Abstracts

Rationale:
Dravet syndrome (DS) is an infantile-onset developmental and epileptic encephalopathy characterized by febrile seizures in the first year of life, followed by the appearance of afebrile seizures which are almost always drug-resistant. Approximately 80% of patients have SCN1A pathogenic variants. EEG is typically normal at the time of first presentation, but various abnormalities may be seen later, including generalized or focal slowing, generalized spike-wave, and focal or multifocal spikes or spike-wave discharges. EEG could be useful in differentiating DS from other entities (e.g. febrile seizures plus); however, the timing at which various abnormalities appear in DS has not been well-delineated. We aimed to clarify the typical age-related evolution of EEG in DS through a meta-analysis, reviewing EEG findings in DS patients with SCN1A pathogenic variants reported in the literature.
Method:
We conducted a search of PubMed for the term combination “Dravet and EEG.” Non-English articles and animal studies were excluded. We also included additional papers identified from the reference lists of identified papers. Inclusion criteria were: (1) clinical diagnosis of DS, (2) SCN1A pathogenic variant identified, (3) a description of EEG findings and age at the time of EEG. We determined the earliest ages at which different abnormalities were identified. We also determined the percentage of patients showing different abnormalities for different age ranges: < 1 y, 1-2 y, 2-3 y, 3-4 y, 4-6 y, 6-8 y, 8-12 y, 12-16 y, 16-20 y, > 20 y.
Results:
The initial literature search yielded 249 results, from which 33 studies were included. From these studies, 214 EEGs from 149 patients were included (66 (44%) males, 74 (50%) females, 9 (6%) sex not specified). Average age at the time of EEG was 6.8 ( 7.8) y, with range 3 mths to 43 y. Fifty-seven (27%) of studies recorded sleep. One-hundred and sixty-nine (79%) of the EEGs were abnormal.   The earliest detected generalized background slowing occurred at 11 months of age. The earliest ages at which generalised and focal interictal epileptiform abnormalities were found were 6 and 8 months of age, respectively. For each age range, the frequency of patients with focal/multifocal epileptiform versus generalized epileptiform abnormalities are shown in Figure, along with the percentage of patients with any abnormality on EEG.
Conclusion:
Our data show that in DS the likelihood of having focal or generalised epileptiform abnormalities increase with age. By 2 years of age, over 90% of EEGs will be abnormal.
Funding:
:Research Institute of the McGill University Health Centre