Clinical diagnosis is made by systematic, logical, inductive probablistic reasoning facilitated by pattern matching. We recognize Tom because we know what he looks like especially if we have seen him before. This chapter shares various common patterns of stroke-related symptoms and signs.

Stroke subtypes

Stroke mechanisms are divided into those that cause ischemia and those related to hemorrhage.

Ischemic mechanisms

These can be divided into three main pathophysiological groups.

Thrombosis

This term is used to indicate a local process within an artery or vein that causes a lack of blood to its supply zone. It includes a variety of vascular pathologies: atherosclerotic plaques and stenosis, dissection, arteritis, fibromuscular dysplasia, etc. The vascular disorder can involve large extracranial or intracranial arteries or small penetrating arteries. The disease process narrows the lumen of the artery diminishing distal blood flow. Often, white and red thrombi form and cause occlusion of the vessel. The signature of the local ‘thrombotic’ process is transient ischemic attacks all in the same vascular territory. If and when a stroke develops, it can occur suddenly or show fluctuations and gradual, stepwise, or stuttering devlopment of neurological signs and symptoms. The local process in the artery (‘thrombosis’) can also be the source of intra-arterial embolism.

Embolism

In this ischemic mechanism, the material that blocks a recipient artery arises from a different proximal donor site. Donor sites include the heart, aorta, and arteries proximal to the recipient artery. The signature of embolism is the very sudden onset of neurological deficits that are maximal at onset. In some patients there may be a single stepwise worsening within 48 hours. Sudden dramatic improvement in a neurological deficit also can occur when emboli pass or are lysed.

Systemic hypoperfusion

Thrombosis and embolism are characterized by blockage of single vessels that cause focal ischemia in the region of supply of the blocked vessels. In contrast systemic hypoperfusion refers to a general decrease in blood flow to the brain. A number of systemic disorders can be responsible including myocardial infarction, cardiac arrythmia, pulmonary embolism, gastrointestinal or other sites of blood loss, etc. Patients feel light headed and vision can become dimmer and noises sound more distant. They lose the ability to think clearly and feel as if they will pass out and many do lose consciousness. Lateralized motor, sensory, and visual symptoms and signs are not present.