Definition and causes of Neuromuscular diseases

Neuromuscular diseases form a group of diseases that affect the communication between the brain and the muscles. There are several subgroups depending on which parts are affected. These subgroups are:

• Motor Neurone Disease (MND): The root of the disease is found in the nerve cells in the spinal cord which transmits signals from the brain to the muscles (the motor neurone). Most diseases in this group are hereditary caused by a defect in the gene, which maintains the motor neurone. As a result the motor neurone is destroyed and the muscles controlled become paralysed. Under motor neurone disorders falls ALS (Amyotrophic Lateral Sclerosis), a number of hereditary spinal muscle atrophy diseases for example Kennedy's disease. Also Polio might lead to motor neurone disorder.
• Nerve Inflammation: Here it is usually nerve cell ends (axons), where the probelm is. Nerve signals cannot be transmitted from the brain to the muscles.
• Diseases of the neuromuscular transmission system: Here the disease is a disorder in the transition from nerve cell ends and muscles. The most common form is myasthenia gravis. Similar reactions are found in poisoning with botulinum toxin (sausage poison) or by some types of snake bites.
• Muscle Disease: Here the disease is in the muscle itself, which cannot respond to nerve signals. This group of diseases are also known as muscular dystrophy (includes in particular Duchenne Muscular Dystrophy), and stems from hereditary defects in parts of the muscle. The fact that this disorder falls under neuromuscular diseases, although the disease only connected with the muscle, is because the symptoms are similar, the diagnosis the same determined by the same methods and because the treatment is almost the same.

Symptoms of neuromuscular diseases

• Reduction in muscle strength: This may affect all the muscles in your body or be mostly pronounced in the arms or legs. In the most serious cases the breathing muscle (diaphragm) is also affected and there may be problems with breathing itself.
• Muscle atrophy: The muscle mass is reduced from inactivity.
• Spasticity: The core muscle is increased, leading to a constant spasmodic contraction of the muscle.
• Changed reflexes: When using a reflex hammer on for example the knee stretch tendon the reflex may be too weak or too lively.
• Changed body posture: This might stem from weakness in the muscles keeping the person upright.
• Accelerated muscle fatigue: Children born with a neuromuscular disease, for example Duchenne muscular dystrophy, may be delayed or lack the ability to crawl and walk. There might also be abnormal movement patterns. Often, there will be others in the family who have, or have had, similar symptoms.

Complications of the neuromuscular diseases

There are complications connected with neuromuscular disorders as muscles and the surrounding connective tissue contract and result in wrong alignment of the connected joints. This might lead to severe pain and physical debilitation. In the worst cases it impossible for the patient to sit normally and eventually the breathing is affected requiring respirator assistance.

Precautions and diagnosis

If you experience such symptoms you must consult your General Practitioner, who then can refer for further investigation. Depending on the type of suspected neuromuscular diseases various tests might be carried out to determine the problem.

• Blood test: By special analysis the blood can be examined for hereditary diseases. Moreover, the level of a particular enzyme, which comes from muscles, can be measured. This enzyme is called creatine kinase, and it might increase as a result of a neuromuscular disease. In myasthenia gravis antibodies can be found in connection with the muscle cell, which should receive nerve signals (the acetylcolinreceptor).
• Electromyography (EMG): This is a study of the electrical activity of a muscle at rest, by slight contraction and at maximum contraction.
• Determination of nerve cord speed: This is a test to determine the nerve cell endings ability to transmit the nervous signal.
• Muscle Biopsy: This is a muscle tissue microscope test to determine if the muscle tissue structure is normal.
• It may be decided to perform a CT or MRI scan of the brain to eliminate the possibility of disorders there.

Treatment of neuromuscular diseases

For most types of neuromuscular diseases, there is no treatment that can cure the disease. However, there are some possibilities to relieve the symptoms.

• Physiotherapy: This is done both to maintain optimum muscle function and to avoid the progressing or permanent contractions of the muscles.
• Operation: If, for example, the back muscles are too weak to keep the body upright it is possible to insert a support in the back and it is possible to surgically correct malformations.
• Medicine: In myasthenia gravis medication might be prescribed, which increases the availability of nerve signals substance (acetylcholine). In addition, adrenal cortical hormones might be precribed.
• Equipment: Depending on the severity of the disease there might be the need for different appliances such as crutches, wheelchairs or respirator.

Outlook and progression of neuromuscular diseases

Most neuromuscular diseases mean life long suffering. In particular, the hereditary motor neuron diseases and muscular dystrophy can be difficult debilitating and lead to death at an early age. Other types of neuromuscular diseases will only be lightly debilitating with the person being almost fully functional and with no diminished life span.

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