Page 126 - ILAE_Lectures_2015

distribution. There are no other discernible clinical seizures though video-EEG may often
demonstrate ‘phantom absences’.

The following syndromes are not recognised by the ILAE:

Eyelid myoclonia with absences (EMA). TA are frequent, typically associated with marked,
rhythmic, and fast jerks of the eyelids, often with jerky upward deviation of the eyeballs and
retropulsion of the head. Absences are brief (3–6 seconds) and occur mainly after eye closure.
GTCS and random myoclonic jerks of the limbs may occur infrequently, most likely after
sleep deprivation, fatigue, and alcohol intake. Marked photosensitivity is the rule but declines
with age. EMA usually starts in early childhood but may be resistant to treatment. The ictal
EEG manifestations consist mainly of generalised polyspikes and slow-waves at 3–6 Hz40,41.
Patients practising self-induction should be differentiated from pure EMA and treated
accordingly.

Perioral myoclonia with absences (PMA). Here, TA are also frequent and usually brief,
associated with a variable impairment of consciousness and rhythmic myoclonus of the
perioral facial or masticatory muscles. Clusters of absences or absence status occur
commonly, and may precede GTCS. The latter are not frequent. PMA starts in childhood or
early adolescence and TA and GTCS may be resistant to medication. Ictal EEG discharges
are often irregular, and consist of rhythmic multiple spike-waves and slow-waves at 3–4 Hz.
Photosensitivity is not encountered42,43.

Idiopathic generalised epilepsy with phantom absences. The term ‘phantom absence’ denotes
simple TA, which are so mild that they are inconspicuous to the patient and imperceptible to
the observer. This syndrome also includes (usually late onset) GTCS, and absence status in
50% of the patients. TA are disclosed by video-EEG (prompted by the GTCS) and breath
counting or other cognitive testing during hyperventilation, when brief (up to 4 seconds) 3–
4 Hz spike or multiple spike-wave discharges interfere with cognitive performance18.

Absences with specific modes of precipitation (photic, pattern, video-games, emotional
upset, intense thinking, and reading) and their underlying mechanisms have been recently
reviewed44. Photosensitivity is estimated to occur in approximately one-fifth of patients
with onset of absences in childhood or adolescence and it is associated with unfavourable
prognosis. Apart from all patients with EMA and up to 30–40% of those with JME who are
photosensitive, others with spontaneous and photically provoked absences and GTCS may
belong to various syndromes not yet identified.

Absences in symptomatic or cryptogenic (probably symptomatic) focal epilepsies have been
documented only occasionally and in specific topographic and pathologic substrates,
notably in patients with seizures arising from the medial intermediate frontal area45, and in
others with cerebral cortical dysgenesis and involvement of the archicortex46. In both
instances, brief impairment of cognition associated with 3 Hz spike-wave EEG paroxysms
would probably qualify these seizures as TA, but these absence-like events usually coexist
with complex partial seizures with or without secondary generalisation, and require
completely different management. TA may occasionally arise as a consequence of a known
disorder of the central nervous system47, but in most cases an aetiological link is not proven,
and it is likely that they are coincidental. Finally, the co-existence of IGE with TA and
symptomatic partial epilepsy in the same patient is seemingly rare although probably
underdiagnosed6.