The epileptic focus versus the pathological focus.

The relationship between the epileptic focus and the causative lesion has been studied to define when resection of the epileptic focus may be associated with removal of the lesion. Experimental studies reveal that a maturation phase is followed by a progressive autonomisation of the epileptic focus from the induced lesion. Thereafter there may be a progressive course to such experimental epilepsy with spreading of the epileptic lesions and possible creation of a secondary focus. However, in man the findings are less coherent and sometimes contradictory. In long term intractable epilepsy, simple removal of the causative lesion can be effective. A hypothesis is proposed to explain these phenomena--the hypothesis of systemic focal epileptogenesis. It is further proposed that endogenous excitotoxic agents such an quinolinic acid may have effects on the epileptic focus only when the causative lesion is present producing a subtle modification of the blood brain barrier.