Fig. 20. Exposure of the Cerebellum. 



On the left side an incision has been made from the External Occipital 

 Protuberance horizontally outwards as far as the Ear. From either extremity 

 vertical incisions have been made downwards and the muscle-skin flap thrown 

 downwards. The muscles were subsequently dissected out. A large window 

 was chiselled out of the Bone. The Lateral Sinus has been slit open, the 

 Cerebellum is kept inwards by a broad spatula. 



The Cerebellum is much more protected than the Cerebrum. Only a ver}' 

 small surface area comes in contact with the Bone in a region well protected by 

 thick muscles. 



Injury to the Cerebellum is accordingly very rare, but operations in this 

 part are far more difficult owing to its position. A glance at the figure shews 

 that suppuration of middle-ear origin may extend from the Lateral Sinus, Posterior 

 Semicircular Canal or Saccus Endolymphaticus and so give rise to an abscess 

 between the posterior surface of the Petrous portion of the Temporal Bone and 

 the Cerebellum or to a Cerebellar Abscess. 



These purulent collections may be evacuated by an enlargement of the 

 opening made for the exposure of the Lateral Sinus, backwards. If a Temporal 

 abscess has been looked for by opening the skull in VON Bergmann's Rectangular 

 Area (cf. Fig. 18) then further procedure entails enlargement of the osseous opening 

 and incision of the Tentorium CerebeUi in order to compare the superior aspect 

 of the Cerebellum. 



A large opening is necessary for Cerebellar Tumours. When the Lateral 

 Sinus gets in the operator's way, he should push the Dura Mater away from the 

 Bone ligature the Sinus with a double ligature and divide it. Upon the further 

 removal of bone the Cerebellum can be well exposed. 



We desire to draw particular attention to a \'ein which runs from the 

 lowest part of the Lateral Sinus or from the Jugular Bulb to the Vertebral Vein 

 through the Posterior Condylar Foramen. Its further course is horizontal be- 

 tween the Occipital Bone and the Atlas. 



The vein is of great importance in Ligature of the Internal Jugular in 

 cases of Thrombophlebitis of the Lateral Sinus. Cf. Figs. 27 and 28. 



