In 2011, the International League Against Epilepsy (ILAE) proposed a consensus classification system of focal cortical dysplasia (FCD) to distinguish clinicopathological subtypes, for example, "isolated" FCD type Ia-c and IIa-b, versus "associated" FCD type IIIa-d. The histopathological differentiation of FCD type I and III variants remains, however, a challenging issue in everyday practice. We present a unique histopathological pattern in patients with difficult-to-diagnose FCD, which highlights this dilemma, but also helps to refine the current ILAE classification scheme of FCD. We present a retrospective series of 11 male and one female patient with early onset pharmacoresistant epilepsy of the posterior quadrant (mean age at seizure onset = 4.6 years). All surgical specimens were reviewed. Clinical histories were retrieved and extracted from archival patient files. Microscopic inspection revealed abnormalities in cortical architecture with complete loss of layer 4 in all surgical samples of the occipital lobe, as confirmed by semiquantitative measurements (p < 0.01). Clinical history reported early transient hypoxic condition in nine patients (75%). Magnetic resonance imaging (MRI) revealed abnormal signals in the occipital lobe in all patients, and signal changes suggestive of subcortical encephalomalacia were found in seven patients. Surgical treatment achieved favorable seizure control (Engel class I and II) in seven patients with an available follow-up period of 6.1 years. Prominent disorganization of cortical layering and lack of any other microscopically visible principle lesion in the surgical specimen would result in this neuropathological pattern hitherto being classified as FCD ILAE type Ib. However, perinatal hypoxia with distinctive MRI changes suggested primarily a hypoxemic lesion and acquired pathomechanism of neuronal cell loss in the occipital lobe of our patient series. We propose, therefore, classifying this distinctive clinicopathological pattern as a separate variant of FCD ILAE type IIId.

Hippocampal sclerosis (HS) is the most common cause of drug-resistant medial temporal lobe epilepsy (MTLE). Structural abnormalities such as HS, granule cell pathology (GCP), and focal cortical dysplasia (FCD) have been classified histopathologically, possibly allowing a more accurate assessment of prognostic seizure and neuropsychologic outcomes. We correlated seizure outcome with comprehensive temporal lobe pathologic findings, identified according to the most recent classification systems of HS, GCP, and FCD. All the 83 patients who underwent anterior temporal lobectomy (ATL) for drug-resistant MTLE and with a proven diagnosis of HS between April 2001 and May 2014 were collected. Patients were divided in 2 main groups: 1) isolated HS with/without GCP (HS +/- GCP); and 2) HS associated with FCD with/without GCP (HS+FCD +/- GCP). Patients were followed up at least 1 year, and seizure outcome was reported in accordance with Engel classification. Group I: HS +/- GCP: Statistical analysis confirmed a better outcome in HS + GCP patients than in HS-no GCP (P < 0.05). Moreover, a better outcome for the patients affected by GCP type I was observed (P < 0.05). Group II: HS+FCD +/- GCP: Patients with HS variant type I presented a better seizure outcome than the patients with HS type II (Engel class IA HS type I vs. type II: 69% vs. 40%). A pathology-based approach to epilepsy surgery might improve the interpretation of the results, could predict which cases will enjoy a better seizure outcome, and could help to the comprehension of the causes of failures.

Hippocampal sclerosis (HS) is the most frequent neuropathologic finding in patients undergoing surgery for intractable temporal lobe epilepsy (TLE). The International League Against Epilepsy (ILAE) has recently proposed a new classification of HS based on specific patterns of cell loss. The aim of this study was to investigate the relationships between HS types, their etiologic factors, and the short- and long-term postsurgical outcomes of patients undergoing surgery because of drug-resistant TLE with HS. Two hundred thirteen patients with a neuropathologic diagnosis of HS and a minimum follow-up of 2 years were divided on the basis of their ILAE HS type and further classified into: (1) isolated HS, (2) HS associated with focal cortical dysplasia (FCD IIIa), or (3) HS associated with other lesions. Their clinical and neuropathologic data were correlated with their Engel class postsurgical outcomes. The main findings were the following: (1) HS type 1 was associated with a longer duration of epilepsy; (2) >80% of the patients had an Engel class I short- and long-term outcomes, regardless of HS type and associated pathology; (3) short- and long-term postsurgical outcomes were less satisfactory in the patients who were completely seizure-free (Engel class Ia), and patients with HS type 2 had better long-term seizure outcomes than those with type 1; (4) the concomitant presence of FCD contributed to a worse outcome, regardless of HS type; and (5) a shorter duration of epilepsy significantly correlated with an Engel class Ia outcome. These data suggest that HS type and associated pathologies may predict the risk of recurrence, but other variables such as the duration of epilepsy need to be considered. A common neuropathologic classification system may help to identify preoperative predictive factors and improve the selection of patients who may benefit from epilepsy surgery.