(Isaacs' Syndrome; Neuromyotonia)
Isaacs syndrome involves overstimulation of the nerves that stimulate muscle fibers. It causes progressive muscle stiffness, continuous muscle quivering and twitching and cramping.
In people with Isaacs syndrome, muscles, particularly those in the arms and legs, continually quiver and twitch, moving like a bag of worms, and often become progressively stiffer.
Doctors diagnose Isaacs syndrome based on symptoms and results of electromyography and nerve conduction studies.
The anticonvulsants carbamazepine or phenytoin can relieve symptoms, and some people benefit from immune globulin or plasma exchange.
Isaacs syndrome is rare and appears to be caused by an antibody that attacks a specific part of the cell membrane. Isaacs syndrome may occur in people with other disorders, such as cancer, myasthenia gravis, thymomas (a tumor of the thymus gland), Hashimoto thyroiditis, vitamin B12 deficiency, celiac disease, and connective tissue disorders. It can also be inherited.
Muscles, particularly those in the arms and legs, continually quiver and twitch, moving like a bag of worms. This symptom is called myokymia. Spasms and cramps may intermittently occur in the hands and feet. Muscles often become progressively stiffer and take a long time to relax after they have been contracted. Sweating may be increased.
The diagnosis of Isaacs syndrome is based on symptoms and results of electromyography and nerve conductions studies, which show characteristic abnormalities.
Symptoms of Isaacs syndrome can be relieved by the anticonvulsants carbamazepine or phenytoin.
People may also benefit from immune globulin (a solution containing many different antibodies collected from a group of donors), given intravenously, or plasma exchange (filtering of toxic substances, including abnormal antibodies, from the blood).