Stroke - Neuro Flashcards
Definition
- Results from ischemia to a part of the brain or hemorrhage into the brain that results in death of brain cells.
- Stroke is caused by insufficient blood flow into part or all of the brain. Focal stroke conventionally is defined as a neurologic deficit lasting more than 24 hours caused by reduced blood flow in an artery supplying a part of the brain that ultimately results in infarction and permanent damage.
Risk Factors
Age – Occurrence doubles each decade >55 years -Gender – Equal for men & women; women die more frequently than men -Race – African Americans, Hispanics, Native Americans, Asian Americans -- higher incidence -Heredity – family history, prior transient ischemic attack, or prior stroke increases risk -High blood pressure -Diabetes -Cigarette smoking -High blood cholesterol -Obesity -Heart Disease Atrial fibrillation -Oral contraceptive use -Physical inactivity -Sickle cell disease -Asymptomatic carotid stenosis -Hypercoagulability
Blood Supply
- Anterior: Carotid Arteries – middle & anterior cerebral arteries = frontal, parietal, temporal lobes; basal ganglion; part of the diencephalon (thalamus & hypothalamus)
- Posterior: Vertebral Arteries – basilar artery
- Mid and lower temporary & occipital lobes, cerebellum, brainstem, & part of the diencephalon
- Circle of Willis – connects the anterior & posterior cerebral circulation
Pathophysiology
- Atherosclerosis: major cause of CVA
- Thrombus formation & emboli development
- Abnormal filtration of lipids in the intimal layer of the arterial wall
- Plaque develops & locations of increased turbulence of blood - bifurcations
- Increased turbulence of blood or a tortuous area
- Calcified plaques rupture or fissure
- Platelets & fibrin adhere to the plaque
- Narrowing or blockage of an artery by thrombus or emboli
- Cerebral Infarction: blocked artery with blood supply cut off beyond the blockage
- Ischemic Cascade
- Series of metabolic events
- Inadequate ATP adenosine triphosphate production
- Loss of ion homeostasis
- Release of excitatory amino acids – glutamate
- Free radical formation
- Cell death
- Border Zone: reversible area that surrounds the core ischemic area in which there is reduced blood flow but which can be restored (3 hours +/-)
Symptoms
- Sudden numbness or weakness of face, arm, or leg, especially on one side of the body.
- Sudden confusion or trouble speaking or understanding speech.
- Sudden trouble seeing in one or both eyes.
- Sudden trouble walking, dizziness, or loss of balance or coordination
- Sudden severe headache with no known cause.
transient Ischemic Attack
- Temporary focal loss of neurologic function
- Caused by ischemia of one of the vascular territories of the brain
- Microemboli with temporary blockage of blood flow
- Lasts less than 24 hrs – often less than 15 mins
- Most resolve within 3 hours
- Warning sign of progressive cerebrovascular disease
Ischemic Stroke
EIther Thrombic or Embolic
-inadequate blood flow to the brain from partial or complete occlusions of an artery–85% of all strokes
-Extent of a stroke depends on:
Rapidity of onset
Size of the lesion
Presence of collateral circulation
-Symptoms may progress in the first 72 hours as infarction & cerebral edema increase
Thrombotic Stroke
-Lumen of the blood vessels narrow – then becomes occluded – infarction
-Associated with HTN and Diabetes Mellitus
>60% of strokes
50% are preceded by TIA
Lacunar Stroke: development of cavity in place of infarcted brain tissue – results in considerable deficits – motor hemiplegia, contralateral loss of sensation or motor ability
Embolic Stroke
- Embolus lodges in and occludes a cerebral artery
- Results in infarction & cerebral edema of the area supplied by the vessel
- Second most common cause of stroke – 24%
- Emboli originate in endocardial layer of the heart – atrial fibrillation, MI, infective endocarditis, rheumatic heart disease, valvular prostheses
- Rapid occurrence with severe symptoms – body does not have time to develop collateral circulation
- Any age group
- Recurrence common if underlying cause not treated
Hemorrhagic Stroke
- 15% of all strokes
- Result from bleeding into the brain tissue itself
- Intracerebral
- Subarachnoid
Intracerebral Hemorrhage
- Rupture of a vessel
- Hypertension – most important cause
- Others: vascular malformations, coagulation disorders, anticoagulation, trauma, brain tumor, ruptured aneurysms
- Sudden onset of symptoms with progression
- Neurological deficits, headache, nausea, vomiting, decreased LOC, and hypertension
- Prognosis: poor – 50% die within weeks
- 20% functionally independent at 6 months
Subarachnoid Hemorrhage
Intracranial bleeding into the cerebrospinal fluid-filled space between the arachnoid and pia mater membranes on the surface of the brain
- Commonly caused by rupture of cerebral aneurysm (congenital or acquired)
- Saccular or berry – few to 20-30 mm in size
- Majority occur in the Circle of Willis
- Other causes: Arteriovenous malformation (AVM), trauma, illicit drug abuse
- Incidence: 6-16/100,000
- Increases with age and more common in women
Subarachnoid Cerebral Aneurysm
Warning Symptoms: sudden onset of a severe headache – “worst headache of one’s life”
-Change of LOC, Neurological deficits, nausea, vomiting, seizures, stiff neck
-Despite improvements in surgical techniques, many patients die or left with significant cognitive difficulties
-Surgical Treatment:
Clipping the aneurysm – prevents rebleed
Coiling – platinum coil inserted into the lumen of the aneurysm to occlude the sac
Postop: Vasospasm prevention – Calcium Channel Blockers
Clinical Manifestations Middle Cerebral Artery Involvement
Contralateral weakness
- Hemiparesis; hemiplegia
- Contralateral hemianesthesia
- Loss of proprioception, fine touch and localization
- Dominant hemisphere: aphasia
- Nondominant hemisphere – neglect of opposite side; anosognosia – unaware or denial of neuro deficit
- Homonymous hemianopsia – defective vision or blindness right or left halves of visual fields of both eyes
Clinical Manifestations Anterior Cerebral Artery Involvement
- Brain stem occlusion
- Contralateral: weakness of proximal upper extremity
- sensory & motor deficits of lower extremities
- Urinary incontinence
- Sensory loss (discrimination, proprioception)
- Contralateral grasp & sucking reflexes may be present
- Apraxia – loss of ability to carry out familiar purposeful movements in the absence of sensory or motor impairment
- Personality change: flat affect, loss of spontaneity, loss of interest in surroundings
- Cognitive impairment
