## Correct Answer: A. TEE This is an acute ischaemic stroke case presenting within the thrombolytic window (5 hours from onset). The clinical presentation—sudden aphasia (Broca's area) and right arm weakness—localizes to the left middle cerebral artery (MCA) territory. The critical discriminator is the **indication for TEE (transoesophageal echocardiography) in acute cardioembolic stroke**. TEE is the gold-standard imaging modality for detecting **cardiac sources of embolism** in acute stroke, particularly when conventional investigations are inconclusive. It has superior sensitivity (95–98%) compared to transthoracic echo (60–70%) for detecting: (1) left atrial/ventricular thrombus, (2) patent foramen ovale (PFO) with right-to-left shunt, (3) atrial septal defect, (4) endocarditis vegetations, and (5) dilated cardiomyopathy with mural thrombus. In the Indian population, rheumatic mitral stenosis with atrial fibrillation is a common cardioembolic source; TEE can definitively visualize left atrial appendage thrombus and guide anticoagulation decisions. The acute stroke protocol mandates **urgent neuroimaging (CT/MRI) first to exclude haemorrhage**, followed by **cardiac evaluation if cardioembolic source is suspected**. TEE is indicated when: (a) stroke mechanism is unclear after initial workup, (b) young patient (<50 years) with no atherosclerotic risk factors, or (c) recurrent strokes despite antiplatelet therapy. This case—acute MCA stroke with no mention of hypertension, diabetes, or carotid disease—raises suspicion for cardioembolism, making TEE the next indicated investigation after neuroimaging. ## Why the other options are wrong **B. Transthoracic echocardiography** — While transthoracic echo is a reasonable initial cardiac screening tool, it has **poor sensitivity (60–70%) for detecting intracardiac thrombi and PFO**—the most common cardioembolic sources in young stroke patients. In Indian practice, when cardioembolism is suspected and TTE is inconclusive, TEE is the standard of care. TTE may miss left atrial appendage thrombus in atrial fibrillation and small PFOs, making it inadequate for definitive source identification in acute stroke. **C. MRI brain** — MRI brain is essential for **acute stroke diagnosis and tissue characterization** (DWI shows acute infarction), but it does NOT identify the **source of embolism**. MRI answers 'where is the stroke?' but not 'why did it happen?'. In acute cardioembolic stroke, MRI is performed first to confirm ischaemia and exclude haemorrhage, but cardiac imaging (TEE) is required to identify the embolic source and guide secondary prevention (anticoagulation vs antiplatelet therapy). **D. Carotid Doppler** — Carotid Doppler is indicated when **atherosclerotic carotid disease** is suspected (e.g., TIA with ipsilateral carotid bruit, or stroke in elderly with hypertension/smoking). This case shows **no clinical signs of carotid stenosis** (no bruit, acute onset without prodrome). The sudden aphasia + arm weakness in a young patient without atherosclerotic risk factors points toward **cardioembolism, not large-artery atherosclerosis**, making carotid imaging less relevant than cardiac source evaluation. ## High-Yield Facts - **TEE sensitivity for cardioembolic sources is 95–98%** vs TTE 60–70%; TEE is gold standard for detecting PFO, LAA thrombus, and endocarditis vegetations in acute stroke. - **Acute stroke protocol: CT/MRI first (rule out haemorrhage), then cardiac imaging** if cardioembolic source suspected; TEE indicated when TTE inconclusive or young patient with cryptogenic stroke. - **Rheumatic mitral stenosis with AF** is a common cardioembolic source in India; TEE visualizes LAA thrombus and guides anticoagulation decisions. - **PFO paradoxical embolism** is the leading cardioembolic cause in young stroke patients (<50 years); TEE with bubble study detects right-to-left shunt with 90% sensitivity. - **Acute stroke within 5 hours** qualifies for thrombolytic therapy; cardiac source identification (via TEE) determines long-term anticoagulation vs antiplatelet strategy. ## Mnemonics **CARDIO-STROKE: When to use TEE** **C**ardioembolic source suspected (young, no atherosclerosis) | **A**cute stroke <5 hours | **R**ecurrent strokes despite antiplatelets | **D**ilated cardiomyopathy/AF | **I**ncomplete TTE | **O**ther sources ruled out. Use TEE when ≥2 criteria met. **TEE > TTE in Stroke (Memory Hook)** TEE = **T**ransOesophageal = **T**horough (detects 95% of cardiac sources). TTE = **T**ransthoracic = **T**oo insensitive (misses 30–40% of thrombi and PFOs). In acute stroke, 'thorough' beats 'transthoracic'. ## NBE Trap NBE may lure students into choosing **MRI brain** by emphasizing 'acute stroke' and 'investigation'—students conflate 'stroke diagnosis' with 'stroke workup'. However, the question asks for the **indicated investigation** in the context of identifying stroke mechanism; MRI confirms the stroke but does NOT identify the source. TEE is the source-finding investigation in suspected cardioembolic stroke. ## Clinical Pearl In Indian stroke units, a young patient with sudden MCA territory stroke and no hypertension/diabetes should raise immediate suspicion for **cardioembolic source**—particularly rheumatic AF or PFO. TEE is often performed within 24–48 hours of admission to guide anticoagulation initiation, which significantly reduces recurrent stroke risk in cardioembolic cases (vs antiplatelet monotherapy). This distinction directly impacts patient outcomes and long-term management strategy. _Reference: Harrison Ch. 451 (Cerebrovascular Diseases); Robbins Ch. 28 (Nervous System); KD Tripathi Ch. 18 (Cardiovascular Drugs in Stroke)_
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