Figure 2. CHD2 encephalopathy spectrum.

CHD2 encephalopathy presents with a spectrum of severity including age of seizure onset, intellectual outcome, and seizure types. Cases are ranked by their level of intellectual disability and age at onset. All cases had myoclonic seizures and 7 had photic-induced seizures. Cases with a milder intellectual disability had fewer seizure types and were less likely to have atonic seizures, tonic seizures, and convulsive status epilepticus. Photic seizures were equally likely across the spectrum. *A-M-A is likely to be underrecognized. AA = atypical absence; Abs = all absence seizure types; A-M-A = atonic-myoclonic-absence seizure; CSE = convulsive status epilepticus; EMA = absence with eyelid myoclonia; GTCS = generalized tonic-clonic seizures; MS = myoclonic seizures; NCSE = nonconvulsive status epilepticus; TA = typical absence.