While much emphasis on spinal cord injury/dysfunction (SCI/D) has focused on trauma, nontraumatic SCI/D is becoming increasingly common as the population ages. Nontraumatic SCI/D can be caused by a wide variety of etiologies. This chapter will provide a brief review motor neuron diseases (with primary emphasis on amyotrophic lateral sclerosis [ALS]), and myelopathies related to spondylosis, tumors, infection, vascular anomalies, and demyelinating disorders. Basic pathophysiology and rehabilitative techniques in nontraumatic SCI/D are in many cases similar as those in traumatic SCI (see Chapter 14 for a review of these topics.) A more focused review of inflammatory, infectious and cancer related SCI are found in Chapters 16 and 17, respectively.
Nontraumatic SCI/D represents a heterogeneous group of patients, and each underlying etiology presents a unique set of considerations in terms of diagnosis, treatment, and rehabilitation.
ALS is a progressive neurodegenerative motor neuron disease resulting in muscle weakness, progressive disability, and eventually death. ALS primarily affects anterior horn cells of the spinal cord. Other motor neuron diseases such as poliomyelitis, Friedrich's ataxia, and spinal muscular dystrophy, may be central or peripheral in nature. This review will focus on ALS, but the principles can be applied to any motor neuron disorder depending on the functional status of the individual.
ALS is characterized by the death of both lower (anterior horn cells in the spinal cord) and upper motor neurons (motor cortex). Typically, either lower or upper motor neurons are affected at the onset, but eventually both are involved.1
The underlying etiology which causes ALS has not been fully described. Nevertheless, numerous cellular processes have been associated with the disorder; these include apoptosis, mitochondrial dysfunction, protein aggregation and generation of free radicals2 (Fig. 15–1).
(Left panel) Cervical spinal cord in amyotrophic lateral sclerosis shows dramatic atrophy of gray matter in anterior horns (arrow) due to loss of motor neurons. The pale-staining areas in the lateral and anterior columns (arrowheads) of the spinal cord reflect the great loss of myelinated axons in the lateral and anterior corticospinal tracts. (Right panel) Normal cervical spinal cord. (Photo contributor: Kinuko Suzuki, MD, Tokyo Metropolitan Institute of Gerontology; retired faculty, Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC.)
ALS is the most common motor neuron disease, with an incidence of 2 per 100,000 persons.3 It has a predilection for people in their forties, fifties, and sixties, with peak incidence age 65 to 74.4
Objectively, the combination of both upper and lower motor neuron signs defines ALS. Fasciculations in the tongue and ...