Ischemic Stroke Flashcards
Stroke
- injury to brain caused by interruption of its blood flow (ischemic) or by bleeding (hemorrhagic) into or around the brain
- abrupt onset if focal neurologic deficits that frequently result in permanent disability or death
Transient Ischemic Attack
(TIA)
- abrupt onset of focal neurological deficits that resolve within less than 1 hr
- important warning sign for future stroke
Hemorrhagic Stroke
17%
- Intracerebral Hemorrhage: into parenchyme of brain
- Subarachnoid Hemorrhage: bleeding around surface of brain
Ischemic Stroke
83%
- atherosclerotic cerebrovascular disease (20%)
- embolism (20%)
- lacunar (25%)
- Cryptogenic (30%)
Non-Modifiable Stroke Risk Factors
- Age: doubles each decade > 55y
- Gender: male 1.5 x risk of female
- Race: AA 2 x risk of european americans
- Family History: genetics
Modifiable Stroke Risk Factors
- HTN (inc. 3-5)
- Diabetes
- Hyperlipidemia (2)
- Carotid Artery Stenosis (2)
- Atrial Fibrillation (5-17)
- Obesity (2)
- Physical Inactivity (2.7)
- Smoking (1.5)
Stroke Pathogenesis
- hyperthermia & hyperglycemia accelerate & worsen stroke brain injury
- with loss of blood supply, brain energy stores are depleted through metabolism of of glucose via glycolytic pathways with the accumulation of lactic acid (if not fixed cell dies by catabolic mechanisms)
Goal for stroke intervention?
- normalize elevated body temperature
- treat hyperglycemia
Stroke Pathogenesis by Section
- Core: severe ischemia, tissue dies <1hr
- Penumbra: moderate ischemia, tissue dies in ~4-6hr
Cerebral Blood Flow Autoregulation
- stays constant with mean arterial pressure from 55 to 155 mm Hg
- severe hypotension leads to reduced CBF & syncope
- elevation of MAP above 155mm HG cause hypertensive encephalopathy
- in chronic HTN curve shifts to right ( now 75mmHg)
CBF
measured in ml/100 gm brain/min is proportionally related to the mean arterial pressure (MAP) divided by the cerebral vascular resistance
Neurologic Deficits that are commonly produced by a stroke?
- weakness or paralysis
- loss of sensation
- loss of vision in one eye or field
- difficulty in talking or in understanding what is being said
- difficulty with organization or perception
- clumsiness or lack of balance
Anterior Circulation
-Internal Carotid, Middle Cerebral, Anterior Cerebral Arteries and any of their branches
Posterior Circulation
-Posterior cerebral, vertebral, superior cerebellar, anterior inferior cerebellar, posterior inferior cerebellar arteries and any of their branches
Size of Blood Vessel: Ischemic Stroke Subtypes
Large Small (long & short penetrating branches of these arteries)
Functional Brain Areas Supplied by Middle Cerebral Artery
- larynx, tongue, lips, face, thumb, fingers, hand, arm, shoulder, trunk, hip
- frontal eye fields
Functional Brain Areas Supplied by the Anterior Cerebral Arteries
-Foot, leg, hip
Blood Supply to Midbrain
- Posterior cerebral artery
- Superior Cerebral Artery
Blood Supply to Mid-Pons
-Short circumferential branches of basilar artery
Blood Supply Caudal Pons
-Anterior Interior Cerebral artery
Blood Supply to Rostral Medulla
-post inf. cerebellar artery
Medullary Stroke Syndrome (Wallenberg)
-loss of pain & temp. from ipsilarteral side of face
(lesion to spinal trigeminal nucleus & tract)
-dysarthria & dysphagia (leasion to nucleus ambiguus)
-loss of pain & temp on contralateral side of body’
(lesion to spinothalamic tract)
-gait ataxia on the ipsilateral side of the body
(lesion to spinocerebellar tracts)
Pontine Stroke Syndrome
- gaze disorders due to a lesion to the medial longitudinal lasciculus (CN VI)
- loss of discriminative touch, vibration & conscious proprioception on the contralateral side of the body due to a lesion of the medial lemniscus
- cerebellar lesions on both sides of the body due to lesion to the pontine nuclei & transverse cerebellar fibers originating from both the ipsilateral & contralateral sides
- contralateral hemiparesis due to lesion of the corticospinal tract
Midbrain Stroke Syndrome (Benedikt Syndrome)
- ipsilateral CN III palsy & loss of pupillary constriction due to damage of the oculomotor nuclear complex including the parasympathetic Edinger-Westphal nucleus
- Loss of discriminative touch on the contralateral side of the body due to a lesion of the medial lemniscus
- Contralateral tremor & ataxia due to a lesion of the red nucleus
