Understanding Stroke: Types, Causes, and Symptoms

Posted on Jan 10, 2025 in Biology

Stroke: Neurological Deficits

A stroke, also known as a cerebrovascular accident (CVA), is characterized by neurological deficits. Except for subarachnoid hemorrhage (SAH), it typically presents with focal symptoms that develop over hours or days. It is not a seizure and lasts for more than 24 hours. It is caused by vascular disease.

Transient Ischemic Attack (TIA)

A transient ischemic attack (TIA) is a clinical syndrome characterized by an acute loss of brain function or monocular vision that lasts less than 24 hours without evidence of acute ischemia.

Types of Stroke

  • Ischemic Stroke:
    • Atherothrombotic
    • Cardioembolic
    • Lacunar
  • Hemorrhagic Stroke:
    • Intraparenchymal
    • Subarachnoid

Ischemic Stroke: Mechanism

Ischemic stroke results from a blockage of a blood vessel, interrupting the supply of oxygen to the cells, causing their death.

Vascular Occlusion

  • Lacunar
  • Atherothrombotic
  • Embolism
  • Unknown

Atherothrombosis

Atherothrombosis involves atherosclerotic plaques in the intima of medium to large arteries. Common locations include bifurcations such as the carotid, vertebrobasilar, and middle cerebral arteries.

Formation of Atherosclerotic Plaque

  • First Stage: Early injury. Fatty streaks. LDL cholesterol-laden macrophages. Diffuse elevation of the intima.
  • Second Stage: Fibrous plaque appears. Growth of muscle fibers and connective tissue.
  • Third Stage: Complication of plaque, including calcifications, intraplaque bleeding, rupture of endothelium with ulceration, and thrombus formation. Infarcts can occur due to embolism or thrombi.

Lacunar Infarcts

Base occlusion of a perforating artery leads to lacunar infarcts and subcortical ischemic lesions. It can be caused by hypertensive arteriosclerosis, lipohyalinosis (microatheromas), and microemboli of arterial or cardiac origin.

Thromboembolic Stroke

Thromboembolic stroke involves vessel occlusion from a variable source. A red thrombus is caused by activation of the coagulation cascade. A white thrombus is associated with atherosclerosis. Chronic atrial fibrillation is a very prevalent cause of strokes of cardiac origin, increasing the risk of stroke sevenfold. Patent foramen ovale (PFO) is also associated with increased embolic risk.

Causes of Stroke of Cardiac Origin

  1. Myocardial infarction (MI)
  2. Valvular lesions
  3. Rhythm disturbances
  4. Cardiomyopathy (dilated, with heart failure)
  5. Atrial myxoma
  6. Valve prosthesis
  7. Septal defects

Stroke Territories

Carotid Artery

Clinical aspects of anterior and middle cerebral artery involvement. Symptoms include contralateral hemihypoesthesia and hemiplegia, aphasia (in the dominant hemisphere), and sometimes hemianopsia. Ophthalmic artery involvement can cause monocular blindness.

Middle Cerebral Artery

The middle cerebral artery irrigates motor areas 4 and 6, centers for lateral conjugate gaze, Broca’s area, and the parietal cortex and subcortical white matter.

Posterior Cerebral Artery

The posterior cerebral artery irrigates visual areas 17, 18, and 19, as well as the lower, medial, and anterior thalamus. Symptoms include contralateral homonymous quadrantanopia or hemianopia (in the dominant hemisphere), alexia, anomia, and visual agnosia.

Ischemia in the Posterior Cerebral Circulation

  • Signs: Nystagmus, vertical gaze palsy, ophthalmoplegia, paraparesis, hemianopia, dysarthria.
  • Symptoms: Vertigo, gait ataxia, paraparesis, diplopia, paresthesias, visual disturbances, dysphagia.

Hemorrhagic Stroke

Hemorrhagic stroke involves rapid onset and prolonged retinal hemorrhages. The early deficit does not follow an anatomical artery pattern.

Causes of Spontaneous Cerebral Hemorrhage

  • Hypertension: 60%, typically in individuals aged 45-65.
  • Other causes: Tumors, vascular malformations.

Cerebral Hemorrhage: Signs and Symptoms

  • Headache
  • Nausea and vomiting
  • Stiff neck
  • Retinal hemorrhages
  • Focal neurological deficit
  • Altered consciousness

Putaminal Hemorrhage

Symptoms include contralateral hemihypoesthesia, contralateral hemiparesis, contralateral conjugate gaze paresis, contralateral homonymous hemianopia or neglect, and aphasia.

Thalamic Hemorrhage

Symptoms include contralateral hemihypoesthesia, contralateral hemiparesis, contralateral conjugate gaze paresis, downward deviation of the eyes, altered consciousness, and small pupils.

Transient Ischemic Attack (TIA) Symptoms

  • Diplopia
  • Vertigo
  • Paresis