Stroke

=**Stroke**=


 * 1. Describe Stoke Subtypes, both ischemic and hemorrhagic.**


 * __Primary Hemorrhagic (20%, more severe):__**

__Subarachnoid hemorrhage:__ is bleeding into the subarachnoid space. It presents with a sudden onset of severe headache often with loss of consciousness. Etiologies: "berry" aneurism or Arteriovenousmalformation (AVM).

__Intracerebral hemhorrage:__ is bleeding within the brain parenchyma. It is usually progresses over the course of hours presenting with headache in 1/3 of the cases. Etiologies: hypertension (most common), drug induced (stimulants increase BP), Cerebral amaloidosis (most common in nonhypertensive elderly), AVM.


 * __Primary ischemic (80% less severe):__**

__Large vessel occlusive:__ Blockage of a large cerebral vessel due to a pathological process in that vessel. It is often preceded by a transient ischemic attack (TIA). It is usually progressive and 75% occur in the anterior circulation. Etiologies: Atherothrombotic (most common), Traumatic dissection, Vasospasm, Hyperviscosity/Hypercoagulable state.

__Small vessel occlusive:__ Blockage of a small cerebral vessel due to a pathological process in that vessel. It is sometimes preceded by a transient ischemic attack (TIA). Often found by CT/MRI in subcortical locations. Can affect motor causing arm or leg weakness often in the internal capsule, Sensory causing loss of sensation often in the thalamus, or dysarthria/clumsy hand usually in the internal capsule or basal pons. Etiologies: Lipohyalinosis or microatheromatous disease associated with diabetes of hypertension, Vasculitis, Hyperviscosity/hypercoaguabliity, Rarely embolic.

__Embolic Stroke:__ Blockage of cerebral vessel by material originating elsewhere. Maximal neurologic deficit at onset, often middle cerebral artery. Embolic sources: Heart (atrial fibrillation), Internal carotid artery plaque, other rare forms (air, deep vein thrombosis with R-L shunt.


 * 2. Describe stroke pathogenesis.**

Ischemic cascade is the cellular, metabolic, and biochemical events that result from the focal disruption of blood flow to the brain.
 * 1) Oxygen deficiency prevents oxidative phosphorylation and curtails ATP production.
 * 2) Loss of ATP for ionic pumps causes rapid loss of K from the cell resulting in membrane depolarization.
 * 3) Depolarization opens voltage gated Ca channels and buildup of extra cellular glutamate.
 * 4) Over stimulation of Glutamate receptors leads to uncontrolled Ca entry into neurons and impaired mitochondrial function with further decrease of ATP
 * 5) Activation of Nitric oxidase synthetase and enzymes that degrade proteins, nucleic acid, and phospholipids leads to production of free radicals
 * 6) Free radical formation leads to cell death.

__core region:__ irreversibly injured brain tissue, infarcted __Penumbral region:__ revirsably injured neurons, may progress to infarction, or neurons may die by apoptosis.


 * 3. Identify the location of the cerebral infarct in common clinical stroke syndromes.**

__Middle Cerebral Artery:__ Contralateral weakness typically involving face and arm, contralateral sensory loss typically involving face and arm, Aphasia, and Contralateral hemonymous hemianopsia. __Anterior Cerebral Artery:__ Rare, cause contralateral weakness and sensory loss typically involving the leg __Posterior Cerebral Artery:__ Contalateral hemonymous hemianopsia. If posterior thalamus is involved there may be contralateral loss of sensation. Contalateral weakness may occur if there is involvement of the crus cerebri or posterior limb of the internal capsule. Amnesia may result from hippocampal infarction, and higher cortical deficit may result from thalamic damage. __Vertebral basilar:__ __Small vessel stroke:__ *see above
 * Unilateral, bilateral, or "crossed" face and/or extremity weakness
 * Unilateral, bilateral, or "crossed" face and/or extremity sensory loss
 * Dysarthria
 * Diplopia
 * Vertigo
 * Ataxia
 * Dysphagia
 * Locked-in syndrome (patient is aware and awake, but cannot move due to paralysis of voluntary muscles)
 * Depression of consciousness
 * Hearing loss (unilateral)
 * Nystagmus