218 CEREBRAL LOCALIZATION 



4. Tremor is only occasionally in evidence, 



5. Nystagmus. — These curious jerkings of the eyes 

 are of considerable importance in the diagnosis of 

 cerebellar affections, because, although seen in such 

 conditions as disseminated sclerosis, they are very 

 unusual with localized intracranial tumours. Un- 

 fortunately they are not constantly present even 

 when the lesion is in the cerebellum, and, on the 

 other hand, are usually to be observed in patients 

 with disease of the labyrinth (vestibule and semi- 

 circular canals). Seeing that most cases of cerebellar 

 abscess follow otitis media, it has been very difficult 

 to be certain, in the past, whether any nystagmus 

 in a patient with a suppurating ear was due to the 

 labyrinth, or the cerebellum, or both. 



Barany, of Vienna, has shown that it is possible 

 to induce nystagmus in a normal person by stimulat- 

 ing the labj^rinth. This may be done either by 

 rotating the patient, or by allowing hot or cold (not 

 tepid) water to trickle in as far as the membrana 

 tympani. Hot water in the right ear causes a 

 nystagmus in which the eyes slowly turn to the left 

 and are corrected by rapid jerkings to the right ; 

 with cold water the rapid jerkings would be to the 

 left. 



If a patient with a suppurating ear has nystagmus, 

 and it is desired to know whether this is due to 

 affection of the labyrinth or of the cerebellum, hot 

 or cold water should be injected to see if the nystagmus 

 can be reversed in direction. If it can, the labyrinth 

 cannot be at fault ; it must be the cerebellum. 



Again, a patient with severe vertigo following on 



