Presynaptic Immune mediated disorders
In order to transfer between nerve and muscle is essential to mobilize quanta of acetylcoline in the synaptic vesicles, which is not possible without the penetration of calcium into nerve endings. Equally needed is a mutual exchange of potassium and sodium. The realization of these processes are the nerve endings in the membrane calcium, and potassium sensitive sodium channels.
Investigatin of antibodyes in the laboratory in theOxford (Prof. A. Vincent)
Lambert - Eaton myasthenic syndrom (LEMS)
Lambert-Eaton Myasthenic syndrome is a rare autoimmune disorder. It is usually associated with auto-immune self antibodies against the pre-synaptic voltage-gated calcium channel which leads to neuromuscular block. The test for antibodies against the acetylcholine receptor may be positive in some cases.The symptoms of LEMS may resemble myasthenia gravis but in contrast to MG many patients have symptoms like dry mouth or impotence, reflexes are usually reduced or absented and the proximal parts of the legs are more affected.
While LEMS may be found as a solitary disease, 60% of cases have an associated small-cell lung cancer (40% even before the first symptoms appear) . Patients may be also diagnosed with other malignancies or thymoma.
In addition to clinical findings and the certificate of antibodies is characterized by reaction to the electrophysiological examination. You can see a reduction of amplitude CMAP and high frequency stimulation, the increment (increase) aplitudy action potential (picture).
Corticosteroids, azathioprine and 3.4-diamidopyridin are used in treatment of LMS. An acetylcholinesterase inhibitors are less efficient.Patients with LEMS associated with lung cancer are likely to come to clinical remission after the tumor is removed.
Plasma exchange provides improvement in some patients with LEMS, as may intravenous immunoglobulin (IVIG). .
Other information:
Lambert - Eaton myasthenic syndrome, D E Sicker, D B Sanders, emedicine.medscape.com, jan. 2009
http://www.wrongdiagnosis.com/l/lambert_eaton_myasthenic_syndrome/intro.htm
Acquired Neuromyotonia (Isaacs syndrome)
Isaacs syndrome is spontaneous muscular activity resulting from repetitive motor unit action potentials of peripheral origin. Some patients may show antibodies to voltage controlled sensitive potassium channels in the terminal ends of peripheral nerve.
The most remarkable symptoms is involuntary muscle contraction together with muscle weakness.
Some patients may be diagnosed with thymoma, lung tumor or very rarely with myasthenia gravis.
There is no known cure for neuromyotonia. Phenytoin, gabapentin and carbamezepin, usually provide significant relief from the stiffness, muscle spasms, and pain associated with neuromyotonia. Plasma exchange may provide short-term relief for patients with some forms of the acquired disorder.