Jornal Internacional de Neurorreabilitação

Stereotactic Radiotherapy in the Management of Epilepsy

Abstract

MS Mat Samuji and Frederik Vernimmen

Although the main stay of epileptic therapy is pharmacological certain forms of epilepsy such as temporal lobe epilepsy and epilepsy associated with benign diseases of the brain can also be successfully managed surgically. A neurosurgical procedure has the advantage of an immediate therapeutic result. When surgery is not possible, therapeutic irradiation is an option, but there is always a latent time between the radiation and the improvement in the epilepsy. This radiation is under the form of photon radiation produced by Cobalt sources in a Gamma knife® or by Linear accelerators. Special beam collimation techniques produce a sharp beam allowing for a high dose to be delivered to the target without side effects on the normal surrounding brain. The desired therapeutic effect comes from the late radiation effects, and hence is not immediate. The absorption in tissue of photon radiation is such that there is always an exit dose, and this contributes to radiation side effects on normal tissue. Particle radiation beams such as a proton beam have a dose absorption advantage over photons because there is a lower entry dose and no exit dose. This has the potential to treat the brain with a lower risk of side effects, and a lower integral dose. Presently radiation dose selection is aimed at causing tissue destruction in the target volume. Dose schedules that do not cause tissue necrosis but have a neurophysiologic therapeutic effect are presently under investigation. New irradiation technologies such as micro photon beams using synchrotron radiation and mini proton beams are been studied especially for their potential in epilepsy therapy. These technologies could greatly improve the therapeutic ratio as they cause no damage to brain tissue. If proven to have a therapeutic effect these new developments would expand the role of radiation in managing epilepsy.