Multifocal motor neuropathy

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Multifocal motor neuropathy ( MMN ) is a worsening condition in which the muscles in the extremities gradually weaken. Disorders, pure motor neuropathy syndromes, are sometimes mistaken for amyotrophic lateral sclerosis (ALS) because of the similarity in the clinical picture, especially if muscle fasciculation is present. MMN is considered autoimmune. This was first described in the mid-1980s.

Unlike ALS that affects the upper and lower motor nerves, MMN only involves lower motor nerves. However, definitive diagnosis is often difficult, and many MMN patients deliver for months or years under ALS diagnosis before finally getting MMN determinations.

MMN usually involves very little pain but muscle cramps, convulsions and twitches can cause pain for some sufferers. MMN is not fatal, and does not reduce life expectancy. Many patients, after treatment, experience only mild symptoms during prolonged periods, although these conditions remain progressive slow. However, MMN can cause significant defects, with loss of functionality in the hand that affects the ability to work and perform daily tasks, and "footprints" that cause inability to stand and walk; some patients end up using aids such as sticks, splints and pedestrians.

Video Multifocal motor neuropathy

Symptoms

Usually starting in one or both hands, MMN is characterized by weakness, muscle atrophy, cramps, and often excessive fasciculation (muscle twitching). The symptoms are progressive for a long time, often in a gradual way, but unlike ALS can often be treated.

The sensory nerves are usually unaffected.

Wrists and foot fall (leading to travel and fall) are common symptoms. Another effect can be the gradual loss of finger extension, leading to a claw-like appearance. Cold & amp; Hot temperatures exacerbate the symptoms of MMN in such a way, unlike other neuropathies, which are being investigated as a diagnostic tool.

Maps Multifocal motor neuropathy

Cause

MMN is thought to be caused by changes in the immune system, so certain proteins (antibodies) that normally protect one of the viruses and bacteria start attacking the peripheral nerve constituents. Antibodies can be directed against "GM-1", a ganglioside located in the Node of Ranvier. These antibodies have been detected in at least one-third of MMN patients. More recent studies have also shown that new tests for antibodies directed against GM-1 are combined with a number of associated gangliosides, positive in over 80% of MMN patients. Thus, there is an increasing reason to believe that these antibodies are the cause of MMN.

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Diagnosis

The diagnosis of MMN depends on showing that the patient has a pure motor disorder affecting the individual nerve, that there is no UMN mark, that there is no sensory deficit, and that there is evidence of conduction blocks. This criterion is designed to distinguish disorders from ALS (pure motor but with UMN mark), Lewis-Sumner Syndrome variant of Inflammatory Demyelinating Polyneuropathy (CIDP) (similar to MMN but usually with significant sensory loss), and "vasculitis" (a type of multiple syndrome mononeuropathy caused by inflammatory damage to blood vessels in the nerves that also cause sensory and motor symptoms). A neurologist is usually required to determine a diagnosis, based on history and a physical examination along with an electrodiagnostic study, which includes neural conduction studies (NCS) and needle electromyography (EMG). NCS usually shows conduction blocks. This can be done by showing that the neural signals can not pass through "lesions" at some point along the nerve. For example, if a nerve is blocked in the forearm, an electrical impulse can be easily obtained from the wrist to the hand if the stimulus is placed on the wrist. However, the signal will be blocked from reaching the hand if the stimulus is applied at the elbow. In MMN, the sensory conduction along the same path should be normal. The EMG part of the test looks for signals by burning muscles. In MMN will most likely reveal abnormalities indicating that some percentage of the motor axon has been damaged. Laboratory testing for GM1 antibodies is often done, and can be very helpful if they are abnormal. However, since only one-third of patients with MMN have these antibodies, a negative test does not rule out the disorder. Spinal fluid examination usually does not help.

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Treatment

Multifocal motor neuropathy is usually treated by receiving intravenous immunoglobulin (IVIG), which in many cases can be very effective, or immunosuppressive therapy with cyclophosphamide or rituximab. Treatment of steroids (prednisone) and plasmapheresis is no longer considered a useful treatment; prednisone may aggravate symptoms. IVIg is the main treatment, with about 80% of patients responding, usually requiring regular infusions at intervals of 1 week to several months. Other treatments are considered in the case of a lack of response to IVIg, or sometimes because of the high cost of immunoglobulins. Subcutaneous immunoglobulins are being studied as a less invasive and more convenient alternative to childbirth IV.

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References

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External links

• A review of MMN at the National Institute of Neurological Disorders and Stroke

Source of the article : Wikipedia