Neurology

Like any new therapy, the Vagal Nerve Stimulator (VNS) is finding its clinical niche. After several years of evaluation, we are convinced that the VNS can benefit carefully selected patients. This evaluation is based on our clinical experience and the available published scientific data.

It is appropriate to consider the VNS for patients who do not become seizure-free following initial trials of anti-seizure medications. This device offers the possibility of obtaining the same or improved seizure control with less medication. Therefore, the VNS can improve the quality of life for people with epilepsy by achieving the best possible seizure control with the minimum of medication side effects. It should be understood, however, that the VNS is a palliative treatment for intractable epilepsy; it is very unlikely that its use will make a patient seizure free.

Proper selection of patients for implantation of the VNS is critical to the appropriate use of this new therapy. Based on our experience, we have developed three criteria that a patient must meet before we implant the device.

• The patient has a correct diagnosis of epilepsy.
  
  This is an obvious criterion, but one that is often overlooked. Diagnosis of epilepsy is difficult based only on historical information. Many other conditions can produce behavioral phenomena that closely mimic epileptic seizures. In particular, psychological disorders can exhibit "pseudoseizures" that are difficult for even a health care professional to distinguish from epilepsy. Approximately one-third of the patients we evaluate in our monitoring unit turn out not to have epilepsy.The most reliable diagnostic method for epilepsy is long-term video/EEG monitoring, and this procedure should be strongly considered for any patient whose seizures are resistant to medication. Furthermore, some patients, particularly children and developmentally delayed individuals, can have a mixture of both epileptic seizures and non-epileptic seizure-like behaviors. Correctly determining whether a patient has responded to anti-seizure medication requires that one know precisely what behaviors are truly epileptic. In the absence of long-term monitoring, we feel that a patient must have very strong clinical evidence supporting a diagnosis of epilepsy and EEG confirmation of epileptic activity.
  
  
• Adequate trials of anti-seizure medications have failed to control the patient's seizures.
  
  Determining whether a patient has failed to be controlled by medication can be complicated, and it is best done on an individual basis. Nevertheless, we have arrived at some general guidelines. We feel that a patient must have failed to attain seizure control with at least four different medications, either as monotherapy or in combination. These should include carbamazepine or oxcarbazine, valproate or lamotrigine, topiramate and levetiracetam. If intolerance is the reason for failure, then another medication with a similar mechanism of action should have been tried.
  
  
• The patient is not a candidate for resective epilepsy surgery.
  
  Since the VNS is only a palliative treatment, we feel that one should always consider whether a patient could be cured of his or her epilepsy by resective surgery. Any patient who has localization-related (focal) epilepsy is a potential candidate for epilepsy surgery, particularly if the epileptogenic zone (focus) is in the temporal lobe. Therefore, if a patient has EEG or behavioral evidence suggesting localization-related epilepsy, we feel that they should undergo further evaluation before considering VNS.

The Strong Epilepsy Center will be pleased to receive a referral for VNS implantation for any patient who meets these criteria. Furthermore, if there is any question about any of these criteria relating to an individual patient, we would be happy to discuss the case.