right in August, 1958. Protamine, x-ray therapy, avulsion of the right supraorbital nerve, and undermining of the affected skin failed to produce relief. Because of persistence of the pain, she was admitted to Duke Hospital in July, 1960, for stereotactic thalamotomy. Neurological examination revealed a complete anesthesia in the distribution of the first division of the right trigeminal nerve; otherwise, it was

Ocular motility defects occurring as a result of unilateral stereotactic thermal lesions in the midbrain pretectal areas have been observed in 16 patients. The preponderance of convergence defects leads to the conclusion that convergence function is not focally localized to the midline but is mediated more diffusely from pretectal regions of the midbrain. It appears as if midline structures are not the primary center for convergence. Miotic pupils in 15 patients suggests a diffuse association of accommodation and pupillary reaction which can be symmetrically affected by a unilateral lesion. The observation of skew deviation suggests that vertical gaze is also more diffusely organized in the dorsolateral midbrain. A unilateral stereotactic lesion can cause both bilateral paralysis of vertical gaze as well as skew deviation.

This report describes the ocular manifestations observed in alert humans when the diencephalon and mesencephalon were electrically stimulated through chronically implanted depth electrodes. Stereotactic neurosurgical operations were done in 18 persons with intractable pain and involuntary movement disorders. Lesions for the relief of symptoms were localized to the thalamus, field of Forel H, and mesencephalic tegmentum and resulted in specific disorders of the eyes. Contralateral and ipsilateral conjugate eye movements resulted from diencephalic and mesencephalic stimulation. Pupillary dilation resulted from diencephalic stimulation while constriction occurred with midbrain stimulation. Following a unilateral lesion in the midbrain for relief of intractable pain, there occurred nystagmus retractorius, retraction nystagmus, convergence nystagmus, and pupillary abnormalities. A unilateral lesion in the fields of Forel H resulted in a temporary loss of downward conjugate gaze, miosis, and lack of convergence.

Phosphenes have been produced by direct stimulation of the dorsal mesencephalon in the region of the superior colliculus of an alert man. Electrodes were implanted in the midbrain for the purpose of localizing the ascending sensory pathways in a patient who was suffering from intractable phantom limb pain prior to a stereotactic lesion to relieve the pain. One electrode was situated just beneath the left colliculus. Electrical bipolar stimulation was done over a period of several weeks and resulted in the patient experiencing phosphenes in the contralateral visual fields which were associated with lateral conjugate eye movements toward the side of the visual phenomena. These observations point to the possible role of superior colliculus in the organization of visual phenomena in man.