Childhood absence type epilepsy or pycnolepsy: causes, symptoms, diagnosis, treatment

By Cristiano Antonino On Aug 12, 2022

Pycnolepsy in medicine refers to a morbid picture peculiar to childhood and early adolescence, which manifests itself with numerous and very brief suspensions of consciousness (and sometimes of motor functions) similar to those of the small epileptic disease

Epilepsies are distinguished into:

A) generalised (or ‘primary’) epileptic seizures distinguished in:

grand mal seizure or tonic-clonic seizure
small malady or absence;

B) partial (or ‘focal’ or ‘secondary’) seizures distinguished in:

simple or elementary
complex.

Pycnolepsy, childhood absence type epilepsy

Infantile absence-type epilepsy (also called ‘pycnolepsy’) is a very common form of absence, characterised by sudden and fleeting loss of consciousness in school-age children.

Spread of pycnolepsy

Childhood absence-type epilepsy accounts for about 10% of all school-age epilepsies.

Its highest incidence is between 5 and 7 years of age.

It is more frequent in the female sex.

Pycnolepsy, causes and risk factors

Childhood absence type epilepsy currently has no known specific causes.

As with other forms of epilepsy, pycnolepsy has a strong familial predisposition so a risk factor is the presence of another case of epilepsy in the family.

Symptoms and signs

Pycnolepsy is characterised by rapid and fleeting losses of consciousness occurring several times a day (even more than 10 times a day); in this sense, pycnolepsy represents the most classic picture of typical absence.

The sudden losses of consciousness are not associated with motor seizures and generally last between 5 and 20 seconds (never more than 30 seconds); given their age and the absence of tonic-clonic manifestations, affected children are very often noticed by their teachers.

Diagnosis of pycnolepsy

Absence seizures can be evoked by hyperpnoea (inviting the child to blow repeatedly to make a small pinwheel move) or non-REM sleep.

It is possible to record the brain’s electrical activity during the seizure by means of the electroencephalographic tracing; in fact, in the context of a regular background rhythm, complex 3-cycle-per-second (3 Hz) spikes appear during the seizure.

This finding is sufficient for diagnosis.

Differential diagnosis

Childhood absence type epilepsy is a typical ‘simple absence’: simple absences are not accompanied by other manifestations.

Complex absences, on the other hand, are characterised by other manifestations such as:

clonic contractions that may involve the eyelids, the corners of the mouth or the proximal portions of the limbs;
muscular atony or hypotonia (atonic absences) that often results in falls to the ground due to collapse of the lower limbs;
muscle hypertonus (tonic absences), especially of the postural muscles, with a rigid fall (‘statue fall’);
automatisms;
skin redness or pallor; incontinence or enuresis.

Infantile absence-type epilepsy is a ‘typical absence’.

The EEG during the seizure distinguishes typical from atypical absences: whereas typical absences are characterised by 3-4 Hz tip-wave complexes with normal background rhythm, in atypical absences the tip-wave complexes are slower (2.5 Hz) and with slowed background rhythm.