Abnormal proximal axons of Clarke's neurons in sporadic motor neuron disease

Selective and asymmetric vulnerability of corticospinal and spinocerebellar tracts in motor neuron disease

The spinal cords of 10 cases of motor neuron disease were compared with those of six age-matched controls using myelin and silver impregnation methods, and the Marchi reaction for myelin degradation products. These studies revealed striking asymmetry in involvement of the lateral and anterior corticospinal tracts, without concordance in the pattern of involvement of these crossed and uncrossed corticospinal pathways. In addition there was prominent involvement of the posterior and anterior spinocerebellar tracts, but less marked abnormality was seen in the reticulospinal pathways. These findings highlight the asymmetrical involvement of the upper and lower motor neuron components of the motor system that is a characteristic feature of the disease, and demonstrate that involvement of the spinocerebellar system is a frequent finding.

Morphometric study of the sensory nerve in classical (or Charcot disease) and juvenile amyotrophic lateral sclerosis

Analysis of the superficial peroneal nerve sampled in 9 cases of classical amyotrophic lateral sclerosis (classical ALS, Charcot disease) and compared with 8 age-matched controls showed a very significant reduction of all myelinated fibres (P less than 0.001), affecting small-diameter (P less than 0.01) and large-diameter (P less than 0.02) fibres. Moreover, the small-diameter unmyelinated fibres were very significantly reduced (P less than 0.001) and the large-diameter fibres were highly increased (P less than 0.01). These results suggest a phenomenon of chronic axonal degeneration. Analysis of the same nerve in 7 patients suffering from juvenile ALS and compared with 4 age-matched controls showed a significant reduction (P less than 0.05) of myelinated fibres. The small-diameter and overall unmyelinated fibres were not significantly reduced while the large-diameter fibres, were significantly increased (P less than 0.01). The same analysis of 4 patients presenting an early-onset ALS compared with 3 controls showed lesions of a severity half-way between that of the classical and the juvenile form. Our study showed that the lesions of the sensory nerve are of the same type in classical ALS and in juvenile ALS, but of differing severity. The nosologic place of juvenile ALS compared with classical ALS and with heredodegenerative diseases of the nervous system is discussed.

Amyotrophic lateral sclerosis: Part 1. Clinical features, pathology, and ethical issues in management

Amyotrophic lateral sclerosis (ALS) is a progressive degenerative disease of the motor system in adults that occurs in sporadic, familial, and Western Pacific forms. Involvement of non-motor pathways has been increasingly recognized, both clinically and pathologically. Although the usual course is relentlessly progressive with death in half the cases within three years from onset, it can sometimes be protracted. Degeneration and loss of large motor neurons in the cerebral cortex, brainstem, and cervical and lumbar spinal cord are characteristic. Marked reduction in the number of large myelinated fibers is notable in the cervical and lumbar ventral roots. Peripheral nerves show reduced numbers of large myelinated fibers, acute axonal degeneration at all levels, and distal axonal atrophy. Motor end-plates reveal small or absent nerve terminals. Subclinical non-motor system involvement includes neuronal loss in Clarke's nucleus and dorsal root ganglia, degeneration of non-motor tracts in the spinal cord, loss of receptors in the dorsal horns of the spinal cord, and myelinated fiber loss with segmental demyelination in sensory and mixed nerves. The serious implications of the diagnosis of ALS make it mandatory to exclude similar potentially treatable disorders. Management should be multidisciplinary, and discussions with the patient and family members should be frank and frequent. Discussions about ventilatory support should take place early in the disease so that death from respiratory failure can be prevented, when that is desired, and conversely to obviate the discontent and anger that accompany involuntary life on a ventilator.

Morphometric and biochemical studies of peripheral nerves in amyotrophic lateral sclerosis

Phrenic nerves of 11 patients with amyotrophic lateral sclerosis studied postmortem contained only 33% of the normal number of large myelinated fibers (9 controls; p less than 0.001). In the phrenic nerves of these patients, there were 18% fewer large myelinated fibers in the distal segment than in the proximal segment (p less than 0.025). The ratio of axonal circumference to myelin lamellae in large myelinated fibers in the distal segment was 34% greater than that in control fibers (p less than 0.002). The proportion of acute axonal degeneration was the same at all levels (48.0 +/- 13.7%). Sural nerves of 21 patients with amyotrophic lateral sclerosis had more acute axonal degeneration and 30% fewer myelinated fibers (p less than 0.05) than controls; evidence of degeneration also extended to unmyelinated fibers. The amount of axonal transport of acetylcholinesterase in 9 sural nerves determined in vitro was reduced by 24% (p less than 0.05) and the apparent transport rate was reduced by 44% (p less than 0.01) compared with 4 controls. These findings show that in amyotrophic lateral sclerosis a small degree of dying-back change and of distal axonal atrophy is superimposed on the degeneration of motor neuron cell bodies, and that the disease effects spread beyond the motor neurons.