Stroke is neurological vascular disorder occurs when a blood vessel carries oxygen and nutrients to brain is either blocked by clot (ischemic stroke) or ruptures (hemorrhagic stroke).
World health organization defines stroke as “rapidly developing clinical signs of focal (at times global) disturbance of cerebral function, lasting more than 24 hours or leading to death with no apparent cause other than that of vascular origin.”
In United States, more than 795,000 people suffer stroke every year andabout 610,000 of these are new cases, while 185,000are recurrent strokes.
Stroke is fifth leading cause of death in United States and almost 130,000 Americans each year die of stroke.
There are two major types of stroke: Ischemic Stroke and Hemorrhagic Stroke.
Ischemic stroke is the most common type and accounts for 87% of all strokes. It occurs due to blockage of blood vessel usually by a blood clot or by fatty deposits. The blockage can form in the artery supplying the brain or it can develop elsewhere in the body and travel through the blood to an artery in the brain which is called embolism.
Hemorrhagic stroke accounts for 13% of all strokes and results from rupture of a weakened blood vessel with resultant bleeding into the surrounding brain.The most common cause of vessel rupture is uncontrolled high blood pressure. There are three vascularconditions which make blood vessels weak and prone to bleed: Aneurysm, Arteriovenous Malformation (AVM), and Dural Arteriovenous Fistula (DAVF).
Transient ischemic attack (TIA)is ischemic type of stroke which occurs due to temporary blockage of blood flow to the brain and often lasts less than five minutes. It is often labelled as “mini-stroke”. A TIA does not cause permanent neurological deficit but it increases the risk of getting full blown ischemic stroke later.
There are multiple risk factors which increase the risk of stroke. These risk factors are lifestyle risk factors like high blood pressure, high cholesterol, diabetes, smoking, physical inactivity, obesity, stress, atrial fibrillation, atherosclerosis, peripheral arterial disease. There are certain hereditary non-modifiable risk factors such as age, family history of stroke, race. A previous history of TIA, stroke or heart disease also increases the risk of new or recurrent stroke.
The symptoms and signs of stroke depend on the type of stroke and the affected area of the brain by the diseased vessel. The key factor is the sudden onset of any of the following symptoms:
- Speech difficulty
- Weakness or numbness of one side of the face, arm or leg. In some cases, both sides may be involved
- Sudden loss or change in vision in one or both eyes
- Sudden, severe headache, often described as “the worst headache of life”
- Dizziness or loss of balance and coordination
- Sudden confusion or loss of memorySudden c
- hanges in behavior
American Stroke Association coined an easy to remember pneumonic FASTto spot warning signs of stroke and to seek emergency medical care.
FAST stands for Face drooping, Arm weakness, Speech difficulty and Time to call 911.
The most important step in management of acute stroke is to determine the type of stroke and the areas of brain which are being affected. In addition to history and clinical examination, following investigation studies are important in the early management:
- Blood test to check baseline levels of blood biochemistry
- Imaging studies including CT, CTA and MRI. CT head is the most important initial study in acute management of stroke which can rule out hemorrhagic cause of stroke
- Carotid ultrasound to check for blood flow in carotid arteries
- Echocardiogram to find a cardiac source of clot in case of ischemia stroke due to large vessel occlusion
- Cerebral angiogram which is a minimally invasive diagnostic test to acquire high resolution images of blood vessels of brain. It serves as a definitive diagnostic test to detect or confirm vascular abnormalities of brain. It also provides a therapeutic tool for patients who require endovascular treatment.
Figure: CT head without contrast:
(A) axial image showing hyperdense sign indicative of acute vascular occlusion causing an ischemic stroke.
(B) Axial CT image showing intra cerebral hemorrhage
The medical management of ischemic stroke entails therapy with clot-busting drugs, which should be started within 3 hours of stroke onset. Intravenous tissue-plasminogen activator (t-PA) is the most common drug used for lysis of clot and to restore blood flow in the brain. In hemorrhagic stroke, emergency medical treatment is focused on controlling the bleeding in the brain. It involves lowering of blood pressure, stopping and reversal of any blood thinner medication, preventing vasospasm and seizure, and potential surgery for removal of the bleeding.
In cases of ischemic stroke, endovascular treatment is minimally invasive procedure, which is recommended if medical treatment with IV t-PA fails or contra-indicated and if the clot is in a larger vessel amenable to endovascular treatment, the so called Large Vessel Occlusion (LVO-ischemic stroke).
It involves physical removing of blood clot with the help of stent retrievers and/or aspiration device, process called mechanical thrombectomy. In recent changing standards of ischemic stroke management, endovascular treatment with mechanical thrombectomy is the standard of care if the resources and skilled physicians are available due to better effectiveness and larger treatment window of 8 hours from stroke onset.
Surgical or endovascular treatment of hemorrhagic stroke depends on the vascular abnormalities.
If aneurysm is the source of bleeding then it can be repaired by surgical clipping or by endovascular embolization of metallic coils into the aneurysm.
Arteriovenous malformation (AVM) can be removed surgically or by endovascular embolization of coils or small particles with glue like properties. Often endovascular treatment is done in preparation for surgical removal of AVM.
Dural Arteriovenous Fistula (DAVF) can be treated by neuro-intervention or surgery. The bleeding from a ruptured DAVF can be removed surgically.
References
- American Heart Association. Heart Disease and Stroke 2017 Statistics At-a-glance.
- Wahlgren, N., Macho, J. Killer M., Liebeskind D., Jansen O. Final Results from the Trevo Study (Thrombectomy Revascularization of large Vessel Occlusions in acute ischemic stroke). International Stroke Conference, 2012.