Unknown. ~100 cases have been reported but this may be an underestimate. Neonates with such a severe disease and early death may escape clinico-EEG diagnosis.
Age at onset
Mainly around the first 10 days of life, sometimes intra-uterine or up to 3 months of age. Epileptic spasms occur in 1.5 to 5 per 1000 newborns post-partum.
Males slightly predominate.
Neurological and mental state
The most common cause is malformations of cerebral development such as hemimegalencephaly, porencephaly, Aicardi syndrome, olivary-dentate dysplasia, agenesis of mamillary bodies, linear sebaceous nevus syndrome, cerebral dysgenesis, and focal cortical dysplasia. Rarely, other lesional brain or metabolic disorders may also be responsible.
Mainly tonic spasms that usually consist of a forward tonic flexion lasting from 1 to 10 sec that is singular or in long clusters, 10 to 300 times every 24 hours. They may be generalized and symmetrical or lateralized. They occur in both the wake and sleep stages. Less often, 1/3 of the neonates may have erratic focal motor clonic seizures or hemiconvulsions. Alternating hemiconvulsions or generalized tonic clonic seizures (GTCS) are exceptional. Myoclonic seizures are rare. Erratic myoclonias are not featured.
As for neonatal seizures, in order to detect an etiological cause and possible treatment, brain imaging is used. Brain imaging usually shows severe abnormalities and malformations of cortical development. Metabolic screening is mandatory if brain imaging is normal.
Pseudorhythmic repetitive suppression-burst pattern without physiological rhythms. There is an age-related evolution to hypsarrhythmia of West syndrome and then to slow spike-wave patterns of Lennox-Gastaut syndrome.
The suppression-burst pattern is associated with tonic spasms of variable duration concomitant with the burst phase. Tonic spasms may also occur with the following EEG features:
- Diffuse desynchronization with disappearance of suppression-burst activity when tonic spasms cluster in intervals of 5 to 10 sec.
- A pattern in which the suppression-burst pattern becomes more frequent, more diffuse, and of higher amplitude compared to the inter-ictal pattern.
Devastating syndrome associated with high mortality and morbidity. Half of the patients die within weeks or months from onset, and the others soon develop permanent, severe mental and neurological deficits.
The main differential diagnosis of Ohtahara syndrome is from early myoclonic encephalopathy.
There is no effective drug treatment. Neurosurgery in focal cerebral dysplasia is sometimes beneficial.
This section was adapted from: The educational kit on epilepsies, The epileptic syndromes By C. P. Panayiotopoulos Originally published by MEDICINAE 21 Cave Street, Oxford OX4 1BA First published 2006 and reprinted in 2007