Convulsive status epilepticus (SE) is rarely difficult to diagnose. Other forms of SE, however, may be mistaken for altered mental status from other causes, or for movement disorders. These other forms include both generalized seizures and partial or focal seizures.
The management of other forms of SE is often similar, though less urgent, than the management of convulsive SE.
Absence SE implies generalized epileptiform EEG discharges. Synonymous (and somewhat confusing) terms include "spike wave stupor" and "epileptic twilight states."
Because of the difficulty of detection, it is hard to know how often absence SE occurs. It may occur one-fourth as often as convulsive SE. Three different syndromes have been described:
Onset may be sudden or gradual. Patients may be awake, walking and talking, although they are often confused. Motor activity may be preserved but clumsy. There is occasionally some blinking or myoclonus.
Absence SE can persist for days or weeks without being recognized. A history of epilepsy is suggestive. Most cases may be missed, but EEG can readily confirm the diagnosis. Some EEGs show generalized 3-Hz epileptiform discharges. Some may be secondarily generalized from a focus.
EEG of a 33-year-old woman with a history of epilepsy, now ambulatory and speaking, but confused at the time of office visit; approximately 3-HZ generalized spike-and-slow wave discharges with a frontal and central emphasis.
Especially in younger patients with primary generalized epilepsies, benzodiazepine therapy is often rapidly successful. Valproic acid may be better at preventing recurrences. Most patients return to normal, although recurrence of absence SE is relatively common. In older patients and those whose SE has a less certain cause, the response to anticonvulsant therapy can be delayed.
The typical absence status of patients with prior epilepsy is not thought to be life-threatening, but occasionally episodes end with a generalized convulsion. Absence SE is probably the most benign type of SE in terms of potential neuropathophysiologic consequences and may warrant less aggressive treatment than other forms of SE. For example, treatment with anesthetic drips is usually not pursued in this situation.
Myoclonic status epilepticus (MSE) also occurs in several forms. The most severe form, which is highly associated with the eventual death of the patient, occurs after anoxia. Persistent myoclonus due to a severe encephalopathy without MSE is potentially reversible. The EEG helps determine whether myoclonus is the sporadic sign of an encephalopathy (with a better prognosis) or part of MSE. After anoxia, MSE is better considered a sign of a severely damaged brain than a treatable epileptic condition. MSE may have motor manifestations limited to "subtle" status, also an ominous sign after anoxia.
Less severe forms of MSE occur as a manifestation of generalized epilepsies such as juvenile myoclonic epilepsy. This form of MSE may include prolonged epileptic myoclonus without loss of consciousness. The EEG shows very characteristic generalized polyspike and slow wave discharges with a normal background between episodes. Episodes may go on for hours (with preserved consciousness), but the prognosis is excellent given the prior normal neurologic function.
Patients can also return to baseline in the MSE of progressive myoclonus epilepsies, although the epilepsy may be part of a progressive debilitating disease.
In all these conditions, the EEG can help distinguish MSE from encephalopathies with less rhythmic abnormalities.
Tonic SE is rare. It is seen primarily in children, particularly those with Lennox-Gastaut syndrome. This form of SE does not respond well to medications, as is true of most seizure types in Lennox-Gastaut syndrome. Rarely, benzodiazepines have been cited as triggering tonic status. Tonic (and atonic) SE is distinctly uncommon in adults, especially those with normal interictal neurologic function.
Generalized clonic SE is also a pediatric condition. Clonus is often of low amplitude. Both sides of the body are usually involved but may move asynchronously.
Complex partial status epilepticus (CPSE) implies impairment of consciousness due to seizures with a focal cortical origin. The disorder is sometimes called fugue state or psychomotor status.
Confusion is the most common symptom. A sudden alteration in behavior, particularly in a patient with prior epilepsy, should suggest the possible diagnosis of CPSE. A diagnosis of CPSE is frequently invoked to explain bizarre behavior, but this type of SE is actually uncommon. Some patients may have complex partial seizures with a prolonged postictal phase. CPSE may be continuous or include frequent discrete seizures without recovery between them; the latter series of spells account for some of the prolonged episodes.
CPSE can go on for weeks or even months, and patients may have prolonged cognitive deficits after CPSE. It can be very difficult to distinguish from absence SE. Patients with CPSE may exhibit more bizarre behavior during seizures, so the disorder also is confused with psychiatric disease or metabolic encephalopathies with delirium.
The usual site of origin is assumed to be mesial temporal structures with limbic connections, but recordings obtained from implanted electrodes have shown that frontal lobe onset is common. The EEG may show the seizure clearly (but this is less likely in frontal areas without implanted electrodes) or may show just persistent focal slowing. Seizures may spread rapidly, and nonconvulsive SE with generalized discharges ("absence SE") may actually arise from a focus.
Increasing reports of cognitive and other sequelae following prolonged CPSE have lent a greater urgency to its interruption, but treatment is usually not as aggressive as for generalized convulsive SE. Most CPSE responds relatively rapidly to anticonvulsants but may recur frequently and even regularly in the same patient, even with adequate anticonvulsant therapy.
Epilepsia partialis continua (EPC) usually refers to partial motor status. Continuous unilateral facial or hand clonic jerking are most commonly observed, but any group of muscles can be involved. An acute structural lesion must be considered and ruled out, but lesions are not always found even with contemporary imaging. Consciousness may be impaired because of secondary effects of the structural lesion. The EEG often demonstrates periodic lateralizing epileptiform discharges (PLEDs) in a corresponding distribution.
EPC is unresponsive to medication but generally abates over time, presumably due to the resolution of the acute cerebral changes associated with the original cerebral insult. Persistent EPC raises concerns about Rasmussen's syndrome.
Nonconvulsive status epilepticus (NCSE) includes many of the syndromes already described. Most patients have absence SE; fewer have CPSE. SE with simple partial sensory or autonomic symptoms and all SE without convulsions are included.
The EEG can vary tremendously in NCSE, often exhibiting slower discharges than expected. It usually shows generalized rather than focal abnormalities.
In electrographic SE (ESE), patients have continuous epileptic discharges evident on the EEG, but their significance is unknown or controversial. Children with ESE during sleep (ESES) may have no clear clinical concomitant, but most have mental retardation and epilepsy. Many of these children have markedly impaired language function. In waking, they tend to be healthier than patients with Lennox-Gastaut syndrome. Medications may improve the EEG without affecting overall health or behavior. ESES can be associated with neuropsychologic regression after previously normal development.
ESE can also be seen in adults, in some cases representing absence SE or occurring after generalized convulsive SE. It also may be an unexpected finding in patients with severe medical illness with encephalopathies. Its clinical significance in these cases is uncertain. Some patients have subtle motor phenomena, but in others coma is the only manifestation. Diagnosis rests on the EEG. Anticonvulsant therapy can be helpful but may be unrewarding, primarily because of the severe underlying illness.
Reviewed and revised January 2004 by Thaddeus Walczak, MD, MINCEP® Epilepsy Care, Minneapolis, MN
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