Analysis of optokinetic nystagmus in patients with localized lesions of unilateral visual cortices

Analysis of optokinetic nystagmus in patients with lesions on the left unilateral parietal lobe or the entire left hemisphere

Optokinetic nystagmus (OKN) was studied by computer analysis in nine patients with lesions on the left unilateral parietal lobe (group A) and in five patients with lesions on the entire left hemisphere (group B), as confirmed by CAT or MRI scans. OKN stimulation and recordings were evaluated based on the optokinetic pattern (OKP). In group A, there was no directional preponderance. However, in group B, the Electronystagmography recordings showed typical asymmetry of OKP. This asymmetry was revealed by a low amplitude and a significantly impaired slow-phase eye velocity of the right OKP. Asymmetry of OKP resulted from the impaired slow-phase eye velocity of the contralateral OKN to the damaged hemisphere because of a slight change in fast-phase eye velocity.

Computer analysis of the optokinetic pattern test in acoustic tumors, brain stem and cerebellar lesions. Slow and fast phase velocities of optokinetic nystagmus

Optokinetic pattern (OKP) abnormalities in 36 patients with infratentorial lesions were analyzed by microcomputer (7T18 Nihondenki-Sanei). The parameters used for analysis consisted of slow phase velocity (S-VEL) and fast phase velocity (F-VEL) in optokinetic nystagmus. In 16 patients with acoustic tumors, S-VELs were normal or borderline when the tumors were less than 2 cm in diameter, but when the tumors were more than 2 cm, S-VELs were severely impaired. In 20 patients with brain stem and/or cerebellar lesions, S-VELs were abnormal in all the patients with the exception of 3. F-VEL abnormalities were seen in only 5 patients with brain stem lesions, especially pontine lesions. These findings suggest that S-VEL is a sensitive indicator of infratentorial lesions and F-VEL an important indicator of pontine lesions.

Computer analysis of optokinetic pattern test for patients with localized lesions of unilateral frontal eye fields

Four patients with localized lesions of the left frontal eye field as demonstrated at autopsy or MRI were studied. Their electronystagmography (ENG) recordings, which were induced by optokinetic stimulus, were analyzed by computer. Four factors were calculated by the ENG analyzing program. We conclude that the asymmetry of OKP in patients with localized lesions of the unilateral frontal eye fields is primarily caused by impaired S-VEL and F-VEL of the contralateral OKN compared with the side of the frontal eye field lesion.

Slow and fast phase velocities of optokinetic nystagmus induced by the optokinetic pattern test in infratentorial lesions

Optokinetic pattern (OKP) abnormalities in 36 patients with infratentorial lesions confirmed by CT or MRI were analyzed by microcomputer. The computer analysis system enabled the OKP data to be changed to digital data consisting of the slow phase velocity (S-VEL) and the fast phase velocity (F-VEL) in optikinetic nystagmus. In 16 patients with acoustic tumors. S-VELs were normal or borderline when the tumors were less than 2 cm in diameter, but when the tumors were more than 2 cm. S-VELs were severely impaired. F-VEL abnormalities were not seen in our study except in one patient. In 20 patients with brain stem and/or cerebellar lesions, S-VELs were abnormal in all the patients with the exception of 3. There was no significant difference in S-VEL between the group with brain stem lesions and that with cerebellar lesions. F-VEL abnormalities were seen in only 4 patients with brain stem lesions, especially pontine lesions. These findings suggest that S-VEL is a sensitive indicator for infratentorial lesions and F-VEL an important indicator for pontine lesions.