Etiology & Classification of Pediatric Stroke

Question	Answer
1. What is the definition and classification of Stroke in children?	Pediatric stroke is an acute focal neurological deficit of vascular origin persisting $>24$ hours (or confirmed on neuroimaging). It is broadly classified into: 1. Arterial Ischemic Stroke (AIS) (~50%), 2. Cerebral Venous Sinus Thrombosis (CVST) (~20%), and 3. Hemorrhagic Stroke (~30% / Intracerebral or Subarachnoid Hemorrhage).
2. What are the leading causes of Arterial Ischemic Stroke (AIS) in children?	1. Focal Cerebral Arteriopathies (FCA) (~50% / Post-varicella arteriopathy, transient cerebral arteriopathy, arterial dissection); 2. Cardioembolic Causes (~30% / Cyanotic Congenital Heart Disease with right-to-left shunts, Rheumatic Heart Disease, Infective Endocarditis, Cardiomyopathies); 3. Hematological / Prothrombotic States (~15% / Sickle Cell Anemia, Protein C/S deficiency, Antiphospholipid Syndrome); 4. Moyamoya Disease / Syndrome; 5. Metabolic Disorders (Homocystinuria, MELAS).
3. What is Post-Varicella Arteriopathy (Focal Cerebral Arteriopathy), and when does it occur?	It is an acute inflammatory, non-atherosclerotic focal narrowing of the distal internal carotid artery (ICA) or proximal middle/anterior cerebral arteries occurring characteristically 2 to 6 months following primary Varicella (chickenpox) infection, caused by transaxonal migration of the Varicella-Zoster Virus (VZV) via the ophthalmic branch of the trigeminal nerve to the cerebral arterial adventitia.
4. What are the primary predisposing causes of Cerebral Venous Sinus Thrombosis (CVST) in children?	Severe dehydrating gastroenteritis, systemic sepsis, Nephrotic Syndrome (urinary loss of Antithrombin III and hyperfibrinogenemia), severe Iron Deficiency Anemia with microcytosis/thrombocytosis, head and neck infections (mastoiditis, sinusitis), and underlying inherited thrombophilias.
5. How does the etiology of stroke in children fundamentally differ from adults?	Atherosclerosis and hypertension account for $>85\%$ of adult strokes; in contrast, pediatric strokes are dominated by arteriopathies (FCA, dissection, Moyamoya), cardiac malformations (cyanotic CHD), infections, and inherited hematological/prothrombotic conditions.

Vascular Anatomy & Clinical Localization

Question	Answer
1. How do you clinically differentiate an MCA territory stroke from an ACA territory stroke?	Middle Cerebral Artery (MCA) Stroke: Weakness and sensory loss predominantly affect the Face and Upper Extremity > Lower Extremity, often accompanied by expressive/receptive aphasia (if dominant hemisphere) and homonymous hemianopia; Anterior Cerebral Artery (ACA) Stroke: Weakness and sensory loss predominantly affect the Contralateral Lower Extremity > Upper Extremity, with primitive reflexes (grasp reflex) and abulia/urinary incontinence.
2. What is the clinical presentation of an Internal Capsule (Dense Capsular) Hemiplegia?	Because descending motor fibers from the face, arm, and leg converge closely within the posterior limb and genu of the internal capsule, a small lacunar/striate infarct causes dense, equal hemiplegia of the face, arm, and leg (Face = Arm = Leg) without associated cortical signs (no aphasia or visual neglect).
3. How does conjugate eye deviation help localize a hemispheric vs brainstem lesion in acute stroke?	In a Cortical / Hemispheric (Frontal Eye Field) Lesion, the eyes deviate towards the side of the lesion (away from the hemiplegic limbs); in a Pontine / Brainstem (PPRF) Lesion, the eyes deviate away from the side of the lesion (towards the hemiplegic limbs).
4. What are the characteristics of a "Posterior Cerebral Artery (PCA)" stroke in a child?	Contralateral Homonymous Hemianopia with macular sparing, visual agnosia, alexia without agraphia, and thalamic sensory pain/hemisensory loss; motor weakness is minimal or absent unless cerebral peduncles are involved.
5. What is the "Alternating (Crossed) Hemiplegia" of brainstem vascular syndromes?	An ipsilateral Lower Motor Neuron cranial nerve palsy paired with a contralateral Upper Motor Neuron hemiplegia/hemiparesis: Weber Syndrome (Ipsilateral CN III palsy + Contralateral hemiplegia); Millard-Gubler Syndrome (Ipsilateral CN VI & VII palsy + Contralateral hemiplegia).

Clinical Examination & Semiological Signs

Question	Answer
1. How do you clinically distinguish between Congenital (Perinatal) Hemiplegia and Acquired Infantile Hemiplegia?	Congenital / Perinatal Hemiplegia: Manifests early with handedness before 1 year of age, fisting of one hand, marked limb length discrepancy (>1 cm shortening of affected arm/leg), and small thumb/fingernails (contralateral parietal lobe growth arrest); Acquired Hemiplegia: Sudden catastrophic onset in a previously normal child with symmetric limb lengths and normal nail size.
2. How do you differentiate Upper Motor Neuron (UMN) Facial Palsy from Lower Motor Neuron (LMN) Facial Palsy?	UMN Facial Palsy (supranuclear cortical/capsular lesion): Involves only the lower half of the face (flattened nasolabial fold, mouth deviation), with sparing of forehead wrinkling and eye closure due to bilateral cortical innervation of the frontalis and orbicularis oculi muscles; LMN Facial Palsy (nuclear/infranuclear CN VII lesion): Involves both upper and lower halves of the ipsilateral face (loss of forehead wrinkles, lagophthalmos, Bell's phenomenon, and mouth deviation).
3. What are the clinical phases of tone evolution following an acute stroke?	Phase 1 (Acute / Shock Phase, first 24h to 1–2 weeks): Flaccidity (hypotonia) and hyporeflexia due to sudden withdrawal of supraspinal facilitation (cerebral shock); Phase 2 (Chronic / Recovery Phase, >1–2 weeks): Spasticity (clasp-knife hypertonia), brisk hyperreflexia, clonus, and positive Babinski extensor response due to uninhibited spinal reflex arch overactivity.
4. What is the typical "Hemiplegic / Wernicke-Mann" posture and gait?	Posture: Upper limb held in adduction, elbow flexion, forearm pronation, wrist and finger flexion; Lower limb held rigidly in hip extension, adduction, knee extension, and ankle plantarflexion (equinovarus); Gait: Circumduction Gait (child swings the stiff lower leg outward in a lateral semi-circle to clear the toe off the ground during walking).
5. Why should you always auscultate the skull and orbits in a child presenting with stroke?	To detect a Cranial or Orbital Bruit, which signifies high-velocity turbulent blood flow through an underlying Arteriovenous Malformation (AVM), Vein of Galen aneurysm, or carotid-cavernous fistula.

Diagnostic Workup & Neuroimaging Protocols

Question	Answer
1. What is the gold-standard imaging modality for acute pediatric ischemic stroke, and why?	MRI Brain with Diffusion-Weighted Imaging (DWI) and ADC Mapping: DWI detects cytotoxic intracellular edema as a bright hyperintense signal within minutes of arterial occlusion (far superior to CT, which can remain completely normal in the first 12–24 hours of ischemic stroke).
2. What is the role of Magnetic Resonance Angiography (MRA) of the head and neck?	MRA visualizes the intracranial circle of Willis and cervical carotid/vertebral arteries to identify focal arterial stenosis, post-varicella arteriopathy, Moyamoya disease, fibromuscular dysplasia, or arterial dissection (intimal flap/intramural hematoma).
3. What laboratory tests should be included in the initial prothrombotic screening?	Complete Blood Count (polycythemia, thrombocytosis), PT/INR, aPTT, Fibrinogen, D-Dimer, Fasting Serum Homocysteine, Protein C and S activity, Antithrombin III, Factor V Leiden mutation, Prothrombin gene mutation, and Antiphospholipid Antibodies (Lupus Anticoagulant, Anticardiolipin, Anti-$\beta_2$-glycoprotein 1).
4. Why must comprehensive thrombophilia testing be repeated 3 to 6 months after the acute stroke?	In the acute phase, severe thrombosis and tissue injury consume circulating levels of endogenous anticoagulants (Protein C, S, Antithrombin III), yielding falsely low levels; accurate baseline thrombophilia evaluation requires repeat testing after acute inflammatory recovery and off anticoagulant therapy.
5. What is the role of 2D Echocardiography with Bubble Contrast in childhood stroke?	To identify cardioembolic sources: intracardiac thrombi (left atrial appendage/LV apex), vegetation in infective endocarditis, and Right-to-Left shunts across a Patent Foramen Ovale (PFO) or Atrial Septal Defect using agitated saline contrast during Valsalva maneuver to confirm paradoxical embolization.

Specific Syndromes & Clinical Entities

Question	Answer
1. What is Hemiconvulsion-Hemiplegia-Epilepsy (HHE) Syndrome?	A catastrophic pediatric syndrome occurring in children <4 years, characterized by prolonged unilateral clonic status epilepticus (hemiconvulsion) during a febrile illness $\rightarrow$ followed immediately by persistent, dense flaccid hemiplegia on the convulsing side $\rightarrow$ followed months to years later by the development of intractable focal epilepsy with hippocampal sclerosis.
2. What is Moyamoya Disease, and what is its classic clinical and radiological hallmark?	A progressive, non-atherosclerotic, non-inflammatory vasculopathy characterized by bilateral chronic stenosis or occlusion of the supraclinoid internal carotid arteries and proximal circle of Willis; leading to a dense compensatory basal collateral network resembling a "puff of cigarette smoke" (moyamoya in Japanese) on conventional or MR angiography.
3. What classic trigger precipitates transient ischemic attacks (TIAs) or strokes in children with Moyamoya?	Hyperventilation (e.g., crying, blowing on hot food, playing wind instruments, strenuous exertion); hyperventilation induces hypocapnia, leading to cerebral vasoconstriction and acute hypoperfusion in already compromised collateral vascular beds.
4. How does traumatic Internal Carotid Artery Dissection classically occur in toddlers?	Direct blunt trauma to the soft palate and posterior pharynx when a child falls with a pointed object (pencil, lollipop stick, toothbrush, or spoon) held in the mouth; the object compresses the internal carotid artery against the adjacent cervical transverse processes, tearing the intima and inducing acute thrombosis and embolization to the MCA.
5. What is Alternating Hemiplegia of Childhood (AHC)?	A rare neurodevelopmental genetic channelopathy caused by ATP1A3 gene mutations, characterized by recurrent, episodic attacks of hemiplegia alternating from one side of the body to the other, paroxysmal ocular movements (monocular nystagmus), dystonic posturing, and autonomic dysfunction, characteristically disappearing completely during sleep.

Acute & Long-Term Management Protocols

Question	Answer
1. What is the initial emergency medical management of childhood Arterial Ischemic Stroke?	Maintain airway, breathing, circulation; support oxygenation (SpO₂ $\ge 95\%$); maintain permissive hypertension (do not lower blood pressure acutely unless extreme); strict normoglycemia (avoid dextrose boluses); maintain normothermia ($<37.5^\circ\text{C}$); initiate isotonic normal saline hydration; and administer Aspirin ($3\text{–}5\text{ mg/kg/day}$) once hemorrhage is excluded on MRI/CT.
2. Is Intravenous Tissue Plasminogen Activator (IV rt-PA / Thrombolysis) routinely recommended in pediatric stroke?	NO. Unlike adult stroke, IV thrombolysis is not standard of care in pediatric stroke due to lack of randomized controlled trial data, diagnostic delays, and differing etiology; it is considered only in highly selected adolescents $\ge 16$ years meeting strict adult criteria within a 4.5-hour window at specialized comprehensive pediatric stroke centers.
3. What are the specific indications for Anticoagulation (Heparin / LMWH) in pediatric stroke?	1. Confirmed cardioembolic stroke with identifiable intracardiac thrombus; 2. Extracranial or intracranial arterial dissection; 3. Cerebral Venous Sinus Thrombosis (CVST); 4. Severe documented thrombophilia (e.g., Antiphospholipid Syndrome with high titers).
4. What is the role of Corticosteroids in Focal Cerebral Arteriopathy (FCA) / Post-Varicella Stroke?	A short course of Oral Prednisolone ($1\text{–}2\text{ mg/kg/day}$ for 3–5 days, tapered over 2–4 weeks) reduces vessel wall inflammation, halts progressive arterial narrowing, and significantly lowers the rate of stroke recurrence.
5. What is Constraint-Induced Movement Therapy (CIMT) in pediatric stroke rehabilitation?	An evidence-based neurorehabilitation protocol where the unaffected (normal) upper limb is restrained in a cast/mitt for several hours a day, forcing repetitive, intensive functional use and cortical neuroplastic reorganization of the hemiparetic arm.

High-Yield VIVA TRAPs & Counter-Questions

Question	Answer
1. VIVA TRAP: The examiner asks: "A 3-year-old child presents with sudden hemiplegia 30 minutes after a convulsion. Can you immediately diagnose Todd's Post-Ictal Paresis and discharge the child?"	ABSOLUTELY NOT. In children, acute arterial ischemic stroke classically presents with a focal seizure at onset (stroke-onset seizure). Diagnosing Todd's paresis is a diagnosis of exclusion that can only be made retrospectively after the weakness completely resolves within 24 hours AND an urgent MRI brain with DWI rules out acute infarction.
2. VIVA TRAP: Examiner counter-question: "The blood pressure of a 5-year-old with acute ischemic stroke is 135/85 mmHg. Should you immediately start IV labetalol to normalize blood pressure?"	NO. Permissive hypertension is vital during the acute stroke phase to maintain adequate Cerebral Perfusion Pressure ($CPP = MAP - ICP$) and maintain collateral blood flow through the ischemic penumbra; acutely lowering BP can expand the infarct core and cause catastrophic neurological deterioration. Antihypertensives are used only if systolic BP exceeds 99th percentile $+5\text{ mmHg}$ or hypertensive encephalopathy develops.
3. VIVA TRAP: "A child with Nephrotic Syndrome develops sudden severe headache, vomiting, and focal seizures with bilateral papilledema. What is the most likely diagnosis, and what imaging will you order?"	Cerebral Venous Sinus Thrombosis (CVST) (due to urinary loss of Antithrombin III and severe hypercoagulability); order an urgent MR Venography (MRV) or Contrast CT Venography (showing the classic "Empty Delta Sign" in the superior sagittal sinus).
4. VIVA TRAP: "A 6-year-old boy presents with right hemiplegia, and on examination, his right arm is 2 cm shorter than the left arm. What does this indicate about the timing of the stroke?"	The stroke is NOT acute; a limb length discrepancy $>1\text{ cm}$ signifies a congenital or perinatal arterial ischemic stroke occurring in utero or in early infancy, which arrested somatic and epiphyseal bone growth of the contralateral parietal-motor axis over years.
5. VIVA TRAP: "Why is a Non-Contrast CT (NCCT) head insufficient to rule out an acute stroke in a toddler who presented 3 hours ago?"	NCCT has very low sensitivity ($<20\text{–}30\%$) in the first 6–12 hours of acute arterial ischemic stroke and is often completely normal; MRI with Diffusion-Weighted Imaging (DWI) is mandatory because it detects cytotoxic edema within minutes of arterial occlusion.
6. VIVA TRAP: "A child with Cyanotic Congenital Heart Disease (Tetralogy of Fallot) develops sudden hemiplegia with fever. What two crucial intracranial complications must you differentiate?"	Brain Abscess versus Cardioembolic Stroke / Venous Thrombosis. Right-to-left shunting bypasses pulmonary phagocytic filtration, allowing septic emboli to produce brain abscesses (ring-enhancing on contrast CT/MRI), while severe polycythemia and hyperviscosity predispose to cerebral arterial and venous sinus thrombosis.