 Tonic–clonic seizures can also be induced deliberately with electroconvulsive therapy.In the case of symptomatic epilepsy, the cause is often determined by MRI or other neuroimaging techniques; showing that there is some degree of damage to a large number of neurons.The lesions (i.e., scar tissue) caused by the loss of these neurons can result in groups of neurons forming a seizure 'focus' area with episodic abnormal firing that can cause seizures if the focus is not abolished or suppressed via anti-convulsant drugs.