AMYOTROPHIC LATERAL SCLEROSIS
Motor neuron disease is another common neurode-generative disease, with amyotrophic lateral sclero-sis (ALS) being the most prevalent. The cause of ALS is unknown, although small numbers of patients with the familial form of the disease have a defect in the superoxide dismutase-1 gene. ALS is a rap-idly progressive disorder of both upper and lower motor neurons. Clinically, patients present in the fifth or sixth decade of life with muscular weakness, atrophy, fasciculation, and spasticity. The disease may initially be asymmetric, but over the course of 2–3 years becomes generalized, involving all skeletal and bulbar muscles. Progressive respiratory muscle weakness makes the patient susceptible to aspira-tion and eventually leads to death from ventilatory failure. Although the heart is unaffected, autonomic dysfunction can be seen. There is no specific treat-ment for ALS.
The primary emphasis in management is judi-cious respiratory care. As with other patients with lower motor neuron disease, succinylcholine is con-traindicated because of the risk of hyperkalemia. Adequacy of ventilation should be carefully assessed both intraoperatively and postoperatively; an awake extubation is desirable. Difficulty in weaning patients from mechanical ventilation postoperatively is not uncommon in patients with moderate to advanced disease.