Diagnosis and Treatment of Nonconvulsive Status Epilepticus

A Unique Type of Seizure That May Surprise You

Doctor holding oxygen mask over male patients mouth in intensive care unit
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Most people believe they know what a seizure looks like. Someone with a seizure starts to shake uncontrollably, falls to the ground, and loses consciousness. But this isn't always the case. Seizures can present in unusual ways, sometimes just affecting one part of the body, and sometimes just affecting part of the brain with no stereotypical convulsing at all.

Status epilepticus is the most serious kind of seizure — it's a seizure that won't stop.

In addition to effectively putting the patient into a coma, status epilepticus can kill and lead to permanent brain damage. Status epilepticus is a medical emergency.

About a decade ago, researchers from Columbia University in New York created a stir in the medical community when they evaluated patients in the ICU with electroencephalography. Although there was no suspicion that these patients had seizures, that's just what these researchers found. About ten percent of non-responsive patients in the ICU were actually in non-convulsive status epilepticus, NCSE.

What is Nonconvulsive Status Epilepticus?

In nonconvulsive status epilepticus, the brain is either continually seizing, or seizing so frequently that the patient never has a chance to recover from the period of extreme confusion that normally follows a seizure. This recovery period is called the post-ictal state.

For the most part, people in nonconvulsive status epilepticus look like many other ICU patients who are unresponsive due to an encephalopathy or any number of other disorders of consciousness.

However, if evaluated with an EEG, we can see that in actuality, the patient is in status epilepticus.

The distinction is important, because status epilepticus may respond to medications. Normally, it would be a terrible idea to give an encephalopathic patient a benzodiazepine like Ativan (lorazepam), because these medications reduce brain activity.

In a patient who is already not thinking very well, benzodiazepines can make the problem worse.

Seizures, on the other hand, are caused by too much abnormal brain activity. In these cases, an anti-epileptic medication, such as a benzodiazepine, might actually help the patient regain consciousness after the status epilepticus is interrupted.

Diagnosis of Nonconvulsive Status Epilepticus

Of course, in order to treat nonconvulsive status epilepticus, you need to first determine that the patient is seizing. Overall, nonconvulsive status epilepticus is underdiagnosed, meaning that many patients go untreated. Part of the reason is that NCSE is a relatively newly described phenomenon, and by its nature it isn't dramatically obvious as convulsive status epilepticus.

Another reason for the underdiagnosis of NCSE is that it can appear in many different ways, many of which are more usually caused by something more common. For example, around half of patients in the hospital suffer from delirium, which can appear similar to NCSE, but is much more common.

In some major academic centers for neurology, it's becoming common practice to attach EEG leads to all ICU patients. However, in most hospitals the physician needs to carefully consider which patient merits closer evaluation with EEG.

Treatment of Nonconvulsive Status Epilepticus

How to best treat NCSE is an evolving area of medicine. The best approach varies by patient age, other illnesses, and certain aspects of the seizure. For example, NCSE sometimes follows more obvious convulsive status epilepticus. In these cases, there is a clear danger to the NCSE, and aggressive treatment in an intensive care unit (ICU) is called for. However, in other cases where NCSE is not preceded by convulsions, it may actually be better for patients not to be exposed to an ICU, especially if the patients are elderly. This may be because anticonvulsant medications also have side effects, and because of the added risks of staying in an ICU.

Age also matters when treating NCSE in the very young, as the causes of the seizures are usually very different than older patients. Children often have seizures due to genetic disorders, whereas older patients may have seizures due to an acquired problem, like a stroke.

In cases where status epilepticus is accompanied by other medical problems, one of the cornerstones of treatment is to address the underlying problems. Seizures are made worse when the body is imbalanced by infection or other medical problems. For example, if the patient has severe kidney and liver damage, adding anticonvulsants may make the condition worse. As is usually the case, treatment of NCSE should be tailored to the needs of each patient as an individual.

Sources:

J Claassen, Mayer SA, Kowalski RG, Emerson RG, Hirsch LJ. Detection of electrographic seizures with continuous EEG monitoring in critically ill patients. Neurology. 2004 May 25;62(10):1743-8.

Frank W. Drislane, M.D.1Presentation, Evaluation, and Treatment
of Nonconvulsive Status Epilepticus Epilepsy & Behavior 1, 301-314 (2000)

Simon Shorvon What is nonconvulsive status epilepticus, and what are its subtypes? Epilepsia, 48(Suppl. 8):35-38, 2007

Litt B, Wityk RJ, Hertz SH, Mullen PD, Weiss H, Ryan DD, Henry TR. Epilepsia. Nonconvulsive status epilepticus in the critically ill elderly. 1998 Nov;39(11):1194-202.

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