Convulsive SE

Convulsive status epilepticus (SE) is often associated with poor outcome. This section presents the etiology, related electrophysiology, course and consequences of convulsive SE.

 

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Complications and prognosis
Author: FW Drislane

Important clinical lessons about the effects and prognosis of convulsive SE have emerged from studies:

  • Some damage appears to accrue from the epileptic neural activity itself, although systemic factors such as hypotension, hypoxia, and acidosis may add to the neurologic complications.
  • The longer the duration of SE, the more refractory it becomes and the more neuronal damage occurs.
  • Clinical and experimental data suggest that 30 minutes of convulsive SE is a critical duration in neurologic function and probably in prognosis. This figure is far less certain for other forms of SE, particularly nonconvulsive forms.

Complications

Convulsive SE can cause numerous complications.Table: Complications of SE Cardiac and autonomic changes, which can be severe, include hypertension, tachycardia, arrhythmias, diaphoresis, hyperthermia, and vomiting. Cardiac arrhythmias may be precipitated by lactic acidosis and elevated catecholamines. Hyperthermia may result from excessive convulsive muscle contractions as well as from hypothalamic effects. The electrocardiogram (ECG) may show conduction abnormalities or ischemic patterns. Autonomic dysfunction and cardiac arrhythmias may explain much of the mortality of SE and some other unexplained sudden death in epilepsy patients.

Cerebral blood flow and metabolism are elevated in early SE but decline eventually, and the excessive metabolism of discharging neurons may outstrip the oxygen and glucose supply. As seizures continue, autoregulation may break down and contribute to cerebral edema, particularly in children. Compensatory physiologic changes in early SE appear to break down after about 30 minutes, with subsequent hypotension, hypoxemia, hypoglycemia, and increasing acidosis and hyperkalemia. Hypotension and bradycardia may be worsened further by anticonvulsants and other medications. Hypotension or volume depletion may complicate medical and metabolic disorders or lead to venous stasis and even cerebral venous thrombosis.

Inhibitory GABA receptors are progressively lost, which may help to determine the critical period at which SE becomes more refractory to treatment and more dangerous physiologically.

SE prompts cortisol and prolactin release, although prolactin may become exhausted and return to normal levels in prolonged SE.

Leukocytosis and spinal fluid pleocytosis may occur, but these problems should not be attributed to the SE itself until infection or some other cause of inflammation has been excluded.

Aspiration pneumonia is common if airway protection is not assured. Respiratory failure is probably more often due to medications than to SE itself. Pulmonary edema may also occur.

Rhabdomyolysis can occur after repeated convulsive seizures. Together with hypotension, it may result in renal failure.

EEG patterns

Patients may exhibit an orderly sequence of electroencephalogram (EEG) changes in SE:

Clinical convulsions abate as the EEG progresses through these stages. Patients in later EEG stages have seizures that are particularly refractory to the usual anticonvulsants and have a worsened prognosis.

Persistent EEG discharges generally are a sign of continuing and damaging SE, so an EEG is necessary when a patient's convulsions have ended and the patient has not awakened. The EEG can show whether comatose patients are in a postictal state or still having seizures. Even without motor phenomena, EEG evidence of SE warrants aggressive treatment.

Findings from animal studies

Abundant experimental animal evidence indicates that convulsive SE (whether induced by electrical stimulation, kainic acid, or lithium and pilocarpine) leads to neuronal damage due directly to the neuronal epileptic activity. The cellular activity of SE releases excitatory amino acids, which are neurotoxic in excessive amounts. Hippocampal damage and a subsequent recurrent seizure disorder are among the consequences. Systemic factors, however, especially hypotension, respiratory failure, and hypoxia, worsen the prognosis and contribute to cerebral damage.

Repetitive electrical stimulation produces SE after 30 minutes or so-the same time at which human homeostasis appears to deteriorate during convulsive SE. Thus, both clinical and experimental data implicate 30 minutes as a critical time before which convulsive status should be interrupted if damage is to be avoided. Experimental data using electrical stimulation-induced SE also suggest that phenobarbital is far more effective than phenytoin at breaking this SE. These effects are more difficult to substantiate in humans, but pyramidal cell loss in the hippocampus has been identified after SE in humans.

Prognosis

It has become increasingly clear that SE in patients with prior epilepsy and SE in those with a new diagnosis are almost different conditions. Patients who have had prior epilepsy or whose SE has been precipitated by withdrawal from an anticonvulsant or another medication do far better. The reason may be earlier detection and diagnosis, partial treatment from earlier anticonvulsants, or the absence of acute severe insults that worsen the prognosis in other patients.

Children also fare far better than adults, perhaps because older patients often have underlying illnesses with a higher associated morbidity and mortality.

The underlying disease is the most important prognostic factor in generalized convulsive SE. Mortality has declined in recent decades and should be below 2% from the SE itself with reasonable treatment. Mortality due to the condition causing the convulsive SE may be substantially higher, often about 30%. Underlying conditions predicting a worse outcome include:

The presence of more than one medical complication, especially cardiac arrhythmias, hypotension, kidney or liver failure, and intracranial hypertension, also predicts a worsened outcome.

Studies have found other factors that influence outcome:

SE may cause subsequent intellectual impairment, but studies suggesting that this is the case have generally been retrospective and have usually included only subjects who have had prolonged SE, who have had prior substantial neurologic and intellectual impairment, and who were taking several anticonvulsants. SE may worsen chronic epilepsy.

Adapted from: Drislane FW. Status epilepticus. In: Schachter SC, Schomer DL, eds. The comprehensive evaluation and treatment of epilepsy. San Diego, CA: Academic Press; 1997. p. 149-172.
With permission from Elsevier (www.elsevier.com)

Reviewed and revised January 2004 by Thaddeus Walczak, MD, MINCEP® Epilepsy Care, Minneapolis, MN

 

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Symptoms and causes
Author: FW Drislane

Generalized convulsive status epilepticus (GCSE) is the most dramatic, most dangerous, and best-studied type of SE. It is potentially life-threatening but also treatable. A plan for medical management and pharmacotherapy is crucial. The clinician needs to understand its etiology, electrophysiology, pathophysiology, course, and consequences.

Symptoms

Convulsive SE is readily recognizable. It may start with simple or complex partial seizures but often begins with a generalized convulsion. Convulsions recur, most lasting only a minute or so, along with intervals of persistent unresponsiveness. Each convulsion may begin with several seconds of a tonic phase with tensing of extensor muscles and forced expiration, followed by a clonic phase with gradually slowing clonic movements. Both phases usually involve bilateral and symmetric movements, although there may be a focal onset with head or eye deviation, even without unilateral limb movement. Consciousness is impaired, at least from the time of tonic seizures.

Less often, convulsions are continuous. In this case clonic movements eventually diminish, often being replaced by repetitive jerking movements of the eyes, eyelids, or facial muscles alone or sometimes with intermittent limb jerking. These signs constitute "subtle" SE and imply continuing epileptic brain activity with a "decoupling" of electrical and motor systems.

Incidence

The incidence of convulsive SE is usually estimated to be about 60,000 cases each year in the United States (probably over half of them in children), but population-based surveys suggest that it may occur several times as often. The incidence of other forms of SE is less well documented.

Etiology and epidemiology

Convulsive SE is not a disease itself but, rather, a serious manifestation of some underlying disorder. The following list shows etiologies and percentages of patients affected; these figures are obtained from a summary of several studies of adult patients.

Factor Percentage
Anticonvulsant withdrawal 25
Alcohol withdrawal 25
Cerebrovascular (stroke, anoxia, hemorrhage) 22
Metabolic: acute encephalopathy (e.g., hypoglycemia, systemic infection) 22
Trauma 15
Drug toxicity 15
CNS infection 12
Tumor   8
Congenital lesion   8
Prior epilepsy 33
Idiopathic 30

These percentages total more than 100% because of multiple causes. For instance, a patient with a congenital lesion and chronic epilepsy may experience anticonvulsant withdrawal or infection.

The causes of convulsive SE may vary tremendously in different populations. In urban hospitals, for example, SE is more often related to alcohol and drugs. The causes or precipitants of convulsive SE are also different in patients with known epilepsy than in those presenting with acute, new illness. Congenital abnormalities and infection increase in importance in children.

Often, there is an interaction between acute systemic illness and earlier neurologic disease, including epilepsy and other earlier neurologic insults. A history of epilepsy is often assumed, but in actuality about two-thirds of SE cases occur in patients who have not had prior seizures.

About 1% of patients with epilepsy will have an episode of SE in a given year. Anticonvulsant withdrawal is often assumed in patients with epilepsy, although this may be less frequent than presumed. Anticonvulsant changes initiated by physicians may cause withdrawal seizures as often as patient noncompliance. Adding new anticonvulsants may alter metabolism and lead to subtherapeutic or toxic levels of prior medications.

Infections may have a role in epileptogenicity, but several antibiotics also can precipitate seizures and alter anticonvulsant metabolism.

The epidemiology of convulsive SE has several clinical implications:

  • Convulsive SE usually has an identifiable cause. Look for it. Trauma, new or prior vascular disease, metabolic derangements, drug toxicity (due to prescribed or "recreational" drugs), and infection not only help to explain the SE but often determine the subsequent course; they must be found to be treated appropriately. Alcohol abuse and benzodiazepine withdrawal are common contributors.
  • There is often more than one cause or precipitant: medication withdrawal, infection, or sleep deprivation may add to an earlier illness and precipitate convulsive SE. In some series, up to 50% of patients have either an infection or a recent medication change. Conversely, even in acute illness, convulsive SE occurs more often in people with prior neurologic deficits.
  • Convulsive SE can be the first sign of neurologic disease, especially in children, in whom up to 10% of initial seizures (particularly febrile seizures) may be SE.

Adapted from: Drislane FW. Status epilepticus. In: Schachter SC, Schomer DL, eds. The comprehensive evaluation and treatment of epilepsy. San Diego, CA: Academic Press; 1997. p. 149-172.
With permission from Elsevier (www.elsevier.com)

Reviewed and revised January 2004 by Thaddeus Walczak, MD, MINCEP® Epilepsy Care, Minneapolis, MN

 

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