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Cerebrovascular Disorder, Stroke
often results in paralysis of one side…
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- often results in paralysis of one side of body
- risk in african-americans greater
- CNS
- PNS
- Cranial nerves & spinal nerves
- Spinal cord
- motor neurons descend
- sensory neurons ascend
- Upper neurons: in brain
- Lower neurons: spinal cord
- Corticospinal tract
- upper motor neurons that descend into spinal cord
- Contralateral (80%)
- Ipsilateral (20%)
- Decussation: brainstem area of crossover
- Corticobulbar tract
- Run parallel to corticospinal tract
- Spinothalamic tract
- sensory neurons from periphery to brain
- cross over at some level spinal cord
- Cerebral injury
- presentation often on opposite side of body
- Cerebrum
- upper most region of brain
- right and left hemisphere
- corpus callosum: connection
- Categorial hemisphere
- language, sequential-analytic
(L hemisphere in most)
- Representational hemisphere
- face recognition, music, visual-spatial
(R hemisphere in most)
- Speech and language center
- Aphasia
- difficult to speak or understand language
- Broca's area
- speak language
- expressive aphasia
- Wernicke' area
- comprehend language
- receptive aphasia
- Cranial nerves originate
- midbrain
- auditory and visual responses, motor movement
- Pons
- medulla oblongata
- Smooth movement
- Ataxic gait
- Posture and equilibrium
- Atherosclerosis can affect blood flow to cerebellum
- Vertebral-basilar insufficiency (VBI)
- can affect blood flow to cerebellum
- R and L vertebral arteries
- Internal and external carotids
- internal carotid:
- serves brains anterior and middle cerebral arteries
- anterior cerebral artery: frontal lobe
- middle cerebral artery: lateral cortex, 80% of brains tissue
(most strokes involve branch of this artery)
- Circle of Willis
- base of brain, provides collateral circulation
- Base of brain
- Formed by posterior cerebral artery and internal carotid
- Common site for aneurysms (weakness in arterial wall)
- twelve pairs
- number I through XII
- Either motor, sensory, or both
- brain injury, tumor, or stroke can disrupt cranial nerve function
- cranial nerve abnormalities may be a sign of increasing intracranial pressure
- Brain
- most energy-consuming organ
- 20% of oxygen
- brain cells not capable of anerobic metabolism
- irreversible damage may occur
- Glucose for energy
- Hypoglycemia and hypoxia affect brain function
- Two types
- Ischemic (85%)
- Hemorrhagic (15%)
- Transient Ischemic attack (TIA)
- Ischemic injury ("mini stroke"):
disruption of cerebral circulation lasting less than 24hr
no permanent injury
- most common in internal carotid and middle cerebral artery
- Causes
- cerebral arteriosclerosis
- carotid stenosis
- atrial fibrillation (stasis of blood leads to clot formation)
- temporary and resolves
(20-25% of TIAs progress to a stroke)
- neurological changes may go unnoticed by patient
- Lacunar infract
- small infarcts in brain due to occlusion of tiny blood vessels
- Artery rupture, results in bleeding
- causes:
- hypertension (most common cause)
- Aneurism rupture (most commonly in circle of Willis)
- subarachnoid hemorrhage
(arterial branch in subarachnoid space ruptures)
- blood flows into brain, compresses and displaces brain tissue
- blood causes vasospasm of adjacent blood vessels
- blood released is toxic to surrounding cells
- anoxic encephalopathy
- lack of oxygen delivery causes decreased level of consciousness
- cerebral edema may occur, putting pressure on brain tissues
- If hemorrhage is large, hematoma and clot form; may expand in first 24 hours worsening symptoms
- hypertension (HTN)
- hyperlipidemia
- diabetes
- smoking
- obesity
- lack of exercise
- A. Fib
- oral contraceptives
- excess alcohol
- family history
- age 55+
- gender (males risk is greater)
- ethnicity (African American risk is greater than Caucasian)
- sickle cell disease
- Transient ischemic attack (TIA)
- amyloid accumulation
- Subarachnoid hemorrhage (SAH)
- presents differently than most hemorrhagic strokes
- sudden onset ("worst headache ever")
- Vertebrobasilar insufficiency (VBI)
- ischemia of vertebrobasilar circulation
- dizziness, vertigo, headache
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- Intravenous thrombolysis
- Rt-PA: recombinant tissue-type plasminogen activator
- not all ischemic stroke patients are candidates
- must be used within four hours of the beginning of the stroke symptoms
- aspirin or another antiplatelet drug
- surgical thrombectomy for eligible candidates
- Rehabilitation
- first four weeks post-stroke especially important to regain function