Neuromuscular disorders are acquired or inherited (genetic) conditions that affect some part of the neuromuscular system. Neuromuscular disorders tend to be progressive in nature, and result in muscle weakness and fatigue. Some neuromuscular disorders are present at birth, some manifest in childhood, and others have an adult onset. The disease may be genetically passed down or due to a spontaneous genetic mutation, may be due to an abnormal immune response, inflammation, poisoning, toxins or tumors. Some neuromuscular disorders simply have no known cause.
Neuromuscular disorders can be categorized as:
- muscular dystrophies – involving the structure of the muscle cells
- peripheral motor neuron diseases – involving muscle-controlling nerve cells of the arms, legs, neck and face
- motor neuron diseases – involving nerve cells in the spinal cord
- neuromuscular junction diseases – involving the site where nerves and muscles meet
- myopathies – involving tone and contraction of muscles controlling voluntary movements; may include inflammation of muscles or related tissues
- metabolic diseases of the muscle – involving errors in metabolism in producing energy in muscle cells
Signs and symptoms of neuromuscular disorders
Symptoms of muscle disease may include muscular weakness, rigidity, loss of muscular control, numbness, tingling, twitching, spasms, muscle pain and certain types of limb pain.
Although muscle wasting is not painful, the resulting weakness can cause cramping, stiffness, joint deformities, chronic aches and pain, and sometimes the tightening and freezing of joints, which is known as contracture.
Diagnosing neuromuscular disorders
Diagnosing a neuromuscular disorder starts with direct clinical observation, which can identify atrophy or loss of muscle bulk and/or tone. Blood tests can determine abnormal levels of various chemicals and antigens in the blood common in certain neuromuscular diseases.
Electromyography, commonly referred to as EMG, can assess the health of muscles and motor neuron nerve cells that control those muscles. EMG results are used to help diagnose or rule out a number of neuromuscular disorders.
Treating neuromuscular disorders
There is no cure for most neuromuscular disorders, but some can be effectively managed and treated. Some common interventions include:
Drug therapy – Immunosuppressive drugs can treat certain muscle and nerve diseases and diseases of the nerve-muscle junctions. Anticonvulsants and antidepressants may be used to treat the pain of neuropathy.
Referrals to appropriate specialists – Patients may receive referrals to surgeons for neurological surgery, thoracic surgery, orthopedic surgery or other types of surgery. They may also be referred to physical, occupational, speech or rehabilitation specialists; physiatrists; pulmonary medicine specialists; or ophthalmologists.
Patient and family education and counseling – In addition to individual and family sessions, treatment may include referral to appropriate support groups or genetic counselors. Further testing – Various specialists, such as physical therapists and nutritionists, may evaluate patients as needed.