Transient Ischemic Attack

• Focal cerebral ischemia and the ischemic penumbra: TIAs occur when thromboembolism, hemodynamic insufficiency, or vasospasm reduces CBF to 20-40 mL/100g/min (critical threshold below which the neuronal membrane ion pumps fail, typically requiring > 80% vessel occlusion). At this flow threshold, synaptic transmission fails (causing neurological symptoms) but oxidative metabolism persists (preventing infarction), creating the ischemic penumbra—tissue at risk but not yet infarcted. The ABCD2 score concept reflects that shorter symptom duration and higher blood pressure at presentation suggest more severe ischemia that resolves more quickly. In TIA, collateral circulation is sufficiently robust or the thromboembolus spontaneously lyses (via endogenous fibrinolysis) before the ischemic cascade advances to excitotoxicity, calcium overload, and neuronal death.

• Embolic mechanisms and thrombus formation: The most common TIA mechanism is arterial embolism (45-50% of cases), wherein thrombi originating from carotid atherosclerotic plaques, the heart (atrial fibrillation, acute myocardial infarction, dilated cardiomyopathy), or paradoxical embolism (patent foramen ovale in cryptogenic cases) lodge in intracranial arteries. The thrombus triggers a cascade: tissue factor (TF) on the plaque surface activates Factor VII, initiating the extrinsic coagulation cascade; thrombin generation activates Factor XIII, crosslinking fibrin into a stable clot. Simultaneously, platelets adhere via von Willebrand factor and integrin αIIbβ3 interactions, amplifying thrombosis. However, unlike in stroke, spontaneous thrombolysis via tissue plasminogen activator (tPA) (endogenous fibrinolytic activity) or mechanical dislodgement restores flow before neuronal death. Neuroimaging in TIA patients reveals silent microinfarcts in 10-30% of cases (diffusion-weighted imaging [DWI] positive), suggesting that successful spontaneous thrombolysis occurs after some infarction has already begun.

• Hemodynamic insufficiency and flow-dependent ischemia: Tandem lesions (e.g., severe carotid stenosis with intracranial small vessel disease) or hypotension-triggered TIAs result from inadequate perfusion pressure rather than thromboembolism. In flow-dependent ischemia, vascular occlusion reduces mean arterial pressure distal to the stenosis below the autoregulatory threshold (typically 50-60 mmHg), causing focal ischemia in the watershed zone (junction between major arterial territories like the middle cerebral artery [MCA] and anterior cerebral artery [ACA]). Medications that lower blood pressure immediately after a TIA can paradoxically extend infarction by further reducing perfusion pressure in the ischemic region. Distinguishing hemodynamic from embolic TIA is critical: hemodynamic events warrant urgent revascularization (carotid endarterectomy, angioplasty/stenting), while embolic events require anticoagulation or antiplatelet therapy.

• Atherosclerotic plaque rupture and platelet aggregation: Rupture of an atherosclerotic plaque (particularly lipid-rich plaque with a thin fibrous cap) exposing tissue factor and phosphatidylserine triggers extrinsic pathway activation and rapid platelet adhesion via von Willebrand factor. The resulting platelet microthrombi (10-50 micrometers) can temporarily occlude small arteries, cause transient ischemia, and subsequently embolize distally or lyse spontaneously. This mechanism explains crescendo TIAs—multiple TIAs in quick succession indicating active plaque destabilization and high imminent stroke risk.

• Migraine-associated TIA and cortical spreading depression: A minority of TIAs (< 1%) are migraine-related, wherein cortical spreading depression (a slowly propagating wave of neuronal depolarization followed by hyperpolarization) causes transient focal neurological symptoms that mimic TIA. Spreading depression induces oligemia (reduced CBF to 20-40 mL/100g/min) without infarction by triggering sustained arteriolar constriction through endothelial dysfunction and impaired vasodilation. Risk is increased in migraine with aura, particularly in patients using estrogen-containing contraceptives or with patent foramen ovale.

• Large-artery atherosclerosis (45-50% of cases): Atherosclerotic plaques in the internal carotid artery (ICA), vertebral artery, or major intracranial vessels (middle cerebral artery, basilar artery) account for the largest proportion of TIAs. Carotid atherosclerosis presenting with ipsilateral monocular blindness (amaurosis fugax—TIA in the ophthalmic artery distribution) or contralateral motor/sensory symptoms is the classic presentation; ≥70% stenosis warrants consideration for carotid endarterectomy or stenting. Vertebrobasilar TIAs from vertebral atherosclerosis present with diplopia, ataxia, or bilateral symptoms. Plaque morphology predicts risk: lipid-rich (soft) plaques with thin fibrous caps are prone to rupture and ulceration, generating thrombi; calcified plaques are more stable.

• Cardioembolic sources (20-25% of cases): Atrial fibrillation (AF) is the most common cardioembolic source, conferring 4-5 fold increased stroke/TIA risk via stasis-induced thrombus formation in the left atrial appendage. Other major sources include: acute myocardial infarction with wall motion abnormality (especially anteroapical infarction with thrombus formation); dilated cardiomyopathy (ejection fraction < 35%); valvular disease (rheumatic mitral stenosis, prosthetic valves, infective endocarditis); paradoxical embolism through patent foramen ovale (PFO) (particularly with concurrent venous thromboembolism); and left ventricular thrombus (after MI or in restrictive cardiomyopathy). The CHADS2 score stratifies AF stroke risk: C=congestive heart failure (1 point), H=hypertension (1), A2=age ≥75 (2), D=diabetes (1), S2=prior stroke/TIA/thromboembolism (2). Score ≥2 generally warrants anticoagulation rather than antiplatelet therapy.

• Small-vessel disease/lacunar pathology (15-20% of cases): Lipohyalinosis (hypertensive arteriolosclerosis affecting small penetrating arteries) accounts for most lacunar TIAs, particularly in patients with chronic hypertension and diabetes. Lipohyalinosis causes wall thickening, narrowing, and microatheroma formation in arterioles (< 400 micrometers diameter), with classic TIA patterns: pure motor stroke (contralateral weakness without sensory loss, from lesions in the internal capsule or cerebral peduncle), pure sensory stroke, ataxic hemiparesis, or dysarthria-clumsy hand syndrome. Unlike large-artery disease, small-vessel TIAs rarely show high-grade stenosis on imaging; instead, T2/FLAIR white matter hyperintensities and lacunar infarcts on prior imaging are markers of disease.

• Arterial dissection (1-5% of cases, higher in younger patients): Carotid artery dissection (CAD) and vertebral artery dissection (VAD) cause TIA/stroke through thromboembolism from the dissection flap or hemodynamic insufficiency from severe luminal narrowing. Risk factors include recent head/neck trauma (though 20-30% are spontaneous), connective tissue disorders (Marfan syndrome, Ehlers-Danlos syndrome, fibromuscular dysplasia), and sudden head movement. CAD presents with ipsilateral headache, neck pain, Homer's syndrome (miosis, ptosis, anhidrosis), and ipsilateral TIA/stroke; VAD causes occipital headache, neck pain, and vertebrobasilar TIA symptoms. Dissection is increasingly recognized as a cause of cryptogenic stroke/TIA in young patients; diagnosis requires CT/MR angiography (showing tapered narrowing, pseudolumen, or intimal flap) or carotid ultrasound (showing elevated resistance index).

• Hypercoagulable states: Antiphospholipid syndrome (APS) is a major thrombophilia, with anticardiolipin and anti-β2-glycoprotein I antibodies causing endothelial activation and thrombin generation; TIA/stroke occurs in 20-30% of APS patients, often recurrent. Protein C and S deficiencies, Factor V Leiden, and prothrombin G20210A mutations account for inherited thrombophilia; testing is considered in younger TIA patients (< 50 years) without traditional risk factors. Active malignancy (especially adenocarcinoma, lung, pancreas) triggers tissue factor expression on cancer cells and cancer-associated thrombosis, predisposing to TIA/stroke.

• Other major risk factors: Hypertension (most modifiable risk factor, increasing stroke risk 3-4 fold); diabetes mellitus (increasing risk via endothelial dysfunction and accelerated atherosclerosis); smoking (increasing plaque instability and thrombogenicity); hyperlipidemia (particularly LDL >70 mg/dL increases plaque burden); obesity (BMI > 30); physical inactivity; and heavy alcohol use. Acute infections (respiratory, urinary tract) transiently increase TIA/stroke risk via inflammatory activation and platelet aggregation.

• Motor symptoms (55-70% of TIAs): Acute-onset focal weakness (typically unilateral) results from ischemia in the motor cortex (Brodmann area 4) or descending corticospinal tract (internal capsule, cerebral peduncle, brainstem). MCA territory TIAs cause contralateral arm and/or face weakness (with possible speech difficulty if dominant hemisphere); posterior circulation TIAs cause ipsilateral facial weakness with contralateral limb weakness (crossed syndrome) or isolated lower extremity weakness. Monoparesis (single limb weakness) is rare and should prompt consideration of spinal cord pathology or focal lesions. Weakness is flaccid acutely (before spasticity develops over days to weeks); hyperreflexia and Babinski sign may be present if pyramidal tract is involved. Mild weakness (difficulty with fine motor tasks) is more common in TIA than dense paresis in acute stroke.

• Sensory symptoms (20-30%): Paresthesias or numbness in the contralateral face, arm, and/or leg reflect cortical sensory strip involvement (postcentral gyrus) or thalamic lesions. "Cortical sensory loss" (disproportionate loss of graphesthesia, two-point discrimination, and stereognosis relative to primary sensation) suggests cortical involvement and anterior circulation TIA. Thalamic sensory loss includes contralateral face, arm, and leg with possible "thalamic pain syndrome" (dysesthesia), though permanent pain syndromes are more common in stroke than TIA.

• Speech disturbance (20-25%): Expressive (Broca's) aphasia—difficulty producing language with relatively preserved comprehension, agrammatism, and anomia—indicates left inferior frontal lobe/MCA territory involvement; receptive (Wernicke's) aphasia—preserved fluency with impaired comprehension—indicates left temporal/superior temporal lobe. Dysarthria (slurred speech from motor weakness) differs from aphasia (language disorder) and suggests bilateral MCA or brainstem involvement. Stuttering or hesitation with intact comprehension suggests stuttering-TIA, often from small-vessel disease.

• Amaurosis fugax (2-5% present with this symptom, though prevalence in TIA population is higher): Transient monocular blindness with sensation of a shade or curtain descending across the visual field (positive symptom) or sudden vision loss in one eye, lasting seconds to minutes, indicates ophthalmic artery TIA (ipsilateral to carotid artery disease). This occurs when microemboli lodge in the ophthalmic artery (first branch of the ICA) or from hemodynamic insufficiency from severe ICA stenosis. Carotid ultrasound is urgently indicated to assess for ≥70% stenosis warranting revascularization. Amaurosis fugax is a particularly strong predictor of imminent stroke (10-15% within 3 months if untreated).

• Posterior circulation TIA symptoms (15-20% of all TIAs): Vertebrobasilar ischemia presents with combinations of: vertigo/dizziness (not isolated dizziness, but vertigo with other neurological signs); diplopia (binocular, from CN III, IV, or VI palsies, or monocular from CN II involvement); bilateral/alternating motor or sensory symptoms; ataxia (gait unsteadiness from cerebellar involvement); dysarthria; dysphagia (from brainstem or bilateral hemispheric involvement); nystagmus; visual field defects (homonymous hemianopia from occipital lobe ischemia). Isolated vertigo, isolated diplopia, or isolated numbness is not typically posterior circulation TIA—consider vestibular neuritis, CN palsy, or local causes respectively.

• Global aphasia or encephalopathic presentation: Bilateral hemisphere involvement (rare in TIA) can cause expressive plus receptive language impairment, confusion, or altered consciousness; this is more suggestive of acute ischemic stroke, posterior reversible encephalopathy syndrome (PRES), or encephalitis than TIA. Complete recovery of global aphasia within hours would be highly unusual and warrant investigation for alternative diagnoses.

• Physical examination findings: Focal neurological deficits present acutely and then improve over minutes to hours; by definition, the exam should be normal or near-normal upon evaluation (since evaluation often occurs after symptom resolution). Key exam findings when deficits are present: focal motor weakness (grade ≤ 4/5); sensory level or sensory loss to pin/light touch; expressive or receptive language disturbance; cranial nerve palsies (CN VII in facial droop, CN III/IV/VI in eye movement abnormality); nystagmus or gaze deviation (conjugate gaze preference toward the lesion in acute stroke, away from hemiparesis); homonymous visual field defect (confrontational testing); gait ataxia

Immediate bedside steps

• Fingerstick glucose: first test in any transient deficit — hypoglycemia is the classic reversible mimic and is corrected before anything else.
• Non-contrast head CT: obtained emergently to exclude intracranial hemorrhage, subdural hematoma, and mass lesion, not to confirm TIA. A normal CT does not exclude infarction.
• 12-lead ECG plus continuous telemetry: screens for atrial fibrillation, and for MI with wall-motion abnormality as an embolic source.

Confirmatory imaging

• MRI with diffusion-weighted imaging (DWI): the preferred/gold-standard brain study, ideally within 24 hours. DWI restriction (bright DWI, dark ADC) means infarction occurred — the event is reclassified as ischemic stroke, which changes prognosis and urgency.
• Non-invasive vascular imaging of head and neck: CTA or MRA (or carotid duplex) is mandatory to find the culprit lesion. Symptomatic internal carotid stenosis of 70–99% by NASCET criteria identifies patients for revascularization; dissection shows a tapered lumen, intimal flap, or crescentic mural hematoma.
• Echocardiography: transthoracic first; transesophageal or bubble study when PFO, valvular vegetation, or aortic arch atheroma is suspected. Prolonged ambulatory rhythm monitoring is indicated when the mechanism remains cryptogenic.
• Laboratory panel: CBC, coagulation studies, electrolytes, lipid panel, and hemoglobin A1c; thrombophilia and antiphospholipid testing reserved for young patients without conventional risk factors.

Risk stratification

• ABCD2 score: Age ≥60 (1), BP ≥140/90 (1), Clinical features — unilateral weakness (2) or speech disturbance without weakness (1), Duration ≥60 min (2) or 10–59 min (1), Diabetes (1). Score ≥4 marks higher early stroke risk, but the AHA/ASA cautions that ABCD2 alone should not decide disposition — imaging and mechanism drive management.

Immediate decisions

• No thrombolysis: IV alteplase/tenecteplase is not given once deficits have fully resolved — there is no salvageable deficit and only bleeding risk. If any deficit persists, the patient is treated as acute ischemic stroke.
• Permissive blood pressure in the acute window: the AHA/ASA advises against aggressive acute BP lowering, since perfusion distal to a stenosis is pressure-dependent and hypotension can convert penumbra to infarct. Long-term target is <130/80 mm Hg, typically with a thiazide, ACE inhibitor, or ARB.

First-line antithrombotic therapy

• Antiplatelet monotherapy: aspirin started immediately for non-cardioembolic TIA; clopidogrel is an accepted alternative.
• Short-course dual antiplatelet therapy (DAPT): for high-risk TIA (ABCD2 ≥4) or minor stroke, AHA/ASA recommends aspirin plus clopidogrel (loading dose then daily) begun within 24 hours and continued 21 days, then single-agent therapy — based on the CHANCE and POINT trials. Ticagrelor plus aspirin for up to 30 days (THALES) is an alternative, notably in clopidogrel non-metabolizers (CYP2C19 loss-of-function).
• Anticoagulation for cardioembolic source: with atrial fibrillation, a DOAC (e.g., apixaban) is preferred over warfarin; warfarin is required for mechanical valves and moderate-to-severe rheumatic mitral stenosis.

Risk-factor and definitive management

• High-intensity statin: atorvastatin 80 mg daily, targeting LDL-C below 70 mg/dL; ezetimibe or a PCSK9 inhibitor if the goal is unmet.
• Carotid revascularization: carotid endarterectomy for symptomatic 70–99% stenosis (and selected 50–69%), ideally within 2 weeks of the index event; carotid artery stenting for high surgical risk, hostile neck, or radiation-induced stenosis.
• Other: glycemic control, smoking cessation, treatment of obstructive sleep apnea, and PFO closure in selected younger patients with otherwise cryptogenic embolic events.

Contraindicated or discouraged

• Long-term DAPT (bleeding exceeds benefit beyond ~3 weeks), routine anticoagulation for non-cardioembolic TIA, and reflexive BP normalization in the first hours.

Complications of the disease

• Early recurrent ischemic stroke — the emergency: risk is front-loaded in the first 48 hours to 7 days, when the culprit plaque is still thrombogenic or the cardiac source unaddressed. Any new fixed deficit mandates immediate stroke-code activation and reperfusion assessment.
• Crescendo TIA / stuttering deficits: repeated stereotyped events over hours signal active plaque rupture with ongoing platelet embolization or a flow-limiting stenosis. This is an emergency warranting hospitalization and expedited vascular imaging and revascularization.
• Vascular cognitive impairment: accumulating silent DWI-positive microinfarcts and confluent white-matter disease produce executive dysfunction and slowed processing.
• Myocardial infarction and vascular death: carotid atherosclerosis is a marker of systemic atherosclerosis, so cardiac events rival recurrent stroke as a cause of death.
• Post-event depression and driving/occupational restriction: commonly overlooked, but screened for at follow-up.

Complications of treatment

• Bleeding on antithrombotics — emergency when intracranial: DAPT and anticoagulants raise GI and intracranial hemorrhage risk; new headache, vomiting, or depressed consciousness demands urgent non-contrast CT and reversal (andexanet or 4-factor PCC for factor Xa inhibitors, idarucizumab for dabigatran).
• Statin adverse effects: myalgia, transaminase elevation, and rarely rhabdomyolysis with dark urine and markedly elevated creatine kinase.
• Cerebral hyperperfusion syndrome after endarterectomy or stenting — emergency: chronically dilated, autoregulation-impaired vessels are suddenly exposed to normal pressure, producing ipsilateral throbbing headache, seizures, and intracerebral hemorrhage; strict BP control is the treatment.
• Cranial nerve injury after endarterectomy: hypoglossal (tongue deviates toward the side of injury), recurrent laryngeal (hoarseness), and marginal mandibular branch of the facial nerve.
• Perioperative stroke or MI, and baroreceptor-mediated bradycardia/hypotension during carotid stenting; late restenosis at the treated segment.
• Over-lowering blood pressure in a patient with severe stenosis can precipitate watershed hemodynamic infarction.

• TIA is defined by tissue, not time: transient focal deficit with no infarction on DWI. If DWI lights up, call it an ischemic stroke — the distractor answer is "TIA because symptoms lasted <24 hours."
• First action in any transient focal deficit is a fingerstick glucose, then non-contrast head CT to exclude hemorrhage. The single best next step after stabilization in a patient with resolved deficits and a carotid bruit is non-invasive carotid imaging, not angiography.
• Amaurosis fugax ("curtain descending over one eye") localizes to the ipsilateral internal carotid via the ophthalmic artery, and the contralateral hemibody is weak. Retinal Hollenhorst plaques (cholesterol emboli) on funduscopy clinch it.
• ABCD2 — Age, Blood pressure, Clinical features, Duration, Diabetes — with unilateral weakness and duration ≥60 minutes each worth 2 points. Score ≥4 supports short-course DAPT, but per AHA/ASA the score alone must not decide admission.
• Aspirin + clopidogrel for 21 days, then monotherapy in high-risk TIA/minor stroke (CHANCE, POINT). Indefinite DAPT is the classic wrong answer — bleeding outweighs benefit.
• Atrial fibrillation changes the drug class: a DOAC, not an antiplatelet. Warfarin only for mechanical valves or moderate-to-severe rheumatic mitral stenosis.
• Symptomatic carotid stenosis 70–99% → endarterectomy within about 2 weeks, plus high-intensity statin and BP control. Do not delay for "medical optimization," and do not operate on a completely occluded carotid.
• Mimics examiners love: Todd paralysis after a seizure (postictal, gradual recovery), migraine aura (positive, slowly marching visual symptoms), hypoglycemia, and multiple sclerosis in a young patient. Ischemia is sudden, maximal at onset, negative (loss of function) — aura spreads.