[The corticospinal tract of amyotrophic lateral sclerosis--a morphometric analysis of the myelinated fibers].

The myelinated fibers in the lateral corticospinal tract at the C6, T7, L4 levels in amyotrophic lateral sclerosis (ALS) and control cases were morphometrically examined. ALS cases consisted of 6 males and 2 females with ages ranging between 48 and 85 years, and were all the common or bulbar form in clinical manifestation. As for controls, 10 cases who died of non-neurological diseases, with age ranging 36 to 90 years were served. The population and the diameter profile of the myelinated fibers in the corticospinal tract of the C6, T7, L4 levels were measured by the method previously described and expressed as number per mm2. In control subjects, fiber-size histograms of myelinated fibers showed a bimodal pattern with a sharp peak of small fibers (less than 7.28 microns) and a broad peak of large fibers (greater than or equal to 7.28 microns) in all the spinal levels. In ALS cases, large myelinated fibers were predominantly diminished in number, a small myelinated fibers were also decreased in some cases. The degree of fiber loss was extremely variable among cases; well populated in large fibers in some cases. As for the rostral caudal distribution of myelinated fiber loss, a caudally-accentuated fiber loss particularly in large fiber was seen in some of the cases. The topographical distribution of fiber loss in the horizontal plane of the corticospinal tract in ALS did not show a distinctive pattern.