236 CEREBRAL LOCALIZATION 



reflexes, extensor plantar response, and a little 

 rigidity. 



Of course, if this should chance to be associated 

 with paralysis of a cranial nerve, such as the sixth, 

 the temptation to diagnose a lesion of the pons would 

 be very great. Fortunately, this would not be of 

 much surgical importance, as the pons is not an 

 accessible structure. Pontine tumours are often 

 unilateral, and optic neuritis is usually absent ; 

 whereas in the class of cases we are now considering, 

 optic neuritis is marked and old-standing, and there 

 is a long history of headache, vomiting, or other signs, 

 previous to the development of spasticity or cranial 

 ner\'e palsy. 



In other cases, misleading locahzing signs may 

 arise from patches of secondary thrombosis, spreading 

 oedema, or meningitis ; but none of these is common. 



The suspicious feature about all the signs here 

 mentioned is their late development. Localizing 

 S5miptoms appearing when headache, vomiting, optic 

 neuritis, or other evidences have been present for 

 months or years are little to be trusted. Early 

 localizing signs, on the other hand, are trustworthy 

 in the main. 



A few words may be said about the significance 

 of ataxia. This is of course evidence of a lesion of 

 the cerebellum, but it may be seen in other conditions 

 also. Putting aside ataxia due to affections of the 

 labyrinth, Friedreich's ataxia, and other general 

 nervous diseases, it may also be caused by a tumour 

 in the neighbourhood of the red nucleus in the 

 isthmus, or in the pons. 



