Neonatal seizures as onset of Inborn Errors of Metabolism (IEMs): from diagnosis to treatment. A systematic review.

Neonatal seizures (NS) occur in the first 28 days of life; they represent an important emergency that requires a rapid diagnostic work-up to start a prompt therapy. The most common causes of NS include: intraventricular haemorrhage, hypoxic-ischemic encephalopathy, hypoglycemia, electrolyte imbalance, neonatal stroke or central nervous system infection. Nevertheless, an Inborn Error of Metabolism (IEM) should be suspected in case of NS especially if these are resistant to common antiseizure drugs (ASDs) and with metabolic decompensation. Nowadays, Expanded Newborn Screening (ENS) has changed the natural history of some IEMs allowing a rapid diagnosis and a prompt onset of specific therapy; nevertheless, not all IEMs are detected by such screening (e.g. Molybdenum-Cofactor Deficiency, Hypophosphatasia, GLUT1-Deficiency Syndrome) and for this reason neonatologists have to screen for these diseases in the diagnostic work-up of NS. For IEMs, there are not specific semiology of seizures and EEG patterns. Herein, we report a systematic review on those IEMs that lead to NS and epilepsy in the neonatal period, studying only those IEMs not included in the ENS with tandem mass, suggesting clinical, biochemical features, and diagnostic work-up. Remarkably, we have observed a worse neurological outcome in infants undergoing only a treatment with common AED for their seizures, in comparison to those primarily treated with specific anti-convulsant treatment for the underlying metabolic disease (e.g.Ketogenic Diet, B6 vitamin). For this reason, we underline the importance of an early diagnosis in order to promptly intervene with a targeted treatment without waiting for drug resistance to arise.