Benign neonatal seizure (nonfamilial) is a benign syndrome characterized by clonic seizures that begin around the fifth day of life and may recur during the following 2 to 3 days.
History & terminology
Dehan et al 1977[1] first reported a neonatal convulsive disorder of unknown etiology that occurs around the fifth day of life and associated with a favorable outcome.
Prior & Macourt (1981)[2] described the features in 90 infants with the condition and coined the term “fifth day fits”
In 1989, the ILAE Commission on Classification and Terminology proposed the term “benign neonatal seizures”
The updated ILAE 2017 classification categorizes it under Conditions with epileptic seizures that are traditionally not diagnosed as a form of epilepsy per se.
Genetics
Claes et al 2004 reported three de novo mutations in KCNQ2 in 4 patients with benign neonatal seizures without a family history (Claes et al 2004).
Ishii et al 2009 also reported another de novo mutation was reported in a neonate with benign neonatal seizures and no family history of seizures.
KCNQ2 variants have been described in patients with benign familial neonatal seizures suggesting an overlap between the 2 syndromes.
Clinical features
seizures are mainly clonic
median duration is around 20hrs (status epilepticus)[3]
onset is around fifth day of life
EEG
ictal EEG usually shows localised spikes
interictal EEG usually shows theta pointu alternant. It may also show focal or multifocal, non-specific abnormalities or a discontinuous pattern or it may be normal in ~10%.
1.aDehan M, Quillerou D, Navelet Y, D'Allest AM, Vial M, Retbi JM, Lelong-Tissier MC, Gabilan JC. [Convulsions in the fifth day of life: a new syndrome?].Arch Fr Pediatr. 1977 Oct;34(8):730-42. [PMID: 931532]