Light and ultrastructural studies in sural biopsies of the pseudopolyneuropathic form of ALS.

The aim of this work was to study the neuropathological picture of the sural nerve in the pseudopolineuropathic form of A.L.S. Five patients were considered: in all cases the clinical and electromyographic follow-up excluded other diseases. EMG-studies were repeatedly performed: they showed the progressive evolution of the spinal anterior horn cell pathology from lower spinal to cervical levels. The sural nerve was processed according to the procedure used in our laboratory for light and ultrastructural examination. Quantitative analysis of myelinated fiber density was carried out on photographic enlargement and reported on histograms. The light and ultrastructural examination showed a severe loss of myelinated fibers; the decrease affected all types of fibers, but predominated in the largest ones. In the axons there was an increase of mitochondria, dilation of the small vesicles and increase in the number of neurofilaments. It is our opinion that all histopathologic data obtained in the sural nerve biopsy in this form of A.L.S. reveal a clear involvement of the sensory neurons of the spinal ganglia and the results can be useful for the study of precocius lesions in the A.L.S.