Salient Features

• 10 year old girl• Poor academic performance• Absent minded – Recurrent, periods of blank staring and inattention– Accompanied by eye blinking, reflex scratching of

her head, lip smacking and chewing movements – Occurs many times a day

Clinical Impression

Absence Seizure

• A type of generalized seizure, lasting for several seconds to minutes and may occur several times a day

• Children with idiopathic generalized epilepsies may present with a history of staring spells, but infrequent absence seizures may not be diagnosed until a generalized tonic-clonic seizure has occurred.

Segan, S. (2009). Absence Seizures. American Academy of Neurology and American Epilepsy Society

Absence Seizure • Other symptoms, such as behavioral problems may be

the presenting complaint– Although the brief attacks are unrecognized, the lapses of

awareness interfere with attention

• Decline in school performance may be an indication of the onset or breakthrough of absence seizures

• In symptomatic generalized epilepsies, atypical absence seizures often occur in the setting of developmental delay or mental retardation.

Segan, S. (2009). Absence Seizures. American Academy of Neurology and American Epilepsy Society

Absence Seizure

• On clinical examination, typical absence seizures appear as:– Brief staring spells• Patients have no warning phase, and if engaged in

gross motor activity, such as walking, they may stop and stand motionless or they may continue to walk

– Unresponsive during the seizure• Children have no memory of what happened during the

attack; they are generally unaware that a seizure has occurred

Segan, S. (2009). Absence Seizures. American Academy of Neurology and American Epilepsy Society

Pathophysiology• The pathophysiology of absence seizures is not fully

understood• Abnormal oscillatory rhythms are believed to develop

in thalamocortical pathways

– This involves GABA-B–mediated inhibition alternating with glutamate-mediated excitation

– GABA-B inhibition appears to be altered in absence seizures

– Enhanced burst firing in selected corticothalamic networks may increase GABA-B receptor activation in the thalamus, leading to generalized spike-wave activity

Segan, S. (2009). Absence Seizures. American Academy of Neurology and American Epilepsy Society

Absence Seizure vs Complex Partial Seizure

• An absence seizures can sometimes be confused with a complex partial seizure but each type has its own distinctive features:– Asence seizures :

• never preceded by an aura• are of briefer duration – seconds rather than minutes• begin frequently and end abruptly• the absence attack is always associated with the strikingly

typical EEG abnormality of spike and slow wave discharges, usually at a frequency of 3Hz which occur can occur interictally and ictally and are often provoked by hyperventilation