What are the four major Vascular Malformations of the CNS?
1) Arteriovenous Malformation (AVM)
2) Cavernous Angioma
3) Telangiectasia
4) Venous Angioma
What is arteriovenous malformation?
- most common congenital vascular malformation
- dilated vascualr channels in the brain
What is the cause of arteriovenous malformation and where are they located?
- cerebral arteries, veins
- central cortex and contiguous white matter
- hemorrhage (subarachnoid, intracerebral) 2nd and 3rd decade
What is cavernous angioma?
- congenital vascular malformation
- large vascular spaces compartmentalized by prominent fibrous walls
- most asymptomatic; some IC bleeding, epilepsy, nero deficet
What is Teleangiectasia?
- focal aggregate of uniformally small vessels
- w/ intervening neural parenchyma
- may initiate seizures, rarely ruptures
What is venous angioma?
- few enlarged veins in spinal cord/brain
- distributed randomly
- generally asymptomatic
What are cerebral aneurysms?
intravascular pressure exploits weakness in arterial walls and causes saccular dilations
What are the causes of cerebral aneurysms?
1) Developmental defects- Berry Aneurysms
2) Atherosclerotic Aneurysms
3) Bacterial infections- Mycotic Aneurysms
4) Hypertension-associated which induces interparenchymal Charcot-Bouchard Aneurysms
What are the causes of berry aneurysms?
- arterial defects at arterial bifurcation (Y-shaped)
- muscular layer of vessel weakened
- vessel bridged only endothelium and elastic lamina
- *90% in circle of willis**
How do berry aneurysms evolve?
- bloodstream pressure on bifurcation point
- endothelium and elastic membranes degrade
- saccular aneurysm evolves; wall formed only by adventitia
Where are berry aneurysms typically located?
1) anterior cerebral artery
2) junction of:
a. internal carotid artery
b. posterior communicating artery
c. anterior cerebral artery
3) trifurcation of middle cerebral artery
What is the most feared complication of berry aneurysms?
- rupture causing subarachnoid hemorrhage
- large aneurysms can create palsies of CN III, IV, VI
How do berry aneurysms present clinically?
- sudden severe headache heralds onset of SAH followed by coma
- progressive decline in consciousness
Where are atherosclerotic aneurysms?
-larger cerebral vessles (vertebral, basilar, internal carotid arteries)
What is the cause atherosclerotic aneurysms?
- fibrous replacement of media and destruction of internal elastic membrane
- weakened arterial wall
- prevents aneurysmal dilatation
What are the shapes of artherosclerotic aneurysms?
fusiform and elongate the vessel as they enlarge
What is the major complication of atherosclerotic aneurysms?
thrombosis leading to stroke
What is mycotic aneurysms?
- arterial wall infection
- etiology: endocarditis causes septic emboli to lodge in middle cerebral artery
- inflammation causes rupture
What are hypertension-associated aneurysms?
lipid and hyaline material deposits in walls of small interparenchymal cerebral arterioles
What happens to the thin walls deep inside the brain of a hypertension-associated aneurysm?
Charcot-Bouchard aneurysms [small fusiform dilatations] form on trunk rather than bifurcation
Where do hypertensive intercerebral hemorrhages occur?
1) basal ganglia-thalamus* (75%)
2) pons
3) cerebellum
How does a patient present with a hypertensive intracerebral hemorrhage?
- weakness [abrupt onset of symptoms]
- death occurs within hours to days
What is meant by interventricular hemorrhage?
- rupture of a small vessel into a ventricle rapidly distends entire lateral ventricular system with blood
- 3rd and 4th ventricle expand
- causes death by compressing vital centers in medulla
What is characteristic clinically about cerebellar hemorrhages?
- bleeding into cerebellum causes abrupt ataxia
- severe occipital headache and vomiting
- acute life threatening through medulla compression and tonsil herniation through foramen magnum
