Neurologic Diseases: Petit mal Seizure

Petit mal seizure, also called as absence seizure is a type of generalized epilepsy.

Its incidence is much higher in children compared to adults. This seizure starts almost always in childhood or adolescence and in some patients these types of seizures may persist into adulthood.

It is called as a generalized seizure and it means the seizure activity starts over the both cerebral hemispheres simultaneously and there is no focal onset.

This seizure is seen in both idiopathic and symptomatic settings.

Idiopathic type belongs to PGE (primary generalized epilepsy) where there are no known causes other than genetic predisposition, patients cognitive functions are normal (no mental retardation) and EEG shows typical 3 HZ spike and wave findings. Childhood & juvenile absence seizures are examples. These are called typical petit-mal seizures.

In the symptomatic setting it may be seen in conditions like Lennox-Gastaut syndrome. Patients have varying degrees of mental retardation and EEG differs from the above type as discussed below. These are called atypical petit-mal seizures.

These are brief episodes lasting for several seconds may be up to about 30 seconds and generally less than a minute. Patient suddenly becomes unresponsive and loses the awareness and contact with the surrounding. Interestingly (and luckily) they do not lose muscle tone or fall down during these attacks.

No significant motor activities like stiffening, convulsions etc are seen. Some eye lid blinking, twitchings are seen. Patient characteristically presents with blank staring. No tongue bites, losing bladder control etc occur. Hyperventilating may precipitate attacks. Patients do not have any warning of these episodes, also they totally come out of these episodes without any residual symptoms (no post ictal episodes).

These attacks may occur in clusters and several episodes per day. These kids may be considered day dreaming or having ADD (attention deficit disorder) etc.

If the typical history is available then this seizure especially the idiopathic type can be diagnosed clinically however an EEG is commonly obtained to confirm the diagnosis. Patient may be asked to hyperventilate during the EEG with the hope of precipitating the typical episodes and confirm the diagnosis.

In the idiopathic or PGE type EEG will show the typical interictal 3 HZ spike & wave complexes. There is no slowing of the background activity. During the seizure long runs of rhythmic such activity is seen and it is so characteristic finding that once it is seen it will be like a spot EEG diagnosis for the interpreting physician like a neurologist.

In the symptomatic type the frequency of the spike and wave complexes is 1.5 to 2.5 Hz/second also there is slowing of the background seen.

Imaging study of the brain like a CT or MRI is unnecessary in typical idiopathic cases but if there are atypical features and if we are dealing with symptomatic seizures then these tests may be ordered especially the brain MRI scan.

If scanty episodes occur and do not bother the patient at all then it is wiser not to treat the patients as the side effects of the mediations may outweigh the benefit.

However if frequent episodes are happening, then patients are treated, and the following medication are the usual choices;

• Sodium valproate
• Ethosuximide
• Lamotrigine etc.

Sodium valproate is preferred if petit mal seizures are associated with grand mal seizures otherwise ethosuximide is generally preferred.

A neurologist is frequently involved in the management of petit mal seizure patients.