Acute Neuromuscular Weakness - Causes and Treatment

Introduction

The functioning of the muscles in the human body is controlled through the stimulation of their activity by motor nerves. A motor nerve carries signals from the central nervous system (the brain and spinal cord) toward the muscles to facilitate muscular movements like lengthening, shortening, or tightening while performing an activity. Any disturbances in the signal transmission of nerves by nerve or muscle disease may lead to the weakening of muscles. Weakness of the muscles may progress into loss of functioning of the muscles.

What Is Acute Neuromuscular Weakness?

Acute neuromuscular weakness is a disorder that involves the sudden weakening of muscles that may progress and becomes severe within several days to weeks. The bulbar muscles (muscles of the head and neck) and respiratory muscles (muscles used in pumping air in and out of the lungs) are rarely involved. Muscle weakness may be localized, affecting a few muscles, or generalized, affecting many muscles. If generalized muscle weakness affects the respiratory muscles, respiratory failure may occur, which may be more critical than lung disease. This is because even though the development of respiratory muscle weakness may be gradual, it is followed by sudden failure of the respiratory system leading to life-threatening decreased oxygen levels in the body tissues.

What Are the Causes of Acute Neuromuscular Weakness?

Acute neuromuscular weakness occurs due to disturbances in the pathway of motor nerves. The two major factors causing acute neuromuscular weakness are as follows:

• Myasthenia Gravis: Myasthenia gravis is a disease characterized by weakness and sudden fatigue of the skeletal muscles (muscles that are connected to the bones and are under voluntary control). Muscle weakness becomes severe after periods of activity and improves following periods of rest. It occurs as a result of disruption in the communication between nerves and muscles. The commonly affected muscles are the muscles that control movements of the eye, facial expressions, talking, and swallowing. Muscles that are responsible for breathing and movement of limbs (arms and legs) may also be affected.

• Guillain-Barre Syndrome: Guillain-Barre syndrome is a disorder in which the peripheral nervous system is attacked by the body’s immune system. The peripheral nervous system consists of a network of nerves that lie outside the brain and spinal cord. Guillain-Barre syndrome begins initially with weakness of arms and legs, which may eventually lead to paralysis of the whole body and inability to breathe independently.

What Are the Symptoms of Acute Neuromuscular Weakness?

The common symptoms observed in acute neuromuscular weakness are as follows:

• Difficulty in movement.

• Numbness or tingling sensation.

• Loss of balance.

• Weakness of muscles that may lead to cramps, twitching, and pain.

• Difficulty in swallowing.

• Lack of coordination.

• Difficulty in breathing.

• Drooping of eyelids.

• Difficulty in smiling and forming facial expressions.

• Double vision (feeling of viewing two images of a single object).

• Fatigue (feeling of tiredness).

• Weakness of neck muscles that leads to difficulty in holding the head up.

How Is Acute Neuromuscular Weakness Diagnosed?

There is no definitive test to diagnose acute neuromuscular weakness. However, the following methods help in diagnosing acute neuromuscular weakness.

• Physical Examination and Medical History: The doctor takes a detailed history of the symptoms experienced by the patient. The doctor also collects information about the pre-existing medical problems and medications of the patient. The doctor enquires about the onset and severity of the symptoms. The doctor also checks for the ability of the patient to perform activities like climbing stairs, speaking, rising from a chair, and walking.

• Blood Tests: Blood tests are done in patients with neuromuscular weakness to detect the presence of certain antibodies and enzymes which are released into the bloodstream when there is an abnormality in the functioning of muscle cells. A complete blood test helps to rule out the possibility of other disorders and infections that might have similar symptoms.

• Computed Tomography (CT) Scans and Magnetic Resonance Imaging (MRI): Computed tomography is an imaging test that uses X-rays and a computer to create detailed images of the organs and tissues present in the body. Magnetic resonance imaging is a test that uses a computer, radio waves, and magnetic fields to obtain three-dimensional images of the body tissues. Both these imaging tests are carried out to examine the abnormalities in the nerves and other structures associated with muscle weakness.

• Electromyography: Electromyography is a procedure that is used to evaluate the health of muscles and nerve cells that control the functioning of muscles. During this procedure, a needle electrode is directly inserted into the muscle to record the electrical activity of the muscle. Electrode stickers placed on the skin surface help detect the strength and speed of signals transmitted through nerves. Electromyography helps in finding out the problems like muscle dysfunction, nerve dysfunction, or nerve-to-muscle signal transmission.

How Is Acute Neuromuscular Weakness Treated?

There is no definitive treatment for acute neuromuscular weakness. The treatment measures of acute neuromuscular weakness vary depending upon the severity of symptoms. The methods employed in treating acute neuromuscular weakness are as follows:

• Physical Therapy: Physical therapy involves the evaluation and treatment of abnormal functions and movements of the body by a therapist. The exercises and massages suggested by the therapist help the patient strengthen the muscles and prevent muscle weakness. It helps in improving the difficulties associated with movements like walking and maintaining balance.

• Occupational Therapy: Occupational therapy mainly focuses on making the patient capable of performing the day-to-day activities like eating, buttoning the shirt, and climbing stairs. Occupational therapists help patients mentally adapt to their disabilities. The therapists recommend exercises and assistive devices that help strengthen the body and perform daily activities.

• Medications: Medications may be prescribed to those patients who have severe pain. As most cases of acute neuromuscular weakness are autoimmune (the body’s immune system cannot differentiate between the normal and foreign cells thereby attacking its healthy cells) in nature, medications to suppress the immune system are also given.

• Mechanical Ventilation: Mechanical ventilation is advised for patients who have difficulty breathing due to the weakness of respiratory muscles. A mechanical ventilator keeps the airway open and delivers oxygen until the patient can breathe without the ventilator.

Conclusion

Acute muscular weakness is a serious condition that may affect the movement and day-to-day life activities of the person. If left untreated, the condition may lead to respiratory muscle weakness which can cause difficulties in breathing. Hence identifying the symptoms at an early stage and prompt treatment by a doctor in combination with physical and occupational therapies would help the patient lead a normal life.