**9.4 Etiology**

In most patients the cause of LKS remains unknown. Autoimmune etiology has been suspected because of minor immunological irregularities reported in a number of patients and because of the response of LKS patients to immunotherapy [23]. Mutations in GRIN2A (16p13.2) have been reported as a major genetic cause of LKS and of the syndrome known as epileptic encephalopathy with continuous spikes and waves during slow-wave sleep (CSWS) [99]. Children with LKS have, most

of the time, a normal development until the start of language regression. Seizures of LKS often respond well to treatment with AED, but the speech and language impairments often persist, despite seizure control [100]. Occasional cases can be secondary to structural lesions such as benign temporal lobe tumors with improvement after focal resection [101].
