Pediatric Epilepsy Surgery (cont.)

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What tests are used to determine if a child is a candidate for epilepsy surgery?

As previously mentioned, surgery is only preferred once it is clear that the child is resistant to or does not respond well to antiepileptic medications. Many tests are used to make this determination.

Electroencephalograms (EEG) are very important in determining the type of epileptic seizures as well as the area of the brain that is responsible for the seizure disorder. When the routine EEG (usually one hour long) does not give enough information, the child might need to be hospitalized (usually in special EEG wards) for a prolonged EEG with video monitoring. During the hospital admission (which may last several days) the EEG is recorded continuously throughout the entire day. The goal is to record epileptic events for further analysis. In some children it is necessary to stop the antiepileptic medications while the child is in the hospital to facilitate the emergence of an epileptic event.

Neuroimaging studies are very important to help determine the presence of brain lesions. A CT scan and an MRI, in some cases, might be helpful to point to the specific area of the brain that is abnormal. These tests are very effective to identify developmental abnormalities, brain tumors, scars due to prior bleeding events, or the presence of vascular malformations that might be responsible for the epileptic seizures.

In some children, functional MRI (fMRI), positron emission tomography (PET), single photon emission computed tomography (SPECT), magnetoencephalography (MEG), or ictal SPECT (an SPECT obtained at the time of the epileptic event) might also be indicated in order to determine the area of the brain to be excised.

In some cases the localization of the epileptogenic area requires invasive monitoring. In these children, electrodes that record the brain activity are placed either inside the brain (intracerebral electrodes) or directly on top of the brain (subdural electrodes). This procedure may be done at the time of the surgery or days before, in which case it requires a small operation and admission to the hospital for several days for continuous EEG recording.

Resective surgery (removing specific areas of brain tissue) may result in functional deficits. The functional deficits relate to the area of the brain involved in the surgery. For example, operations near the motor area might result in motor paralysis; surgery in the posterior area of the brain (the occipital lobe) might result in visual deficiencies. Of particular importance is the surgery that is performed in or near the temporal lobe which, among other functions, is responsible for language comprehension and memory. In such cases a special test, called the WADA test, is performed to ensure that removal of the local lesion does not result in severe memory or language functional deficits.

Once the evaluation is completed the team will decide if the patient is a viable candidate for surgery and in that case, what type of surgery is indicated.

It is worthwhile to mention that not all of the above-mentioned tests are necessary in all patients.

Medically Reviewed by a Doctor on 2/25/2014


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