This article includes discussion of benign neonatal seizures, benign neonatal convulsions, benign neonatal seizures (nonfamilial), BNS, and fifth-day fits. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.
Benign neonatal seizure (nonfamilial) is a syndrome characterized by clonic seizures that begin around the fifth day of life and may recur during the following 2 to 3 days. It is a benign syndrome, but its diagnosis requires a workup to eliminate other potentially more serious epileptic syndromes during this period. In the following article, the author discusses many issues related to this syndrome, including etiology, pathogenesis and pathophysiology, epidemiology, and differential diagnosis.
Historical note and terminology
This syndrome was first described by Dehan and colleagues in 1977. They reported a neonatal convulsive disorder of unknown etiology that occurs around the fifth day of life and is associated with a favorable outcome (Dehan et al 1977). In 1989, the Commission on Classification and Terminology of the International League Against Epilepsy proposed the term "benign neonatal seizures" (Anonymous 1989). Currently, it is classified under the idiopathic generalized epilepsies, although partial seizures are common. Indeed, Watanabe and colleagues reported only partial seizures in 16 infants with the syndrome (Watanabe et al 1999), raising questions about the accuracy of the inclusion of benign neonatal seizures under the rubric of idiopathic generalized epilepsies.
This issue may be resolved with the proposed diagnostic scheme of the ILAE commission report of 2001 (Engel 2001). One paper reviewed 94 new cases of neonatal seizures and showed some of the advantages of using the proposed classification (Mastrangelo et al 2005). Specifically, benign neonatal seizures would be classified as an Axis 3 syndrome separate from seizure semiology, relieving the problem of classifying it as an idiopathic generalized epilepsy. The extent to which we will be able to diagnose any additional cases of benign neonatal seizures based on the proposed classifications is yet to be seen. Three de novo mutations in KCNQ2 were found in 4 patients with benign neonatal seizures without a family history (Claes et al 2004). Another de novo mutation was reported in a neonate with benign neonatal seizures and no family history of seizures (Ishii et al 2009). Because mutations in KCNQ2 have been described in patients with benign familial neonatal seizures, these data suggest an overlap between the 2 syndromes.
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