This occurs only in patients with idiopathic generalized epilepsy, usually as part of the subcategory childhood absence epilepsy, in which a history of absence status occurs in about 3 -9%. The attacks can recur, and can last for hours or occasionally days. The episodes are typically precipitated by factors such as menstruation, withdrawal of medication, hypoglycaemia, hyperventilation, flashing or bright lights, sleep deprivation, fatigue, stress, or grief. The principle clinical feature is clouding of consciousness. This can vary from slight clouding to profound stupor. At one extreme patients have nothing more than slowed ideation and expression, and deficits in activities requiring sustained attention, sequential organization or spatial structuring; amnesia may be slight or even absent. At the other extreme there may be immobility, mutism, simple voluntary actions performed only after repeated requests, long delays in verbal responses, and monosyllabic and hesitant speech. Typically, the patient is in an expressionless, trance-like state with slow responses and a stumbling gait. Motor features occur in about 50% of cases, including myoclonus, atonia, rhythmic eyelid blinking, and quivering of the lips and face. Facial, especially eyelid, myoclonus is common in absence status, but rare in complex partial status. Episodes of absence status are often terminated by a tonic-clonic seizure. The diagnostic electrographic pattern is continuous or almost continuous bilaterally synchronous and symmetrical spike-wave activity, with little or no reactivity to sensory stimuli.
Typical absence status can usually be rapidly and completely abolished by benzodiazepine therapy given as intravenous bolus doses. The usual drugs are diazepam 0.2-0.3 mg/kg, clonazepam 1 mg (0.25-0.5 mg in children) or lorazepam 0.07 mg/kg (0.1 mg/kg in children). The bolus doses can be repeated if required. If this is ineffective, intravenous clomethiazole, phenytoin or valproate may be needed. In childhood absence epilepsy, maintenance therapy with valproate, ethosuximide or other agents is required once the status is controlled.
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