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Epileptic syndromes

Benign idiopathic neonatal convulsions (fifth-day fits)
Benign idiopathic neonatal convulsions occur around the fifth day of life (day 1 to day 7, with
90% between day 4 and 6) in otherwise healthy neonates. At present the aetiology is unknown.
Seizures are clonic, mostly partial and/or apnoeic23. The inter-ictal EEG shows ‘théta pointu
alternant’ in 60%, in the remaining neonates the background activity is either discontinuous,
with focal or multifocal abnormalities, or normal. Ictal recordings show unilateral or
generalised rhythmic spikes or slow-waves. Treatment may not be necessary, but the diagnosis
is one of exclusion. Seizures usually resolve within days. The outcome is good, but increased
risk of minor neurological impairment has been reported24,25.

Benign familiar neonatal convulsions
Benign familiar neonatal convulsions constitute a rare disorder with autosomal dominant
inheritance (mutations in the voltage-gated potassium channel genes: most cases 20q13.3, few
families 8q24). Seizures occur mostly on the second or third day of life in otherwise healthy
neonates and tend to persist longer than in benign idiopathic neonatal convulsions. They are
mainly clonic, sometimes with apnoeic spells; tonic seizures have rarely been described. The
background activity is normal with no specific pattern. Therapy is controversial and seizures
usually resolve within weeks. The outcome is favourable, but secondary epilepsy may occur23.

Early myoclonic encephalopathy
Early myoclonic encephalopathy26 is a syndrome often associated with inborn errors of
metabolism, but cerebral malformations have also been reported. Onset is nearly always in the
first month of life and ictal manifestations are as follows: (1) partial or fragmented myoclonus;
(2) massive myoclonias; (3) partial motor seizures; (4) tonic spasms. Background activity is
abnormal consisting of complex bursts of spikes and sharp waves lasting for 15 seconds
alternating with flat periods of 310 seconds in both waking and sleep. The EEG later evolves
towards atypical hypsarrythmia. Seizures are resistant to treatment, though ACTH may have
some temporary effect. All infants are severely neurologically abnormal and half of them die
before the age of one year.

Early infantile epileptic encephalopathy with burst-suppression pattern (Ohtahara syndrome)
Age of onset is in the first three months of life with frequent tonic spasms (100300 per day),
often in clusters27. Partial motor seizures may also occur. The EEG is characterised by true
burst-suppression pattern, both in sleep and waking. It may be asymmetric. During seizures
desynchronisation is seen. This syndrome is usually associated with cerebral malformations,
e.g. Aicardi syndrome or porencephaly. Seizures are resistant to treatment, though ACTH may
have some temporary effect. The prognosis is serious, but may be somewhat better than for
early myoclonic encephalopathy. Evolution into infantile spasms is common.

Both EME and Ohtahara syndrome have clinically and electrographically distinct features.
However, there are also similarities, which have prompted some to suggest that they are not
two syndromes, but rather part of a spectrum of a single disorder26.

Inborn errors of metabolism presenting with neonatal seizures
There are also a group of metabolic disturbances, which may present as otherwise medically
intractable seizures: 58,59

• Pyridoxine dependency
• Pyridoxal phosphate dependency
• Folinic acid responsive seizures
• Serine deficiency