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Erratic, fragmentary or more generalised myoclonic jerks are often associated with tonic
spasms, with multifocal clonic or tonic patterns, or with mixed seizure types. They may persist
into infancy (infantile spasms). Myoclonic seizures can easily be distinguished from benign
neonatal sleep myoclonus by the absence of myoclonia during wakefulness and a normal EEG.

Focal tonic seizures are characterised by stereotyped, abrupt or slower tonic posturing of limb,
and/or trunk or eyes, often accompanied by apnoea, flushing, or mild cyanosis. The EEG
background is often abnormal and ictal discharges are common. Although still considered in
the Volpe seizure classification, generalised tonic posturing is unlikely to be epileptic seizures,
but rather to represent transient decerebrate or decorticate posturing, which can be triggered by
stimulation and show no ictal EEG correlates. EEG background activity is severely abnormal
and the outcome is poor. This seizure type is not classified as being of epileptic origin in the
Mizrahi classification.

A characteristic feature of neonatal seizures is the phenomenon of electro-clinical dissociation:
seizures can be electroclinical, electrographic (subclinical) or clinical only13. The significance
of clinical only seizures is unclear. There is an ongoing controversy as to whether electrical-
only seizures have an impact on long-term outcome and thus require treatment or not. There is
now evidence that they have a similar impact on long-term outcome as electro-clinical
seizures14.

Traditionally, the ILAE has also included some neonatal epileptic syndromes in its
classification61. Most recently, the ILAE proposed a revised syndromic classification that now
includes: benign neonatal familial seizures, early myoclonic encephalopathy (EME), and
Ohtahara syndrome (early infantile epileptic encephalopathy, EIEE)55. These will be discussed
later.

Investigations

The large differential diagnosis following a neonatal seizure (Table 2) demands that the initial
investigations should concentrate on the common aetiologies requiring prompt specific
treatment. Certain clues to the aetiology may be present, such as a history of perinatal asphyxia
or maternal narcotic abuse, but other causes such as hypoglycaemia, hypocalcaemia, and CNS
infection may coexist and need excluding. Investigations include:

 Septic screen, including blood cultures and lumbar puncture
 Laboratory: always glucose, electrolytes, blood gas, packed cell volume, if necessary

bilirubin, ammoniac, metabolic screening, TORCH, screening for drug abuse
 Consider therapeutic trial of pyridoxine and pyridoxal phosphate
 Always cranial ultrasound scanning, consider MRI
 EEG.

Neuroimaging
Cranial ultrasound scanning is readily available in most centres and is useful as a first-line
imaging investigation for exclusion of gross CNS pathology (CNS malformations,
periventricular haemorrhage). If initial ultrasound examination is normal, but the infant
continues to have seizures or has abnormal inter-ictal neurological signs, a CT or MRI
examination has to be carried out to detect other forms of clinically important pathology, such
as cerebral infarction, subdural and subarachnoid haemorrhage or cerebral malformations.