Abstracts

Rationale: In a Norwegian retrospective study of 19 children with LKS, a striking feature was the great variability in clinical expression within this syndrome (Cockerell I et al.Landau Kleffner syndrome in Norway: Long-term prognosis and experiences with the health services and educational systems. Epilepsy Behav 2011;21:153 9.) Landau-Kleffner syndrome (LKS) is a rare childhood epileptic encephalopathy. The ICD 10-criteria of LKS include: (1) normal language development followed by loss of impressive and expressive language, (2) preserved general intelligence, (3) paroxysmal abnormalities in EEG at debut of symptoms, (4) age of onset between 3 and 7 years, and (5) epileptic seizures present in most cases. Exclusion criteria are unspecific language disturbances, disintegrative disorders, and autism. The diagnosis of LKS syndrome is based on the case history, language assessment and electroclinical findings. However, to diagnose LKS may be difficult as both the definition and diagnostic criteria of LKS are not consistent in the literature. It is not fully agreement whether the diagnostic criteria convey the impression of a discrete entity, or if it may be conceptualized as a spectrum of epileptiform neurocognitive disorders. Some claim that LKS is part of a specter of related disorders, including benign childhood epilepsy with centro- temporal spikes (BCECTS) and continuous spike waves during slow sleep (CSWS). It has also been suggested that autism may be part of this specter. Methods: In the period 1989-2010, a total of 25 children were treated for LKS at the National Center for Epilepsy in Norway. The children and their parents were contacted by mail, and 19 (76 %) agreed to participate in the study. The study data was based partly on the children s medical records, and partly on the answers provided by the parents during a semi-structured interview. Results: In EEG, all 19 children had interictal epileptiform discharges while awake.18 had epileptiform discharges during sleep, and in 17 the occurrence of these discharges increased considerably during sleep compared to the awake state. Only nine children (47%) had epileptic seizures. All had loss of impressive and expressive language of varying degrees. Three children did not meet ICD 10-criteria at the time of the LKS diagnosis. They had all a general intelligence below normal range. Two had a subnormal language development prior to the onset of LKS. Currently, two patients have a diagnosis of an autistic disorder, and for one of them the diagnosis of autism has resulted in retraction of the LKS diagnosis. Conclusions: It appears that different clinicians interpret the ICD 10-criteria differently, and a consensus about the definition and diagnostic criteria in LKS is warranted both for clinical and research purposes. A more distinct limitation of the diagnostic criteria may have important implications for many of these children, both regarding treatment and prognosis.