Before jumping onto the different forms of motor neuron disease let’s have a small review of what is motor neuron disease? It is a group of different conditions that affect the nerves located in the brain and spine that starts losing their function over time. These are the rare neurodegenerative conditions that affect the motor neurons. Motor neurons are the type of cells that send the electrical impulses to the muscles to function properly. These diseases can appear at any age but the symptoms are more commonly seen at the age of 40-45 years. The disease is more common in men when compared to women.
Some people suffer from the severe symptoms of motor neuron disease which are usually widespread. However, in some conditions, the disease initially affects the single-limb, especially it’s motor function which then progresses faster to become a generalized disease. Motor neuron disease usually results in wasting or weakness of the muscles leading to twitching or fasciculation which is visible underneath the skin. Motor neuron disease can affect both upper and lower motor neurons. If the upper motor neurons are affected, it results in muscle stiffness while the involvement of lower motor neurons results in fasciculation. Initially, any of these neurons are involved but as the disease progresses it involved both the neurons. The motor neuron disease is divided into different forms which are classified on the types of neurons involved and the body part where these symptoms begin.
PROGRESSIVE BULBAR PALSY: In this motor neuron disease, both lower, as well as upper motor neuron lesions, are affected. It results in the wasting and weakness of the swallowing and speech muscles. The nerves which are designated for these functions are present in the lower portion of the brain which is the bulb due to which this paralysis is known as progressive bulbar palsy. In the later stages, limb muscles are also involved.
AMYOTROPHIC LATERAL SCLEROSIS OR LOU GEHRIG’S DISEASE: in this motor neuron disease both upper and lower motor neurons are affected leading to the wasting and weakness of limb muscles. It is one of the most common types of motor neuron disease which results in stiffness or muscle weakness with over-active reflexes. Some patients with this disease might also experience emotional changes. In initial stages, the limbs stop working and in later stages the muscles involved in swallowing, speech and breathing are affected. In many parts of the world, motor neuron disease is also known by the term Amyotrophic lateral sclerosis. It affects around 30,000 Americans with 5600 diagnoses each year.
PRIMARY LATERAL SCLEROSIS: This type of motor neuron disease mainly affects the upper motor neurons. It is a very rare form of the disease which is provisionally diagnosed.
PROGRESSIVE MUSCULAR ATROPHY: This form of motor neuron disease mainly affects the lower motor neurons. This form of the disease progresses at a slower rate with a longer survival rate when compared to other types of motor neuron disease. It is characterized by generalized muscle weakness and wasting of the muscles, absent reflexes, weight loss along with muscle twitching. This disease is quite hard to diagnose as most of the people with this disease eventually develop the signs associated with upper motor neuron lesions.
SPINAL MUSCULAR ATROPHY: Spinal muscular atrophy is the inherited form of motor neuron disease which mainly affects children. It occurs due to genetic change in SMA1. The disease affects the legs, arms and trunk muscles.
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Team Doctor ASKY!