Stroke 1 & 2 PDF

 Stroke DR Ramezani  Definition Stroke is a syndrome characterized by the acute onset of a neurologic deficit that persists for at least 24 hours, reflects focal involvement of the CNS, and is the result of a disturbance of the cerebral c...

 Stroke DR Ramezani  Definition Stroke is a syndrome characterized by the acute onset of a neurologic deficit that persists for at least 24 hours, reflects focal involvement of the CNS, and is the result of a disturbance of the cerebral circulation Epidemiology ► Stroke is the third most common cause of death in the United States and the most common disabling neurologic disorder ► The incidence increases with age, with about two- thirds of all strokes occurring in those older than 65 years ► is somewhat higher in men than in women Risk factors for stroke ► systolic or diastolic hypertension ► Hypercholesterolemia ► cigarette smoking ► Diabetes ► heavy alcohol consumption ► oral contraceptive use CIRCULATION ANTERIOR CIRCULATION ► The anterior cerebral circulation, supplies ► most of the cerebral cortex and subcortical white matte ► basal ganglia ► internal capsule ► consists of the internal carotid artery and its branches ► symptoms a and signs: ► indicate hemispheric dysfunction such as ► aphasia ► Apraxia ► Agnosia ► Also hemiparesis, hemisensory disturbances, and visual field defects, which can also occur with posterior circulation strokes POSTERIOR CIRCULATION ► supplies ► the brainstem ► Cerebellum ► thalamus ► portions of the occipital and temporal lobes ► consists of the paired vertebral arteries, the basilar artery, and their branches: ► the posterior inferior cerebellar arteries ► anterior inferior cerebellar arteries ► superior cerebellar arteries ► posterior cerebral arteries ► thalamoperforate ► thalamogeniculate branches Posterior circulation ► Posterior circulation strokes produce ► symptoms and signs of brainstem dysfunction ► Coma ► drop attacks ► Vertigo ► nausea and vomiting ► cranial nerve palsies ► Ataxia ► crossed sensorimotor deficits ► Hemiparesis, hemisensory disturbances, and visual field deficits also occur, but are not specific to posterior circulation strokes Types of stroke ► Ischemia accountes for about two-thirds 1. Thrombosis 2. Embolism ► hemorrhage accounts for about one-third of strokes 1. Intracerebral hemorrhage 2. Subarachnoid hemorrhage 3. Subdural or epidural hemorrhage ► Unlike ischemic stroke 1. intracerebral hemorrhage tends to cause more severe headache and depression of consciousness 2. neurologic deficits that do not correspond to the distribution of any single blood vessel 3. Hypertensive hemorrhage occurs without warning, most commonly while the patient is awake Ischemic stroke Ischemic stroke ► Thrombosis ► Symptoms typically evolve over minutes to hours ► Thrombotic strokes are often preceded by TIAs, which tend to produce similar symptoms because they affect the same territory recurrently ► Embolism ► Emboli in the anterior cerebral circulation most often occlude the middle cerebral artery or its branches, since approximately 85% of the hemispheric blood flow is carried by this vessel ► Emboli in the posterior cerebral circulation usually lodge at the apex of the basilar artery or in the posterior cerebral arteries ► Embolic strokes characteristically produce neurologic deficits that are maximal at onset ► When TIAs precede embolic strokes, especially those arising from a cardiac source, symptoms typically vary between attacks  Lacunar infarction ► results from the occlusion of small penetrating branches of the major cerebral arteries ► ranges in diameter from 0.5 to 15.0 mm ► lacunar infarcts are most common in deep nuclei of the brain (putamen, 37%; thalamus, 14%; caudate nucleus, 10%), the pons (16%), and the posterior limb of the internal capsule (10%) ► They occur in lesser numbers in the deep cerebral white matter, the anterior limb of the internal capsule, and the cerebellum Lacunar infarction ► caused by either ► atherosclerosis or ► degenerative changes in arterial walls (including lipohyalinosis and fibrinoid necrosis) that are related to long-standing hypertension ► Both hypertension and diabetes appear to predispose to this type of stroke ► Headache is absent or minor, and the level of consciousness is unchanged ► the likelihood of future lacunar strokes can be reduced by treating the hypertension Venous or sinus thrombosis ► is typically associated with a predisposing condition such as otitis or sinusitis, a postpartum state, dehydration, or coagulopathy ► Clinical features include; ► Headache ► papilledema ► impaired consciousness ► Seizures ► focal neurologic deficits ► CSF pressure is typically increased Venous or sinus thrombosis ► CT scan with contrast sometimes shows a filling defect corresponding to the clot (delta sign) ► MRI with contrast is the diagnostic procedure of choice in most cases. The diagnosis may be confirmed by MR angiography ► Septic thromboses are treated with antibiotics ► Anticoagulation has been used for aseptic thrombosis CARDIAC DISORDERS 1. Mural thrombus 2. Rheumatic heart disease 3. Arrhythmias 4. Endocarditis 5. Mitral valve prolapse 6. Paradoxic embolus 7. Atrial myxoma 8. Prosthetic heart valves HEMATOLOGIC DISORDERS 1. Thrombocytosis 2. Polycythemia 3. Sickle cell disease 4. Leukocytosis 5. Hypercoagulable states Hyperviscosity Estrogen therapy oral contraceptive use postpartum postoperative states cancer Antiphospholipid antibodies Hereditary coagulopathies ❖ heparin cofactor II deficiency, protein C deficiency, defective release of plasminogen activator, and factor XII deficiency Clinical syndrome of ACA occlusion ► are uncommon ► There is a contralateral paralysis and sensory loss affecting the leg ► Voluntary control of micturition may be impaired because of failure to inhibit reflex bladder contractions MCA Anatomy Clinical syndromes of middle cerebral artery occlusion a. Superior division stroke b. Inferior division stroke c. Occlusion at the bifurcation or trifurcation of the middle cerebral artery d. Occlusion of the stem of the middle cerebral artery lateral medullary (Wallenberg) syndrome ► ipsilateral 1. cerebellar ataxia 2. Horner syndrome 3. facial sensory deficit ► contralateral 1. impaired pain and temperature sensation 1. Nystagmus 2. Vertigo 3. Nausea-vomiting 4. Dysphagia 5. Dysarthria 6. Hiccup ► The motor system is characteristically spared because of its ventral location in the brainstem ► Posterior inferior cerebellar artery occlusion Structures Affected 1. Vestibular nuclei (medial and inferior) 2. Inferior cerebellar peduncle 3. Nucleus ambiguus and/or root fibers 4. Glossopharyngeal root fibers 5. Spinal lemniscus 6. Spinal trigeminal nucleus and/or tract 7. Lateral tectotegmentospinal tract (not shown) 8. Medial reticular formation (inspiratory center) INVESTIGATIVE STUDIES A.BLOOD TESTS ► 1. Complete blood count ► 2. Erythrocyte sedimentation rate ► 3. PT,PTT ► 4. Serum glucose ► 5. Serum cholesterol and lipids B. ELECTROCARDIOGRAM C. CT SCAN OR MRI  CT SCAN OR MRI ► A CT scan or MRI should be obtained routinely to 1. distinguish between infarction and hemorrhage as the cause of stroke 2. exclude other lesions (e.g., tumor, abscess) 3. Localize the lesion ► CT scan is usually preferred for initial diagnosis because 1. it is widely available and rapid 2. can readily make the critical distinction between ischemia and hemorrhage ► MRI may be superior to CT scan for 1. demonstrating early ischemic infarcts 2. showing ischemic strokes in the brainstem or cerebellum 3. detecting thrombotic occlusion of venous sinuses TREATMENT 1. Antiplatelet therapy ► Of the various medical treatments proposed for stroke prophylaxis, antiplatelet agents appear to have the best benefit-to-risk ratio 1. Aspirin interferes with platelet function by irreversibly inhibiting the enzyme cyclooxygenase-1 (30 and 1300 mg orally daily) 2. Clopidogrel and ticlopidine irreversibly inhibit the binding of adenosine diphosphate (ADP) to its platelet receptor (75 mg orally daily), (250 mg orally twice daily) 3. Dipyridamole increases concentrations of cAMP, which decreases platelet activation (200 mg twice daily) Anticoagulation ► Indications: 1. TIAs caused by cardiac embolus 2. TIAs caused by hypercoagulable state ► is typically continued indefinitely or for as long as the cause of embolization (e.g., atrial fibrillation or prosthetic heart valve) persists ► The value of anticoagulation for TIAs from arterial thrombosis is uncertain STROKE IN EVOLUTION ► Anticoagulation ► particularly in cases of high-grade, large-vessel stenosis or occlusion ► the efficacy of this approach has not been proven ► Thrombolytic agents ► tissue plasminogen activator (t-PA) ► administered in the hyperacute phase of stroke (