Tests Used in Pre-surgical Evaluation:
- Electroencephalography (EEG)
- Simultaneous video-EEG monitoring
- Computerized tomographic (CT) scans
- Magnetic resonance imaging (MRI)
- Neuropsychological tests
- Single photon emission computed tomography (SPECT) scans
- A cerebral angiogram (X-ray)
- WADA (intracarotid sodium amobarbital) test
- Positron emission tomography (PET)
In trying to decide whether an individual patient is likely to benefit from surgery, the medical team will want to know:
- Is the problem really epilepsy? Up to 25 percent of adults presenting with uncontrollable seizures at one epilepsy center were, in fact, suffering from paroxysmal episodes not produced by excessive electrical discharge in the brain.
- Is this the type of seizure that can be helped by an operation? Although the number of techniques now in use, routinely or experimentally, has increased the number of people who may benefit from surgery, surgery is still limited to certain types of seizures.
- Have there been sufficient efforts to control the seizures with drugs or, in the case of young children, with drugs and diet?
- Might the condition get better without surgery?
- Might it get worse without surgery?
- Do the benefits outweigh the risks?
Answers to these questions come from a variety of sources — the medical history of the patient or the patient’s family; physical examinations; medical records; and a battery of pre-surgical tests.
Pre-surgical evaluation begins with a complete physical and neurological examination and a thorough seizure history. Most of the tests are to identify the precise location and extent of the seizure focus, the character of the seizures, and the relationship of the seizure focus to other brain functions, such as speech. How many tests have to be done depends on the type of operation being planned and how much information each test produces.
If the tests do not provide enough information on the site of the seizure focus, invasive surgical procedures such as implanting depth electrodes or placing subdural or epidural strips directly on the brain to monitor seizure discharges may be required. Depth electrodes are thin wires placed deep in the brain through narrow rods. Subdural or epidural strips or grids are small plastic strips or sheets with electrodes embedded in them. The goal is to capture actual ictal (seizure) events on the EEG to localize the epileptic focus as precisely as possible. Pre-surgical candidates are weaned from their antiepileptic drugs to increase the chances that a typical seizure will occur during the evaluation period.
The depth electrodes or strips may be kept in place for some time before the major operation is performed. Electrodes placed directly onto the brain to identify functional areas (electrocorticography) may be used during surgery to help determine the extent of the resection and help identify functional areas of the cerebral cortex. Surgery may be done under general anesthetic or with the patient awake but under local anesthetic. This is possible because brain tissue is not sensitive to pain.
Surgery for epilepsy is complex and must be carefully planned for good results. It is therefore best undertaken in a center that specializes in epilepsy surgery and has a successful track record.
In addition, some surgical cases offer a greater challenge than others and may require more testing and evaluation before an operation takes place.
Because of this variation, the cost of surgery also varies. A range of between $50,000 to more than $200,000 is possible, depending on the kind of procedures that have to be done. Families should review their coverage with their third-party payer (insurance company) and the surgeon.