Recently, HA was detected in adult patients with Dravet syndrome who received STP for the first time in addition to VPA and clobazam (CLB): 77% of the small cohort of 13 patients were found to have hyperammonaemic encephalopathy after introduction of STP despite concomitant reduction of VPA and CLB doses. This evidence concerns the gene CLYBL and encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.