Mitochondrial alterations in the spinal cord of patients with sporadic amyotrophic lateral sclerosis

Little information is available about morphologic changes of mitochondria in sporadic amyotrophic lateral sclerosis (ALS). We examined the anterior horns of the lumbar spinal cord in 14 patients with sporadic ALS and 15 age-matched controls by electron microscopy to illuminate the subject. In the controls, one patient showed occasional swollen mitochondria with markedly increased cristae and marked accumulation of mitochondria in the somata of anterior horn neurons. Another patient had periodic, stubby protrusions on the outer membrane. Among the patients with ALS, 7 showed filamentous structures in the inner compartment of the mitochondria mainly of the somata and only occasionally of the axons. The structures were composed of a stack of multilayered cristae consisting of linear structures on a longitudinal section. Other abnormal structures were periodic transverse processes like rungs of a ladder predominantly in somata and only occasionally in the axons, marked accumulation of mitochondria in the somata, dendrites or proximal axons (axon hillock and initial segment), stubby protrusions on the outer membrane, and swollen mitochondria with markedly increased cristae in the somata. The findings in this study may reflect the metabolic disturbance of mitochondria, probably associated with the pathomechanism of degenerative processes of anterior horn neurons in sporadic ALS.