Focal accumulation of phosphorylated neurofilaments within anterior horn cell in familial amyotrophic lateral sclerosis

Distribution of phosphorylated neurofilament proteins within anterior horn cells in three cases of familial and six cases of sporadic amyotrophic lateral sclerosis (ALS) and ten control cases were investigated by using a monoclonal antibody. Two distinct staining patterns of perikarya were observed; (1) homogeneous pattern; either the entire or a part of the perikaryon was immunostained homogeneously (homogeneously diffuse or partial pattern); (2) focal pattern: perikarya contained very distinct, inclusion-like focal accumulation of immunoreactive products of various morphologies such as round, ring-shaped, cord-like, tube-like and more irregular shapes. The homogeneous pattern was found in all three groups but was most common in sporadic ALS. On the other hand, the focal pattern was seen almost exclusively in familial ALS. The focal accumulation of neurofilaments appears at least in part to be related to the Lewy body-like hyaline inclusion which is known to contain neurofilaments. In addition, cord-like swellings of neurites in familial ALS also showed focal neurofilament accumulation. These observations suggest that the focal accumulation of phosphorylated neurofilaments is characteristic of familial ALS, although it may not be specific to the entity. The pathological process(es) producing the neurofilamentous abnormality may play an important role in anterior horn cell degeneration in familial ALS.