Brain Herniation

Question 1

When a space occupying lesion is causing the cerebral hemispheres to enlarge, a consequence may be that the hindbrain is forced caudally (herniates). Name this condition, and briefly describe the herniation (2)

Answer 1

Coning of the medulla – tonsils of cerebellum herniate through foramen magnum, compressing the brain stem.

Question 2

List three (3) functional consequences of herniation and indicate in each case the specific brain area involved (6)

Answer 2

Decreased level of consciousness – distortion of the reticular formation (2)

Decreased pupillary light reflexes & dilation of pupils – impairment of 3rd Nerve function, due to compression (2)

Decreased vital function involving both respiratory and cardiac function - compression of the medulla (2)

Question 3

Is it advisable under these circumstances to do a lumbar puncture in order to draw a sample of CSF? (½) Give one (1) reason for your answer (1)

Answer 3

No, a lumbar puncture should not be performed.

Removing CSF would reduce the CSF pressure below the foramen magnum and therefore the condition would be aggravated due to increased coning of the medulla.

There would also be progressive loss of consciousness and further impairment of breathing, which may ultimately be fatal.