Paediatrics: Neonatal seizures

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 condi-tions 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 catego-rized as ‘benign’ or ‘idiopathic’ seizures. Neonatal stroke is increasingly recognized.

Investigation and management

This should include family history, history of pregnancy and delivery, com-plete 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 underlying cause. When to start anticonvulsants is controversial because risks and benefits of treatment have not been properly evaluated; usual indication is >3seizures/hr or single seizure lasting >3–5min particularly if evidence of cardio-respiratory compromise.

·  First-line anticonvulsant: IV phenobarbital (10–20mg/kg bolus; give further 10–15mg if seizures persist after 30min; maintenance dose 5mg/day).

·  Second-line IV clonazepam, IV midazolam, or IV phenytoin.

·  For intractable seizures consider therapeutic trial of parenteral pyridoxine (50mg). Depending on 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 idi-opathic seizures, sleep myoclonus, hypocalcemia, and benign familial ne-onatal 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 er-rors of metabolism.