抄録
Two cases of the localized metastatic carcinoma to the midline cerebellar structure were studied neuro-otologically.
The first was a fifty-seven year old woman, whose chief complaint was a feeling of unsteadiness.
Computed tomography showed a localized midline cerebellar tumor and this tumor was extirpated.
Neurological examinations revealed truncal ataxia, but no other cerebellar sign.
Neuro-otological examinations revealed the lack of a nystagmus, smooth pursuit eye movement, normal caloric response and normal optokinetic nystagmus.
Vertical downbeat nystagmus was demonstrated by the positioning nystagmus test from sitting to head down position.
The second patient was a fifty-three year old woman who complained of an unsteady gait.
Neurological examinations revealed a disturbance in tandem gait and left finger to nose test.
A cerebellar tumor slightly shifted to the left was demonstrated by computed tomography.
Lateral gaze nystagmus predominantly beating to the left was evident.
Pursuit eye movement and optokinetic nystagmus was slightly disturbed.
Suboccipital craniotomy was performed and the tumor was found to extend into the fourth ventricle from the cerebellar vermis.
The lesion in the second patient as seen at surgery was not only in the cerebellum itself but in the brain stem.
These two localized cerebellar midline tumors revealed the following:
1) Lateral gaze nystagmus was not demonstrated in a pure cerebellar midline lesion.
2) Smooth pursuit eye movement and optokinetic nystagmus was also normal.
3) The most striking finding neuro-otologically was vertical downbeat nystagmus seen on the positioning nystagmus test.
