436 THE PINEAL ORGAN 



The aqueduct of Sylvius lying below the gland is very liable to be 

 occluded and produce a severe degree of internal hydrocephalus when 

 pressed upon by a pineal tumour. 



The cerebellum lies immediately posterior to the pineal and is often 

 invaded by growths arising in that neighbourhood. 



A contributory factor in the production of the internal hydrocephalus 

 is the fact that the vein draining the choroid plexuses — the vein of Galen — 

 is very liable to be compressed, with the result that engorgement of the 



Fig. 287. — Schematic Representation of the Various Ways in which a 

 Pineal Tumour may extend and cause Pressure Symptoms : (1) on the 

 Corpora Quadrigemina ; (2) on the Aqueduct of Sylvius and Midbrain ; 

 (3) downwards on the Cerebellum, causing Cerebellar Symptoms ; (4) on 

 the Midbrain Thalamic and Subthalamic Regions ; and (5) on the 

 Cerebral Hemisphere. 



choroid plexuses is produced and possibly an increased secretion of the 

 cerebrospinal fluid. 



Tumours which arise in the pineal may extend in various directions, 

 and Fig. 287 illustrates the common methods of extension. 



Eye Signs. — Tumours may extend into the corpora quadrigemina 

 and oculomotor region and produce a clinical syndrome which is character- 

 ized by loss of pupillary reaction to light, reaction to accommodation, and 

 upward, downward, and lateral movement of the eyes, in that order of 



