ABCD2 score for transient ischaemic attack (also searched with possessive/alternate eponym spelling where applicable, ICD-10: G45.9) is a widely adopted clinical prediction rule designed to quantify the early risk of stroke in patients presenting with a transient ischaemic attack (TIA) ^1,3. Defined clinically as a transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia without acute infarction, TIA represents a critical clinical warning sign ^2,3. Because the risk of subsequent stroke is exceptionally high in the immediate days following an index event—with nearly half of early recurrent strokes occurring within the first 48 hours—rapid risk stratification is mandatory ^1,3. The ABCD2 score stratifies patients into low, moderate, and high-risk categories based on five clinical parameters: Age, Blood pressure, Clinical features, Duration of symptoms, and Diabetes mellitus ^1,3. By quantifying these variables, clinicians can reliably identify individuals who require urgent hospital admission, neurovascular imaging, and secondary stroke prevention therapies ^1,3.

Etiology & Risk Factors

Thromboembolic Mechanisms: Arterio-arterial embolization originating from atherosclerotic plaques within the carotid bifurcation or intracranial vasculature is a primary etiology.
Cardioembolic Sources: Conditions such as non-valvular or valvular atrial fibrillation, recent myocardial infarction, infective endocarditis, and patent foramen ovale facilitate thrombus formation and subsequent cerebral migration.
Small Vessel Disease: Lipohyalinosis and fibrinoid necrosis of penetrating cerebral arterioles lead to lacunar ischemic events.
Hypercoagulable States: Malignancy, inherited thrombophilias, oral contraceptive use, and systemic inflammatory disorders elevate thrombotic risk.
Traditional Vascular Risk Factors: Essential hypertension, diabetes mellitus, dyslipidemia, cigarette smoking, advanced age, and positive family history of cerebrovascular disease^1,3.

Pathophysiology

The pathophysiological cascade underlying a transient ischaemic attack involves a temporary, critical reduction in regional cerebral blood flow below the metabolic threshold required for normal neuronal function, yet remaining above the threshold for irreversible cellular necrosis. Interruption of blood flow precipitates rapid cellular ATP depletion, failure of ATP-dependent membrane ion pumps, and a net influx of sodium and calcium ions accompanied by cytotoxic edema. If perfusion is restored spontaneously via endogenous fibrinolysis or collateral recruitment before the ischemic penumbra transitions to core infarction, tissue damage remains reversible, and neurological function normalizes. The clinical features of the TIA correspond directly to the specific vascular territory affected—such as the anterior circulation via the middle cerebral artery or posterior circulation via the vertebrobasilar system. The ABCD2 score captures clinical markers that reflect underlying plaque instability, hemodynamic reserve exhaustion, and thrombotic burden, which collectively correlate with the likelihood of subsequent fixed cerebral infarction^1,2.

Clinical Presentation & Classic Clinical Signs

History & Cardinal Symptoms: Patients typically report the sudden onset of focal neurological deficits that reach maximal intensity at onset. Classic symptoms include unilateral motor weakness (face, arm, or leg), sensory loss, hemianopia, dysarthria, or aphasia. Retinal ischemia manifests as transient monocular visual loss (amaurosis fugax).
Physical Examination & Named Clinical Signs: By definition, neurological deficits resolve completely within 24 hours, frequently within 30 to 60 minutes. Physical examination during or immediately after an event may reveal carotid bruits, irregular cardiac rhythms such as irregularly irregular pulses indicative of atrial fibrillation, elevated systemic blood pressure readings, or subtle residual coordination deficits. Absence of acute structural lesions on initial neuroimaging confirms the transient nature of the ischemic insult³.

Diagnostic Workup & Interpretation (Laboratory, Imaging & ECG/Pathology)

Diagnostic Modality / Test	Expected Clinical & Radiological / Laboratory Finding
Gold-Standard Investigation	Diffusion-weighted magnetic resonance imaging (DW-MRI) demonstrating no acute restricted diffusion, or identifying small, reversible ischemic foci corresponding to clinical symptoms.
Laboratory Panel	Complete blood count, comprehensive metabolic panel, fasting lipid profile, and glycated hemoglobin (HbA1c) to evaluate underlying vascular risk factors and hypercoagulable states.
Imaging / Radiology (X-ray, US, CT, MRI)	Urgent computed tomography (CT) or magnetic resonance (MR) angiography of the head and neck to assess for high-grade carotid stenosis, intracranial large vessel occlusion, or plaque morphology. Carotid duplex ultrasonography serves as an accessible alternative.
ECG / Histopathology / Procedural	12-lead electrocardiogram and prolonged outpatient cardiac telemetry (e.g., 24-hour Holter monitor or loop recorder) to screen for paroxysmal atrial fibrillation or other occult arrhythmogenic sources.

Staging, Classification & Clinical Scoring Systems

Criterion / Stage / Score Component	Clinical Threshold, Points & Management Implication
Age (A)	Age $\ge$ 65 years = 1 point; Age < 65 years = 0 points. Reflects cumulative vascular aging and atherosclerotic burden.
Blood Pressure (B)	Systolic blood pressure $\ge$ 140 mmHg or diastolic blood pressure $\ge$ 90 mmHg at presentation = 1 point; lower readings = 0 points. Highlights acute or chronic hypertensive stress on the cerebral vasculature.
Clinical Features (C)	Unilateral weakness = 2 points; speech disturbance without weakness = 1 point; other symptoms = 0 points. Motor deficits signify greater involvement of critical motor pathways.
Duration of Symptoms (D)	Duration $\ge$ 60 minutes = 2 points; 10 to 59 minutes = 1 point; < 10 minutes = 0 points. Prolonged ischemia correlates with higher risk of infarction.
Diabetes Mellitus (D)	History of diabetes mellitus = 1 point; no history = 0 points. Identifies systemic metabolic dysfunction accelerating endothelial injury.
Risk Stratification & Action	Score 0–3 (Low risk): outpatient evaluation. Score 4–5 (Moderate risk) and Score 6–7 (High risk): urgent specialist assessment, hospital admission or rapid-access TIA clinic evaluation within 24 hours^1,3.

Differential Diagnosis

Differential Condition	Distinguishing Clinical, Biochemical & Imaging Features
Migraine Aura	Typically presents with visual or sensory symptoms that propagate gradually over 5 to 20 minutes, frequently accompanied by headache and positive scintillating scotomas, contrasting with the abrupt, maximal-at-onset deficit of TIA.
Focal Seizure / Todd Paresis	Characterized by positive motor phenomena (clonic movements), jacksonian march, or post-ictal focal paralysis that resolves gradually, often associated with epileptiform activity on electroencephalography.
Hypoglycemia	Presents with acute neuroglycopenic symptoms that mimic focal ischemia but resolve rapidly upon intravenous administration of glucose or oral carbohydrate intake, confirmed by low bedside capillary blood glucose.
Peripheral Vestibular Disorders	Benign paroxysmal positional vertigo or vestibular neuritis causes spinning vertigo and nausea exacerbated by head movement, typically lacking the focal neurological signs (such as aphasia, hemiparesis, or visual field cuts) seen in vertebrobasilar TIA.

Management & Treatment Protocol

Initial Stabilization & Resuscitation: Assess airway, breathing, and circulation. Monitor vital signs continuously, maintain adequate oxygen saturation above 92%, and establish intravenous access while ruling out hemorrhagic stroke via urgent neuroimaging.
First-Line Medical / Pharmacological Therapy (with exact adult dosing): Initiate antiplatelet therapy immediately after excluding intracranial hemorrhage. Standard dual antiplatelet therapy consists of a loading dose of aspirin 162 to 325 mg followed by 81 mg orally daily, combined with a loading dose of clopidogrel 300 mg followed by 75 mg orally daily for up to 21 to 90 days, transitioning thereafter to single antiplatelet therapy. Alternatively, monotherapy with aspirin 81–325 mg daily, clopidogrel 75 mg daily, or extended-release dipyridamole/aspirin (200/25 mg twice daily) may be utilized. Initiate high-intensity statin therapy (e.g., atorvastatin 80 mg orally daily) regardless of baseline low-density lipoprotein levels. Manage hypertension aggressively if chronic, avoiding overly rapid drops during acute phases unless indicated.
Surgical / Interventional Indications: Patients with ipsilateral extracranial internal carotid artery stenosis of 70% to 99% (or 50% to 69% with high-risk plaque features) should be evaluated for urgent carotid endarterectomy or carotid artery stenting, ideally within 2 weeks of the index event.

Complications & Prognosis

The primary acute complication of transient ischaemic attack is progression to completed cerebral infarction, with the highest vulnerability concentrated within the first 24 to 72 hours following the initial event^1,3.
Secondary complications include cognitive impairment, recurrent vascular events, myocardial infarction, and psychological distress including anxiety and depression related to fear of subsequent stroke.
Prognosis is heavily dictated by the ABCD2 score stratification: low-risk patients experience minimal short-term stroke rates, whereas high-risk individuals face up to a 12% risk of stroke within 7 days and up to 20% within 90 days if prompt secondary prevention measures are not instituted³. Rapid-access evaluation in specialized stroke clinics significantly mitigates this risk and improves long-term functional outcomes¹.

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ABCD2 score for transient ischaemic attack