Absence status epilepsy

Absence status (AS), or "Petit Mal status" is a polymorphic condition that can complicate many epileptic syndromes. Diagnosis is difficult on the basis of clinical semiology alone, and requires emergency EEG. Although heterogeneous, the most typical ictal pattern is constituted by slow generalized rhythmic spike-waves (SW) or polyspike-waves (PSW) complexes. In a number of cases, clinical and EEG normalization is obtained after intravenous (i.v.) benzodiazepine (BZ) injection. In some difficult cases, neuropsychological investigations before and after BZ injection is useful: a significant improvement of the neuropsychological score should occur following BZ injection. On a nosographic point of view, literature data indicate that 4 types of AS may be recognized. Typical AS occurs as part of an idiopathic generalised epilepsy most often characterized by absences. Isolated impairment of consciousness, at times with subtle jerks of the eyelids, is the essential symptomatology. The EEG correlates with repetitive absence seizures and shows symmetric and bilateral synchronous SW or PSW complexes faster than 3 Hz. The immediate prognosis is excellent. Atypical AS occurs in patients with symptomatic or cryptogenic generalized epilepsies and is characterized by a fluctuating confusional state with more prominent tonic and/or myoclonic and/or lateralized ictal manifestations than occur in typical AS. The EEG shows continuous or intermittent diffuse irregular slow SW or PSW complexes. The immediate prognosis is guarded, as these episodes tend to recur and to be resistant to medication. "De novo" absence status of late onset is characterized by toxic or metabolic precipitating factors in middle-aged or elderly subjects with no previous history of epilepsy. Patients often have a history of psychiatric illness with multiple psychotropic drug intake. The electroclinical characteristics and the immediate prognosis are variable. These episodes of AS generally represent acute symptomatic seizures and may not recur if the triggering factors can be controlled or corrected. Long-term antiepileptic drugs may thus not be needed. Absence status with focal characteristics occur in subjects with a pre-existing or newly developing partial epilepsy, most often of extra-temporal origin. The EEG shows bilateral but often asymmetric ictal discharges. The immediate prognosis is variable. Some of these cases are difficult to distinguish from complex partial status epilepticus of frontal lobe origin.