2.16 Neuropathology: CNS Atherosclerosis

Question 1

What are the four vascular malformation of the CNS?

Answer 1

1. Arteriovenous Malformation (AVM)
2. Cavernous Angioma
3. Telangiectasia
4. Venous Angioma

Question 2

What is a Telangiectasia?

Answer 2

• A focal aggregate of uniformly small vessels, with intervening neural parenchyma
• May initiate seizures, but rarely ruptures

Question 3

What is a venous angioma?

Answer 3

• Consists of a few enlarged veins distributed randomly in the spinal cord or brain
• The lesion is generally asymptomatic.

Question 4

What are Arteriovenous malformations (AVM)?

Answer 4

• It evolves during embryonic development which permits direct communication between cerebral arteries and veins, which gradually enlarges.

Question 5

Where are arteriovenous malformations?

Answer 5

-The resultant conglomeration of abnormal vessels is usually located in the cerebral cortex and the contiguous underlying white matter.

Question 6

What is the end result of arteriovenous malformations?

Answer 6

-Seizures, subarachnoid and intracerebral hemorrhages can occur in the 2nd or 3rd decades.

Question 7

What is a Cavernous angioma?

Answer 7

Composed of large vascular spaces compartmentalized by prominent fibrous walls.

Question 8

What is the end results of Cavernous angioma?

Answer 8

-Most remain asymptomatic, although a minority of patients have intracranial bleeding, epilepsy, or focal neurologic disturbances

Question 9

What are the four types of cerebral aneurysms?

Answer 9

1. Developmental defects- Berry Aneurysms
2. Atherosclerotic Aneurysms
3. Bacterial infections- Mycotic Aneurysms
4. Hypertension-associated which induces interparenchymal Charcot-Bouchard Aneurysms

Question 10

Define berry aneurysm and it causes?

Answer 10

They are caused by arterial defects that originate during embryonic development, when the bifurcation of an artery creates Y-shped configuration

Question 11

Where do 90% of all berry aneurysms occur?

Answer 11

• Circle of Willis
  1. Anterior Cerebral Artery and the Anterior Communicating Artery.
  2. The complex of the Internal Carotid Artery-Posterior Communicating Artery-Anterior Cerebral Artery.
  3. The trifurcation of the Middle Cerebral Artery.

Question 12

Explain the pathology of berry aneurysms?

Answer 12

-The bloodstream from the parent vessel exerts relentless pressure on the crotch of the Y, and with time, the endothelium and internal elastic membrane degenerates and fragments.

Question 13

Large aneurysms of the internal carotid complex can cause palsies in which cranial nerves?

Answer 13

Large aneurysms of the internal carotid complex can produce palsies of the 3rd, 4th, and 6th cranial nerves and seizures initiated by the compression of the medial aspect of the temporal lobe.

Question 14

How do berry aneurysms present clinically?

Answer 14

• A sudden severe headache heralds the onset of the SAH and may be followed by coma.
• Patients who survive for 3-4 days often manifest a progressive decline in consciousness, due to arterial spasm and consequent cerebral ischemia and infarction.
• Survivors of the initial episode may rebleed, in which case the prognosis is worse.

Question 15

Where are atherosclerotic aneurysms located?

Answer 15

Usually localized to the larger cerebral vessels (vertebral, basilar, and internal carotid arteries).

Question 16

What is a atherosclerotic aneurysms?

Answer 16

-There is fibrous replacement of the media and destruction of the internal elastic membrane weaken the arterial wall and permit aneurysmal dilatation.

Question 17

What is the general characteristics of an atherosclerotic aneurysms?

Answer 17

-Are characterisically fusiform, and elongates the vessel as they enlarge.

Question 18

What are the clinical features of an atherosclerotic aneurysms?

Answer 18

-They rarely rupture, but the major complication is thrombosis, leading to strokes.

Question 19

What is a mycotic aneurysm?

Answer 19

-Infections of the arterial walls that results from septic emboli, usually from an infected cardiac valve (endocarditis) that lodges itself in a branch of the middle cerebral artery.

Question 20

What is Charcot-Bouchard aneurysms?

Answer 20

Aneurysms, associated with long-standing HTN

Question 21

Where do Charcot-Bouchard aneurysms normally occur?

Answer 21

Occurs in a geographic distribution that closely corresponds to the pattern of intercerebral hemorrhage

Question 22

What are Hypertension-Associated Aneurysms?

Answer 22

-The integrity of small interparenchymal cerebral arterioles is compromised by hypertension through the deposition of lipid and hyaline material in their walls (lipohyalinosis).

Question 23

What happens to thin walls deep inside the brain that have a hypertension-associated aneurysm?

Answer 23

-The resulting weakening of the walls leads to the formation of Charcot-Bouchard aneurysms, small fusiform dilatations located on the trunk of a vessel, rather than at a bifurcation, and are predisposed to rupture, causing hypertensive cerebral hemorrhage

Question 24

Where are hypertensive hemorrhages?

Answer 24

• The Basal Ganglia Thalamus (75%)
• The Pons (15%)
• The Cerebellum (10%)

Question 25

What are the clinical features of intercerebral hemorrhages?

Answer 25

• Onset of symptoms is abrupt and weakness usually dominates.
• Death occurs within hours to days.
• Causes death by transtentorial herniation

Question 26

What happens if a rupture of a small vessel into ventricle (intrventricular)?

Answer 26

• Ventricle rapidly distends the entire lateral ventricular system with blood, with expansion of the 3rd and 4th ventricle.
• The rush of blood through the ventricular system seemingly
• Causes death by distention of the 4th ventricle and the compression of vital centers in the medulla.

Question 27

What is a cerebellar hemorrhages?

Answer 27

• Bleeding into the cerebellum causes abrupt ataxia, with occipital headache and vomiting.
• Compression of medulla via herniation of the cerebellar tonsils through foramen magnum

Question 28

What is a cerebral ischemia?

Answer 28

Inadequate perfusion of the brain may result from extra cerebral events, such as shock or cardiac arrest.

Question 29

What are the two types of cerebral infarcts?

Answer 29

Hemorrhagic or bland

Question 30

What are hemorrhagic cerebral infarcts?

Answer 30

In general, infarcts caused by embolization are the sites of hemorrhage

Question 31

What are bland cerebral infarcts?

Answer 31

-Whereas those initiated by thrombotic occlusion are largely ischemic and therefore bland.

Question 32

How do acute infarcts present histologically?

Answer 32

-Acute infarct of the brain transforms the cerebral tissue into a liquefactive, necrotic putty-like debris with Neutrophils

Question 33

How do healed infarct present?

Answer 33

• Cerebral infarcts are not repaired by fibroblasts, and as an early response, capillaries and astrocytes proliferate at the margin of the lesion and become numerous by the 5th day. (Gliosis)
• Within months, the necrotic area is excavated by phagocytosis and a permanent cyst is formed, and at the same time the neovascularity regresses.

Question 34

What types of infarctions are localized in the middle cerebral artery?

Answer 34

• Is a favored site not only for the lodgement of emboli

- Also for atherosclerosis, which promotes thrombosis in-situ.

Question 35

What type of deficits for cerebral cortex?

Answer 35

-This deprives the cerebral cortex of circulation and produces motor and sensory deficits, as well as aphasias, when the dominant hemisphere is involved.

Question 36

What vessels are involved in lacunar infarcts?

Answer 36

Parenchymal Arteries and Arterioles

Question 37

What are lacunar infarcts?

Answer 37

These vessels are not predisposed to atherosclerosis like the larger arteries, but they can become damaged by hypertension and become stenotic because of secondary arteriolosclerosis, the narrowing causing small ischemic lesions called lacunar infarcts.

Question 38

What does lunar infarcts cause?

Answer 38

These minute infarcts can impair cognition and create the entity termed multi-infarct dementia.

Question 39

What are fat embolism?

Answer 39

-Small emboli, composed of fat, can occlude capillaries in the brain and lungs, as a result of traumatic leg bone fractures

Question 40

What happens when fat emboli lodge?

Answer 40

Their semifluid consistency creates a major barrier to blood flow. The distal capillary endothelium becomes hypoxic and permeable, and petechiae develop, restricted to the white matter.