Describe the physiology of cerebrospinal fluid (CSF). (70% of marks) Describe the anatomy relevant to the performance of a lumbar puncture. (30% of marks) 

[Click here to toggle visibility of the answers]

College Answer

Most candidates performed well in this question. The physiology of cerebrospinal fluid (CSF) 
required candidates to write about CSF formation, circulation and absorption, compare the 
composition of CSF to plasma and describe normal volumes and pressures. The functions of 
CSF also need to be listed. Some candidates described the displacement of CSF when 
intracranial pressure rises as a function of CSF. No marks were given for this.
The best approach to the anatomy of a lumbar puncture was to describe the lumbar 
intervertebral space at which the lumbar puncture is done and then describe the anatomical 
structures that the needle would traverse from the skin to the subarachnoid space. 
Mentioning the indications for a lumbar puncture was not required.