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Pre-surgical and post-surgical data were examined and compared from 215 consecutive patients undergoing surgery for intractable epilepsy. Patients were selected on the basis of a proven histopathological diagnosis of type I focal cortical dysplasia (FCD I), alone or associated with other lesions. The patients were divided into five sub-groups: i) 66 with isolated FCD I, ii) 76 with FCD I and hippocampal sclerosis, iii) 49 with FCD I and tumours, iv) 16 with FCD I and other malformations of cortical development and v) eight with FCD I and anoxic-ischaemic or inflammatory diseases. The duration of epilepsy was greatest in patients with FCD I associated with hippocampal sclerosis, and those with isolated FCD I showed the highest seizure frequency at the time of surgery. Hippocampal sclerosis and tumours were the most frequent pathological lesions associated with FCD I in temporal lobe epilepsy. Febrile seizures significantly correlated with the presence of hippocampal sclerosis and FCD I. Isolated FCD I was observed in 31% of the patients, characterized by frequent seizures, negative magnetic resonance imaging, and frequent frontal or multilobar involvement. In comparison to patients with FCD I associated with hippocampal sclerosis, MCD or tumours, the patients with isolated FCD I had a worse post-surgical outcome (46% in class I). Our findings indicate that there is a high incidence of FCD I associated with other apparently distinct pathologies, particularly those affecting the temporal lobe, and highlight the need for a comprehensive clinicopathological approach for the classification of FCD I.

Focal cortical dysplasias (FCDs) are highly epileptogenic malformations associated with drug‐resistant epilepsy, susceptible to surgical treatment. Among the different types of FCD, the type II includes two subgroups based on the absence (IIa) or presence (IIb) of balloon cells. The aim of this retrospective study was to investigate possible differences in electroclinical presentations and surgical outcomes between the two subgroups in 100 consecutive surgically treated patients with type II FCDs. All patients underwent a comprehensive presurgical assessment including stereo‐EEG (SEEG) when necessary. No significant differences in gender, age at epilepsy onset, duration of epilepsy, age at surgery or seizure frequency were found between the two subgroups. Patients with type IIb FCD frequently showed sleep‐related epilepsy. Their peculiar electrographic pattern was characterised by localised rhythmic or pseudo‐rhythmic spikes or polyspikes (“brushes”) enhanced during non‐REM sleep and also associated with well‐localised, brief, low‐voltage fast activity. The incidence and frequency of short bursts of fast discharges, interrupted by activity suppression, increased during slow‐wave sleep and often recurred pseudoperiodically. The occurrence of “brushes”, present in 76% of the patients with type IIb FCD, was significantly associated (p<0.001) with the presence of balloon cells. We discuss the possible pathogenetic mechanisms underlying this activity. MRI diagnosis of type II FCD was made in 93% of the patients with balloon cells (BCs), suggesting that the presence of balloon cells might be, at least partially, responsible for the MRI features. Patients had very good postsurgical outcomes (83% in Engel class I) even after a long period of follow‐up.