INFARCTION STROKE

INFARCTION STROKE

MECHANISM OF ISCHEMIC INFARCTION

1. Thrombotic

Ø  Thrombotic infarction occurs when a thrombus superimposed on an atherosclerotic plaque

Ø  May be precipitated by an abnormality of blood cloting

2. Embolic

Ø  Occlusion of an arteri by an embolus

3. Hemodynamic

Ø  Severe stenosis or occlusion of the proximal arteries

Ø  Collateral compensatory blood flow is inadequate

Ø  Global cerebral perfusion is critically decreased          ( e.g. cardiac output decreased )

CLINICAL CATEGORIES

1. Atherothrombotic infarction

Ø  Medical history è one or more risk factors

Ø  Headache and vomiting are unusual

Ø  The onset come rapily, may continue to worse over hours or days

Ø  The trombus is superimposed on the atherosclerotic plaque

Ø  Atherosclerotic plaque è extracranial or intracranial arteries

Ø  There are 2 mechanisms :

a.       Atherosclerotic plaque enlarge è stenotic / occlusion

b.      Embolism or plaque fragments è occlusion ( artery – to – artery embolus )

CLINICAL CATEGORIES

2. Cardioembolic

Ø  The onset is rapid, focal deficit completely and may worsening

Ø  Usually at activity

Ø  The source of embolus :

ü  Cardiac conditions :

v  Atrial fibrillation, acute myocardial infarction, congestive heart failure, mitral or aortic valve disease

ü  Transcardiac conditions ( paradoxical embolus )

v  Right to left cardiac shunt

v  The source of clot : peripheral venous thrombus

Ø  Sometimes clinical finding; isolated homonymous hemianopsia or isolated aphasia

Ø  Brain imaging :

ü  Involve the cortex, commonly in the distribution of branches of the MCA

ü  Possible haemmorhage infarction

3. Lacunar infarction

Ø  Small lesions, involvement of deep, small, penetrating arteries

Ø  The arteries to branch at 90⁰ ( e.g. lenticulostriate arteries and brain stem )

Ø  The causes are :

ü  Poor collateral connection

ü  Blood obstruction by arterial disease

ü  Thrombus

ü  Embolus