Stroke

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Core Mechanism: Stroke syndromes are broadly divided into ischemic (thrombotic or embolic vascular occlusion) and hemorrhagic (intracerebral or subarachnoid rupture). Both pathways result in an abrupt cessation of blood flow to specific brain territories, triggering localized cellular hypoxia, failure of ATP-dependent membrane pumps, cytotoxic edema, and progressive neuronal death.
• The Ischemic Penumbra: Surrounding the unsalvageable core of necrotic tissue is the ischemic penumbra—a zone of severely hypoperfused but potentially viable brain tissue. The entire premise of acute stroke resuscitation (permissive hypertension, thrombolytics, and endovascular thrombectomy) relies on rapidly restoring perfusion to save this exact tissue layer.
• The TIA Paradigm Shift: The definition of a Transient Ischemic Attack (TIA) has shifted from a time-based definition (<24 hours) to a strictly tissue-based definition: a transient episode of neurologic dysfunction caused by focal brain, spinal cord, or retinal ischemia, without evidence of acute infarction on advanced imaging.

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• Immediate Stabilization: Secure the ABCs, establish continuous cardiac monitoring, and place at least two large-bore IVs; however, do not delay emergent brain imaging for prolonged IV access attempts.
• Targeted Oxygenation & Positioning: Maintain SpO2 $\ge$ 94%; routine supplemental oxygen in normoxic patients should be avoided. For patients with acute large vessel occlusion (LVO) in the pre-thrombectomy phase, 0-degree (flat) head-of-bed positioning is a protective maneuver to maximize cerebral collateral blood flow and maintain clinical stability.
• Blood Pressure Management: Do not routinely lower blood pressure in the acute post-stroke period. Permissive hypertension is necessary to perfuse the penumbra. You must only intervene if the systolic BP is >220 mm Hg or diastolic >120 mm Hg, OR if there is a concurrent hypertensive emergency (e.g., aortic dissection, pre-eclampsia, myocardial infarction).
• Thrombolytic Therapy (Alteplase/t-PA):
• Indication: Eligible patients presenting within 3 hours of symptom onset (up to 4.5 hours for select patients 18-80 years old) with no contraindications.
• BP Threshold for t-PA: BP must be strictly lowered to <185/110 mm Hg prior to administration. Use IV Labetalol (10 mg over 2 min) or a Nicardipine infusion (5 mg/hr).
• Dosing: Alteplase 0.9 mg/kg (maximum 90 mg). Administer 10% as an initial IV bolus, and the remaining 90% as a continuous infusion over 1 hour.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

• "Can't-Miss" Mimics & Etiologies:
• Hypoglycemia: The most critical, easily reversible metabolic mimic.
• CNS Infections: Meningitis, encephalitis, or brain abscesses can present with focal deficits and altered mental status.
• Seizure / Todd's Paresis: A transient focal deficit following a seizure.
• Cervical Artery Dissection: A common cause of stroke in young patients, classically preceded by unilateral neck or face pain.
• Prioritized Diagnostic Workup:
• Point-of-Care (POC) Glucose: Absolutely mandatory before any other intervention to rule out hypoglycemia.
• Non-Contrast Head CT: The gold standard initial test to quickly exclude intracranial hemorrhage.
• CT Angiography (CTA) & CT Perfusion: Required emergently to identify large vessel occlusions (LVO) amenable to endovascular thrombectomy (EVT).
• ECG: To screen for atrial fibrillation or concurrent acute myocardial infarction (mural thrombus).

4. THE VISUAL BOARD (ECG / POCUS / Imaging)

• Non-Contrast Head CT Findings: Actively look for the hyperdense middle cerebral artery (MCA) sign, which represents acute intraluminal thrombus. Look for early ischemic signs such as loss of gray-white matter differentiation or obscuration of the lentiform nucleus [158/implied].
• ECG Co-occurrence: Recognize that acute ischemic stroke and acute myocardial infarction can occur simultaneously (e.g., via a paradoxical embolus traversing a patent foramen ovale or a Type A aortic dissection extending into the carotids).
• Neurologic Exam Patterns:
• Crossed Deficits: Ipsilateral cranial nerve deficits combined with contralateral extremity motor/sensory weakness localize the lesion specifically to the brainstem.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• National Institutes of Health Stroke Scale (NIHSS): A validated 15-item exam scoring system ranging from 0 (normal) to 34 (maximal injury) used to quantify stroke severity and determine thrombolytic eligibility. An NIHSS >25 is a relative contraindication to fibrinolytic therapy.
• ABCD2 Score (For TIA Risk Stratification): Predicts short-term stroke risk following a TIA based on: Age >60 years (1 point), BP >140/90 (1 point), Clinical features (unilateral weakness = 2 points, speech impairment without weakness = 1 point), Duration ($\ge$60 min = 2 points, 10-59 min = 1 point), and Diabetes (1 point).
• ROSIER Score (Recognition of Stroke in the ER): Awards points for asymmetrical facial/arm/leg weakness and speech/visual defects (+1 each), and subtracts points for LOC/syncope (-1) or seizure (-1). A score $\le$0 makes stroke highly unlikely.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• Deadly Cognitive Trap (Reflexive BP Control): Giving antihypertensives to "normalize" an asymptomatic elevated blood pressure in an acute stroke patient. Critical Action: You must allow permissive hypertension to perfuse the ischemic penumbra unless the patient is receiving t-PA, or the BP is critically elevated (>220/120), or there is a co-occurring emergency like aortic dissection.
• Deadly Cognitive Trap (Missing Posterior Strokes): Failing to recognize vertebrobasilar strokes because the patient lacks classic unilateral limb weakness. Critical Action: Posterior circulation strokes often present with vague but deadly symptoms: isolated vertigo, ataxia, nausea/vomiting, dysphagia, homonymous visual deficits, or "crossed" cranial nerve deficits.
• Critical Action (The "Time Zero" Definition): Do not anchor on the time the patient was found with symptoms. The time of onset must strictly be defined as the last known time when the patient’s condition was at their baseline (i.e., "last known well" time).

7. MCQ MASTERCLASS (Written Exam Tips)

• The TIA Definition Trick: An exam question will ask for the current definition of a TIA. The distractor will be "resolution of symptoms within 24 hours." Correction: Choose the option that defines TIA as a transient episode of ischemia without evidence of acute infarction on advanced imaging (tissue-based definition).
• The t-PA Contraindication Distractor: A patient presents 2 hours after a severe stroke. The stem notes they take warfarin daily, but their INR is currently 1.1. The distractor options will push you to administer t-PA since the INR is "subtherapeutic." Correction: Any oral anticoagulant treatment is an absolute contraindication to fibrinolysis in the 3- to 4.5-hour treatment window, regardless of the patient's INR.
• High-Yield Buzzwords: "Wallenberg syndrome" (lateral medullary syndrome) = vertigo, ipsilateral Horner syndrome, ipsilateral facial numbness, and contralateral loss of pain/temperature sensation. "Hyperdense MCA sign" = early CT sign of acute intraluminal thrombus.

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

• The Initial Assessment Hook: "Given the acute onset of focal neurologic deficits, I am activating the acute stroke team. My absolute immediate priorities are securing the ABCs, obtaining a STAT point-of-care blood glucose to rule out a hypoglycemic mimic, and establishing the exact 'last known well' time."
• The Diagnostic Command: "I will maintain the patient's head-of-bed flat at 0 degrees to optimize cerebral perfusion and perform a rapid NIH Stroke Scale. I am ordering an emergent non-contrast CT of the head to rule out hemorrhage, alongside a CTA of the head and neck to evaluate for a large vessel occlusion amenable to endovascular thrombectomy."
• The Intervention Pivot: "The CT head shows no hemorrhage. Because the patient is within the 4.5-hour window and has no contraindications, I will administer IV Alteplase at 0.9 mg/kg. However, since their blood pressure is currently 195/100, I must first initiate an IV Labetalol push or Nicardipine infusion to strictly lower the BP to <185/110 mm Hg prior to administering the lytics."