Amyotrophic lateral sclerosis or ALS describes a neurological disease of the neurons in the nervous system. Motor neurons that are responsible for muscle movement begin to degenerate and die. This damage causes severe muscle weakness and eventually causes total paralysis. Currently there are no definitive causes of ALS; however, scientists have isolated several links that may lead to possible causes.
Free Radicals
The Muscular Dystrophy Association describes free radicals as molecules with electrical charges that damage cells through a chemical process called oxidation. It's thought that in the case of ALS, these free radicals accumulate to toxic levels causing damage to the motor neurons of the nervous system.
Genetics
Dr. Carmel Armon, a neurology professor at Tuft University School of Medicine, states that 5 to 10 percent of ALS cases run in families. This type of ALS is commonly called familial ALS.
Scientists have found that a mutation of the gene that creates the enzyme SOD1 shows up in patients with familial ALS. How SOD1 causes damage to motor neurons remains unknown, reports the National Institute of Health.
Excess Glutamate and Toxins
The National Institute of Health reports that patients with ALS have higher levels of glutamate in their blood and spinal fluid. Glutamate is a chemical within the nervous system that neurons use to send messages. Higher than normal levels of glutamate cause neuron death.
Heavy metals such as lead and mercury are also currently being studied for a possible link to ALS.
Cell Defects
Several abnormalities in cells may play a part in the destruction of motor neurons in ALS. Defects of mitochondria or neurofilaments within the nerve cells are a suspected cause of ALS.
Dr. Armon also reports the possibility that ALS nerve cells go through a process of cell death called apoptosis.
Autoimmune and Viral Disorders
Another theory on the cause of ALS consists of autoimmune disease. An autoimmune disorder occurs when the body's immune system sees normal cells as foreign and attacks them. It is thought that antibodies attack the motor neurons in the nervous system causing ALS symptoms.
Viral infections may also play a part in the cause of ALS.
Smoking
In 2009, Dr. Armon conducted a review of studies on risk factors for non-familial ALS. Separating good research from poor, she isolated four studies implicating smoking as a risk factor for developing ALS. One study provided results of a decreased risk of ALS based on the number of years after smoking ceased.
Like other environmental causes, smoking is now considered a risk factor for developing ALS.
