Management of drug-resistant epilepsy

Drug-resistant epilepsy (DRE), also known as refractory epilepsy or pharmacoresistant epilepsy, is defined as failure of adequate trials of two tolerated and appropriately chosen and used antiepileptic drugs (AED schedules) (whether as monotherapies or in combination) to achieve sustained seizure freedom. The probability that the next medication will achieve seizure freedom drops with every failed AED; for example after two failed AEDs the probability that the third will achieve seizure freedom is around 4%. Drug-resistant epilepsy is commonly diagnosed after several years of uncontrolled seizures however in most cases it is evident much earlier. Approximately 30% of people with epilepsy have a drug-resistant form.

When 2 AEDs regimens have failed to produce sustained seizure-freedom, it is important to initiate other treatments to control seizures. Next to indirect consequences like injuries from falls, accidents, drowning and impairment in daily life, seizure control is critical because uncontrolled seizures -specifically generalized tonic clonic seizures- can damage the brain and increase the risk for sudden unexpected death in epilepsy called SUDEP. The first step is for physicians to refer their DRE patients to an epilepsy center in which a presurgical evaluation can be carried out in order to assess whether a patient is a candidate for epilepsy surgery or not. For those patients who are not surgical candidates, those who decline brain surgery or those in which brain surgery fails to produce long term seizure freedom, vagus nerve stimulation and/or a diet can be recommended.

In epilepsy surgery a distinction can be made between resective and disconnective procedures. In a resective procedure the area of the brain that causes the seizures is removed. In a disconnective procedure the neural connections in the brain that allow the seizures to spread are disconnected. In most cases epilepsy surgery is only an option when the area of the brain that causes the seizures - the so-called epileptic focus can be clearly identified and is not responsible for critical functions such as language. Several imaging techniques such as magnetic resonance tomography and functional techniques like electrocorticography are used to demarcate the epileptic focus clearly.

Temporal lobe epilepsy (TLE) in which the epileptic focus is in the temporal lobe, is one of the most common types of epilepsy in adolescents and adults. Hence temporal lobe resection, during which the whole temporal lobe or just a part of the temporal lobe for example the hippocampus or the amygdala is removed, is the most common epilepsy surgery procedure. Between 40 and 60% of patients that undergo temporal lobe resection are continuously seizure free The surgery itself is very safe with a mortality of 0%. The risk for neurologic complications from a temporal lobe resection is around 3 to 7%

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