What Is Muscle Weakness? What Conditions Can Cause It?

Muscle weakness, commonly seen in many neurological conditions such as multiple sclerosis, stroke, muscle diseases, and polyneuropathies, can occur anywhere in the body. The first step in effectively managing weakness is determining the cause of your condition.

Weakness can also result from disuse of muscles or from intrinsic muscle diseases and cellular abnormalities within the muscle. In many cases, a person's general activity level decreases due to fatigue, pain, imbalance, or other symptoms.

In myopathies (muscle diseases), weakness, wasting, and sometimes pain or cramps occur in muscles due to disease of the muscle fibers themselves. These muscle disorders can be inherited (familial) or acquired due to external factors.

Although the abnormality causing hereditary muscle diseases is present from birth, the age of symptom onset varies; some individuals show signs from birth while others manifest later in life. Being knowledgeable about muscle disease and inheritance patterns in the family is important for preventing the birth of new affected children, anticipating problems that affected individuals may face and taking preventive measures when possible, and avoiding consanguineous marriages. There is no cure for hereditary muscle diseases.

Diagnosis of muscle diseases is made after examination by a specialist physician followed by necessary investigations. These include blood tests measuring muscle enzymes (particularly creatine kinase), electromyography that demonstrates whether muscles and nerves are functioning properly, genetic testing when possible, and muscle biopsy when needed.