Landau-Kleffner Syndrome and Central Auditory Disorders in Children by Makiko Kaga & Kimitaka Kaga

Author:Makiko Kaga & Kimitaka Kaga
Language: eng
Format: epub
ISBN: 9789811014796
Publisher: Springer Singapore

4.3 Current Genetic Research

The recent development of molecular biology has inspired a lot of competition in the localization of genes and in their expressions in all areas of medicine. The field of epileptology seems to be no exception. Roll et al in 2006 identified the gene SRPX2 (Sushi Repeat Containing Protein, X-Linked 2) which is the gene that induces Rolandic seizures and is related to speech and cognitive impairment. In addition, they found that the SRPX2 gene and the ELP4 gene (elongated acetyltransferase complex, subunit 4) were both associated with childhood epilepsies in terms of cell motility¸ migration, and adhesion to their molecular bases.

Rudolf et al. also described the genetic features common to both LKS and CSWS in terms of language and cognitive deficits (Rudolf et al. 2009). In their article, they indicated that although benign childhood epilepsy with centro-temporal spikes (BCECTS) or benign Rolandic epilepsy had been classified as different disease entities from those of LKS and CSWS, they included their four patients as a single continuous spectrum of disorders.

Electroencephalographic studies have shown that some LKS patients have focal epilepsy, epileptic encephalopathy with ESES or CSWS during LKS. These patients show centro-parietal spikes in their EEG findings. Some researchers in molecular biology have, thus, focused on idiopathic focal epilepsy which shows Rolandic spikes but then GRIN2A gene was discovered (Lemke et al. 2013). GRIN2A is a gene which codes for the protein GluN2A which is an α subunit of N-methyl-D-aspartate (NMDA) glutamate receptor. Lemke et al. discovered new mutations in the GRIN2A gene in two independent cohorts (27/359). Among their patients with a more severe type of CSWS (continuous spike waves in slow sleep), 17.6% of them had a higher incidence of mutation of the GRIN2A gene than in those patients with a mild type of CSWS (BECTS, 4.9%). Exon-disrupting microdeletion was found in 3 of these 286 patients (1.0%). On this basis, the authors concluded that mutation of the gene encoding the NMDA receptor, NR2A subunit, was a genetic risk factor for idiopathic focal epilepsy. This research was revealing to but not intended for the study of LKS itself.

Turner et al., in 2015, reported that 20% of their patients with epilepsy-aphasia spectrum (EAS) revealed GRIN2A gene mutations and those patients with these mutations showed obvious speech and language symptoms. The authors proposed that this finding might assist in the diagnosis of LKS. In addition, and regarding EAS, they found copy number variation (CNV) in molecules related to this RNA binding and to cell adhesion. At this point in time, the GRIN2A gene is considered to be the gene involved in language disorders and epilepsy. However, the GRIN2A gene is not the only responsible one to induce LKS and typical LKS patients without abnormalities of their GRIN2A gene have been found. Of course, not all of the patients with an abnormality of their GRIN2A gene have LKS. Genetic evaluations of patients with defined LKS have only just begun.

Among our patients, the most typical patient of LKS with long-term follow-up (Patient D) was examined by molecular biology techniques.

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