Central Nervous System

Question 1

What are the common sites of berry aneurysm? What is the natural history/pathological sequelae of a ruptured berry aneurysm? What factors increase the likelihood of rupture of these aneurysms?

Answer 1

1. Common sites of berry aneurysm is at arterial branch points of Circle of Willis
   - Anterior cerebral artery, anterior communicating artery
   - Middle cerebral artery, anterior choroidal artery
   - Internal carotid artery, posterior communicating artery
   - Basillar artery, posterior communicating artery
2. Pathological sequelae of ruptured berry aneurysm
   - Acute: Ischaemic injury due to vasospasm of vessel
   - Late: Meningeal fibrosis and scarring causing secondary hydrocephalus
   - Death
3. Increase likelihood of rupture with
   - Increased size of aneurysm -> >10mm has >50% risk
   - Increased ICP -> Straining, orgasms

Question 2

What is the most frequent cause of subarachnoid hemorrhage? What is the etiology of saccular aneurysms?

Answer 2

1. Most frequent cause of subarachnoid hemorrhage
   - Ruptured berry aneurysm
   - Other causes -> Trauma, HTN, AV malformation, tumor, bleeding risk
2. Etiology of saccular aneurysm
   - Generally unknown
   - Some genetic risk as seen in patients with -> Polycystic kidney disease, CTD (Marfan’s, Ehler’s Danlos), aortic coarctation
   - Predisposing factors -> Smoking, HTN

Question 3

What type of vessels have been damaged to produce subdural bleed seen in the CT? Which groups of patients are most at risk of SDH and why? How does an extradural hematoma occur? Define and describe diffuse axonal injury.

Answer 3

1. Subdural hematoma is due to
   - Tear of bridging veins between dura venous sinus and brain
   - Bleed into space between dura and arachnoid
2. Patients at risk of SDH
   - Elderly -> Brain atrophy -> Increase cerebral movement during trauma -> Tears on bridging veins
   - Infants -> Thin walled cerebral veins
3. Extradural hematoma occurs due to
   - Tearing of middle meningeal artery
   - Causes bleed into space between skull and dura
4. Diffuse axonal injury is
   - Microscopic axonal injury
   - Axonal swelling and focal hemorrhages
   - Damage to axons at junction of node of Ranvier
   - Alteration to axoplasmic flow
   - Seen in patients with coma but no cerebral contusions