Status Epilepticus

Published on 07/03/2015 by admin

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Chapter 61 Status Epilepticus

Ala Nozari, MD, PhD , Corey R. Fehnel, MD , Lee H. Schwamm, MD, FAHA

1 What is the definition of status epilepticus (SE)?

SE has typically been defined as repetitive seizures lasting 30 minutes or longer, or seizures without full return of consciousness between episodes. This definition was recently challenged because it does not incorporate the practical considerations of patient management and because shorter periods of seizure activity can cause neuronal injury. Therefore others have recommended defining SE as seizures lasting ≥5 minutes or two or more seizures between which there is incomplete recovery of consciousness or function.

2 Name important features of SE

In patients with no prior seizure history, SE is usually a manifestation of cortical irritation or injury. Treatment of the underlying disorder is therefore critical. Relapse of seizure in patients with known seizure disorder, on the other hand, commonly reflects subtherapeutic levels of antiepileptic drugs (AED) and usually responds to a bolus of the maintenance drug. Most cases of convulsive SE in adults start as partial seizures that generalize.

3 Describe the classification and clinical presentation of SE

SE can be classified in several forms, including convulsive SE, focal SE, myoclonic SE, and nonconvulsive SE (NSE).

Generalized convulsive SE involves tonic flexion of the axial muscles, flexion in the arms and legs followed by extension, clenching of teeth, forced expiration, dilation of the pupils or sluggish pupillary light responses, and upward or lateral eye deviation. The uninterrupted jerking or shivering during the clonic phase may gradually resolve, but tonic spasm may occur again with a similar pattern of jerking and resolution. As the duration of the seizures increases, the movements and muscle contractions may become reduced despite continued generalized electrical activity in the brain.

Focal SE can be simple without loss of consciousness or complex with impaired consciousness. Jerking of one ipsilateral arm or leg or continuous clonic movements of one or two extremities can be observed. When confined to focal motor clonic seizures without Jacksonian march, it is often referred to as epilepsia partialis continua (EPC); the motor activity lasts for hours, days, weeks, or longer. Consciousness is not altered, but postictal weakness is frequent. In most cases, the ictal focus is cortical, and anticonvulsants help prevent generalization but are frequently ineffective at aborting the seizures. EPC is often caused by a structural lesion (e.g., tumor, chronic infarction) or a progressive neurodegenerative disease (particularly in children). Focal SE of all forms is often related to acute hemispheric lesions such as a hemorrhage or brain metastasis.

Myoclonic SE is seen in patients after cardiac arrest or asphyxiation and consists of synchronous brief jerking of the limbs, face, or diaphragm. It can also be seen after electrical injury, drug intoxication, or decompression sickness and often denotes severe cortical laminar necrosis in association with thalamic and spinal cord injuries.

4 What defines NSE?

The same principles apply of prolonged duration (>5 minutes) or lack of return to baseline mental status in between seizures. However, NSE can be difficult to diagnose because of lack of pronounced motor activity. NSE is commonly divided into complex partial status and absence status, which are often mistaken for behavioral abnormalities or a psychiatric disorder. Clinical presentation is diverse and can involve blank staring or eye movement abnormalities and subtle periorbital, facial, or limb myoclonus. Absence SE is characterized by a reduction in vigilance, lack of attention, and automatism. Given the challenge of clinical diagnosis of NSE, electroencephalography (EEG) is often required to establish the diagnosis. Careful examination of the fully undressed patient with attention to the eye movements (versive saccades) and hands and face can often reveal subtle rhythmic movements of the mouth or digits suggestive of subtle generalized motor status, especially in patients who have received anticonvulsants.

5 Name common causes of convulsive SE

The most common cause of SE in a patient with a known seizure disorder is subtherapeutic AED levels. However in young patients, febrile seizure is a common precipitator, and central nervous system (CNS) infection with common pathogens such as Haemophilus influenzae and Streptococcus pneumoniae should be ruled out by lumbar puncture. Metabolic and electrolyte disturbances, traumatic brain injury, tumor, and drug intoxication are among other common causes. Ischemic strokes rarely produce seizures in the acute period, but chronically areas of encephalomalacia can provide substrate for intractable seizures. Proconvulsant drugs include β-lactam antibiotics and quinolones, bronchodilators, certain antidepressants, and immunosuppressants. SE caused by low AED levels or alcohol abuse is associated with a relatively good prognosis, whereas outcome is generally poor after cerebrovascular disease or anoxic injury.

6 Why is urgent treatment of SE a medical necessity?

SE can be life threatening with the development of pyrexia, deepening coma, and circulatory collapse. Aspiration is common and may result in respiratory failure with hypoxemia, systemic inflammatory response, and disseminated intravascular coagulation with multiple organ failure. Continuous seizures can result in rhabdomyolysis with risk for acute renal failure, lactic acidosis, and cardiac arrhythmias. Of importance, repetitive electric discharges can result in irreversible neuronal injury after as little as 5 to 20 minutes; cell death is common after 60 minutes. Neuronal injury can, understandably, also result from the acute insult that provoked the SE. A mortality rate of between 10% and 12% has been reported, of which the majority is related to the underlying process producing the SE. The highest mortality occurs in elderly patients and those with SE after a stroke or anoxia, whereas children, patients with SE related to subtherapeutic AED, or those who have unprovoked SE have usually a better outcome.

7 Name general treatment measures for SE

The immediate management of the patient should include measures to establish an airway, provide oxygenation, and stabilize circulation.

An oral airway can be used if feasible, although most patients with prolonged SE may benefit from early endotracheal intubation.

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