Multifocal motor neuropathy (MMN) is a progressively worsening condition where muscles in the extremities gradually weaken. The disorder, a pure motor neuropathy syndrome, is sometimes mistaken for amyotrophic lateral sclerosis (ALS) because of the similarity in the clinical picture, especially if muscle fasciculations are present. MMN is thought to be autoimmune. It was first described in the mid-1980s.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.Sensory nerves are usually unaffected.Wrist drop and foot drop (leading to trips and falls) are common symptoms.
Liver function tests will typically be normal or unchanged from baseline as the infection does not involve the liver parenchyma. If a D-dimer is ordered, which it often is when there is pleuritic torso pain, it will usually be markedly elevated but other testing for pulmonary embolism will be normal. CT of the abdomen with IV contrast may show subtle enhancement of the liver capsule, but this may be missed by radiologists if they are not advised to look for it. Testing for gonorrhea and chlamydia should be performed to make the diagnosis. An endocervical or low vaginal swab should be taken to test for these organisms. Antibody testing is rarely required but may be considered if other tests are non-diagnostic and suspicion is high.Laparoscopy is also rarely required, but may be performed when the diagnosis is uncertain and may reveal "guitar string" adhesions of parietal peritoneum to liver. Treatment
Treatment involves a course of antibiotics to cover the appropriate organisms, typically ceftriaxone plus azithromycin. Laparoscopy for lysis of adhesions may be performed for refractory pain. References
Further reading
Pregerson, Brady (2010). Quick Essentials: Emergency Medicine (4th ed.). ISBN 978-0-9761552-3-2. Pregerson, D. Brady (2012). Tarascon Emergency Department Quick Reference Guide. Jones & Bartlett. ISBN 978-0-7637-8789-9. == External links ==