Multifocal motor neuropathy

Introduction to multifocal motor neuropathy Multifocal motor neuropathy (MMN) is also known as multifocal demyelinating motor neuropathy. It is a rare demyelinating peripheral neuropathy that has been recognized in recent years. From 1985 to 1986, Parry et al. and Roth et al reported almost 4 cases of pure motor neuropathy. The clinical manifestations were progressive asymmetric limbs. Incapable, mainly due to distal involvement, electrophysiological features are persistent multifocal block (CB) on motor nerves, while sensory nerves have no or only very light involvement. In 1988, Pestronk et al first reported elevated levels of anti-ganglioside GM1 antibodies in the serum of patients with this disease and responded to immunotherapy. Since then, most scholars believe that this disease is different from chronic inflammatory demyelinating polyneuropathy (CIDP) and motor neuron disease, but a single disease called multifocal motor neuropathy. As early as 1982, Lewis et al reported five cases of motor-like neuropathy with clinical and electrophysiological features similar to this, and two cases improved after treatment with corticosteroids. Currently, most scholars believe that these cases are variants of CIDP. The difference between it and MMN is that the former has sensory nerve involvement and is effective for corticosteroid treatment. So far, more than 300 MMNs have been reported worldwide. basic knowledge Sickness ratio: 0.05% Susceptible people: no special people Mode of infection: non-infectious Complications: myasthenia gravis

Causes of multifocal motor neuropathy

(1) Causes of the disease

Little is known about the etiology of this disease. It is speculated that it may be related to Campylobacter jejuni infection. It has been reported that 3 patients have clinical manifestations of MMN and anti-GM1 antibody titer after suffering from Campylobacter jejuni enteritis, possibly jejunal curvature The lipopolysaccharide component (LPS) of the bacteria induces an anti-ganglioside antibody production.

There are at least two evidences that the disease is associated with autoimmunity. One is that 20% to 84% of patients have elevated serum GM1 antibodies, and the other is a significant proportion of patients with immunosuppressive drugs (intravenous immunoglobulins and cyclophosphamide). The treatment is effective.

(two) pathogenesis

The pathogenesis is still unclear, serum anti-ganglioside GM1 antibody is elevated, and the use of immunotherapy can improve the symptoms, suggesting that the disease is immune-mediated, the exact mechanism of immune response and potential target antigens still It is unclear that serum anti-ganglioside GM1 antibody and anti-asialo-GM1 antibody are often elevated in MMN. After the therapeutic antibody titer is decreased, some patients have improved symptoms and support such antibodies in the pathogenesis of this disease. However, in vitro experiments with the rat sciatic nerve showed that there was anti-GM1 antibody binding at the Langfei node and secondary complement activation, while the nerve conduction test showed no abnormality. Some patients responded to immunotherapy, but some patients responded to immunotherapy. Its serum anti-ganglioside antibody is not high; on the other hand, anti-GM1 antibodies may also be present in some patients with Guillain-Barre syndrome (GBS), motor neuron disease, sensorimotor peripheral neuropathy and CIDP. Elevated, these findings have questioned the pathogenic role of these antibodies, and the correlation between the specificity of these antibodies and different clinical symptoms has not been confirmed, so it is not yet Why Chu similar antibodies can cause different diseases.

In order to confirm the pathogenic role of anti-GM1 antibodies in MMN, many experiments were performed in vivo and in vitro, when intraperitoneal injections or exposure of nerves to multi-focal CB, high titers of MMN patients without motor neuron disease Anti-GM1 antibody serum can induce focal CB in vivo and in vitro, but the results of the latter have not been confirmed with purified anti-GM1 antibody. Recently, serum of MMN patients with and without high titer anti-GM1 antibody In the case of the mouse distal motor, a similar blocking effect can be induced, suggesting that the currently used method for detecting anti-GM1 antibodies is not sensitive enough, or that the serum component of MMN patients, rather than anti-GM1 antibody, causes CB. .

The mechanism of MMN selective motor nerve damage is unclear, which may reflect different antigenic components or different expressions of motor and sensory nerves, probably due to the difference in GM1 sphingosine structure of motor nerves from sensory nerves, and thus The affinity of the GM1 antibody is related to, or reflects, the difference in the susceptibility of the motor and sensory nerves to damage, or the ability to repair the damage.

Motor nerve biopsy near the part of the motor block showed that the main pathological changes were the onion-like structure formed by demyelination and Schwann cell proliferation, no inflammatory cell infiltration, and mild axonal changes in the sural nerve biopsy. Sexual and demyelinating changes, the only 3 cases of MMN autopsy data show nerve root and peripheral nerve changes, but also the spinal anterior horn neurons loss and Nissl body dissolution, 2 cases have Bunina body, 2 cases had corticospinal tract damage.

Therefore, the relationship between multifocal motor neuropathy and motor neuron disease has been controversial. Some scholars believe that there are some cases in which the perinuclear part of the neurons and the peripheral nerves can be damaged at the same time, not just tired. One.

Multifocal motor neuropathy prevention

There are no good preventive measures for autoimmune diseases. Pay attention to the following points in clinically cured patients to prevent recurrence:

1. Strengthen nutrition, enhance physical fitness, and prevent colds.

2. Practice correct coughing and coughing methods to prevent secondary infections in the lungs.

Multifocal motor neuropathy complications Complications Myasthenia gravis

The condition may be repeated. The acute phase is similar to the performance of the Guillain-Barre syndrome, but the respiratory muscles are not tired, and often the daily life cannot be taken care of by the muscle weakness.

Symptoms of multifocal motor neuropathy Common symptoms Muscle myasthenia dysfunction conduction block neck and back muscle spasm

1. Insidious onset, a small number of patients may be acute or subacute onset, the age of good hair is 20 to 50 years old, more common in men, the ratio of male to female is 4:1.

2. 90% of the patients had onset of the distal extremity, mainly involving the upper limbs. In the early stage, the muscle weakness was dominant, and the bilateral sides were asymmetrical. The distribution of the area was mostly consistent with the phrenic nerve, the ulnar nerve and the median nerve. Muscle atrophy can occur, and 2/3 of patients may have fasciculation and muscle spasm.

3. A small number of patients may have transient shoulder pain and mild paresthesia, but no positive and constant sensory disturbances.

4. The sputum reflex is normal or weakened. Occasionally, sputum reflex is active, no pyramidal tract sign, and cranial nerve and respiratory muscle involvement are rare.

5. Neuromuscular electrophysiological examination showed that the characteristic changes were persistent, multifocal, and partial motor block. The latter refers to selecting two points at the proximal and distal ends of the limb to stimulate the motor nerve. The amplitude and area of the resulting compound muscle action potential are reduced by more than 20%, sometimes as high as 70% or more, and without an abnormally short dispersed phase. The conduction block can occur simultaneously in multiple peripheral nerves or the same nerve. In different segments, conduction block is easily detected in the ulnar nerve, median nerve, and phrenic nerve.

6. Laboratory tests have a slight increase in serum creatine kinase (CK), a small number of patients with cerebrospinal fluid protein may have a transient mild increase, 20% to 84% of patients with serum anti-ganglioside (GM1) antibody positive, domestic In 6 cases, serum GM1 antibody was significantly elevated in 4 cases, and the other 2 cases were slightly elevated.

Examination of multifocal motor neuropathy

1. Serological examination: serum CK is slightly increased; 20% to 84% of patients with serum anti-ganglioside (GM1) antibody positive, serum heavy metal (lead, mercury, arsenic, antimony, etc.) concentration detection, is conducive to differential diagnosis .

2. Cerebrospinal fluid examination: protein can be transiently elevated slightly.

3. Muscle and neurophysiological examination: It is of great significance to identify neurogenic and myogenic damage, the location of peripheral nerve damage, and the distinction between axonal degeneration and demyelination. Neuromuscular electrophysiological examination showed that the multifocal motor neuropathy may have characteristic changes, which are persistent, multifocal, and partial motor block.

4. Peripheral nerve biopsy: an important laboratory test for differential diagnosis of peripheral neuropathy.

Diagnosis and differentiation of multifocal motor neuropathy

According to the main clinical features of this disease, when the patient presents with chronic progressive muscle weakness with peripheral nerve distribution, muscle atrophy, left and right asymmetry, mainly affected by distal limb involvement, no or very mild sensory symptoms, should be thought of The possibility of MMN is that neurological electrophysiological examination must be performed. The characteristic findings of this disease are focal conduction block of one or more motor nerves and the sensory conduction test of the corresponding nerve is normal. Other abnormalities such as distal latency and F wave Mild prolongation of latency, mild reduction of conduction velocity, and abnormal time dispersion are also common in motor nerves, and have certain value for diagnosis.

Neuroelectrophysiological examination found that some motor nerve block and normal sensory nerve are necessary conditions for the diagnosis of MMN. The increase of serum anti-ganglioside GM1 antibody is helpful for diagnosis.

1. Identification with chronic Guillain-Barre syndrome (CIDP)

The neurobiopsy pathology of both showed myelin loss and Schwann cell proliferation. The neuroelectrophysiological examination showed changes in nerve conduction velocity, and the immunosuppressive drugs, especially cyclophosphamide and intravenous immunoglobulin, responded well. It is easy to be confused.

However, CIDP has objective and long-lasting sensory disturbances in clinical practice. The sensory symptoms of MMN are few and mild. MMN may have active tendon reflexes and fasciculation. However, CIDP has no such signs. The cerebrospinal fluid protein of CIDP is obviously and persistent, and MMN is normal. Or slightly elevated, CIDP responded well to prednisone, while MMN was more effective than prednisone treatment. Anti-GM1 titer was common in MMN, rarely seen in CIDP, and neurobiopsy CIDP had obvious inflammatory cell infiltration, while MMN no.

2. Identification with amyotrophic lateral sclerosis (ALS or SMA)

MMN sometimes has obvious muscle weakness and muscle atrophy with fasciculation, hyperreflexia, and is easily confused with ALS or SMA. Motor nerve biopsy reveals demyelination changes and IVIG experimental treatment effectively supports MMN. Magnetic resonance spectroscopy has cortisol Loss of aspartic acid and magnetic stimulation of the motor cortex revealed that central motor conduction damage suggests ALS.

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