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Seizures

One of the prime functions of the brain is to receive, interpret, and send information. From the outside of the body, this information comes in the form of sight, sounds, smells, and so on. Within the brain, this information is passed along in the form of electrical signals relayed back and forth by specialized cells called neurons. These signals are usually ordered: the body detects something hot; the brain interprets the signal and sends another signal for the body to pull away. During a seizure, the brain misfires, sending overwhelming amounts of conflicting signals through the brain at the same time.

Although medicine has a reasonably good idea of what is going on in the brain during a seizure, what makes certain people at risk for seizures and what triggers a seizure is not as well known. Some seizures occur for no immediately apparent reason; some seizures are recurring while others will stop; and the effect of seizures may progress or remain unchanged over time. In the newborn baby, seizures are not necessarily followed by the development of epilepsy. Many will stop abruptly after the newborn period.

Despite this, we know that babies who have experienced severe asphyxia in the womb, asphyxia during birth, and babies with infections such as meningitis are at risk for seizures. Additionally, metabolic imbalances, such as increased or low levels of sodium or calcium among others, may put a baby at risk for seizures. These types of metabolic imbalances can be due to the immaturity of the kidneys and the hormone and metabolic systems. Babies who had a severe intraventricular hemorrhage (IVH), or bleeding into the ventricles of the brain, are also at risk of seizure.

In adults, seizures can take many forms: people may lose all control of their bodies and go into rhythmic convulsions for a short time or their gaze may simply become fixed as if they are day dreaming. Babies, however, generally do not exhibit the more obvious physical manifestations of seizures. When a premature baby has a seizure, it is usually a much more subtle event. Usual signs include:

  • apnea, or absence of breathing effort
  • twitching of the arms or legs
  • fluttering of the eyelids
  • arching of the back
  • rhythmic arm or leg movements, sometimes characterized by a swimming, rowing, or pedaling motion

During a seizure, the brain uses up a considerable amount of energy. Oxygen and glucose consumption is high, and in some cases ends up depriving the brain of those essential substances. For this reason, long, sustained seizures are more potentially harmful than brief episodes.

Although seizures are sometimes associated with epilepsy, in the case of premature babies, most are not. Epilepsy is an ongoing, life long disorder; premature babies who have one or two seizures in the days following birth may never have another and do not usually have epilepsy.

Seizures are usually treated with medications that sedate the brain, such as phenobarbital or other anticonvulsant medications. In many cases, only a single dose is needed and many premature babies who have a seizure will not go on to have any more. Sometimes it is impossible to eliminate all seizures and there are limits to administering medications; few babies remain on these drugs for long. Although phenobarbital works well at suppressing seizures by sedating the brain, this sedation may have other negative effects that reduce the benefits that preventing or minimizing a seizure would have. For this reason, any decision to treat must be weighed against these risks. Sometimes, brief and transient seizures, those that do not last and produce few or minor effects, may not be treated, because the risks of respiratory depression or low blood pressure outweigh the benefits.

More information

Hilary Whyte, MSc, MB, BCh, BAO, MRCPI, FRCPC

10/31/2009




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