By: Tony Wang
Imagine not being able to control how you chew your food. Imagine staring at your arms as they twitch erratically, unable to control them. Imagine growing weaker day by day, but not knowing why. As horrible as this may sound, it is, unfortunately, the reality for two in every 100,000 people. These two individuals have a condition that is known as Motor Neuron Disease (MND).
Now, you may be wondering what exactly MND is. Well, MND is a condition that can cause the neural cells that control movement to degrade; this, in turn, can disrupt the transfer of signals between the body’s lower and upper motor neurons. The disruption of these signals may cause muscles to stiffen, weaken, and uncontrollably twitch. It should be noted that MND is not one disease, rather, it is a whole category of neurodegenerative disorders. It includes various disorders within itself, several of which this article will go over in detail.
Interestingly, causes of MNDs are, for the most part, unknown; 85-90% of all MND cases are sporadically developed, with the remaining ones being familial. The most common MND is Amyotrophic Lateral Sclerosis (ALS), which affects more than 30,000 people at any given time in the US. 90% of all ALS cases are sporadic, though they are most likely to occur in men. In the other 10% of cases, which are familial, it has been documented that there are 15-disease causing genes. The most common defect occurs in a gene known as “chromosome 9 open reading frame 72” (C9ORF72). Most ALS patients experience stiffness and weakening of various muscles. One famous individual who had ALS was Stephen Hawking, a revolutionary physicist. Interestingly, Stephen Hawking defied all expectations surrounding his life expectancy following his diagnosis. Most people who have ALS are told that they may not survive for more than three to five years following their diagnosis. In rare cases, the patient may survive for 10 or more years. Stephen Hawking, however, survived for 55 years.
Another common MND is Spinal Muscular Atrophy (SMA), which is an inherited disease that is one of the most frequent causes of infant mortality. SMA is caused by a defect in the SMN1 gene, which results in decreased production of the SMN (Survival Motor Neuron) protein. The SMN protein plays roles in cellular trafficking and RNA development, which includes the transport and regulation of mitochondrial activity. When there is a decreased performance in this protein, the body’s muscles weaken due to lower motor neuron deterioration. SMA is a very serious disorder that is divided into 3 categories based on age, severity, and progression.
Unfortunately, there are no true cures for MNDs; there are only different medications that can slow the progression of the disease. Such drugs include Riluzole and Nusinersen, the former of which can increase a patient’s life span by about 10%. Riluzole allows for protection of the damaged motor neurons by reducing the release of glutamate and blocking the sodium ion channels.
As of now, the research being done on MND is very extensive, with private organizations and government organizations alike working to understand its complexities. For instance, the National Institute of Neurological Disorders and Stroke (NINDS) is currently researching antisense oligonucleotides as potential drugs. Stem cell research is also being done, as stem cells have the ability to transform into motor neurons. There’s also research being performed on autologous mesenchymal stem cells, which are cells made from a person’s own bone marrow and injected into their cerebrospinal fluid. For aspiring scientists and neurologists, MND will certainly be a principal region of research.
Citations:
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What Did You Learn?
Questions:
Is Progressive Bulbar Palsy an MND?
Yes, Progressive Bulbar Palsy (PBP), which is also known as Progressive Bulbar Atrophy, is an MND. PBP attacks lower motor neurons that are connected to the brain stem. It causes weakness in the bulbar muscles (as indicated by the name). This results in the inability to speak, chew, and swallow. Sometimes, the patients may choke on their own food and saliva due to the weakening muscles. They may also have random emotional changes, which known as the pseudobulbar effect.
How are MNDs diagnosed?
MNDs can be diagnosed via a variety of methods, one of which is electromyography. Electromyography is a process in which a recording instrument attached to a thin needle electrode is placed in the patient’s muscle. The instrument then records electrical activity. If there are abnormal electrical signals, it means that there has been damage in the motor neurons. Another method is nerve conduction study: This study is often done in conjunction with electromyography. Small jolts of electricity are sent through the patient’s skin using tiny electrodes. The electrical signals received can be read using a recording machine. Once this has been done, by using the nerve conduction study, one can assess whether there are any abnormalities in sensory nerves.
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