Stroke

Chapter 62 Stroke



Corey R. Fehnel, MD , Ala Nozari, MD, PhD , Lee H. Schwamm, MD, FAHA




1 What is the definition of stroke?


Stroke is a sudden, focal neurologic syndrome due to cerebrovascular ischemia. Strokes are sudden, or apoplectic, by definition. A slow progression of neurologic symptoms should make the clinician consider alternative diagnoses. Strokes occur in two broad categories:



image Ischemic stroke due to arterial occlusion


image Hemorrhagic stroke due to vessel rupture



2 Name two common conditions that mimic stroke symptoms


Seizure and complicated migraine. Although at times difficult to distinguish, the clinician can often differentiate between these conditions on the basis of the temporal nature of symptom onset. Strokes generally produce a deficit that is sudden and maximal at onset. Seizures progress rapidly over a few seconds and may be associated with stereotyped motor movements and often impairment or loss of consciousness. Migraines can produce stereotypical visual, sensory, motor, or language symptoms in a predictable fashion because of the presumed mechanism of “cortical spreading depression” occurring over minutes. Spreading depression is an extracellular wave of neuronal depolarization thought to be related to rising levels of potassium concentration in the extracellular space that produces migratory symptoms as it spreads across the surface of the cortex.



3 What are the most important aspects of evaluating an acute ischemic stroke?


The last time the patient was known to be at his or her baseline is key to all acute stroke interventions. The earlier a thrombolytic can be given, the greater the chance for saving neurons and reversing disability. Three- and 4.5-hour windows for intravenous (IV) thrombolysis relate primarily to the risk of hemorrhage, whereas patients receiving thrombolytic treatment within 90 minutes of symptom onset have the greatest benefit. Time is brain.



4 Who should be administered IV recombinant tissue plasminogen activator (IVtPA)?


All patients seen within 3 hours of onset of acute neurologic deficit thought to result in significant disability (generally a National Institutes of Health Stroke Scale [NIHSS] score >3-4)and having intracerebral hemorrhage excluded by head computed tomography (CT) should be administered IVtPA.



5 Who should not receive IVtPA?


See Box 62-1.



Box 62-1 Contraindications for IVtPA



Absolute contraindications to IVtPA




image Presence of hemorrhage or large territory infarction on unenhanced head CT


image Central nervous system lesion with high likelihood of hemorrhage (tumor, vascular malformation, aneurysm, abscess, contusion)


image Known bacterial endocarditis



Relative contraindications to IVtPA (these are often interpreted widely and it may be reasonable to treat selected patients in the presence of one or more of these risk factors)




image Minor or rapidly improving symptoms


image Seizure at stroke onset


image Previous stroke or serious head trauma within 3 months


image Major surgery within 14 days or minor surgery within 10 days


image History of prior intracerebral hemorrhage


image Blood pressure >185/110 mm Hg (may be corrected with antihypertensive)


image Pregnant or less than 10 days post partum


image Arterial puncture at noncompressible site within 7 days


image International normalized ratio >1.7 (or prothrombin time >15/sec), partial thromboplastin time >40/sec, platelet count <100,000/μL


image Glucose <50 mg/dL or >400 mg/dL


image NIHSS score >22



6 Who are candidates for extended-window IVtPA?


Patients presenting between 3 and 4.5 hours after symptom onset may be candidates for extended-window IVtPA. There are additional exclusion criteria for extended-window tPA: age >80 years, NIHSS score >25, greater than one-third middle cerebral arteries (MCA) territory infarction by CT or magnetic resonance imaging (MRI), any oral anticoagulant use, prior stroke, or diabetes.



7 What are the benefits and risks of IVtPA?


IVtPA is supported by level I evidence and results in 30% reduction in disability at 3 months compared with placebo. Symptomatic hemorrhage rates vary depending on the study but range from 3% to 6%. An additional one in three patients given treatment with IVtPA will improve by one grade on the modified Rankin scale, and an additional one in eight will have complete reversal of deficits.



8 When should you consider intraarterial thrombolysis or a catheter-based clot retrieval?


Intraarterial interventions remain an experimental therapy for acute ischemic stroke, although use of direct lytics via intraarterial catheter has a limited recommendation based on the Prolyse in Acute Cerebral Thromboembolism (PROACT) trial. Use of this intervention varies by institution. Intraarterial administration of thrombolytics is limited to 6 hours from last seen well time, whereas mechanical retrieval tends to be limited to 8 hours from symptom onset. Patients generally must have more severe neurologic deficits (NIHSS score >6) and a proximal arterial occlusion to be considered for intraarterial therapy. Full-dose IVtPA is not a contraindication to patients undergoing a catheter-based intervention.



9 Describe the cerebral vasculature


Four arteries supply the brain. Two common carotid arteries bifurcate into external and internal segments. The internal segment penetrates the base of the skull and travels within the cavernous sinus. The carotid emerges from the sinus to bifurcate into anterior cerebral arteries (ACA) and MCA. The carotid arteries terminating in ACA and MCA branches compose the anterior circulation. The posterior circulation is supplied by two vertebral arteries traveling within the lateral foramina of the sixth to second cervical vertebrae, which then penetrate the dura mater and join at the midline at the level of the pons to form the basilar artery. The basilar bifurcates to form the posterior cerebral arteries (PCA). Anterior and posterior circulations are joined by the posterior communicating arteries creating the circle of Willis.



10 Describe a lacune and the common lacunar syndromes


A lacune literally means pit. Lacunar infarcts represent a series of small perforating vessel occlusions that result in clinical symptoms that differ from large artery infarctions. Lacunar strokes tend to be either motor or sensory and typically lack cortical findings such as alterations of consciousness or corticosensory modalities (i.e., graphesthesia, stereognosis). See Box 62-2.



Box 62-2 Lacunar syndromes




Pure motor weakness: Face, arm and leg all involved equally. No cognitive, sensory, or visual field loss. Usually in contralateral pons or internal capsule.


Pure sensory syndrome: Numbness or paresthesias of face, arm, and leg without cognitive, motor, or visual field cut. Most commonly localized to the contralateral ventroposterolateral or medial thalamus.


Ataxic hemiparesis: Contralateral ataxia and weakness without cognitive, sensory, or visual field cut. Localizes to posterior limb of internal capsule or pons.


Dysarthria or clumsy hand: Contralateral hand clumsiness. Face or tongue weakness and slurred speech. Localizes to the pons.

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Jul 6, 2016 | Posted by in CRITICAL CARE | Comments Off on Stroke

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