Sunday, October 12, 2008

Raising Awareness of ALS

Brief Overview of Amoyotropic Lateral Sclerosis

Also known as "Lou Gehrig's Disease," it is a fatal neurodegenerative disease that causes nerve cells in the brain and spinal cord to degenerate.

Patients affected with this disorder progressively lose their ability to control voluntary muscles, and in the later stages, become completely paralyzed. For most people, the muscles start to atrophy from their arms or legs, so there is difficulty performing everyday activities. Muscle atrophy causes the limbs to become thin and weak. The senses are not affected since this disease only attacks motor neurons, and there has been no proven effect on cognition. In later stages, paralysis spreads to the muscles affecting swallowing and breathing, eventually leading to death. 1

It still has not been found what the definitive cause of ALS is, and there is currently no cure.

Some factors researches suspect can be a cause of ALS are viruses, neurotoxins, DNA defects, immune system and enzyme abnormalities. There have also been links to patients who were exposed to heavy metal for prolonged periods of time.2
Nothing has been found to reverse the effects of ALS, but there has been one federally approved drug (Riluzole)
that can slow down the progression.

How bioelectricity helps us diagnose and understand ALS

  • Detecting that a neuromuscular disease is Amyotrophic Lateral Sclerosis is hard, since many of its symptoms are found in other disorders. It is sometimes confused with Multiple Sclerosis, since both are neurological diseases usually affected the spinal cord. As mentioned in class, MS is a disease of myelin, not primarily of nerve cells. However, the principle characteristic in the pathology of ALS is loss of motor nerve cells. There is loss of large myelinated axons, but this is consequent to the loss of motorneurons, as compared to primary demyelination in MS.
  • The Normal Diagnosis-Nerve conduction velocity (NCV) and electromyography (EMG) helps to diagnoses these disorders. With NCV, electrodes are placed on the skin over a nerve supplying a specific muscle. An electrical stimulus goes through the electrodes and the response of the muscle is measured and amplified. With ALS, the speed of the nerves is usually slowed, but compound muscle action potentials decreased. EMG measures the nerve impulses by placing electrodes in the muscles and observing electrical responses. Tracking of the electrical signals show that these responses are abnormal in cases of ALS.3
  • But... As I mentioned earlier in this post, the senses are not affected. It is common to find normal sensory potentials, however a recent study (Mar. 4, 2008) showed that 6 patients had a reduced sensory nerve action potential (SNAP) amplitude or reduced conduction velocity (CV) or both. This first standardised multicentre study on sensory potentials show that mild sensory abnormalities should possibly be part of the diagnosis of ALS.
  • What we know so far- ALS Mice with mutated human gene SOD1 - To test electrophysiological properties of motorneurons in mice, a wide range of electrical properties influencing motorneruon excitability was measured during current clamp. There weren't any differences in the resting potential, input conductance, action potential shape, or afterhyperpolarization between mutated genes and control motoneurons. The relationship between firing frequency and injected current was changed, and the slope of the relation was much greater. This shows that the hyperexcitability observed is induced by an aberration in the process of generating an action potential.7
This study shows that motor neurons with this mutant SOD1 will survive when implanted with a minimum number of cells surrounded by glial cells and normal SOD1. Gene or stem cell therapy implanting these cells may be a way to repair motorneurons in the spinal cord. But there is still the question if muscles are doing part of the destruction.

HOPE for a cure!
For those who read until the end, sorry I had not intended for this post to be lengthy. I just want to shed some light on a rare disease that affects only one to two people out of 100,000, so you can imagine the difficult fight for the ALS community to raise funding for research. Especially in America, patients who are diagnosed with ALS are told by their doctors to live the years they have left and are discouraged from trying to stop the disease. But, families never want to give up on their loved ones and are always fighting for a way. I strongly believe one day we will find a cure, and in fact just recently we have hit two big milestones in ALS history. On October 2, 2008, a $5 Million ALS Research Bill was signed by President Bush, which will fund ALS reserachers across the country. The ALS Registry Act was also signed on Wednesday, October 8, which will establish the first national patient registry of people with ALS. This gives us a new tool and hopes that one day a cure will be found.

Clinical Neurophysiology , Volume 119 , Issue 5 , Pages 1106 - 1110
[5] Andrew Eisen, Charles Krieger.
Amyotrophic Lateral Sclerosis: A Synthesis of Research and Clinical Practice. Cambridge University Press.1998


ninatandon said...

hi Sherry,

thanks so much for posting this! I wanted to share a couple of things:

(1) We will be covering electromyography (EMG) later in this class, so stay tuned!

(2) There is a researcher at Harvard (Kevin Eggan) who recently developed an embyonic stem cell-based ALS model, which is really interesting. They haven't yet electrically stimulated these cells, but, hey, maybe you could help them with that (he's really nice I just met him last week, hehehe).

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