Epilepsy can affect people of any age, gender, origin or education. Epileptic seizures may start at any age, even immediately after birth. Often epilepsy is caused by brain damage, e.g. after a stroke, because of lack of oxygen, in childbirth or pregnancy, following traumas, due to tumors, or due to changes in brain blood vessels.
Drug-resistant epilepsy is diagnosed if epileptic seizures do not respond in two months after the treatment with two drugs selected properly and tolerated by the patient. Scientists indicate that incomplete control of seizures (i.e. despite the treatment seizure freedom is not achieved) may imply that:
- Prescribed drugs are not sufficiently effective;
- There are limitations in drug tolerance (when it is not possible to prescribe a larger and more efficient dose of the drug);
- Negative interaction between drugs has been noticed (it means that a larger dose cannot be prescribed, or because of interaction between drugs their concentration changes, and the therapeutic efficacy does as well);
- The regime established for drug administration is not followed (drugs are taken inappropriately, in insufficient doses, etc.)
According to the studies, despite the treatment with anti-epileptic drugs, approximately 30–50% of the patients are not seizure free, i.e. they have a drug-resistant epilepsy.
VNS therapy system is intended to reduce the frequency of epileptic seizures, seizure duration and severity in patients with drug-resistant epilepsy.