4.1 Circle of Willis

Question 1

Describe the Anatomy of the circle of Willis

Answer 1

1. Anastomosis of blood vessels
   found at base brain
   responsible arterial flow to brain and stem
2. Formed unification of anterior an posterior circulations
3. anterior circulation formed from ICA
   gives off x5 branches
   within cranial cavity
4. Posterior comm artery joins w/ posterior cerebral artery to form other Half
5. A.Comm completes ring
   branching from 2x ACA

Diagram page 156

Question 2

Different causes cerebral Aneurysms

most comon locations for aneurysms in circulation

Answer 2

Abnormal local dilation in wall of a blood vessel
usually an artery
D/T defect / disease / injury

1. Saccular
2. Fusiform
3. Dissecting
4. Other

Near 90% found anterior circulation
Carotid
a.comm + p.comm + MCA

<20% found posterior circulation
vertebrobasilar

Question 3

1. Saccular

Answer 3

most common
resulting medial degen
following HD induced vascular injury

Mainly occurs at bifurcation of large vessels

Question 4

2. Fusiform

Answer 4

Older patients

Unusual or excess atherosclerotic breakdown on intima

Question 5

3. Dissecting

Answer 5

Accumulation of blood in wall vessel
between intima and lamina

Spontaneous / following trauma

Also in patient w/ vasculopathy
- usually in vertebral artery

Question 6

Other

Answer 6

AV malformations
vasculitides
tumours

Question 7

SAH Sx and Sy

Answer 7

Sudden onset headache
Worst ever / Thunderclap

Seizures

FND
Eg CN palsy

Fluctuating / reduction / LOC

Meningism

N+V

Hunt and hess scale

Question 8

Measures clin severity on admission

Answer 8

0 Unruptured

1 Asympto / min headache / slight rigidity

2 mod to severe headache
nucha rigidity
no FND other than CN palsy

3 Drowsy
Confused
Mild FND

4 Stupor
Mod -> Severe hemiparesis
Possible early decerebrate rigidity
Vegetative disturbance

5 Deep comma
Decerebrate rigidity
Moribund appearance