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.
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.
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.
·
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 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.
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