Neuromyotonia (NMT), also known as Isaacs' syndrome, is a form of peripheral nerve hyperexcitability that causes spontaneous muscular activity resulting from repetitive motor unit action potentials of peripheral origin.
The three causes of NMT are: 1) Acquired 2) Paraneoplastic 3) Hereditary
The acquired form is the most common accounting for up to 80 percent of all cases and is suspected to be autoimmune mediated, which is usually caused by antibodies against neuromuscular junction.
The exact cause is unknown. However, autoreactive antibodies can be detected in a variety of peripheral (e.g. myasthenia gravis, Lambert-Eaton myasthenic syndrome) and central nervous system (e.g. paraneoplastic cerebellar degeneration, paraneoplastic limbic encephalitis) disorders. Their causative role has been established in some of these diseases but not all. Neuromyotonia is considered to be one of these with accumulating evidence for autoimmune origin over the last few years. Some neuromyotonia cases do not only improve after plasma exchange but they may also have antibodies in their serum samples against voltage-gated potassium channels. Moreover, these antibodies have been demonstrated to reduce potassium channel function in neuronal cell lines.
NMT is a diverse disorder. As a result of muscular hyperactivity patients may present with muscle cramps, stiffness, myotonia-like symptoms (slow relaxation), hyperhidrosis (excessive sweating), myokymia (quivering of a muscle), fasciculations (muscle twitching), fatigue, exercise intolerance and other related symptoms. The symptoms (especially the stiffness and fasciculations) are most prominent in the calves, legs, trunk, and sometimes the face and neck, but can also affect other body parts. NMT symptoms may fluctuate is severity and frequency. Symptoms range from mere inconvenience to debilitating (rare).
There are three main types of NMT: 1) Chronic 2) Monophasic (symptoms that resolve within several years of onset; postinfection, postallergic) 3) Relapsing Remitting
Diagnosis is clinical and initially consists of ruling out more common conditions, disorders, and diseases, and usually begins at the general practitioner level (your primary doctor). You doctor may conduct a basic neurological exam, including coordination, strength, reflexes, sensation, etc. Your doctor may also run a series of tests that include blood work and MRIs.
Full article ▸