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Neuromyotonia is a rare type of nerve disorder that causes excessive, uncontrollable muscle activity. Symptoms can include frequent muscle twitches, stiffness, cramps, and poor reflexes. Most people with the condition experience problems in their arms and legs, though other muscle groups in the torso, neck, or head may also be affected. Research on the causes of neuromyotonia is limited because it is such an uncommon finding, and doctors have not yet discovered a reliable cure for the disorder. The majority of patients are able to experience long-term symptom relief with antiepileptic medications.
Abnormal nerve functioning can have many different causes. Most cases of chronic neuromyotonia appear to be related to an autoimmune disorder in which the protective sheaths around nerve cells become inflamed and damaged. Environmental factors such as exposure to toxic substances and heavy metals can result in sudden neuromyotonia symptoms. Cancer patients with lymphomas or lung tumors are at an increased risk of developing symptoms, though the connection between certain cancers and nerve cell damage are not well understood. Finally, a small number of people who develop neuromyotonia have family histories of the disease, suggesting that genetic factors may be involved.
Symptoms develop when nerve cells fire more rapidly than normal, triggering muscles to contract and tighten. Muscles in the legs, arms, or elsewhere may spontaneously jerk, tremor, or become very stiff. People with neuromyotonia often feel weak and fatigued, and they may have trouble engaging in certain physical activities that require a great deal of movement and fine muscle control. If the face is affected, a person can experience occasional or constant difficulties speaking, chewing food, and swallowing. Additional health problems can also exist, depending on the underlying cause.
Neuromyotonia can be difficult to diagnose because of its rarity. Patients who have muscle tremors are usually scheduled for a series of tests to determine the severity of their problems and to look for possible causes. Electromyography, a painless exam that involves placing electrodes on different parts of the body, can be extremely helpful in pinpointing and quantifying nerve abnormalities. Blood samples also are taken to check for toxins and unusual antibodies that may suggest an autoimmune condition. In addition, computerized tomography scans are useful in screening for tumors and gauging the extent of nerve sheath inflammation.
The most common treatment for mild to moderate neuromyotonia is a daily regimen of antiseizure drugs such as carbamazepine. Such medications depress nervous system activity and allow muscles to relax. Patients with severe symptoms and known autoimmune involvement may be candidates for blood plasma transfusions. Other treatment options may include botulinum toxin injections in particularly active muscles and physical therapy to help patients remain mobile despite their disabilities.