A distinctive distribution of reactive astroglia in the precentral cortex in amyotrophic lateral sclerosis

Morphological changes in astrocytes have been studied in the primary motor cortex of persons dying with or without amyotrophic lateral sclerosis (ALS). Glial fibrillary acidic protein (GFAP) and S-100 protein were used as immunohistochemical markers for reactive astroglia. In 12 brains of individuals without neurological disease glial cells showing moderate immunoreactivity for both GFAP and S-100 protein were uniformly distributed in the primary motor cortex in the upper regions of layer I and layer II. In 8 of 11 ALS cases, intensely immunoreactive cells were additionally found to occur and were scattered irregularly, mostly in layers II and III, but occasionally in layers IV and V. Clusters of these intensely positive cells occurred in patches about 200-400 micron in diameter, each containing about 6 to greater than 20 such cells. GFAP-positive astrocytes were seen in some of the 36 brains from persons with neurological problems other than ALS but the pattern was different. The abnormal appearance of clusters of positive astrocytes of the primary motor cortex may be intimately associated with the ALS disease process.