Axotomy of peripheral nerve triggers events that coordinate a limited inflammatory response to axonal degeneration and initiation of neurite outgrowth. Inflammatory and neurite outgrowth‐promoting ...roles for the receptor for advanced glycation end products (RAGE) have been suggested, so we tested its role in peripheral nerve regeneration. Analysis of immunohistochemical localization of RAGE by confocal microscopy revealed that RAGE was expressed in axons and infiltrating mononuclear phagocytes upon unilateral sciatic nerve crush in mice. Administration of soluble RAGE, the extracellular ligand binding domain of RAGE, or blocking F(ab')2 fragments of antibodies raised to either RAGE or its ligands, S100/calgranulins or amphoterin, reduced functional recovery as assessed by motor and sensory nerve conduction velocities and sciatic functional index and reduced regeneration, as assessed by myelinated fiber density after acute crush of the sciatic nerve. In parallel, in mice subjected to RAGE blockade, decreased numbers of mononuclear phagocytes infiltrated the distal nerve segments after crush. These findings provide the first evidence of an innate function of the ligand/RAGE axis and suggest that RAGE plays an important role in regeneration of the peripheral nervous system.—Rong, L. L., Trojaborg, W., Qu, W., Kostov, K., Yan, S. D., Gooch, C., Szabolcs, M., Hays, A. P., Schmidt, A. M. Antagonism of RAGE suppresses peripheral nerve regeneration. FASEB J. 18, 1812–1817 (2004)
OBJECTIVE AND METHODS Inclusion body myositis is said to have both myopathic and neurogenic features on electrophysiological tests. Twenty one studies from 20 patients with biopsy defined inclusion ...body myosis, 13 of whom had quantitative electromyography (qEMG), were reviewed to determine if this technique added diagnostic specificity (one patient had both needle EMG and a later study with qEMG before muscle biopsy). RESULTS Excessive numbers of polyphasic motor unit potentials (MUPs) (>12% per muscle) were seen in 11 of the 13 patients. In 10 of 13 patients, mean MUP duration was abnormally reduced (26% to 48%). In three patients, mean MUP duration was abnormally reduced only after polyphasic MUPs were excluded. In all 13 patients, the simple MUP duration was reduced. Myopathy was unequivocally diagnosed in all 13 studies that included qEMG; of the remaining eight patients, the conclusions of the electrophysiological studies without qEMG was myopathy (one), neurogenic (four) or non-diagnostic (three). CONCLUSIONS There is no evidence of a neurogenic component in inclusion body myosis if qEMG is used. Quantitative EMG is often necessary to make an electrophysiological diagnosis of a myogenic disorder in patients with inclusion body myosis.
Axotomy of peripheral nerve stimulates events in multiple cell types that initiate a limited inflammatory response to axonal degeneration and simultaneous outgrowth of neurites into the distal ...segments after injury. We found that pharmacological blockade of RAGE impaired peripheral nerve regeneration in mice subjected to RAGE blockade and acute crush of the sciatic nerve. As our studies revealed that RAGE was expressed in axons and in infiltrating mononuclear phagocytes upon injury, we tested the role of RAGE in these distinct cell types on nerve regeneration. Transgenic mice expressing signal transduction‐deficient RAGE in mononuclear phagocytes or peripheral neurons were generated and subjected to unilateral crush injury to the sciatic nerve. Transgenic mice displayed decreased functional and morphological recovery compared with littermate controls, as assessed by motor and sensory conduction velocities;and myelinated fiber density. In double transgenic mice expressing signal transduction deficient RAGE in both mononuclear phagocytes and peripheral neurons, regeneration was even further impaired, suggesting the critical interplay between RAGE‐modulated inflammation and neurite outgrowth in nerve repair. These findings suggest that RAGE signaling in inflammatory cells and peripheral neurons plays an important role in plasticity of the peripheral nervous system.—Rong, L. L., Yan, S.‐F., Wendt, T., Hans, D., Pachydaki, S., Bucciarelli, L. G., Adebayo, A., Qu, W., Lu, Y., Kostov, K., Lalla, E., Yan, S. D., Gooch, C., Szabolcs, M., Trojaborg, W., Hays, A. P.,Schmidt, A. M. RAGE modulates peripheral nerve regeneration via recruitment of both inflammatory and axonal outgrowth pathways. FASEB J. 18, 1818–1825 (2004)
We compared anti-GM1 IgM antibody titers in patients with various neurologic diseases and in normal subjects. We found increased titers in patients with lower motor neuron disease, sensorimotor ...neuropathy, or motor neuropathy with or without multifocal conduction block. In patients with other diseases, titers are similar to those in normal individuals, suggesting that anti-GM1 antibody levels are not increased nonspecifically after neural injury or inflammatory diseases. Anti-GM1 antibodies in many of the patients occur as monoclonal gammopathies, predominantly of lambda light-chain type, but the antibodies are sometimes polyclonal with normal or increased serum IgM concentrations. Most of the anti-GM1 antibodies appear to react with the Gal(beta 1-3)GalNAc epitope which is shared with asialo-GM1 and GD1b, but in some patients the antibodies are more specific for GM1 and associated with motor neuropathy. Patients with motor or sensorimotor peripheral neuropathy or lower motor neuron disease should be tested for anti-GM1 antibodies or anti-Gal(beta 1-3)GalNAc antibodies, as therapeutic reduction in antibody concentrations was reported to result in clinical improvement in some patients.
We studied 169 patients with motor neuron disease. Seventeen showed abnormal amplitude reduction of the compound muscle action potential. Ten had focal loss of both amplitude and area across a ...specific segment (conduction block). Eight of the 10 had slowing of conduction across that segment. Nine were men and had prominent hand involvement. Six had probable or definite upper motor neuron signs. Five of the 10 showed immunologic abnormalities (elevated GM1 antibody titers or paraproteinemia), and eight had had symptoms for more than 4 years. Seven of the 17 patients showed loss of amplitude without corresponding loss of area and focal slowing of conduction (temporal dispersion). Five of the seven were men, five had prominent hand involvement, and five had definite or probable upper motor neuron signs. Two had immunologic abnormalities, and ony one had had symptoms for longer than 4 years. Among 152 patients with no abnormality of conduction, 64% wee men, hands were dominantly involved in 34%, upper motor neuron signs were definite or probable in 72%, and 3% had immunologic abnormalities. None had symptoms for more than 4 years. Because there were so many exceptions, we could not define a unique syndrome by criteria involving conduction block, GM1 antibodies, or lack of upper motor neuron signs. The clinical syndrome associated with multifocal conduction block seemed uniform, however, and patients with conduction block had slower progression if there were no upper motor neuron signs.
We measured residual latency (RL), motor conduction velocity (MCV), and terminal latency index (TLI) in 15 patients with neuropathy and anti-MAG or SGPG antibodies and compared these to values ...obtained in 103 patients with other types of polyneuropathy (PN) and to 57 normal subjects. Ten patients had anti-MAG antibody titers of 25,600 or higher, and 5 had titers between 800 and 12,600. Patients with the highest titers had longer RL, slower MCV and shorter TLI than those with lower titers, acute or chronic inflammatory demyelinating PN, hereditary neuropathy, and metabolic or axonal neuropathy. In contrast F-wave latencies did not contribute to the differentiation between the groups of demyelinating neuropathies. RL and TLI correlated best with anti-MAG antibody titers, whereas there was a poor correlation with anti-SGPG titers suggesting that MAG more than SGPG may be the antigen in PN, and that the distal nerves are affected more than their proximal segments. The RL rather than TLI turned out to be the best variable to classify the demyelinating type of anti-MAG neuropathy. Sural nerve biopsy in 5 of the patients with the highest titer of anti-MAG antibodies showed deposits of IgM and C3 on the myelin sheaths, pronounced demyelination and widening of the myelin lamellae. In 4 of the patients with lower titers demyelination was absent or less pronounced.
Thirty patients treated for germ cell cancer with six cycles of cisplatin, vinblastine, and bleomycin participated in a follow-up examination of neurotoxicity 49 to 106 months after treatment. Of ...these, 22 patients (73%) had sensory loss; half of them complained of paresthesias. The vibration perception threshold was increased in 24 patients (80%). Auditory stimulation revealed a normal latency of the first component of the brain stem-evoked potentials Pl but an increased interpeak interval between this and Pv; reflecting a central conduction defect. Motor conduction velocity (CV) along the peroneal nerve was normal. The average sural nerve CV was decreased (P less than .01) and the sensory action potential amplitude was reduced (P less than .01). Warm perception threshold was increased in 10 patients (33%). Cortical-evoked potentials after tibial nerve stimulation had increased latencies in 29 patients (97%). The peripheral CV along the tibial nerve was slowed (P less than .01) in 19 patients, and the central conduction time from Th12 to cortex was prolonged in 15 patients (P less than .01). The changes in conduction along peripheral and central pathways after tibial nerve stimulation are compatible with a toxic effect on the sensory root ganglia causing a "dying back" axonal degeneration of central and peripheral nerve fibers.
The compound sensory action potential evoked by electrical stimulation provides a measure of the number and physiological properties of myelinated fibers in the nerve but does not allow evaluation of ...the most distal part of the sensory nerve. This study compares the compound sensory action potential, evoked by electrical and tactile stimuli, and recorded through needle electrodes placed close to the median and sural nerves of 22 normal males aged 16-51 years. The tactile probe, with a slight preindentation, delivered an indentation of the skin of 200 microns at a rate of 400 microns/ms at the tip of digit III and the dorsolateral side of the foot. The responses were recorded from the median nerve at wrist and elbow and from the sural nerve at the lateral malleolus and midcalf. The amplitudes of the responses averaged 0.5 microV and 0.7 microV in the sural and the median nerves (P < 0.02), respectively, which was only 5-10% of the amplitude evoked by electrical stimulation. The mean maximal conduction velocity determined by tactile stimulation was 54 m/s in the sural nerve compared with 65 m/s in the median nerve and similar to that calculated after electrical stimulation. In the median nerve the sensory conduction velocity was 8% faster than the motor conduction velocity. These findings indicated that only a fraction of the fibers in the nerve were activated by the probe and that the response was conducted along large myelinated sensory fibers. The latency of the tactile response was longer than that of the electrically evoked response due to the receptor delay and conduction along thin distal fiber portions. The delay at the mechanoreceptors was about 1 ms in the sural and 0.65 ms in the median nerve (P < 0.01).
We reviewed the clinical and electrophysiologic features of 36 patients with increased titers of IgM anti-GM1 antibodies. Mildly elevated titers of up to 3,200 were not associated with any particular ...clinical syndrome or disease. Clinically, 14 of 16 patients with highly elevated titers of 6,400 or higher had progressive weakness with lower motor neuron signs; six had active tendon reflexes and eight had absent reflexes, but none had definite upper motor neuron signs. Electrophysiologic studies showed spontaneous activity in all 14 patients, one or more motor conduction blocks in nine, slowed motor conductions in one, and normal conductions in four patients. None had abnormal sensory conductions. These patients presented with a syndrome that has features of, but is distinct from, both motor neuron disease and demyelinating neuropathy.
Antibodies to GM1 or Gal(beta 1-3)GalNAc are associated with motor or sensorimotor neuropathy and with motor neuron disease. To investigate the role of these antibodies in the neurological disorder, ...rabbits were immunized with GM1 or with Gal(beta 1-3)GalNAc-BSA, and studied serologically, electrophysiologically and pathologically. Development of antibodies to the immunizing antigens was associated with a fall in the ratio of the amplitudes of the compound muscle action potential evoked by proximal versus distal stimulation of the sciatic nerve. Pathological studies revealed mild axonal degeneration and immunoglobulin deposits at the nodes of Ranvier in peripheral nerve, resembling those reported in a patient with motor neuropathy, motor conduction block and anti-GM1 antibodies. These studies provide evidence that anti-GM1 or anti-Gal(beta 1-3)GalNAc antibodies cause conduction abnormalities and indicate that the antibodies may exert their effect, in part, by binding at the nodes of Ranvier in peripheral nerve.
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