Amyotrophic Lateral Sclerosis

AMYOTROPHIC LATERAL SCLEROSIS

Amyotrophic lateral sclerosis (ALS) is a disease of unknown cause in which there is a loss of motor neurons (nerve cells controlling muscles) in the anterior horns of the spinal cord and the motor nuclei of the lower brain stem. As these cells die, the muscle fibers that they supply undergo atrophic changes. Neuronal degenera-tion may occur in both the upper and lower motor neuron systems. Several theories exist regarding the cause of ALS, including autoimmune disease and free radical damage. The leading theory held by researchers is that overexcitation of nerve cells by the neurotransmitter glutamate leads to cell injury and neuronal degeneration.

The incidence of ALS is 203 cases per 100,000 in the general population (Charles & Swash, 2001; Brown, Meininger & Swash, 2000). ALS affects more men than women, with onset occurring usually in the fifth or sixth decade. It is often referred to as Lou Gehrig’s disease after the famous baseball player who suffered from it.

Clinical Manifestations

Clinical manifestations depend on the location of the affected motor neurons, because specific neurons activate specific muscle fibers. The chief symptoms are fatigue, progressive muscle weak-ness, cramps, fasciculations (twitching), and incoordination (Brown, Meininger & Swash, 2000). Loss of motor neurons in the anterior horns of the spinal cord results in progressive weak-ness and atrophy of the muscles of the arms, trunk, or legs. Spasticity usually is present, and the deep tendon stretch reflexes become brisk and overactive. Usually, the anal and bladder sphincters are intact because the spinal nerves that control mus-cles of the rectum and urinary bladder are not affected.

In about 25% of patients, weakness starts in the muscles sup-plied by the cranial nerves, and there is difficulty talking, swal-lowing, and ultimately breathing. When the patient ingests liquids, soft palate and upper esophageal weakness causes the liq-uid to be regurgitated through the nose. Weakness of the poste-rior tongue and palate impairs the ability to laugh, cough, or even blow the nose. When bulbar muscles are impaired, there is pro-gressive difficulty in speaking and swallowing, and aspiration becomes a risk. The voice assumes a nasal sound, and articulation becomes so disrupted that the speech is unintelligible. Some emo-tional liability may be present, but intellectual function is not im-paired. Eventually, respiratory function is compromised.

The prognosis generally is based on the area of the CNS in-volved and the speed with which the disease progresses. Death usually occurs as a result of infection, respiratory failure, or aspi-ration. The average time from onset of the disease to death is about 3 years. A few patients survive for longer periods.

Assessment and Diagnostic Findings

ALS is diagnosed on the basis of the signs and symptoms because no clinical or laboratory tests are specific for this disease. EMG studies of the affected muscles indicate reduction in the number of functioning motor units. MRI may show high signal intensity in the corticospinal tracts; this differentiates it from a multifocal motor neuropathy (Rowland & Shneider, 2001).

Management

There is no specific therapy for ALS. The main focus of medical and nursing management is on interventions to maintain or im-prove function, well-being, and quality of life (Brown, Meininger

Swash, 2000). One study of 60 patients with ALS found that de-spite the decline in physical function, quality of life and religiosity change little over time (Robbins, Simmons, Bremer et al., 2001).

The medication riluzole (Rilutek), a glutamate antagonist, was approved by the FDA in 1995 after clinical trials found that it slows the deterioration of motor neurons. How riluzole works is not clear, but its pharmacologic properties suggest that it may have a neuroprotective effect in the early stages of ALS. Two ran-domized drug trials showed a dose of 100 mg riluzole per day to be modestly effective in prolonging survival time for patients with ALS (Miller, Mitchell & Moore, 2001).

Symptomatic treatment and rehabilitative measures are em-ployed to support the patient and improve the quality of life. Baclofen (Lioresal), dantrolene sodium (Dantrium), or diazepam (Valium) may be useful for patients troubled by spasticity, which causes pain and interferes with self-care. Several neurotrophic fac-tors that facilitate nutrition and metabolism for nerve tissue are being investigated (Rowland & Shneider, 2001).

Most patients with ALS are managed at home and in the community, with hospitalization for acute problems. The most common reasons for hospitalization are dehydration and malnu-trition, pneumonia, and respiratory failure (Lechtzin, Wiener, Clawson et al., 2001). Recognizing these problems at an earlier stage in the illness will allow for the development of preventive strategies.

A patient experiencing problems with aspiration and swal-lowing may require enteral feeding. The American Academy of Neurology practice guidelines suggest the placement of a percu-taneous endoscopic gastrostomy tube before the forced vital ca-pacity drops below 50% of predicted (Boitano, Jordan & Benditt, 2001). This tube can be safely placed in patients who are using noninvasive positive-pressure ventilation for ventilatory support (Boitano, Jordan & Benditt, 2001).

Mechanical ventilation (using negative-pressure ventilators) is an option when alveolar hypoventilation develops. A small study of patients who used noninvasive positive-pressure ventilation at night showed that hypoventilation and sleep disturbances were at least partially improved, enhancing their cognitive function (Newsom-Davis et al., 2001). The use of noninvasive positive-pressure ventilation also postpones the decision of whether to undergo a tracheotomy for long-term mechanical ventilation (Rowland & Shneider, 2001).

Decisions about life support measures are made by the patient and family and should be based on a thorough understanding of the disease, the prognosis, and the implications of initiating such therapy. Patients are encouraged to complete an advance directive or “living will” to preserve their autonomy in decision-making.

The ALS Association has broad programs of research funding, patient and clinical services, patient information and support, and medical and public information. The ALS Association Quar-terly Newsletter is a source of practical information.