A 6-month-old boy presents with a 3-week history of clusters of brief symmetric spasms involving sudden flexion of the neck, trunk, and arms, occurring predominantly on awakening from sleep. The child has lost previously acquired developmental milestones including social smiling and head control. MRI brain shows cystic encephalomalacia in bilateral watershed zones consistent with prior hypoxic-ischemic injury. An interictal EEG during drowsiness shows the pattern marked **A** in the diagram. Based on this EEG finding and clinical presentation, what is the most likely diagnosis?
A. Ohtahara syndrome with burst-suppression pattern
B. West syndrome (infantile spasms) with hypsarrhythmia
C. Benign rolandic epilepsy with centrotemporal sharp waves
D. Childhood absence epilepsy with generalized 3 Hz spike-and-wave
Explanation
Why West syndrome (infantile spasms) with hypsarrhythmia is right
The pattern marked A — chaotic high-voltage (>200 microvolts) asynchronous slow waves with multifocal spikes arising independently from both hemispheres — is the pathognomonic EEG finding of hypsarrhythmia, the defining third component of West syndrome's diagnostic triad. Combined with the clinical presentation of infantile spasms (brief symmetric flexion spasms in clusters, typically on awakening), developmental regression (loss of social smiling and head control), and structural brain injury (hypoxic-ischemic encephalopathy with watershed zone injury), this constellation is diagnostic of West syndrome. Nelson Textbook of Pediatrics (21st ed., Chapter 611) emphasizes that hypsarrhythmia on interictal EEG is the hallmark electrographic finding that, together with epileptic spasms and developmental arrest, defines West syndrome.
Why each distractor is wrong
Ohtahara syndrome with burst-suppression pattern: Ohtahara syndrome presents with burst-suppression (pattern B), not hypsarrhythmia. It typically manifests in the first 3 months of life with tonic spasms and a characteristic burst-suppression EEG pattern. This patient's age (6 months), clinical semiology (flexion spasms in clusters), and EEG pattern (hypsarrhythmia, not burst-suppression) are inconsistent with Ohtahara syndrome.
Childhood absence epilepsy with generalized 3 Hz spike-and-wave: Childhood absence epilepsy (pattern C) presents with brief episodes of behavioral arrest and staring, not infantile spasms with developmental regression. The EEG shows a distinctive generalized 3 Hz spike-and-wave pattern, not the chaotic asynchronous multifocal spikes of hypsarrhythmia. This condition typically begins between 4–8 years of age, not in infancy.
Benign rolandic epilepsy with centrotemporal sharp waves: Benign rolandic epilepsy (pattern D) is characterized by centrotemporal sharp waves on EEG and presents with focal motor seizures, often nocturnal, in school-age children. It has an excellent prognosis with normal development and does not cause developmental regression. The EEG pattern (centrotemporal sharp waves) and clinical course are entirely different from this case.
High-YieldNEET PG
Hypsarrhythmia (chaotic, high-voltage, asynchronous multifocal spikes) + infantile spasms + developmental regression = West syndrome; early recognition and treatment within 4 weeks are critical for developmental rescue.
Nelson Textbook of Pediatrics, 21st ed., Chapter 611: Seizures in Childhood — Infantile Spasms / West Syndrome
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