Atypical absences (petit mal variant)-This phrase is used in two different ways—to describe absences which are clinically similar to typical absences associated with an EEG record that is not typical, and to describe absences in association with other features which are not typical, of which loss of postural control is the most marked. In these fortunately unusual so-called ‘akinetic drop attacks’, children may crash to the floor with such force and frequency that they have to wear a crash helmet to protect the head from damage.
Clonk seizures-The distinction between these and myoclonic jerks is slight. If jerks are multiple, then the seizures tend to be called clonic.
Tonic seizures-A tonic (rigid) posturing of all limbs without a clonic phase is sometimes seen in some generalized cerebral disorders in childhood. The same name is given to one rare form of partial seizure in which one part of the body briefly maintained abnormal tonic posture. Such seizures may occasionally occur in adults with multiple sclerosis.
Infantile spasms (salaam seizures; West’s syndrome)-These seizures of infancy are characterized by a brief, sudden flexion of head, trunk, and limbs, as if the baby is bowing a ’salaam.’ The infant may appear to be thrown forwards or backwards with the arms outstretched. Each spasm lasts about one second or less. The spasms may occur in runs or clusters
(up to 40-50 spasms per cluster) over a 5-10 minute period; when this happens the infant may appear distressed afterwards and cry. Spasms are more likely to occur at certain times of the day, either just after the infant has woken up from a sleep, or is about to fall asleep. In some children, the spasms may occur almost continuously throughout the day, happening several times an hour. The EEG in infants with this type of seizure shows very abnormal patterns of activity called hypsarrhythmia.