Serial EEG study in a girl with Landau-Kleffner Syndrome associated with continuous spikes and waves during slow sleep

Landau-Kleffner syndrome (LKS) is rare epileptic encephalopathy in childhood, characterized by both acquired epileptic aphasia and abnormal epileptiform discharges in electroencephalogram (EEG). We herein report a serial EEG study in LKS. A 22-month old girl was referred to our hospital because of frequently partial seizures in her left upper limb. On EEG performed and multiforcal spikes were recognized. Oral treatment of carbamazepine was started but her seizures were not controlled. Her language ability did not progress after 2 years of her age. At age 4 years, carbamazepine was switched to valproic acid, leading to reduction in the frequency of seizure episodes. She was able to speak two-word sentences at 4 years of age, but her word output gradually decreased. At 5 years of age, addition of zonisamide further reduced the frequency of seizure episodes, but failed to achieve complete control of seizures. She increasingly asked for questions to be repeated. Auditory brainstem response testing performed at the department of otolaryngology revealed normal hearing ability. She was diagnosed as having intellectual deficits with an intelligence quotient (IQ) of 61 at 7 years of age. The EEG at 8 years of age showed continuous spikes and waves during slow sleep (CSWS), leading to a diagnosis of LKS. After age 11 years, the CSWS on EEG improved without requiring a change in antiepileptic drugs (AEDs). Treatment with the oral AEDs was discontinued at 13 years of her age. Her IQ at 13 years of age was in the low 70s.