Clinical Scenario:
A previously normally developing 5-year-old boy is brought with a 4-month history of progressive loss of previously acquired language. His parents report that he initially stopped understanding spoken instructions and subsequently became unable to express himself verbally. He remains socially engaged and communicates using gestures. He has had two brief nocturnal focal seizures. Neurological examination is otherwise normal. Which of the following is the most likely diagnosis?
A. Rett syndrome
B. Landau-Kleffner syndrome
C. Childhood disintegrative disorder
D. Angelman syndrome
E. Neuronal ceroid lipofuscinosis
Correct answer & Explanation:
Answer: B. Landau-Kleffner syndrome
Discussion
Landau-Kleffner syndrome is an epileptic encephalopathy characterized by acquired language regression, typically occurring in children who previously had normal language development. The characteristic feature is loss of language comprehension (auditory verbal agnosia) followed by impaired expressive language.
Seizures may occur, but they are not always prominent. The neurological examination is often otherwise normal, and social interaction may initially remain relatively preserved, helping distinguish LKS from several neurodegenerative disorders.
The diagnostic hallmark is an EEG showing markedly increased epileptiform activity during sleep, often described as sleep-activated epileptiform discharges. EEG during both wakefulness and sleep is therefore essential when LKS is suspected.
Rett syndrome predominantly affects girls and typically presents between 6 and 18 months with regression of acquired skills, followed by characteristic hand stereotypies and other neurological manifestations.
Childhood disintegrative disorder involves more generalized regression affecting multiple developmental domains after a period of normal development, typically after age 3 years.
Angelman syndrome usually causes severe developmental impairment, absent or minimal speech, seizures, ataxia, and characteristic behavioral features rather than an isolated acquired language disorder after normal language development.
Neuronal ceroid lipofuscinosis can cause regression and seizures but is typically progressive and often develops additional features such as visual impairment, ataxia, and movement abnormalities.
Key exam clue:
Previously normal language → acquired receptive + expressive aphasia → relatively preserved social interaction → sleep-activated epileptiform EEG = Landau-Kleffner syndrome.
