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 antiseizure drugs carbamazepine or phenytoin can relieve symptoms, and some people benefit from immune globulin or plasma exchange.
(See also Overview of the Peripheral Nervous System Overview of the Peripheral Nervous System The peripheral nervous system refers to the parts of the nervous system that are outside the central nervous system, that is, those outside the brain and spinal cord. Thus, the peripheral nervous... read more .)
Isaacs syndrome is rare. It appears to start in the peripheral nerves Overview of the Peripheral Nervous System The peripheral nervous system refers to the parts of the nervous system that are outside the central nervous system, that is, those outside the brain and spinal cord. Thus, the peripheral nervous... read more and 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 Myasthenia Gravis Myasthenia gravis is an autoimmune disorder that impairs communication between nerves and muscles, resulting in episodes of muscle weakness. Myasthenia gravis results from malfunction of the... read more , thymomas (tumors of the thymus gland), Hashimoto thyroiditis Hashimoto Thyroiditis Hashimoto thyroiditis is chronic, autoimmune inflammation of the thyroid gland. Hashimoto thyroiditis results when antibodies in the body attacks the cells of the thyroid gland—an autoimmune... read more , vitamin B12 deficiency Vitamin B12 Deficiency Vitamin B12 deficiency can occur in vegans who do not take supplements or as a result of an absorption disorder. Anemia develops, causing paleness, weakness, fatigue, and, if severe, shortness... read more , celiac disease Celiac Disease Celiac disease is a hereditary intolerance to gluten (a protein found in wheat, barley, and rye) that causes characteristic changes in the lining of the small intestine, resulting in malabsorption... read more 
, and connective tissue disorders Autoimmune Disorders of Connective Tissue . 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 Electromyography and Nerve Conduction Studies Diagnostic procedures may be needed to confirm a diagnosis suggested by the medical history and neurologic examination. Imaging tests commonly used to diagnose nervous system (neurologic) disorders... read more 
, which show characteristic abnormalities.
Treatment of Isaacs Syndrome
Carbamazepine or phenytoin (antiseizure drugs)
Immune globulin and plasma exchange
Symptoms of Isaacs syndrome can be relieved by antiseizure drugs Antiseizure drugs In seizure disorders, the brain's electrical activity is periodically disturbed, resulting in some degree of temporary brain dysfunction. Many people have unusual sensations just before a seizure... read more such as carbamazepine or phenytoin.
People may also benefit from immune globulin (a solution containing many different antibodies collected from a group of donors), given by vein (intravenously), or plasma exchange Plateletpheresis (platelet donation) In addition to normal blood donation and transfusion, special procedures are sometimes used. In plateletpheresis, a donor gives only platelets rather than whole blood. Whole blood is drawn from... read more (filtering of toxic substances, including abnormal antibodies, from the blood).
