Central nervous system disorders

V./4.2.: Etiology

Etiology is reviewed in the pathology chapter in details.

Stroke is caused by acute disturbance of arterial blood supply to an area of the brain. Sudden onset of neurological deficit symptoms (focal or disturbance of consciousness) develop, and last at least 24 hours or lead to death in the same period. In transient ischemic attack (TIA), all symptoms should be temporary, last max 24 hours. Definition of TIA will likely to be changed meaning temporary focal deficit typically last less then 1 hour without lesion by neuroimaging methods.

Based on the Trial of Org 10172 in Acute Stroke Treatment (TOAST) ischemic strokes may be divided into five major subtypes: 1. large artery infarction with atherothrombosis, 2. small vessel, or lacunar infarction, 3. cardioembolic infarction, 4. other, not specified cause, 5. cryptogenic. On the other hand, oxford classification (four subtypes) could also be used (see below).

Of all stroke patients, 85% has ischemic lesion while the 15% has cerebral haemorrhage. Territorial infarction, ischemia in a blood supply territory of a large artery is caused by large artery atherothrombosis  or emboli. Stenosis or occlusion of the common carotid or internal carotid artery may frequently cause infarction in the watershed zones of the brain. In these cases, hemodynamic changes also take part. Severe carotid stenosis will first result in watershed zone infarctions even without territorial ones, because these areas are the most vulnerable to hypoxia. Intracranial collateral circulation could prevent the development of territorial infarction in these cases (see chapter regarding asymptomatic carotid artery stenosis).

Lacunar infarctions caused by microangiopathy through lipohyalinosis and arteriolosclerosis because of hypertension and diabetes. Lacunar lesions are typically max 15 mm in the hemispheres or max 10 mm in the brain stem. Small emboli may also result in lacunar infarction.