When observing the cranial nerve system under a microscope, normal and abnormal boundaries are often unclear or devoid of objective evidence, leading to diagnosis on the basis of the physicians’ experience. If an abnormal structure is present, a particular disease may be inferred; however, “whether an area that looks normal is truely normal and not abnormal” is not widely investigated and considered to be a limitation of morphology. Recently, it has become possible to determine the presence of micromalformations in focal areas resected during brain surgery, e.g., in cases of refractory epilepsy; this has created a new field that cannot be addressed with conventional diagnostic criteria. In future, it is the mission of neuropathology to develop a way to differentiate normal tissues/cells from abnormal ones that can be treated using new methods.
For many years, neuropathology was considered to be the pathology of nerve cells. However, over time, glial cells have been shown to play a major role in the generation and recycling of neurotransmitters, nutritional maintenance, and electrical excitory transmission. Subsequently, many diseases in which glial cell damage may cause secondary neuronal death have been described. In addition, it has recently been found that in the brain of patients with Alzheimer’s disease, abnormal tau proteins that cause neurofibrillary degeneration of neurons aggregate in glial cells called astrocytes. Furthermore, a disease group was found in which morphological indices showing differences in the astrocytic aggregation of abnomal tau were useful for differential diagnoses. Therefore, the diagnosis of disease with regard to disrupted interaction between neuronal and glial cells in the cranial nerve system is very important and constitutes a new area of neuropathology called glial pathology. A new perspective will be essential for changing disease concepts.
The 21st century has been called “the brain century.” It is thought that the establishment of a brain bank in the US and Europe will be necessary to further promote basic research using the human brain. This so-called brain bank involves a soft and hard system of frozen brain tissue, with data principally collected by pathological autopsy. Although various ethical problems will clearly have to be addressed, active activities of the brain bank will support basic research to clarify cranial nerve diseases. In this regard, educational activities will also be important.