Amyotrophic Lateral Sclerosis

– A rapidly progressive, degenerative disease of the upper and lower motor neurons characterized by atrophy of the hands, arms, legs, and, eventually, the entire body. Seventy percent of individuals die within 5 years of diagnosis.

Causes and Incidence

The etiology of amyotrophic lateral sclerosis (ALS) is unknown, but proposed explanations include genetics, metabolic disturbances, and external agents. Although the incidence worldwide is 60 to 70 people per 100,000, with large clusters of cases in the western Pacific, the incidence in the United States is only about 5 in 100,000. The disease usually occurs in men between 40 and 70 years of age.

Disease Process

Patterns of degeneration occur in the brain and spinal cord. The anterior horn cells deteriorate, resulting in denervation of muscle fibers. Atrophy of the precentral gyrus and loss of Betz’s cells occur in the cortex. Motor neurons are lost in the brainstem, although neurons that control the sensory and urinary sphincters are spared. The corticospinal tract and large motor neurons in the spinal cord also atrophy.

Symptoms

Early
Weakness, cramps in the hands and forearms.

Midcourse
Fatigue; dyspnea; slurred speech; dysphagia; asymmetric spread of muscle weakness to the rest of the body; spasticity; fasciculations; hyperactive deep tendon and extensor plantar reflexes.

Late
Paralysis of vocal cords; paralysis of chest muscles, necessitating ventilatory support.

Potential Complications

The end stage of ALS can be complicated by disuse syndrome, contractures, skin breakdown, and aspiration pneumonia.

Diagnostic Tests

Clinical evaluation
Any of the above manifestations; motor involvement unaccompanied by sensory abnormalities.

Electromyography
Fibrillation, positive waves, fasciculations, giant motor units.

Blood
Possible elevation in creatinine phosphokinase.

Spinal tap
Elevated total protein; normal cell and IgG concentrations.

Computed tomography scan
Normal until cerebral atrophy late in disease.

Myelogram
Normal; spinal cord atrophy late in disease.

Treatments

Surgery
Cricopharyngeal myotomy to alleviate dysphagia; tracheostomy; esophagostomy/ gastrostomy

Drugs
Muscle relaxants (e.g., baclofen) to control spasticity; tricyclic antidepressants to control saliva; phenytoin to reduce cramping

General
Physical therapy to maintain muscle strength; occupational therapy for activity of daily living support; speech therapy to aid communication; splints for neutral joint alignment; leg braces, canes, walkers to aid ambulation; nutritional support/tube feedings; cardiac monitoring; mechanical ventilation; counseling for individual and family; respite care or placement if family is unable to provide care.

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