Although amyotrophic lateral sclerosis is a relatively uncommon disorder, it has been the focus of considerable scientific scrutiny. First described by Charcot in 1869, the condition involves degeneration and loss of motor neurons in the cerebral cortex, brainstem, and spinal cord. Although different forms of the disease have been described, a definitive pathologic mechanism has yet to be delineated.
Various synonyms for amyotrophic lateral sclerosis (ALS) include Lou Gehrig's disease, Charcot disease, and motor neuron disease (Rowland, 1995, pp. 1251-1252). The disorder is caused by non-specific degenerative changes of the bulbar and spinal motor neurons and their corresponding cortico-spinal tracts. Moreover, other neuronal systems may become progressively involved. These can include the spinocerebellar pathways and nuclei, the frontal cortex, and the substantia nigra (Swash & Schwartz, 1992, pp. 4-13).
The disease's onset is insidious, and its outcome is typically fatal. Amyotrophic lateral sclerosis patients often present with asymmetrical and focal weakness. This complaint can involve only a few adjacent muscles: Leg weakness is slightly more common than hand weakness. About a third of patients present with bulbar symptoms. One characteristic feature of the disease is arm muscle fasciculation. Jokelainen (cited in Swash & Schwartz, 1992, pp. 4-13) found that patients with bulbar involvement survived for a mean period of 2.2 years; median survival for all ALS cases is 3-4 years.
The pathologic features of ALS are generally asymmetrical and include the loss of both lower cranial nerve nuclei somatic motor neurons and anterior horn cells. Moreover, the widespread loss of anterior horn neurons suggests that interneurons may also be affected. Within the cerebral cortex, there is typically a loss of Betz cells and degeneration of the corticospinal tracts. Other neural systems that may be affected include the...