Multifocal Motor Neuropathy (MMN) is a rare condition in which multiple motor nerves are attacked by one’s immune system. This attack causes weakness of muscles but not loss of sensation. The particular nature of the attack is unique and puzzling, since motor and sensory fibres are intermixed between the nerve trunks of the arms and legs, but only the motor nerves become involved.
MMN causes weakness and there is no numbness or tingling, and pain is not a critical factor. It usually develops without symmetry and tends to begin in the hands. Frequently, the weakness is distinguished as fitting a specific nerve territory. The attack on multiple single nerves is called a multiple mononeuropathy syndrome. This pattern can be observed in other diseases, but MMN is the only condition where the attack is separated to the motor nerve fibres. It must be noted that this is the most important clinical finding to diagnose MMN.
It has been founded that intravenous immunoglobin (IVIg) benefits patients with MMN. IVIg can lead to improvement in most patients with MMN, with response varying from minimal to very large. Usually, all the symptoms of the condition are not completely reversed with the treatment. Patients, who do show positive response towards the treatment, require repeated treatments to keep their improvements.
The exact timing and dosing of the treatment are decided according to individual patient and success isn’t based on any single formula. If the response of the patient towards the treatment starts wearing off, or if the symptoms start worsening despite maintenance therapy, the dosing may need to be adjusted.
IVIg isn’t a cure for MMN and no other therapy has proven effective for it currently. It is fairly known that corticosteroids are ineffective and can actually worsen the condition. Other immune-suppressants have been used, but they have posed greater side-effects and risks.
Newer therapies are needed to treat MMN, and many researchers around the world are working towards a better understanding of it in order to develop more definite treatments.
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