Radiosurgery is now being used as a treatment modality to open resective microsurgery for medically intractable epilepsy. At present, it is being used as a treatment modality for epilepsy associated with vascular malformations, gelastic epilepsy associated with hypothalamic hamartomas, cavernous malformations and mesial temporal lobe epilepsy associated with mesial temporal sclerosis. The two main types of radiosurgery are Gamma Knife and linear accelerator (LINAC). Gamma Knife uses numerous sources of radioactive cobalt to direct gamma radiation to the centre of a helmet in which the patient's head is inserted, with these beams of radiation converging in three dimensions to focus intense doses of radiation precisely on a small volume. LINAC functions similarly, except LINAC uses a different source of radiation produced by X-rays from the impact of accelerated electrons, and the gantry must move in space to change the delivery angle of this radiation.