[Neuro-otological examination in patients with unilateral cerebral lesion--fixation suppression]

Fixation suppression of caloric nystagmus was examined in 33 cases with unilateral cerebral vascular lesion. Only Lesion included the unilateral internal capsule was certified by CT scan in all of the subjects. The rate of fixation suppression (FS%): FS% = (1 - F/D) x 100 was calculated by the mean slow-phase velocity (F) of caloric nystagmus during fixation and the maximum slow-phase velocity (D) during eyes open in darkness. The normal FS% of nystagmus to both sides was observed in 12 cases, the reduction of FS% of nystagmus to the ipsilateral side of the lesion was observed in 11 cases, that of nystagmus to the contralateral side in one, and that of nystagmus to the bilateral side in eight. In 30 out of 32 cases which were able to measure the slow-phase velocity (SPV) of caloric nystagmus, FS% of nystagmus to the ipsilateral side of the lesion was lower than that to the contralateral side, and there was statistically a significant difference between them (p less than 0.05). Furthermore, the difference between the SPV of nystagmus to the ipsilateral side of the lesion and that to contralateral side was examined during fixation and during eyes open in darkness separately. The SPV of nystagmus to the ipsilateral side of the lesion was significantly (p less than 0.01) higher than that to the contralateral side during fixation. There was no significant difference between them during eyes open in darkness. In 15 cases, however, tonic eye deviation over 20 degrees to the slow-phase side was only observed during nystagmus to the ipsilateral side.(ABSTRACT TRUNCATED AT 250 WORDS)