The TPH2 labelling index in the VLM was significantly lower in SUDEP and definite SUDEP groups than non-epilepsy control groups (both non-epilepsy controls and non-epilepsy sudden death controls) (P < 0.005); no significant differences were noted between Dravet syndrome and epilepsy controls compared to non-epilepsy control groups (Table 4 and Fig. 3D). Here, TPH2 is linked to encephalopathy, progressive, early-onset, with brain edema and/or leukoencephalopathy.