Abnormality of the nervous system Gliosis Excess astrocytes in brain Gliosis is the focal proliferation of glial cells in the central nervous system. HP:0002171 Gliosis generally occurs as a response to tissue damage. Gliosis appears bright on T2 scans upon magnetic resonance imaging, unlike encephalomalacia which follows CSF signal on all sequences. Glial cells, the non-neuronal component of the central nervous system, are divided into microglia and macroglia. The latter are in turn divided into astrocytes, oligodendrocytes, and ependymal cells. The astrocytes and the microglia are the glial cells predominantly responsible for tissue response to injury. UMLS:C0017639 SNOMEDCT_US:359580009 Cerebral gliosis SNOMEDCT_US:81415000