Multifocal motor neuropathy

Source: Wikipedia, the free encyclopedia.
Multifocal motor neuropathy
Other namesMultifocal motor neuropathy with conduction block
SpecialtyNeurology

Multifocal motor neuropathy (MMN) is a progressively worsening condition where muscles in the extremities gradually weaken. The disorder, a pure

fasciculations are present. MMN is thought to be autoimmune. It was first described in the mid-1980s.[1]

Unlike ALS, which affects both upper and lower motor neuron pathways, MMN involves only the lower motor neuron pathway, specifically, the peripheral nerves emanating from the lower motor neurons. Definitive diagnosis is often difficult, and many MMN patients labor for months or years under an ALS diagnosis before finally getting a determination of MMN.

MMN usually involves very little pain; however, muscle cramps, spasms and twitches can cause pain for some people. MMN is not fatal, and does not diminish life expectancy. Many patients, once undergoing treatment, only experience mild symptoms over prolonged periods, though the condition remains slowly progressive. MMN can however, lead to significant disability, with loss of function in hands affecting ability to work and perform everyday tasks, and "foot drop" leading to inability to stand and walk; some patients end up using aids like canes, splints and walkers.

Symptoms

Usually beginning in one or both hands, MMN is characterized by weakness, muscle atrophy, cramping, and often profuse

fasciculations (muscle twitching). The symptoms are progressive over long periods, often in a stepwise fashion, but unlike ALS are often treatable.[citation needed
]

Sensory nerves are usually unaffected.[citation needed]

Wrist drop and foot drop (leading to trips and falls) are common symptoms. Other effects can include gradual loss of finger extension, leading to a clawlike appearance. Cold & hot temperatures exacerbate MMN symptoms to such an extent, unlike other neuropathies, that this temperature response is being investigated as a diagnostic tool.[2]

Cause

MMN is thought to be caused by alterations in the immune system, such that certain proteins (antibodies) that would normally protect one from viruses and bacteria begin to attack constituents of peripheral nerves. Antibodies may be directed against "GM-1", a ganglioside found at the

Nodes of Ranvier. These antibodies have been detected in at least one-third of MMN patients. More recent studies also suggest that newer tests for antibodies directed against GM-1, as well as a number of related gangliosides, are positive in over 80% of MMN patients. There are increasing reasons to believe these antibodies are the cause of MMN.[citation needed
]

Diagnosis

The diagnosis of MMN depends on demonstrating that a patient has a purely motor disorder affecting individual nerves, that there are no upper motor neuron (UMN) signs, that there are no sensory deficits, and that there is evidence of conduction block. These criteria are designed to differentiate the disorder from ALS (purely motor but with UMN signs), the Lewis-Sumner Syndrome variant of Chronic inflammatory demyelinating polyneuropathy (CIDP) (similar to MMN but usually with significant sensory loss), and "vasculitis" (a type of multiple mononeuropathy syndrome caused by inflammatory damage to the blood vessels in nerves that also causes sensory and motor symptoms). [citation needed]

A neurologist is usually needed to determine the diagnosis, which is based on the history and physical examination along with the electrodiagnostic study, which includes

Spinal fluid examination is not usually helpful.[citation needed
]

Treatment

Multifocal motor neuropathy is normally treated by receiving

immunosuppressive therapy with cyclophosphamide or rituximab. Steroid treatment (prednisone) and plasmapheresis are no longer considered to be useful treatments(not usually some pt highly recommended);[3] prednisone can exacerbate symptoms. IVIg is the primary treatment, with about 80% of patients responding, usually requiring regular infusions at intervals of 1 week to several months. Other treatments are considered in case of lack of response to IVIg, or sometimes because of the high cost of immunoglobulin. Subcutaneous immunoglobulin is under study as a less invasive, more-convenient alternative to IV delivery.[4]

Ongoing specialist community support, information, advice, and guidance is available from a range of Charities, Non-Government Organisations (NGOs), and Patient Advisory Groups around the world. In the United Kingdom this is provided by GAIN (Guillain–Barré and Associated Inflammatory Neuropathies)[5], in the USA it is provided by GBS/CIDP Foundation International[6], and in The European Union by a range of organisations under the umbrella of EPODIN (European Patient Organization for Disimmune & Inflammatory Neuropathies)[7]

References

  1. PMID 3024989
    .
  2. PMID 20803025
    .
  3. S2CID 20532905
    .
  4. S2CID 20624972
    .
  5. ^ "GAIN Charity: Guillain-Barré Syndrome (GBS) & Associated Neuropathies". GAIN. Retrieved 2024-06-27.
  6. ^ "Home". GBS/CIDP Foundation International. Retrieved 2024-06-27.
  7. ^ "Epodin". Epodin. Retrieved 2024-06-27.

External links

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