Transient Ischemic Attack

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Ischemic Spectrum: A Transient Ischemic Attack (TIA) is defined as a transient episode of neurological dysfunction caused by focal brain, retina, or spinal cord ischemia without radiographic evidence of cellular tissue infarction.
• Atherothromboembolic and Cardioembolic Occlusion: The underlying mechanism is driven by acute luminal occlusion of a cerebral artery. This is most commonly caused by a cardioembolic source (accounting for >30% of cases, primarily associated with atrial fibrillation), large-to-medium-sized vessel atheromatous disease (9% to 13%), or intracranial small vessel disease (20%).
• The Metabolic Crisis and Reversibility: Following arterial obstruction, a rapid decline in local perfusion causes regional oligemia, disrupting normal oxygen and glucose metabolism. This failure halts the sodium-potassium ATPase pump, shifting extracellular water into the intracellular compartment. In a TIA, collateral circulation, spontaneous fibrinolysis, or vessel shear forces restore blood flow before the cellular damage progresses to irreversible tissue necrosis. Symptom duration is historically a key clinical discriminator, but any event lasting more than 1 hour carries a high likelihood of permanent radiographic infarction on magnetic resonance imaging (MRI).

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• Airway and Cardiorespiratory Assessment: Assess airway patency, the ability to clear secretions, and respiratory stability. Provide supplemental oxygen only if the oxygen saturation is <94%; avoid hyperoxia, which is associated with poor outcomes.
• Metabolic and Triage Screening: Immediately obtain a point-of-care capillary glucose test at triage to exclude hypoglycemia, which is a major stroke/TIA mimic.
• Hemodynamic Management:
• In the acute phase (the first 24 hours), maintain the blood pressure below 220/110 mm Hg to preserve cerebral collateral perfusion, unless the patient is a candidate for acute reperfusion therapy (where the goal is <185/110 mm Hg).
• If antihypertensive therapy is required, choose a titratable, short-acting intravenous medication:
• Clevidipine: Initial infusion of 1 to 2 mg/hour IV; titrate by doubling the dose every 2 to 5 minutes to a maximum of 21 mg/hour (up to 32 mg/hour has been studied).
• Labetalol: Administer 10 to 20 mg IV push over 1 to 2 minutes; may repeat or double the dose every 10 minutes (e.g., 20–40 mg) to a maximum of 80 mg per dose (up to 300 mg total).
• Nicardipine: Initial infusion of 5 mg/hour IV; titrate up by 2.5 to 5 mg/hour every 10 minutes to achieve the desired target (maximum rate 15 mg/hour).
• First-Line Antiplatelet and Anticoagulation Therapy:
• Dual Antiplatelet Therapy (DAPT) for High-Risk Cases: In patients presenting with a high-risk TIA (ABCD2 score ≥4) or minor ischemic stroke who did not receive thrombolytics, initiate DAPT with Aspirin and Clopidogrel for a duration of 21 days. Comprehensive trials demonstrate that DAPT is superior to aspirin monotherapy in preventing early recurrent stroke without significantly increasing the risk of major hemorrhage during this brief window.
• Direct Oral Anticoagulants (DOACs) for Cardioembolic TIA: For patients with a newly diagnosed or untreated cardioembolic source (e.g., atrial fibrillation), do not anticoagulate in the ED, but arrange for the prompt initiation of a DOAC. DOACs are preferred over warfarin due to a lower bleeding risk and similar efficacy. Choose one of the following oral agents:
• Apixaban: 5 mg PO every 12 hours (reduce to 2.5 mg PO every 12 hours if creatinine is ≥1.5 mg/dL and the patient is either ≥80 years old or weighs ≤60 kg).
• Edoxaban: 60 mg PO once daily for patients >60 kg (reduce to 30 mg PO daily if ≤60 kg or if creatinine clearance is 15–50 mL/minute).
• Rivaroxaban: 20 mg PO once daily with meals (reduce to 15 mg PO daily if creatinine clearance is <50 mL/minute).
• Mechanical Valves: If a mechanical valve is present, Warfarin is required, typically starting at 5 mg PO daily (or 2.5 mg PO daily in elderly, malnourished, or high-risk patients).

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

Top 5 "Can't-Miss" Mimics

1. Hypoglycemia: Must be excluded immediately on arrival in all patients presenting with focal neurological deficits.
2. Migraine (specifically hemiplegic or complex migraine): Can present with unilateral hemiparesis, sensory loss, or aphasia followed by headache. Distinguish via history and neuroimaging.
3. Seizures with Todd's Paralysis: Seizures present with positive/irritative motor phenomena, whereas TIA presents with negative/ablative neurological symptoms.
4. Syncope: Syncope represents global, transient cerebral hypoperfusion causing loss of consciousness, whereas TIA presents with focal, localized vascular deficits.
5. Ménière Disease / Peripheral Vestibular Disorders: Ménière disease presents with hearing loss, aural fullness, and tinnitus; TIA of the posterior circulation presents with vertigo accompanied by other focal brainstem signs.

Prioritized Diagnostic Workup Strategy

• Point-of-Care Capillary Glucose: The first mandatory test.
• 12-Lead ECG & Telemonitoring: To screen for Atrial Fibrillation or structural arrhythmias.
• Standard Stroke Labs: CBC, BMP, and coagulation profile (PT/INR, aPTT).
• Emergent Non-contrast Head CT: Obtained to rule out acute intracranial hemorrhage, mass lesions, or old strokes that could cause mimicking symptoms.
• CTA of the Head and Neck: Pertinent to assess for intracranial or extracranial arterial stenosis, occlusion, or dissection.
• Gold Standard Parenchymal Imaging (DWI-MRI): Diffusion-weighted MRI (DWI) must be obtained when feasible, as it is the only modality that can reliably distinguish TIA from acute ischemic stroke.
• Echocardiography: Recommended to assess for cardioembolic causes (PFO, left ventricular thrombus, or valvular vegetations).

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

Standard ECG Visual Checklist

• Atrial Fibrillation: Check for an irregularly irregular rhythm with absent P waves.
• Myocardial Ischemia: Scan for ST-segment depressions, elevations, or hyperacute T waves, which can indicate concurrent acute coronary syndrome.
• Left Ventricular Hypertrophy (LVH): Look for deep S waves in V1/V2 and tall R waves in V5/V6, which signify long-standing hypertension.

Point-of-Care Ultrasound (POCUS) Findings

• Echocardiography (Transthoracic or Transesophageal): Check for left ventricular wall motion abnormalities, a patent foramen ovale (PFO), or a left atrial appendage thrombus.
• Carotid Duplex Ultrasound: Assess the carotid bifurcation for calcified plaques or hemodynamically significant stenosis.

Neuroimaging Visual Checklist

• Non-contrast Head CT: Look for a "hyperdense middle cerebral artery (MCA) sign" or "basilar sign" representing an acute thrombus, or focal areas of hypodensity representing old infarcts.
• Brain MRI (DWI and ADC Sequences): Scan the brainstem and hemispheres.
• Ischemic Stroke: Displays as hyperintense (bright white) on DWI and hypointense (black) on ADC maps.
• Transient Ischemic Attack: Brain parenchyma will show no restricted diffusion on DWI sequences.

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

The ABCD2 Risk Score for TIA

Calculate the score to estimate the 48-hour risk of a completed stroke

1. Age: ≥60 years old (1 point)
2. Blood Pressure: Initial BP >140/90 mm Hg (1 point)
3. Clinical Features: Unilateral weakness (2 points) OR Speech impairment without weakness (1 point)
4. Duration of Symptoms: 10–59 minutes (1 point) OR ≥60 minutes (2 points)
5. Diabetes: History of diabetes mellitus (1 point)

• Risk Cutoffs and Stroke Probability:
• 0–3 points (Low Risk): Associated with a 1% risk of stroke in 48 hours.
• 4–5 points (Moderate Risk): Associated with a 4.1% risk of stroke in 48 hours.
• ≥6 points (High Risk): Associated with an 8% risk of stroke in 48 hours.

The Canadian TIA Score

• Developed in a cohort of 3,906 patients across 8 EDs, this highly validated 17-point clinical decision rule incorporates clinical, historical, and head CT findings to predict the risk of a recurrent stroke within 7 days (discriminating risk from 0.01% to 27.6%).

Mandatory Scoring Guidelines

• Scoring systems must not be used as the sole determinant for patient disposition. Risk prediction scores are imperfect and can fail to identify high-risk patients; clinical gestalt and individual patient risk profiles must guide the ultimate decision.

6. THE DANGER ZONE (Pitfalls & Critical Actions)

Deadly Cognitive Traps & Trainee Pitfalls

• The "Resolved Symptoms" Trap: Discharging a patient from the ED simply because they have returned to their neurological baseline. A TIA is a warning sign; up to 12% to 30% of stroke patients experience a preceding TIA, and the recurrent stroke risk is highest in the first 24 to 48 hours.
• The "Low-Risk Score" Illusion: Discharging a patient based solely on an ABCD2 score ≤3 while ignoring high-risk clinical features such as stuttering or crescendo events, a suspected cardioembolic source, or known carotid stenosis.
• Aggressive Acute BP Lowering: Intentionally lowering blood pressure in the acute phase of a TIA when the BP is <220/110 mm Hg. This can cause hypoperfusion through cerebral collaterals and convert salvageable penumbra into an active ischemic stroke.
• Misinterpreting "Positive" Symptoms: Confounding stroke mimics (such as focal seizures or migraines presenting with positive, irritative symptoms like paresthesias) with a true TIA, which presents with negative, ablative neurological deficits.

Mandated Board-Exam Critical Actions

• Obtain a point-of-care capillary glucose test on arrival to rule out hypoglycemia.
• Perform and document a comprehensive cardiovascular exam, checking for an irregularly irregular pulse (Atrial Fibrillation) and listening for a murmur.
• Inquire about the pattern of symptoms, specifically screening for stuttering or crescendo events, which represent high-risk criteria indicating unstable cerebral circulation.
• Ensure that all suspected TIA patients undergo an etiologic workup, including vascular imaging of the neck, during the index visit or in an accelerated outpatient pathway.

7. MCQ MASTERCLASS (Written Exam Tips)

High-Yield Exam "Buzzwords" and Associations

• "Peak Risk Window": The risk of a completed ischemic stroke following a TIA is highest within the first 24 to 48 hours.
• "Positive vs. Negative Symptoms": Seizures and migraines present with positive/irritative signs (paresthesias, shaking); TIA and stroke present with negative/ablative signs (weakness, loss of function, numbness).
• "21 Days of DAPT": High-risk TIA (ABCD2 score ≥4) or minor stroke is treated with DAPT for exactly 21 days; trials show continuing DAPT beyond 21 days increases the 90-day risk of major hemorrhage without providing a further reduction in ischemic events.
• "14-Day Carotid Intervention Window": Symptomatic patients with significant extracranial carotid stenosis (>50% to ≥70%) must undergo carotid endarterectomy or carotid stenting within 14 days of the TIA to maximize the stroke prevention benefit.

Differentiating Distractors

• Distractor: Initiating systemic anticoagulation with a heparin drip in the ED for an acute TIA or stroke.
• Correction: Do not anticoagulate patients in the ED; heparin is not indicated for non-cardioembolic TIA and can increase bleeding risk.
• Distractor: Ordering an MRA or MRV of the head and neck in a pregnant patient with suspected TIA.
• Correction: MRA/MRV are relatively contraindicated in pregnancy due to the risk of gadolinium exposure; uncontrasted head CT or MRI are the preferred diagnostic modalities.

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

Triage and Stabilization Script

• "This patient presents with fully resolved left-arm weakness and speech difficulty. I recognize that a Transient Ischemic Attack is a warning sign of an impending completed stroke. I will place the patient in a monitored resuscitation bay, assess their airway, breathing, and circulation, and obtain an immediate point-of-care capillary glucose test to rule out hypoglycemia as the most common stroke and TIA mimic."

Mandatory Physical Exam Phrasing

• "I will perform a systematic physical and cardiovascular examination. I will palpate the peripheral pulses and check for an irregularly irregular rhythm to evaluate for Atrial Fibrillation, and auscultate the heart for murmurs that could indicate a valvular source of emboli. I will perform a comprehensive, detailed neurologic exam, evaluating language for word-finding difficulty or slurred speech, testing visual fields, checking for carotid bruits, and documenting symmetric extremity motor strength."

Diagnostics and Management Phrasing

• "I will obtain a 12-lead ECG and place the patient on continuous telemonitoring to identify paroxysmal Atrial Fibrillation. I will order standard laboratory tests, including a CBC, BMP, and coagulation studies. I will order an emergent non-contrast head CT scan to rule out acute hemorrhage or mass lesions, and a CTA of the head and neck to evaluate for extracranial and intracranial stenosis."
• "Because this patient has a high-risk TIA with an ABCD2 score of 6, I will initiate Dual Antiplatelet Therapy in the ED with Aspirin and Clopidogrel for a planned 21-day course. I will maintain the patient's blood pressure below 220/110 mm Hg to preserve collateral cerebral perfusion."

Disposition Phrasing

• "I will consult neurology. Because this patient has a high-risk ABCD2 score of 6 and has had stuttering symptoms, she is at extreme risk for a completed stroke. I will admit her to the Stroke Unit or our ED-directed Observation Unit under an accelerated diagnostic protocol to expedite her diffusion-weighted brain MRI, formal carotid imaging, and echocardiography. I will not discharge her home based on her resolved symptoms or risk scores alone."