Histopathology of cortex and white matter in pediatric epileptic spasms: comparison with those of partial seizures

Epileptic spasms in older children have increasingly been recognized as a distinct seizure type and subset of these patients are considered for surgical resection. This study compares histopathology and magnetic resonance imaging (MRI), especially focusing the difference between the cortical grey matter and the subcortical white matter to understand the extensive epileptic brain in patients with epileptic spasms. We examined 22 patients consisting of 11 patients with epileptic spasms and 11 with partial seizures. Scalp video electroencephalography (EEG) showed interictal generalized epileptiform discharges (9 patients with epileptic spasms vs. 1 with partial seizures) and ictal generalized epileptiform discharges (10 vs. 3). We found MRI abnormalities in a single lobe (6 vs. 7) and multiple lobes (2 vs. 1). Surgical resections were performed across multiple lobes (9 vs. 2), comparing within a single lobe (2 vs. 9), (p<0.001). Histopathology showed abnormal cortical organizations as FCD (2 vs. 5) and microdysgenesis (4 vs. 4), normal (4 vs. 1). Two patients with epileptic spasms showed hyaline proteoplasmic astrocytopathy. There were heterotopic neurons (10 vs. 10), cluster of oligodendroglia (8 vs. 7), balloon cells (2 vs. 5) and blurred myelination (1 vs. 4), in the white matter. Seizure-free outcomes were seen in seven patients with epileptic spasms (64%) and four with partial seizures (36%). The multilobar epileptogenic zones existed in patients with epileptic spasms, compared with the focal epileptogenic zone in patients with partial seizures. There was no difference of MRI and histopathology findings in cortex and subcortical white matter between two groups.