A new cause of developmental and epileptic encephalopathy with continuous spike-and-wave during sleep: CDKL5 disorder.

The CDKL5 disorder is characterized by early onset epilepsy, stereotypical hand movement, absent speech and severe hypotonia. Herein, we report epileptic encephalopathy with continuous spike-and-wave during sleep (CSWS) in apatient with CDKL5 disorder. She admitted with complaints of frequently recurring generalized tonic and myoclonic seizures. The diagnoses were confirmed by de novo CDKL5 mutation, c.197_198delCT (p.L67QfsX23). Interictal EEG revealed generalized spike and slow-wave activity, occurring intermittently in wakefulness but present for at least 85% of non-REM sleep, consistent with the diagnosis of CSWS. To our knowledge, this is the first report of CSWS associated with CDKL5 disorder.