A 10-year-old boy presents with a 4-month history of declining school performance and personality changes, followed by progressive clumsiness and rhythmic jerking movements of the head and trunk occurring every 5–10 seconds. His measles vaccination was delayed, and he contracted measles at 11 months of age. EEG is performed, and the pattern marked **B** in the diagram is observed. Based on this characteristic EEG finding and the clinical presentation, what is the most likely diagnosis?
A. Creutzfeldt-Jakob disease (CJD) with sporadic prion infection
B. Rasmussen encephalitis with progressive hemispheric atrophy
C. Juvenile myoclonic epilepsy with secondary cognitive decline
D. Subacute sclerosing panencephalitis (SSPE) caused by persistent defective measles virus infection
Explanation
Why Subacute sclerosing panencephalitis (SSPE) is right
The pattern marked B—periodic, high-amplitude (300–1500 µV), bilaterally synchronous, stereotyped slow-wave complexes (Radermecker complexes) recurring every 4–15 seconds and time-locked to myoclonic jerks—is the pathognomonic EEG hallmark of SSPE. Combined with the clinical history of measles at age 11 months (before vaccination eligibility), insidious cognitive and behavioral decline over months, followed by symmetric myoclonic jerks at 5–10 second intervals in Stage II disease, this constellation is diagnostic of SSPE. SSPE is caused by persistent infection with a defective measles virus lacking the matrix (M) protein, preventing viral budding and allowing slow neuroinvasion. The Radermecker complexes are virtually diagnostic when paired with elevated CSF measles IgG and oligoclonal bands (Dawson criteria). Nelson Textbook of Pediatrics confirms that SSPE typically presents 6–15 years after primary measles infection, with highest risk when measles occurs before age 2, and that the characteristic EEG pattern is essential for diagnosis.
Why each distractor is wrong
Juvenile myoclonic epilepsy (JME): JME presents with generalized spike-and-wave discharges (3 Hz), not Radermecker complexes. JME typically begins in adolescence with morning myoclonic jerks and absence seizures, not progressive cognitive decline and personality changes. The EEG pattern marked B is incompatible with JME.
Creutzfeldt-Jakob disease (CJD): While CJD causes rapidly progressive dementia and myoclonus, the characteristic EEG pattern is periodic sharp-wave complexes (PSWCs) at 1–2 Hz, not the high-amplitude bilaterally synchronous Radermecker complexes at 4–15 seconds. CJD also lacks the prior measles exposure history and does not present with the insidious 4-month prodrome of behavioral change followed by motor symptoms.
Rasmussen encephalitis: This is a progressive hemispheric inflammatory encephalitis with focal seizures, hemiparesis, and unilateral EEG abnormalities (often focal spikes or PLEDs), not the bilateral synchronous Radermecker complexes. Rasmussen encephalitis does not have a measles exposure history and presents with focal neurological deficits rather than symmetric myoclonus.
High-YieldNEET PG
Radermecker complexes (periodic, high-amplitude, bilaterally synchronous, stereotyped slow waves every 4–15 seconds, time-locked to myoclonus) on EEG are virtually pathognomonic for SSPE when combined with a history of early measles and progressive cognitive-motor decline; diagnosis is confirmed by elevated CSF measles IgG and oligoclonal bands (Dawson criteria).
Nelson Textbook of Pediatrics — Subacute Sclerosing Panencephalitis
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