Seizures and electroencephalographic findings in inborn errors of metabolism: Clues to differential diagnosis in the neonatal period, infancy, childhood and adolescence, and review of the literature

Although inborn errors of metabolism (IEM) are a rare cause of epilepsy, seizures are a common presentation in these disorders. Seizures in IEM are frequently refractory to conventional anti-seizure medication and might warrant initiation of specific treatments based on vitamins or dietary modifications or provision of alternative substrates (to bypass a block). In most IEMs, seizures present with variable and non-specific semiology and EEG findings. Nevertheless, certain distinctive electro-clinical features might suggest an underlying IEM and even point towards the etiology. Even though biochemical and genetic tests will confirm the definitive diagnosis, EEG has the great advantage of being rapidly available, before the results of these tests. This article aims to describe through a literature review, illustrated by videos and EEGs from personal cases, seizures, and EEG patterns in IEM. We will focus on distinctive electro-clinical features that may help the clinician to establish an appropriate diagnosis allowing a prompt and specific treatment in order to improve outcome.