Amyotrophic lateral sclerosis (ALS) is probably best known to the majority of the US population as Lou Gehrig’s disease, named for the New York Yankee who died of ALS after a stellar 17-year baseball career in the 1920s and ’30s. Gradually, the general public is gaining familiarity with the characteristics of ALS, a disease with no single identifiable cause and no known cure.
About 5,600 people receive a diagnosis of ALS in the US each year (about 15 per day), making it the most common form of motor neuron disease.1 Most patients present with progressive muscle weakness in an extremity, which ultimately leads to respiratory failure and death.
Generally, patients with ALS have no cognitive disability and are aware of their physical decline. These patients are faced with important decisions as their condition worsens: Will they want nutritional support through a gastrostomy? For respiratory assistance, will their preference be noninvasive ventilation or mechanical ventilation via tracheostomy?
Not only do ALS patients undergo deterioration of motor function, but many experience muscle cramping, generalized pain, and depression. Only one medication is currently approved to treat ALS patients, with the benefit of prolonging life by a few months. In addition to symptom management, supportive measures, including physical, occupational, and speech therapy, exercise, nutrition, support groups, and counseling, are important tools to enhance quality of life for the patient with ALS.2
Primary care providers need to be aware of ALS, recognize its symptoms in their patients, and manage those affected on a case-by-case basis. Because of the challenges in diagnostic evaluation, the rapidly evolving nature of the disease, and the dire prognosis of ALS, any patient suspected of having ALS should be referred immediately to a neurologist. Providers need to educate patients and their caregivers regarding the disease process and ensure that patients receive appropriate care to meet their needs and preferences.
ALS is a progressive neurodegenerative disease that affects both the upper and lower motor neurons. The disease is considered terminal. Although life may be prolonged by the one currently available pharmacologic agent, no treatment option is yet capable of stopping or reversing progression of the disease.3 While ALS was once believed to be a purely motor disorder, the accompanying degeneration of nonmotor brain regions, such as frontal and temporal cortical neurons, is considered by some to be part of the clinicopathologic spectrum of ALS.4
There are two forms of ALS: sporadic and familial. Sporadic ALS is by far the more common, accounting for 90% to 95% of cases. The remaining 5% to 10% of ALS cases are of the familial form, which can be autosomal-dominant or autosomal-recessive.5
The Degenerative Motor Neuron Diseases
Weakness and muscle wasting characterize several degenerative motor neuron diseases. In addition to ALS, these include primary lateral sclerosis, progressive muscular atrophy, progressive bulbar palsy, and pseudobulbar palsy.6
Primary lateral sclerosis involves upper motor neuron (UMN) dysfunction in the limbs.7Progressive muscular atrophy results from degeneration of the anterior horn cells in the spinal cord and is associated with lower motor neuron (LMN) deficits in the limbs.
Progressive bulbar palsy is a progressive UMN and LMN disorder of the cranial muscles. This condition may occasionally stay isolated in the bulbar segment, but more commonly, UMN and LMN signs and symptoms spread to involve other segments. This is then referred to as bulbar-onset ALS. There have been no reports of specific pathology in progressive bulbar palsy.
Pseudobulbar palsy results from an UMN lesion in the corticobulbar pathway in the pyramidal tract. It is characterized by difficulty chewing and swallowing, and slurred speech (manifestations that may also represent the initial presentation of ALS). Patients with pseudobulbar palsy may exhibit inappropriate, excessive yawning and emotional outbursts; these manifestations are referred to as emotional incontinence.8
In North America, it is estimated that ALS affects 1.5 to 2.7 people per 100,000 between ages 20 and 80; most frequently, the disease presents between ages 55 and 65. ALS develops infrequently before age 30.3,9
While no gender difference is apparent in patients with familial ALS, sporadic ALS predominately affects males more than females (although the accepted ratio of 1.5:1 appears to be in decline9). After age 65, men and women are equally impacted.10
Established risk factors for ALS include age and family history. Accumulating evidence suggests that military service and smoking may also contribute to the development of ALS.11-15 Children and siblings of ALS patients are at increased risk for ALS, while military personnel have 1.5 times the risk.11
Investigation of the precise link between military service and ALS is ongoing, but factors may include intense exertion, traumatic injuries, viral infections, and exposure to certain chemicals or metals.11 Research suggests the risk is independent of time period, years of service, or branch of service. Geographic location appears to be an independent factor, although there does seem to be a strong association between deployment during the 1991 Gulf War and the risk for ALS.12-14