Paediatrics: Neonatal seizures

2021-04-15 11:24 AM

Incidence ~2–4/1000 live births. Usually occur 12–48hr after delivery.

Neonatal seizures

Incidence ~2–4/1000 live births. Usually occur 12–48hr after delivery. Can be generalized or focal, and tonic, clonic, or myoclonic. Subtle seizure patterns (lip-smacking, limb-cycling, eye deviation, apnoeas, etc.) can be difficult to identify or differentiate from other benign conditions that may mimic seizures:

  • Startle or Moro reflexes;
  • Normal ‘jittery’ movements (fine, fast limb movements that are abated by holding affected limb);
  • Sleep myoclonus (REM movements).

A large proportion of clinically diagnosed seizures are not associated with electrical seizure activity and many electrical seizures do not manifest clinically.

Causes

Brain injury:

  • hypoxic-ischaemic encephalopathy (HIE);
  • intracranial haemorrhage;
  • cerebral infarction (ischaemic or haemorrhagic);
  • cerebral oedema;
  • birth trauma.

CNS infection:

  • meningitis (e.g. GBS, coliforms);
  • encephalitis (e.g. HSV, CMV).
  • Cerebral malformation.

Metabolic:

  • hypoglycaemia;
  • hypo or hypernatraemia;
  • hypocalcaemia, hypomagnesia;
  • pyridoxine dependent seizures;
  • non-ketotic hyperglycinaemia.

Neonatal withdrawal from maternal medication or substance abuse.

Kernicterus.

Rare syndromes:

  • benign familial neonatal seizures (autosomal dominant);
  • early myoclonic encephalopathy.

With improved access to neuroimaging, fewer infants are being categorized as ‘benign’ or ‘idiopathic’ seizures. Neonatal stroke is increasingly recognized.

Investigation and management

This should include family history, history of pregnancy and delivery, complete examination, evaluation for infection, serum electrolytes, calcium, magnesium, glucose, and blood gas. If available, cerebral function analysis monitoring (CFAM) should be commenced.

If appropriate, further investigation may include radiological evaluation, e.g. cranial MRI, toxicology screening, serum ammonia, urine organic acids, serum amino acids, karyotype, and TORCH screening.

Treatment of neonatal seizures

  • Immediate: give O2, maintain airway, insert IV, treat the underlying cause. When to start anticonvulsants is controversial because risks and benefits of treatment have not been properly evaluated; the usual indication is >3seizures/hr or single seizure lasting >3–5min particularly if evidence of cardiorespiratory compromise.
  • First-line anticonvulsant: IV phenobarbital (10–20mg/kg bolus; givefurther 10–15mg if seizures persist after 30min; maintenance dose 5mg/day).
  • Second-line IV clonazepam, IV midazolam, or IV phenytoin.
  • For intractable seizures consider a therapeutic trial of parenteral pyridoxine (50mg). Depending on the cause probably safe to stop treatment after a few days of no seizures, but many clinicians prefer to wait until several months before ceasing.

 Prognosis

Prognosis varies with the cause of seizures but is generally good for idiopathic seizures, sleep myoclonus, hypocalcemia, and benign familial neonatal seizures. There is a significant risk of adverse neurodevelopmental outcome after meningitis, HIE, hypoglycemia, cerebral infarction, hypo or hypernatraemia, cerebral malformations, kernicterus, and some inborn errors of metabolism.