Diagnostic surgical neuropathology of intractable epilepsy

As neurosurgical treatments have been increasingly applied to patients who have intractable epilepsy, much knowledge on pathological changes in surgically removed brain tissues have become clearer in recent years, as well as on the neuroimaging findings which are analyzed with a variety of techniques, including computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET), single photon emission computed tomography (SPECT) in combination with digital imaging and communication in medicine (DICOM), statistical parametric mapping (SPM), subtraction ictal SPECT coregistered to MRI (SISCOM) and/or PET-guided intraoperative navigation system, as mentioned in detain in another article in this issue by Maehara et al. Representative and relatively common diseases, treated by epilepsy-surgery, are as follows; hippocampal sclerosis, amygdaloid sclerosis, coarse and macroscopic brain malformation (focal cortical dysplasia, hemimegalencephaly, tuberous sclerosis), tumors (dysembryoplastic neuroepithelial tumor, ganglioglioma, etc.), destructive lesions and the others. It is a fact, however, that there remains many problems in the diagnostic criteria or histological grading systems, especially in various cortical dysplasias described above. On the other hand, histologically minor but clinically serious lesions have become to be known through careful observations on surgically removed tissues which showed no neuroradiological findings. A good well-known example is microdysgenesis of the cerebrum which is characterized by the presence of both the white mater ectopic neurons and the vascular meandering abnormalities with glial satellitosis. There must be another important histological phenotypes of microdysgenesis, except the above-mentioned ones, that are not yet established at present. Therefore, it is believed that there remains various problems on the diagnostic neuropathology of epileptic lesions with or without neuroimaging findings in which we have to give answers in a few days to come.