Neuromyotonia (Isaacs syndrome)

Isaacs syndrome – also known as neuromyotonia – is a very rare, chronic neuromuscular condition known for causing continuous muscle spasms. Like many rare diseases, there’s a lot we have yet to learn about it.

Isaacs syndrome is also known as:

• Isaac’s syndrome
• Isaacs’ syndrome
• Isaacs-Mertens syndrome
• Continuous muscle fiber activity syndrome
• Quantal squander syndrome

Isaacs syndrome symptoms

The main Isaacs syndrome symptoms are progressive muscle stiffness and continuously contracting or twitching muscles (myokymia). The muscle twitching is sometimes described as moving like a bag of worms. Other Isaacs syndrome symptoms are:

• Muscle cramping or spasms
• Increased sweating
• Diminished reflexes
• Weight loss
• Increased size of calf muscles
• Rapid heartbeat (bradycardia)

Along with muscle contractions, people also experience delayed muscle relaxation. When someone with Isaacs syndrome clenches their fist and then tries to relax their hand, it may take longer than expected for the muscles to relax. These abnormal muscle reactions make many everyday activities like walking difficult.

In some people, breathing and speech may be affected.

With Isaacs syndrome, muscle contractions continue during sleep or while a person is receiving anesthesia.

Symptoms of Isaacs syndrome may start at any age. However, most symptoms start between ages 15-60.

 

Causes of Isaacs syndrome

The exact cause of neuromyotonia is unknown. Some cases of Isaacs syndrome are inherited from parents. Other cases are acquired and seem to come from an autoimmune condition.

In almost half the people who have Isaacs syndrome, specific antibodies attack a certain part of a peripheral nerve. When nerves are damaged, they send abnormal messages to muscles. Evidence points to the likelihood of there being other antibodies involved that haven’t been identified yet.

Neuromyotonia sometimes occurs in people with other conditions such as myasthenia gravis, cancer, peripheral neuropathies, celiac disease and thymomas (tumors of the thymus gland).

 

Diagnosis of Isaacs syndrome

Diagnosis of neuromyotonia depends on careful evaluation of your potential symptoms of Isaacs syndrome and results of electromyography (EMG) testing. Since the symptoms of Isaacs syndrome overlap with other neuromuscular disorders such as ALS, those other conditions need to be ruled out for an accurate diagnosis.

 

Treatments for Isaacs syndrome

The main treatment for Isaacs syndrome is the use of anticonvulsants – medicines that stop involuntary muscle contractions. In some cases, these medications may be combined with oral corticosteroids or other medications.

For people who have a thymoma, surgery to remove the tumor may be recommended.

Isaacs syndrome treatments with blood products

Your doctor may recommend treatment with blood products for short-term relief from Isaacs syndrome symptoms.

• Blood plasma exchange: Apheresis machine is used to filter the plasma from your blood and replace it with donated plasma.
• Intravenous immune globulin (IVIG) infusion: Immunoglobulins (antibodies) are separated from donated plasma and injected into your bloodstream.

Treatments with blood products take several hours to complete and are usually provided as outpatient procedures.

Clinical trials & Isaacs syndrome

Research projects about Isaacs syndrome are searching for more information about causes and treatments for this rare disease. If you’re interested in participating in clinical trials, be sure to mention it to your health care team.