Seizure
What is a seizure?
What causes status epilepticus?
What are the complications of status epilepticus?
How is status epilepticus treated in a neuro-ICU?
What is the difference between seizures and epilepsy?
What is the role of EEG monitoring in the treatment of status epilepticus?
What can be done if the listed measures fail to stop the seizures?
What is a seizure?
A seizure is caused by an excessive electrical discharge of the neurons of the cerebral cortex of the brain. This abnormal synchronicity of brain cell firing produces stereotyped behaviors such as convulsive movements. Seizures can either partial (focal), in which only a certain region of the brain is affected, or generalized (global), if the entire brain is affected. Partial seizures are further categorized as simple, if the patient maintains consciousness, or complex if consciousness is impaired. "Epilepsy" refers to patients who have recurrent, unprovoked seizures.
The symptoms of a seizure depend on which part of the brain is affected and activated. For instance, if the motor area of the brain is affected then abnormal muscle twitching will occur. If a sensory part of the brain is affected then tingling may occur. Generalized seizures often result in loss of consciousness and convulsions (a generalized tonic-clonic or "grand mal" seizure). Typically, a seizure will last anywhere from seconds to minutes. Among the most dangerous disorders involving seizures is status epilepticus, in which a seizure is prolonged for over 30 minutes. The neuro-ICU is specialized to treat this disorder.
Status epilepticus is defined as a seizure lasting longer than 30 minutes, or as two or more seizures which recur without a full recovery of neurological function in between. For every type of seizure (e.g. generalized, simple-partial, complex-partial) there is a corresponding subtype of status epilepticus. Status epilepticus associated with generalized convulsions and loss of consciousness (generalized tonic-clonic) is both the most common and the most dangerous.The longer a seizure is prolonged, the greater the chance there is of brain damage. A neuro-ICU is specialized to aggressively and efficiently treat both status epilepticus and the underlying disorder causing the condition.
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What causes status epilepticus?
Although status epilepticus may arise from epilepsy, the condition more often arises from a structural or metabolic brain disturbance. The most common cause of status epilepticus in a patient with epilepsy is failure to take prescribed anticonvulsant medications. The common causes of "provoked" status epilepticus include encephalitis, meningitis, stroke, head injury, and drug intoxication.
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What are the complications of status epilepticus?
The presence of a seizure which lasts for over thirty minutes is associated with many complications. The most dangerous of these are low blood pressure (hypotension), low oxygen levels (hypoxia), fever, and cardiac arrythmia.
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How is status epilepticus treated in a neuro-ICU?
The neuro-ICU manages status epilepticus by:
1. Stopping the seizures.
2. Preventing or treating complications of prolonged seizure activity.
3. Establishing a diagnosis and treating the underlying disorder.
Therapy to stop ongoing seizures begins with benzodiazepines such as diazepam and lorazepam. Once the seizures have stopped, the patient is loaded with phenytoin and phenobarbital (if necessary) to prevent recurrent seizures.
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What is the difference between seizures and epilepsy?
Seizures are a symptom of epilepsy. Epilepsy is the underlying tendency of the brain to produce sudden bursts of electrical energy that disrupt other brain functions. Having a single seizure does not necessarily mean a person has epilepsy. High fever, severe head injury, lack of oxygen--a number of factors can affect the brain enough to cause a single seizure. Epilepsy, on the other hand, is an underlying condition (or permanent brain injury) that affects the delicate systems which govern how electrical energy behaves in the brain, making it susceptible to recurring seizures.
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What is the role of EEG monitoring in the treatment of status epilepticus?
The ultimate goal in treating status epilepticus is the complete cessation of all seizure activity. Attaining this goal can be complicated by the fact that in many instances, after prolonged status epilepticus, patients can continue to have electrical seizures of the brain with minimal or no motor manifestations. For this reason, continuous EEG monitoring can be invaluable for allowing the detection of nonconvulsive seizures of this type. A neuro-ICU is specially equipped for EEG monitoring, which involves placement of small electrodes over the scalp and a machine at the bedside which continuously monitors the electrical activity of the brain. Without this type of monitoring, patients can continue to experience harmful occult seizure activity because doctors cannot tell that it is occurring. EEG monitoring of this type requires the special equipment and the expertise of epileptologists who are familiar with this type of neurological monitoring.
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What can be done if the above measures fail to stop the seizures?
In about 80% of cases, status epilepticus can be brought under control with diazepam, phenytoin, and phenobarbital. Patients who continue to have seizures after complete loading doses of these drugs are said to have "refractory status epilepticus." The expertise of a neuro-ICU can be extremely helpful for controlling this dangerous condition. The usual next step is treatment with pentobarbital which is equivalent to general anesthesia and produces a deep comatose state equivalent to "suspended animation." Alternatives to this treatment indlude a midazolam or propofol infusion. In all cases, continuous EEG monitoring is recommended, which is generally only available in a neuro-ICU.
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For more questions regarding NICU please contact Galen V. Henderson, MD
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