A 5-year-old boy with developmental delay presents with multiple daily seizures including drop attacks and tonic seizures during sleep. His EEG shows the pattern marked **B** in the diagram. Which of the following is the most likely diagnosis, and what is the primary reason this EEG finding is pathognomonic for this condition?
A. West Syndrome — hypsarrhythmia with chaotic high-voltage slow waves is the hallmark EEG finding in infantile spasms
B. Rolandic Epilepsy — centrotemporal sharp waves activated by sleep are the diagnostic EEG pattern
C. Childhood Absence Epilepsy — generalized 3 Hz spike-and-wave discharges are the defining EEG feature
D. Lennox-Gastaut Syndrome — the slow spike-and-wave complexes at 1.5-2.5 Hz with paroxysmal fast activity during sleep are characteristic of the syndrome's electroclinical definition
Explanation
Why option 1 is correct
The pattern marked B — slow spike-and-wave complexes at 1.5-2.5 Hz with paroxysmal fast activity during sleep — is the electroclinical hallmark of Lennox-Gastaut Syndrome (LGS). LGS is defined by a triad: (1) multiple seizure types including tonic, atonic (drop attacks), and atypical absences; (2) characteristic EEG findings of slow spike-wave (<2.5 Hz) and generalized paroxysmal fast activity; and (3) intellectual disability with behavioral problems. The clinical presentation of drop attacks, tonic seizures during sleep, and developmental delay in a 5-year-old, combined with the slow spike-and-wave EEG pattern, is pathognomonic for LGS. The paroxysmal fast activity (10–20 Hz) during sleep is particularly suggestive of tonic seizures and is highly specific for this syndrome (Nelson Textbook of Pediatrics, 22nd ed., Epileptic Encephalopathies).
Why each distractor is wrong
Option 2 (West Syndrome): West Syndrome presents with infantile spasms (flexor or extensor) typically between 3–12 months of age and is characterized by hypsarrhythmia (marked C in the diagram), not the slow spike-and-wave pattern. LGS may evolve from West Syndrome but has a different EEG signature and later onset (3–5 years).
Option 3 (Childhood Absence Epilepsy): Childhood Absence Epilepsy presents with brief, frequent absences and is characterized by generalized 3 Hz spike-and-wave discharges (marked A in the diagram). It does not feature drop attacks, tonic seizures, or the slow spike-and-wave pattern at 1.5–2.5 Hz.
Option 4 (Rolandic Epilepsy): Rolandic Epilepsy is a benign focal epilepsy with centrotemporal sharp waves (marked D in the diagram) activated by sleep. It does not cause drop attacks, developmental delay, or the generalized slow spike-and-wave pattern characteristic of LGS.
High-YieldNEET PG
Lennox-Gastaut Syndrome = slow spike-wave (<2.5 Hz) + paroxysmal fast activity + drop attacks + tonic seizures + developmental delay = drug-resistant epilepsy requiring valproate, lamotrigine, rufinamide, or ketogenic diet.
Nelson Textbook of Pediatrics, 22nd ed., Epileptic Encephalopathies
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