Neuro Lect 10
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Occurs when an artery to the brain becomes blocked or ruptures, resulting in death of an area of brain tissue causing sudden symptoms.
What are the types of hemorrhagic strokes?
- intercerebral hemorrhage
- subarachnoid hemorrhage
What are the causes of ischemic strokes?
Why/how do strokes kill?
- 1) cells lose blood supply
- 2) aerobic metabolism stops
- 3) cells die
- 4) dead cells swell
- 5) amount of swelling proportional to volume of dead tissue
- 6) enlarging tissue increases ICP
- 7) blood flow decreases to the head
- 8) increased ICP decreases blood flow/perfusion
- 9) area around infarct becomes progressively hypoxic causing more swelling
- 10) more swelling causes worse blood flow
- 11) brain becomes too big to stay in cranium
- 12) HERNIATION occurs
What are the four components of brain herniation?
- 1) midline shift
- 2) downward displacement of cranium
- 3) uncus and hippocampus herniate into tentorial notch
- 4) cerebellar tonsils herniate through foramen magnum causing DEATH!
Third most common cause of death in the industrialized world and is the most common disabling neurologic disorder.
- Note: 80% are ischemic, 20% hemorrhagic
What percentage of stroke patients die? What is the mortality for survivors each year? What percentage of survivors have residual deficits, and what percentage are incapacitated?
- 20% die within 30 days
- 20% mortality each year
- 90% survivors have residual effects
- 30% survivors are incapacitated
What is the MAIN risk factor for all stroke types?
- arterial hypertension
- Note: systolic and diastolic BP are independent factors
What are the major risk factors for both hemorrhagic and ischemic strokes?
- atherosclerosis (more important for ischemic)
- high cholesterol
- high blood pressure (more important for hemorrhagic)
- A fib
- previous TIA (1/3 will have a full stroke in 5 yrs)
What are some differential diagnoses that may mimic stroke?
- transient global amnesia
- peripheral nerve disorders
- intracranial hemorrhage
- intracranial masses
- neuroses (panic, anxiety)
- metabolic disorders
How do thrombotic strokes happen?
thrombus in artery causes decreased perfusion downstream and subsequent cell death
What are the causes of ischemic strokes?
- large vessel disease (inside & outside head): circle of willis, carotids, vertebral blood vessels
- small vessel disease (aka lacunar infarcts): small arteries from distal vertebral artery, basilar artery and middle cerebral artery stems
- emboli: particle from elsewhere that lands in the brain
What are the causes of large vessel disease that lead to ischemic stroke?
- arterial dissection
What are the causes of small vessel disease that lead to ischemic stroke?
- atheroma formation
What are the variable sources of emboli that can cause embolic (ischemic) stroke?
- cardiac: a fib, valvular disease (endocarditis)
- carotid: atheroma
- aortic atheroma
What does hypoperfusion in the brain cause?
anoxic brain injury (decreased oxygen supply)
What can cause anoxic brain injury (hypoperfusion)?
Type of hemorrhage in which arterioles and small arteries bleed directly into the brain causing a small hematoma that spreads along tissue lines expanding until the pressure compresses arteries or decompresses into the CSF.
intercerebral hemorrhage (ICH)
What are the causes of intercerebral hemorrhage?
- illicit drug use (cocaine and/or meth)
What are the symptoms of an intercerebral hemorrhage?
- confined to tissues that contain bleeding
- evolve over minutes to hours
- do NOT begin abruptly
- are NOT maximal at onset
- eventually causes elevated ICP which causes vomiting, and decreased level of consciousness
Congenital arteriovenous connections without a capillary bed in between causing a high blood flow within blood vessels that are not completely normal.
arteriole-venous malformations (AVM)
Small aneurysms at the base of the brain in the circle of willis that are very common in elderly. Rupture can be life threatening with a fatality rate of 35% on the 1st hemorrhage.
A sudden, severe headache followed by coma that is associated with polycystic kidney disease.
What can increase the ICP enough to can an aneurysm to rupture?
Once blood enters and spreads through the CNS what happens?
- ICP increases, leading to coma, and then death
- Note: blood is NOXIOUS to the brain
What is the pathophysiology of an aneurysm?
- bleeding is typically short: arterial spasm is common as well as rebleeding (fatal)
- clot formation: causes vasospasm
- distal hypoperfusion: results in ischemic damage
hWhat are the causes for subarachnoid hemorrhage?
- ruptured aneurysms (berry)-most common
What are the warning shorts for stroke?
A "warning bleed" present in many patients with aneurysms (10-43% incidence). Causes sudden and severe headaches typically 6-20 days before "THE BIG ONE".
A brief episode of neurological dysfunction resulting from decreased perfusion. Usually means there is an impeding stroke.
- transient ischemic attack
- Note: old school definition says symptoms resolve in <24 hrs, new definition says symptoms resolve in <1 hr
What are the three goals of evaluation and management for strokes?
- identify cause of neurologic deficit
- plan an immediate plan of action
- long term management
What are the three most predictive examination findings for acute stroke (ischemic)?
- asymmetric facial paresis
- arm drift/weakness
- abnormal speech (dysarthria)
What are the diagnostic studies used to identify and diagnose stroke?
noncontrast CT is the most important diagnostic test!
How are ischemic and hemorrhagic stroke differentiated on a noncontrast CT?
- ischemic: looks dark and may be normal in the first 24 hours
- hemorrhagic: loos bright/white and should show up earlier
What is the sensitivity and specificity of a noncontrast CT for an acute SAH?
- sensitivity: 89%
- specificity: 100%
What diagnostic study allows visualization of an acute brain infarction sooner than a CT? What else is this study much better at detecting?
- MRI (infarct appears as a bright lesion within vascular territory)
- detects brainstem and cerebellar strokes better than CT
What are potential contraindications to thrombolysis in acute ischemic stroke patients?
- uncontrollable elevated BP
- bleeding disorder
- stroke/head trauma within last 3 months
- prior hx of intracranial hemorrhage
- major surgery in the past 14 days
- GI or GU bleeding in the previous 21 days
- MI within last 3 months
- LP within last 7 days
- evidence of hemorrhage on head CT
- symptoms suggestive of SAH even with normal CT
- pregnancy or lactation
- active bleeding/acute trauma or fracture
How should thrombolytics be used to treat strokes?
- is a neurology & neurosurgery service (big complication is bleeding)
- transfer pt to a different hospital
- do not push "lytics" in the dark!
What should be given to stroke patients if they are not candidates for TPA (thrombolytic) after exclusion of a hemorrhage on CT?
- **manage BP, vitals and complications of stroke such as swelling**
How is blood pressure controlled in ischemic stroke?
- don't let SBP get >200 or DBP >120
- use labetolol (normodyne, trandate) which works by relaxing blood vessels and slowing the heart rate
How is blood pressure controlled in hemorrhagic stroke?
- keep SBP between 140-160mmHg and monitor for cerebral hypoperfusion induced by fall in BP
- keep SBP <140mmHg in SAH (labetalol is the drug of choice)
What medications are used to control blood pressure in hemorrhagic stroke?
- IV nitroprusside (nitropress): vasodilator that relaxes muscles in blood vessels which lowers BP allowing blood to flow more easily
- necardipines (cardene): treats high BP by relaxing blood vessels so heart doesn't need to pump as hard, also increases supply of blood and oxygen to the heart controlling angina
- labetalol: beta blocker
What is the medical care for strokes that maintains a tight control of temperature?
- liberal use of antipyretics
- decreased stress
- watch for worsening disease (edema-->increased ICP) by doing neuro and vital checks q 2 hrs
How is elevated intracranial pressure in ICH and SAH prevented?
- keep head of bed elevated
- consider sedation (barbituate coma)
- consider mannitol
- consider hyperventilation
How are patients managed after the acute stroke event?
- prophylaxis for DVT & PE
- physical therapy, speech therapy, occupational therapy, swallowing studies
- Note: remember only about half of pts regain independent function
What is included in the urgent evaluation of patients who have had a suspected TIA?
- determine type & location of TIA
- noncontrast CT
- duplex u/s and transcranial doppler
- MRI/MRA can demonstrate circulation and eval for stenosis
- ECG and TEE
- hospitalization (may expedite workup), consider for pt with first TIA in the past 24-48 hrs as well as pts with worsening symptoms >1 hr, known carotid stenosis, a fib or hypercoagulable state
How are patients with TIA treated?
- consider thrombolytic therapy
- antiplatelet therapy (ASA 325mg po qd, ticlopidine 250mg po BID, clopidogrel 75mg po qd)
- carotid endarterectomy
- angioplasty or stenting
What is the primary prevention of stroke and TIA?
- HTN control
- cardiac risk factors (a fib) consider anticoagulation therapy
- other cardiac risk factors include smoking (risk of stroke >50% than in non smokers)
What medical therapy provides protection for all-cause mortality and nonhemorrhagic strokes?
statin therapy (lipids)
What does secondary prevention of stroke and TIA consist of?
- aspirin (non-fatal stroke reduced by 20%)
- carotid endarterectomy for symptomatic patients with >75% stenosis (reduces stroke by 65% compared to medical management)
- aggressive lipid lowering therapy (LDL <100)
- smoking cessation
Screening technique used in the evaluation of suspected stenosis of the intracranial internal carotid artery, middle cerebral artery, or basilar artery.
carotid doppler (vascular screening)
What is the "gold standard" of vascular screening techniques for AVM or SAH but has a 1% risk of stroke during procedure?
What are the vascular screening methods used to detect artery stenosis in the brain?
- carotid doppler
- conventional angiography
Detects cardiogenic and aortic sources for cerebral embolism that can be postoned until after the acute treatment phase.
transthoracic and transesophageal echo (TTE, TEE)
What are the surgical options used to treat hemorrhages and aneurysms?
- surgical clipping or placement of coil for aneurysm
- ligate or embolize AVM
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