Diagnosis And Epidemiology:
Amyotrophic lateral sclerosis (ALS), also referred to as “Lou Gehrig’s disease,” is a progressive motor neuron disease affecting the nerve cells in the brain and spinal cord. Motor neurons are small bundles of nerves that run from the brain to the spinal cord then from the spinal cord to the muscles throughout the body. The progressive degeneration of the motor neurons causes them to die and the brain loses the connection with the muscle which results in a lack of muscle control. This ‘disconnection’ then causes the muscle to lose neuron nourishment and stimulation resulting in muscle atrophy (become smaller in mass).
In about 10% of cases, ALS is due to an inherited genetic defect. In all other remaining cases the cause is unknown. ALS currently affects approximately 5 out of every 100,000 people world-wide. There is no known risk factor for ALS, except for having a family member who has had the hereditary form of the disease. The biological mechanisms that cause ALS are only partially understood and may be due to a particular gene called SOD1. A mutation in this gene is thought to make a protein that is toxic to the motor nerve cells. Due to the accumulation of this toxin, people with ALS progressively lose the ability to function and care for themselves. They no longer have voluntary control over their muscles and eventually lose involuntary control that is required for vital organ systems.
The initial onset of ALS symptoms may be so slight that they are frequently overlooked. Most symptoms develop later in adulthood, usually after the age of 50. However, they can occur in younger people. People who experience ALS have a loss of muscle strength and coordination that gradually gets worse. Muscle weakness may occur in hands, arms, legs or the muscles of speech, swallowing, or breathing. Often the early signs include twitching (fasiculations) and muscle cramps, especially in the hands and feet. These signs can vary significantly from person to person. Often times the symptoms begin with tripping or falling spells, others, however, may present with slurred speech or episodes of crying/laughing.
Muscle weakness is the hallmark sign in ALS, occurring in approximately 60% of patients. Hands and feet maybe affected first. Noted signs of weakness such as difficulty lifting items, buttoning clothes, or walking are common signs. As the disease begins to worsen, it spreads to the trunk muscles of the body. This leads to dysfunction or weakening of speech, swallowing, chewing, and breathing. When breathing muscles become affected the patient will require permanent ventilatory support to survive. These signs represent the end stage of the disease process.
The health care provider will take a medical history and physical exam. The physical exam will usually include an extensive strength and endurance exam. This will assess the patient’s degree of muscle weakness throughout the body. This may show weakness beginning in a particular area, muscle tremors, spasms, twitching, or atrophy. A patient with ALS may even present with an abnormal gait (they may walk stiff or clumsily). Reflexes are often abnormal in that they will be increased at the joint and reduced in the gag reflex. Some patients may have trouble controlling episodes of crying or laughing often termed “emotional incontinence.”
Blood tests may be used to rule out other conditions that lead to muscle weakness. MRI or CT scans may be required to rule out other diseases or injury to the neck which can often mimic ALS symptoms. Electromyelography (EMG) will help to determine which nerves are being affected by the disease. Additional swallowing studies and pulmonary function tests may assist in diagnosis and treatment protocols. Genetic testing is commonly suggested by the physician if there is a family history of ALS or to obtain information for current nerve studies.
Unfortunately, scientists are unaware of what causes ALS and the disease currently cannot be cured. Even though physicians can not reverse the progression and symptoms of ALS, there have been considerable medical advances which extend and improve the life of patients with this disease. Neurologists trained in neuromuscular conditions and other healthcare specialists work as a team to care for patients with this complex condition. Often this treatment is focused on relieving symptoms and maintaining good quality-of-life. Therapy may differ from person to person and modifications to the treatment plan may often be changed with progression of the disease.
Physical therapy is very important to help patients relieve cramping and muscular pain. Passive stretches and daily movement help prevent permanent contraction of muscles. If muscles become contracted they may cause joint problems and develop permanent stiffness. Other therapies, such as speech, may help the patient work mouth and swallowing muscles to extend their function. Some drugs such as riluzole may be prescribed to extend life expectancy by reducing damage to motor neurons. This treatment may not be for every patient, but it has been approved by the FDA for the treatment of ALS. Other drugs such as baclofen (Lioresol®) or tizanadine (Zanaflex®) are used to relieve spasticity. Several drug combinations may be tried by the healthcare team and changes the disease progresses. However, none of these treatment options are a cure for ALS and are only effective at slowing disease progression and prolonging life.
Ashley Loan and Justin F. Fraser, MD