Week 1: Pathophysiology of a Stroke

What is the definition of a stroke?

Death of brain cells due to lack of oxygen, also called hypoxia, caused by either ischemia or hemorrhage.

What is another term previously used for stroke?

Cerebrovascular accident, CVA, a sudden event involving blood vessels of the brain.

What is the FAST acronym, and why is it important?

An acronym by the Stroke Foundation for recognizing stroke symptoms: Face drooping, Arm weakness, Speech difficulty, Time to call emergency services.

What are transient ischemic attacks, TIAs, and why are they important?

Mini-strokes where symptoms last less than 24 hours. They are warning signs of a future stroke.

What are the two main types of stroke?

Ischemic stroke, caused by blocked blood supply, accounts for 85 percent of strokes.

Hemorrhagic stroke, caused by bleeding, accounts for 15 percent.

What is an ischemic stroke, and how common is it?

Caused by blockage of blood supply to the brain and accounts for 85 percent of all strokes.

What is the most commonly affected vessel in ischemic stroke?

Middle cerebral artery.

What are the two major types of ischemic stroke?

Embolic stroke, caused by a traveling clot or plaque fragment.

Thrombotic stroke, caused by a blood clot forming in a cerebral artery.

What is an embolic stroke, and what causes it?

A stroke caused by a traveling clot, embolus, that blocks an artery, commonly from the heart, such as in atrial fibrillation, or from carotid artery plaque.

What is a thrombotic stroke, and what causes it?

A stroke caused by a blood clot forming directly in a cerebral artery, usually due to atherosclerosis.

What happens when an artery supplying the brain is blocked?

Leads to hypoxia, lack of oxygen, causing loss of function in that brain area. Large strokes can cause cerebral edema.

What does a CT scan of a large ischemic stroke show?

Infarcted, damaged, brain tissue in the affected vascular territory, often the frontal, parietal, and temporal lobes.

What is a hemorrhagic stroke, and how common is it?

A stroke caused by bleeding from a ruptured blood vessel, accounting for 15 percent of all strokes.

What are the main types of hemorrhagic stroke?

Intracerebral hemorrhage, ICH, bleeding into the brain tissue. Subarachnoid hemorrhage, SAH, bleeding into the subarachnoid space. Extradural, epidural, and subdural hematomas, bleeding around the brain, usually from trauma.

What is an intracerebral hemorrhage, ICH, and what are its major causes?

A hemorrhage within the brain parenchyma, often caused by hypertension, anticoagulants like warfarin, amyloidosis, tumors, or hemorrhagic transformation of an ischemic stroke.

What does a CT scan of an intracerebral hemorrhage show?

A large hemorrhage in deep white matter, compressing adjacent structures and ventricles, leading to raised intracranial pressure.

What is a subarachnoid hemorrhage, SAH, and what causes it?

Bleeding into the subarachnoid space, commonly caused by a ruptured berry aneurysm or an arteriovenous malformation, AVM.

What are berry aneurysms, and where do they occur?

Outpouchings, ballooning, of cerebral arteries at branch points in the Circle of Willis, commonly in the posterior communicating artery and middle cerebral artery.

What are risk factors for berry aneurysm rupture?

Hypertension, genetic connective tissue disorders such as Ehlers-Danlos or Marfan syndrome, and smoking.

What are the classic symptoms of a subarachnoid hemorrhage?

Thunderclap headache, sudden and severe, the worst headache ever. Photophobia, sensitivity to light. Neck stiffness, due to meningeal irritation.

What does a CT scan of a subarachnoid hemorrhage show?

Blood in the subarachnoid space, often accumulating in the lateral sulcus, Sylvian fissure, or basal cisterns.

How is a subarachnoid hemorrhage diagnosed if CT is inconclusive?

Lumbar puncture detects xanthochromia, yellow cerebrospinal fluid due to blood breakdown. Angiography identifies aneurysm location.

How can subarachnoid hemorrhage lead to vasospasm?

Blood in the subarachnoid space irritates vessels, causing them to constrict, leading to ischemia and secondary stroke.

What are the treatment options for a ruptured aneurysm?

Neurosurgical clipping, open surgery to place a clip on the aneurysm neck. Endovascular coiling, a catheter is inserted and tiny metal coils are placed inside the aneurysm to block blood flow.

How is neurosurgical clipping performed?

A craniotomy is done to access the brain, and a clip is placed across the aneurysm neck under an operating microscope.

What is endovascular coiling, and how does it work?

A minimally invasive procedure where a catheter is threaded into the aneurysm, and tiny metal coils are placed inside to induce clotting and seal the aneurysm.

How can subarachnoid hemorrhage lead to hydrocephalus?

Blood blocks cerebrospinal fluid flow in the basal cisterns, leading to ventricular dilation and increased intracranial pressure.

What does a CT scan of hydrocephalus show?

Dilated lateral ventricles due to cerebrospinal fluid buildup.

What is the prognosis for hemorrhagic stroke?

High mortality and neurological disability, particularly for intracerebral hemorrhages and ruptured aneurysms.

What is hemorrhagic transformation of an ischemic stroke?

A condition where an ischemic infarct develops secondary hemorrhage, leading to worsening neurological deficits.

How does raised intracranial pressure, ICP, occur in stroke?

Swelling from edema, hemorrhage, or hydrocephalus compresses brain tissue, causing herniation and death.

What role does an angiogram play in stroke diagnosis?

Used to visualize vascular abnormalities, such as aneurysms, stenosis, and arteriovenous malformations, AVMs.

How is an angiogram performed?

A catheter is inserted into the femoral artery, advanced to the Circle of Willis, and contrast dye is injected to highlight vessels.

Why is early stroke recognition critical?

Prompt treatment can reduce brain damage, improve outcomes, and enable use of thrombolysis or mechanical thrombectomy for ischemic stroke.