Table 1. Clinical characteristics of a cohort of 26 individuals with CDD.

The cohort is predominantly female, with refractory generalized or mixed epilepsy, and severe global developmental delay. They lack specific malformations of cortical development and have a variety of encephalopathy patterns on EEG. EEG = electroencephalogram, IQR = Interquartile range, MRI = magnetic resonance imaging

Clinical characteristics	N(%) or Median [IQR]
Sex, Female	22/26 (84.6%)
MRI
Normal	15/26 (57.7%)
Diffuse volume loss	7/26 (26.9%)
Benign cysts	2/26 (7.7%)
T2 signal change, white matter and/or deep grey matter	4/26 (15.4%)
Diffuse hyperperfusion (likely seizure related)	1/26 (3.8%)
Ongoing refractory epilepsy	22/26 (84.6%)
Seizure types
Focal	17/26 (65.4%)
Generalized	26/26 (100.0%)
EEG encephalopathy patterns
Hypsarrhythmia	10/26 (38.5%)
Generalized slowing	17/26 (65.4%)
Discontinuity	3/26 (11.5%)
Slow spike and wave	2/26 (7.7%)
Continuous spike and wave in sleep	1/26 (3.8%)
No encephalopathy pattern	5/26 (19.2%)
Vigabatrin use, N (%) and median duration [IQR]	13/26 (50%) 1.7 y [1.1, 3.1]
Developmental features
Global developmental delay, if evaluated at age >1 year	23/23 (100%)
Developmental regression	15/26 (57.7%)
With worsening of seizures	10/15 (66.7%)
Independent of seizures	5/15 (33.3%)
Mobilizes, crawling or walking with or without support	10/26 (38.5%)
Pincer grasp or presses switches	6/26 (23.1%)
Communicates purposefully with words, signs, or augmentative communication	10/26 (38.5%)