Saccadic eye movements in frontal lesion and posthemispherectomy in humans. An electro-oculographic study.

This study was concerned with the assumed role that the frontal eye fields could play in the mechanisms of: the voluntary saccade optokinetic responses. Ten patients with frontal lobe tumors (8 unilateral, 2 bilateral) and two patients with a right hemispherectomy were studied. EOG and EEG were performed in the same session. Left and right voluntary saccadic potentials could be recorded in all cases, no matter where the frontal lesion was located. Minor differences in amplitude were observed between the fast eye movement to the lesion and to the normal side. Horizontal optokinetic responses to a moving drum were a constant finding in all cases. The frequency and amplitude of the fast component of the responses did not show substantial differences with the drum moving to the lesion or to the healthy side. Voluntary saccadic eye movements to the left and left horizontal optokinetic responses to a moving drum to the right, were recorded in the two cases with a right hemispherectomy. The hypothesis that considers frontal eye field as the pulse generator area for the voluntary or reflex saccadic eye movements is discussed.

Electro-oculographic and electroencephalographic correlative study of optokinetic responses in brain lesions.

Electro-oculograms of induced optokinetic responses (OKR) and EEG were recorded in 61 patients with either left or right hemisphere lesions. Of the 61 patients 55 showed focal EEG disturbances as follows: occipito-temporal (7 cases), parieto-temporal (10 cases), occipito-parieto-temporal (26 cases), temporal (9 cases) and frontal (3 cases). Symmetric OKR (21 cases) were recorded when no EEG changes were observed or when these were localized to left or right temporal and frontal electrodes and exceptionally when unilateral occipital and parietal regions were also involved. In 40 cases with unilateral hemispheric lesion a contralateral abnormal OKR was observed. Low frequency OKR with or without amplitude changes, especially of fast (saccadic) component, was mainly observed in parietal localization. In severely disturbed OKR, i.e. random jerks, the abnormal brain waves were mainly localized to the occipito-parieto-temporal region. In all cases in which no response was obtained the affected area was the occipito-parieto-temporal. These findings are discussed with reference to the regulating systems of slow (smooth) and fast (saccadic) eye movements triggered by visual stimuli.

[Ocular diskinesia]. / Disquinesias oculares.

The clinical findings and the electro-oculogram were correlated in four cases (3 postinfectious, 1 vascular) with ocular dyskinesias, of a mixed type in two of them. This correlation led to a more precise recognition of the pattern of opsoclonus, flutter and ocular dysmetria. Ocular dyskinesias have certain resemblances with voluntary saccadic movements; the effects of ocular following and optokinetic stimulation are described. The role of brainstem and cerebellar structures in relation with the physiopathology of these dyskinetic ocular movements is discussed.