The prognostic significance of epileptiform activity (EA) recorded at electrocorticography (ECOG) was examined in a group of 60 consecutive non-tumoral patients with intractable frontal lobe epilepsy (FLE). Pre-excision EA was documented as absent, focal (one gyrus), regional (two gyri), lobar (3 gyri) or multilobar (frontal + temporal gyri). Post-excision EA was documented as absent, restricted to the resection border, or recorded distant to the resection border, and was quantitated by spike frequency. Pre-excision EA fromor = 2 gyri and absence of post-resection EA correlated with Class I or II (Engel classification) outcome while pre-excision EA fromor = 3 gyri and persistent post-resection EA, especially distant to the resection border, correlated with Class III or IV outcome (P0.001). A significant correlation between poorer outcomes and increased abundance of distant post-resection EA was observed (P0.001). EA restricted to the resection border was not significantly correlated with outcome. Presence of a circumscribed lesion correlated with Class I outcome (P0.01) and absence of pathological abnormality correlated with Class IV outcome (P0.05). Neither side nor extent of surgical excision correlated with outcome. EA recorded at ECOG is of prognostic significance in FLE. A lobar or multilobar distribution of pre-excision EA and persistent post-excision EA distant to the resection border, especially when abundant, are highly unfavorable prognostic indicators. In contrast, a restricted distribution of pre-excision EA and absence of post-resection EA both herald a favorable outcome.
