12/28/2012
Amyotrophic Lateral Sclerosis
Amyotrophic lateral sclerosis (ALS) is more commonly known as “Lou Gehrig’s disease”. ALS is a neurodegenerative disease which destroys upper and lower motor neurons in the brain stem, primary motor cortex, corticospinal tracts and spinal cord. Once the motor neurons die, the brain can no longer send messages to muscle fibers that would normally result in movement. “Amyotrophic” refers to the muscle atrophy and weakness which are results of the disease attacking lower motor neurons (Rowland par. 3). “Lateral sclerosis” refers to the hardness of the lateral columns of the spinal cords in autopsy specimens, where gliosis follows degeneration of the corticospinal tracts (Rowland par. 3).
Early signs of the disease depend on the site where the disease has first affected. One muscle group may show signs of ALS before another group. First signs and symptoms may be characterized by twitching, muscle weakness, muscle cramping, and loss of coordination. Most people with ALS experience the disease as a “limb onset” where symptoms first appear in the arms or legs. Fewer people have a “bulbar onset” where the person experiences difficulty speaking or swallowing. A very small amount of people with ALS experience a “respiratory onset” where the intercostal muscles that support breathing are affected first. ALS does not affect the senses and only rarely affects bladder or bowel movement.
In Western countries, the incidence of ALS is estimated to be an average of 1.89 per 100,000/year and the prevalence is estimated to be an average of 5.2 per 100,000 and has a higher frequency in the Western Pacific (Wijesekera par. 1). According to one source, the mean age of people with ALS is 60 years and there is a slightly higher prevalence in males (Wijesekera par. 1). The average onset age is generally about 50 years old but it can develop at younger ages. The disease progression is usually slower if the onset of the disease was prior to...
