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 - Northwestern Memorial Hospital - Chicago

Tests

Pre-surgical evaluation involves many tests that are designed to determine if the seizures are coming from a single location in the brain that may be surgically treated. If all the studies point to a single area as being responsible for the seizures, surgery may drastically reduce, or even eliminate, seizures.

Pre-surgical evaluation involves the following tests:

  • Inpatient video EEG (vEEG) monitoring in the Epilepsy Monitoring Unit (EMU) to precisely correlate the clinical and electrical features of a seizure. Video EEG monitoring is continuous EEG monitoring and videotaping of the patient. The monitoring is usually performed in the hospital over several days. This allows the doctor to observe the behavior that occurs during the seizure and how it is related to the electrical activity in the brain.

    • Electroencephalography (EEG) records the electrical activity in the brain. Electrodes are pasted to the patient’s scalp in specific places, and wires are then connected from the electrodes to the EEG machine. Brain wave activity is then monitored to determine the location in the brain where the seizures are originating. This will also help determine what type of seizures are occurring.
  • Epilepsy-protocol MRI is a high-resolution scan used to help identify subtle structural abnormalities in the brain that may be causing seizures.
     

  • Ictal Single-photon emission computed tomography (Ictal SPECT) scan is conducted at the onset of the seizure. A very low, safe dose of a radioactive substance is injected into a vein in the arm as soon as possible after a seizure begins. The scan is performed soon afterwards, producing an image that highlights the area of greatest blood flow during the seizure.
     

  • Positron emission tomography (PET) scan shows the brain's use of oxygen or sugar (glucose). A very low, safe dose of a radioactive substance is injected into a vein in the arm, and the scanner records its circulation. The image shows areas of the brain that are more active than others. This test can help identify the areas of the brain that are not working well and where partial seizures may begin.
     

  • Neuropsychology testing measures a person’s memory, language and cognition. Testing can sometimes help identify areas of the brain that are not functioning normally, which may help doctors understand where the seizure begins. For example, impaired memory for word lists may indicate abnormal left temporal function.
     

  • Intracranial electrodes and invasive EEG monitoring may be recommended if all of the presurgical studies do not sufficiently show the origin of a person’s seizures. This procedure is performed by placing electrodes on the brain using subdural grids or into the brain using depth electrodes to precisely localize the area causing the seizures.

The Comprehensive Epilepsy Center team discusses the specific risks of surgery with individual patients and their families after their case has been reviewed at the multidisciplinary patient management conference.

Patients are admitted the morning of surgery. The procedure to place the electrodes typically lasts about 4 to 5 hours. Joshua Rosenow, MD, and Stephan Schuele, MD, work together to design a custom arrangement of implanted electrodes to maximize safety and the ability to localize the seizure focus. The surgery is performed using state-of-the-art computerized image guidance technology to allow the safest and most minimally invasive approach available. Patients spend one night in the neurosurgical intensive care unit afterwards.

Patients are then transferred to the Epilepsy Monitoring Unit (EMU) for video EEG monitoring for 5 to 10 days. Epilepsy medications are reduced during their stay; after several seizures have been recorded, the medications are restarted. At this time, the doctors decide whether the area causing the seizures has been localized enough to be safely removed. Patients will then return to the operating room for removal of the electrodes, and hopefully, removal or resection of the area causing seizures.

Once all of the testing has been completed, the team discusses each patient’s case in detail at our monthly multidisciplinary Epilepsy Surgery Patient Management Conference. The entire Comprehensive Epilepsy Center team attends this conference. The team reviews each patient’s case individually, and we make a consensus recommendation about further treatment. We then discuss the individual results of this conference in detail with each patient and his or her family.

Last UpdateJune 8, 2011
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