桑原 聡

Patients with acute motor axonal neuropathy (AMAN) generally recover well. We reviewed clinical and electrophysiologic recovery in 13 patients for up to 5 years. Twelve patients showed rapid recovery over 12 months, whereas in the remaining one the recovery was slow and incomplete at 5 years. In AMAN, axonal degeneration appears to develop predominantly in the motor nerve terminals, and only occasionally more proximally in the nerve roots. Nerve terminal degeneration-regeneration presumably provides a mechanism for good recovery.

Objective: Median-ulnar comparative studies (MUCS) play an important role in the electrodiagnosis of carpal tunnel syndrome, but in diabetes concomitant involvement of Guyon's canal (ulnar nerve compression at the wrist) would reduce the sensitivity of MUGS. This study tested the utility of median-radial comparative studies (MRCS) in diabetic patients. Methods: Anti-dromic MUCS and MRCS were prospectively performed in 120 patients with diabetes, and 64 normal controls. In 28 diabetic patients, latent addition using threshold tracking was performed in superficial radial sensory axons to estimate persistent nodal sodium currents. Results: MUCS was abnormal in 49% of the diabetic patients, and MRCS was abnormal in 58%. Median motor distal latencies were prolonged in 38%, and median sensory nerve conduction velocities were slowed in 40%. The longer latency differences in MRCS were associated with smaller persistent sodium currents, suggesting that intra-axonal sodium accumulation mediated by hyperglycemia enhances nerve compression. Conclusions: MRCS appears to be the most sensitive electrodiagnostic test in the detection of median neuropathy at the wrist in diabetic patients. Nerve conduction slowing across the carpal tunnel may be associated with metabolic abnormalities under hyperglycemia. Significance: Assessment of nerve conduction across the common entrapment sites could provide new insights into the pathophysiology of diabetic neuropathy related to metabolic factors. (C) 2007 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Objective: To investigate whether excitation-contraction (E-C) coupling of muscle is impaired in patients with myasthenia gravis (MG). Methods: In 51 patients with generalized MG and 35 normal subjects, compound muscle action potentials (CMAPs) of the abductor pollicis brevis, and movement-related potentials using an accelerometer placed at the thumb tip were simultaneously recorded after median nerve stimulation at the wrist. The E-C coupling time (ECCT) was estimated by a latency difference between CMAP and movement-related potential. Antibodies against acetylcholine receptor (AChR), ryanodine receptor (RyR), and muscle specific receptor tyrosine kinase (MuSK) were measured by immunoassays. Results: The mean ECCT was significantly longer in patients with MG (mean SEM; 2.79 +/- 0.1 ms; p = 0.002) than in normal controls (2.52 +/- 0.1 ms). Among MG patients, the mean ECCT was longer for patients with thymoma than for those without it (P = 0.04), and was shorter for patients treated with FK506 (an immunosuppressant and also an enhancer of RyR related Ca2+ release) than for those not receiving this treatment (p = 0.04). ECCT had no significant correlation with anti-AChR, anti-RyR, or anti-MuSK antibodies. Conclusions: In MG, E-C coupling appears to be impaired, particularly in patients with thymoma, and FK506 possibly facilitates E-C coupling. Significance: The functional implication of impaired E-C coupling is not established, but it may contribute to muscle weakness in patients with MG. (c) 2007 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Paranodal axo-glial junctions are important for ion channel clustering and rapid action potential propagation in myelinated nerve fibers. Paranode formation depends on the cell adhesion molecules neurofascin (NF) 155 in glia, and a Caspr and contactin heterodimer in axons. We found that antibody to ganglioside GM1 labels paranodal regions. Autoantibodies to the gangliosides GM1 and GD1a are thought to disrupt nodes of Ranvier in peripheral motor nerves and cause Guillain-Barre syndrome, an autoimmune neuropathy characterized by acute limb weakness. To elucidate ganglioside function at and near nodes of Ranvier, we examined nodes in mice lacking gangliosides including GM1 and GD1a. In both peripheral and central nervous systems, some paranodal loops failed to attach to the axo-lemma, and immunostaining of Caspr and NF155 was attenuated. K+ channels at juxtaparanodes were mislocalized to paranodes, and nodal Na+ channel clusters were broadened. Abnormal immunostaining at paranodes became more prominent with age. Moreover, the defects were more prevalent in ventral than dorsal roots, and less frequent in mutant mice lacking the b-series gangliosides but with excess GM1 and GD1a. Electrophysiological studies revealed nerve conduction slowing and reduced nodal Na+ current in mutant peripheral motor nerves. The amounts of Caspr and NF155 in low density, detergent insoluble membrane fractions were reduced in mutant brains. These results indicate that gangliosides are lipid raft components that contribute to stability and maintenance of neuron-glia interactions at paranodes. (c) 2007 Wiley-Liss, Inc.

We analyzed clinical recovery of 92 patients with Miller Fisher syndrome who had been treated with IV immunoglobulin (IVIg; n = 28), plasmapheresis (n = 23), and no immune treatment (n = 41). IVIg slightly hastened the amelioration of ophthalmoplegia and ataxia, but the times of the disappearances of those symptoms were similar among three groups. In Miller Fisher syndrome, IVIg and plasmapheresis seem not to have influenced patients' outcomes, presumably because of good natural recovery.

Objective: Previous axonal excitability studies suggest hyperkalemia or hypokalemia can significantly alter membrane potential and thereby, excitability properties. We studied whether physiological fluctuation of serum potassium levels affects axonal excitability in normal human axons. Methods: Threshold tracking was used to measure strength-duration properties, refractory periods, supernormality, and threshold electrotonus in median motor axons of 12 normal volunteers. In each subject, the excitability indices and serum potassium levels were measured three times (baseline, 2 h later, and 2 weeks later). Results: The pooled data (n = 36) showed significant correlation of the relative refractory period, supernormality, and depolarizing threshold electrotonus with potassium levels. Among each trial (12 subjects) the correlation did not reach statistical significance occasionally. Strength-duration properties, refractoriness, late subnormality, and hyperpolarizing threshold electrotonus were not significantly affected by serum potassium levels. Conclusions: Even in the normal range, serum potassium levels could slightly alter axonal excitability of human axons. Among excitability indices, the relative refractory period, supernormality, and threshold electrotonus are sensitive to potassium levels. Significance: Physiological fluctuation of serum potassium levels could partly be responsible for inter- and intra-subject variability of excitability indices. (c) 2006 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

The presence of antibodies against muscle-specific receptor tyrosine kinase (MuSK) appears to define a subgroup of patients with myasthenia gravis (MG) characterized by weakness predominant in bulbar, facial and neck muscles compared with anti-acetylcholine receptor (AChR) antibody-positive MG. To investigate the patterns and severity of neuromuscular transmission failure in different muscles in MuSK-positive MG, we performed single fiber electromyography (SFEMG) in the facial (frontalis) and limb (extensor digitorum communis, EDC) muscles in three anti-Musk-positive patients, and compared results with those of 11 anti-AChR-positive patients. Only one of the three MuSK-positive patients had abnormal jitter in EDC, but all the three showed clearly increased jitter in the frontalis. By contrast, the AChR-positive patients showed similarly abnormal jitter for the two muscles. These results suggest that when the diagnosis of anti-MuSK-positive MG is suspected, SFEMG should be performed in most prominently affected muscles.

We present the case of a 71-year-old woman with polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes (POEMS) syndrome. Overproduction of vascular endothelial growth factor (VEGF), secreted by plasmacytoma, is considered responsible for the characteristic symptoms, and therefore anti-VEGF monoclonal antibody (bevacizumab) could be a therapeutic option. The patient was treated with bevacizumab 7 years after onset. Despite a dramatic decrease in serum VEGF levels, there was no clinical improvement, possibly because aberrant angiogenesis had already developed systemically. We suggest that careful consideration should be taken for indication of bevacizumab therapy, and this agent may be used in selected patients with a short duration POEMS syndrome.

Objective: To investigate the changes in nodal persistent Na+ currents in human neuropathy and motor neuron disease. In human motor axons, approximately 1.0% of total Na+ channels are active at rest, termed "persistent" Na+ channels, and the conductance can be noninvasively estimated by the technique of latent addition in vivo. Methods: Latent addition was performed in median motor axons of 93 patients with axonal neuropathy (n = 38), lower motor neuron disorder (LMND; n = 19) or amyotrophic lateral sclerosis (ALS; n = 36) and in 27 age-matched normal subjects. Brief hyperpolarizing conditioning current pulses were delivered, and threshold change at the conditioning-test interval of 0.2 ms was measured as an estimator of the magnitude of persistent Na+ currents. Threshold electrotonus and supernormality were also measured as indicators of resting membrane potential. Results: Threshold changes at 0.2ms were significantly greater in patients with neuropathy or LMND (p < 0.05), and tended to be greater in ALS patients (p = 0.075) than in normal controls. Threshold electrotonus and supernormality did not differ in each patient group and normal controls, suggesting that membrane potential is not altered in patients. In the recovery phase of axonal neuropathy, the threshold changes increased in parallel with an increase in amplitudes of compound muscle action potential. Conclusions: Persistent Na+ currents appear to increase commonly in disorders involving lower motor neurons, possibly associated with axonal regeneration or collateral sprouting or changes in Na+ channel gating. Significance: The increased axonal excitability could partly be responsible for positive motor symptoms such as muscle cramping frequently seen in lower motor neuron disorders. (c) 2006 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

In injured adult neurons, the process of axonal regrowth and reestablishment of the neuronal function have to be activated. We assessed in this study whether RhoA, a key regulator of neurite elongation, is activated after injury to the peripheral nervous system. RhoA is activated in motoneurons but not in Schwann cells after mouse sciatic nerve injury. To examine whether the activation of RhoA and its effector, Rho-kinase, retards axon regeneration of injured motoneurons, we employed a Rho-kinase inhibitor, fasudil. Amplitudes of distally evoked compound muscle action potentials are increased significantly faster after axonal injury in mice treated with fasudil compared with controls. Histological analysis shows that fasudil treatment increases the number of regenerating axons with large diameter, suggesting that axon maturation is facilitated by Rho-kinase inhibition. In addition, fasudil does not suppress the myelination of regenerating axons. These findings suggest that RhoA/Rho-kinase may be a practical molecular target to enhance axonal regeneration in human peripheral neuropathies.

The authors reported the neurological disease spectrum associated with autoantibodies against minor gangliosides GM1b and Ga1NAc-GD1a. IgG and IgM antibody reactivity against gangliosides GM1, GM2, GM1b, GDla, Ga1NAc-GD1a and GQ1b was investigated in sera from 7000 consecutive patients who had various neurological conditions. The clinical diagnoses for 456 anti-GM1b-positive patients were Guillain-Barre syndrome (GBS, 71%), atypical GBS with preserved deep tendon reflexes (12%), Fisher syndrome (10%), Bickerstaff's brainstem encephalitis (2%), ataxic GBS (2%) and acute ophthalmoparesis (1%). For 193 anti-GalNAc-GD I a-positive patients, the diagnoses were GBS (70%), atypical GBS (16%), Fisher syndrome (10%) and Bickerstaff's brainstem encephalitis (3%). Of the patients with GBS or atypical GBS, 28% of 381 anti-GM1b-positive and 31% of 166 anti-GalNAc-GD1a-positive patients had neither anti-GM1 nor anti-GDla antibodies. Of those patients with Fisher syndrome, Bickerstaff's brainstem encephalitis, ataxic GBS or acute ophthalmoparesis, 33% of 67 anti-GM1b-positive, and 52% of 25 anti-GalNAc-GD1a-positive patients had no anti-GQ1b antibodies. Autoantibodies against GM1b and GalNAc-GD1a are associated with GBS, Fisher syndrome and related conditions. These antibodies should provide useful serological markers for identifying patients who have atypical GBS with preserved deep tendon reflexes, ataxic GBS, Bickerstaff's brainstem encephalitis or acute ophthalmoparesis, especially for those who have no antibodies to GM 1, GD1a or GM1b. A method to prepare GM1b was developed. (c) 2006 Elsevier B.V. All rights reserved.

Objective: Previous axonal excitability studies in amyotrophic lateral sclerosis (ALS) have suggested that impaired potassium channel function could be responsible for the generation of fasciculations, but the ectopic activity arises predominantly from the motor nerve terminals. This study tested the hypothesis that dysfunction of potassium channels is more pronounced in the more distal parts of axons. Methods: Threshold electrotonus was used to compare accommodation at the motor point of abductor pollicis brevis, and at the wrist portion of the median nerve, between 22 patients with ALS and 19 normal subjects. As target responses for motor point stimulation, movement-related potentials were recorded using an accelerometer. Results: Compared to normal subjects, ALS patients showed greater threshold changes to depolarizing conditioning currents at both the motor point and wrist, suggesting less accommodation by potassium currents. Differences in the threshold electrotonus curves between the normal and ALS groups were much more prominent at the motor point than at the wrist. Conclusions: In ALS, axonal potassium channels are impaired more prominently in distal portions of axons than at the nerve trunk, and this is consistent with evidence that fasciculations mostly arise from the nerve terminals. Significance: Excitability testing at the motor point provides additional information about the pathophysiology of ALS. (c) 2006 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Background: In diabetic nerves, activation of the polyol pathway via an aldose reductase and the resulting impairment of the Na+-K+ pump would lead to a decreased transaxonal Na+ gradient and thereby reduced nodal Na+ currents. Objective: To investigate whether the aldose reductase inhibitor (ARI) epalrestat improves nodal Na+ currents and nerve conduction in human diabetic neuropathy. Methods: The authors conducted a 6-month, open clinical trial with an ARI, epalrestat, in 30 patients with mild-to-moderate diabetic neuropathy. The latent addition technique and measurements of the strength-duration time constant were used to estimate nodal persistent Na+ currents in median motor axons. Excitability testing and extensive nerve conduction studies including F-wave analyses were performed before and 1 and 6 months after the initiation of treatment with oral epalrestat. Results: Within a month of the start of treatment, there was a significant improvement in nerve conduction, particularly in conduction times across the carpal tunnel and F-wave latencies. The results of latent addition (p < 0.05) and strength-duration time constant (p = 0.06) suggested increased nodal persistent Na+ currents. At 6 months, nerve conduction continued to improve. Conclusions: Aldose reductase pathway inhibition could rapidly increase nodal Na+ currents and thereby improve the slowing of nerve conduction, presumably because of a restoration of the membranous Na+ gradient.

Fasciculations are a characteristic feature of amyotrophic lateral sclerosis (ALS), and can arise proximally or distally in the motor neuron, indicating a widespread disturbance in membrane excitability. Previous studies of axonal excitability properties (i.e. threshold electrotonus, strength-duration time constant) have suggested respectively that change in potassium or sodium channels may be involved. To reinvestigate these changes and explore their correlation with disease stage, multiple axonal excitability properties (threshold electrotonus, strength-duration time constant, recovery cycle and current-threshold relationship) were measured for the median nerve at the wrist in 58 ALS patients, and compared with 25 age-matched controls. In ALS, there were greater changes in depolarizing threshold electrotonus (i.e. less accommodation) (P < 0.001) and greater supernormality in the recovery cycles (P < 0.001). These abnormalities were more prominent in patients with moderately reduced CMAP (1-5 mV). Modelling the excitability changes in this group supported the hypothesis that axonal potassium conductances are reduced, resulting in increased supernormality despite membrane depolarization. The tendency for strength-duration time constant to be prolonged in ALS was only significant for patients with normal CMAP amplitude (> 5 mV). Patients with severely reduced CMAP (< 1 mV) alone showed reduced threshold changes to hyperpolarizing current. These results suggest a changing pattern of abnormal membrane properties with disease progression. First, persistent Na+ conductance increases, possibly associated with collateral sprouting, and then K+ conductances decline. Both changes cause axonal hyperexcitability, and may contribute to the generation of fasciculations. These serial changes in axonal properties could provide insights into the pathophysiology of ALS, and implications for future therapeutic options.

Objective: To investigate the effects of hyperglycemia on persistent Na+ currents in human diabetic nerves. eliminating the factors of passive membrane properties as a factor. Previous studies show that strength-duration time constant of a nerve is shortened under hyperglycemia, suggesting reduced axonal persistent Na+ currents. However, the time constant is also affected by changes in passive membrane properties. Latent addition using computerized threshold tracking is a new method that can separately evaluate Na+ currents and passive membrane properties. Methods: Latent addition was used to estimate nodal Na+ currents in median motor axons of 83 diabetic patients. Brief hyperpolarizing conditioning current pulses were delivered, and threshold changes at the conditioning-test interval of 0.2 ms were measured as an indicator of nodal persistent Na+ currents. Seventeen patients were examined before and after insulin treatment. Results: There was an inverse linear relationship between hemoglobin A1c levels and threshold changes at 0.2 ms (P=0.02); the higher hemoglobin A1c levels were associated with smaller threshold changes. After insulin treatment. there was a significant improvement in nerve conduction velocities associated with greater threshold changes at 0.2 ms (P=0.03), suggesting an increase in persistent Na+ currents. The fast component of latent addition, an indicator of passive membrane properties, was not affected by the state of glycemic control. Conclusions: Hyperglycemia could suppress nodal persistent Na+ currents, presumably because of reduced trans-axonal Na+ gradient or impaired Na+ channels, and this can be rapidly restored by glycemic control. Significance: Reduced nodal Na+ currents may partly contribute to the pathophysiology of human diabetic neuropathy. (c) 2006 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Objective: To compare site-dependent changes across the carpal tunnel in axonal persistent Na+ conductances in motor and sensory axons. Positive sensory symptoms are prominent features in carpal tunnel syndrome, and a persistent Na+ current is a major determinant of axonal excitability. Methods: The technique of latent addition was used to estimate persistent Na+ currents in median motor and sensory axons at the wrist and palm of 10 normal subjects. Brief hyperpolatizing conditioning current pulses were delivered, and threshold change at the conditioning-test interval of 0.2 ms was measured as an indicator of persistent Na+ currents. Results: Threshold changes at 0.2 ms were greater in sensory than in motor axons at both the wrist and palm. In motor axons, the threshold changes were significantly smaller at the palm (mean, 4.9%) than at the wrist (10.0%). By contrast, the threshold changes were similar at the two sites of sensory axons (12.6 and 13.1%). The passive membrane time constant was similar for motor and sensory axons at the palm and wrist. Conclusions: Nodal persistent Na+ conductances have substantial site-dependent changes decreasing distally across the carpal tunnel in median motor axons, but not in sensory axons. Significance: Whereas sensory axons generally have higher excitability than motor axons, the sensory-motor differences become more prominent across, and possibly at the carpal tunnel than the nerve trunk, and it is suggested that this contributes to the predominance of positive sensory symptoms in carpal tunnel syndrome. (c) 2006 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Background: Adhesion molecules and matrix metalloproteinases. (MMPs) are known to be relevant to the ongoing development and disappearance of areas of demyelination in the white matter of the CNS of multiple sclerosis (MS) patients. This study examined whether serum matrix metalloproteinase-3 (MMP-3) levels correlate with disease activity in MS. Methods: Serum MMP-3 levels in 47 consecutive patients with relapsing-remitting MS were measured by immunoassay every A weeks over a 15 month period. Results: During the study period, 48 clinical relapses occurred. Serum MMP-3 levels within 1 month of relapse were significantly higher than during the remission phase. Sequential analysis showed that serum MMP-3 levels had increased transiently at the time of clinical relapse but returned to the normal range within a month. Conclusions: Circulatory MMP-3 levels are correlated with disease activity in relapsing-remitting MS. This may contribute to the breakdown of the blood-brain barrier at the time of relapse.

Objective: In patients with hemifacial spasm (HFS), abnormal muscle responses (AMR) are frequently present. The objective of this study was to investigate whether the afferent input of AMR is mediated by antidromic facial nerve stimulation or orthodromic trigeminal nerve stimulation. Methods: AMR in the orbicularis oris muscle were recorded in 28 patients with HFS. When AMR were present, they were recorded after subthreshold stimulation of the facial nerve and weak stimulation delivered to the skin. Results: AMR were recordable in 24 (86%) of the patients, and usually consisted of the early constant component (mean onset latency, 10.0 ms) and late variable component (35.3 ms), similar to R1 and R2 of the blink reflex. The early or late components of AMR, or both, were frequently elicited after subthreshold stimulation of the facial nerve (43%) and skin stimulation (88%). Conclusions: AMR are likely to be mediated by trigeminal afferent inputs, rather than antidromic activation of the facial nerve, and are a type of trigeminal reflex.

Guillain-Barre syndrome (GBS) is currently divided into acute inflammatory demyelinating polyneuropathy and acute motor axonal neuropathy (AMAN). Molecular mimicry of the bacterial lipo-oligosaccharide by the human gangliosides is now considered an important cause of AMAN. Gangliosides GM1, GM1b, GD1a, and GalNAc-GD1a are likely to be the epitopes in AMAN. These antibodies initially causes reversible conduction block followed by axonal degeneration. Glycolipids are important to maintain sodium channel clustering at the nodes and tight axo-glial junction at the paranode. Disruption of axonal membrane at or near the node would result in reduced sodium currents, and loosening of the paranodal axo-glial junction leads to paranodal myelin detachment (a type of paranodal demyelination). These changes would cause nerve conduction block in AMAN.

To investigate whether thymectomy is beneficial for non-thymomatous myasthenia gravis patients with mild generalized weakness and onset age >50 years, clinical course and outcomes were compared between 10 patients receiving thymectomy and 12 without it. At the end of follow-up (mean 9.6 years after onset), the thymectomized group showed the greater percentage of clinical remission (no symptoms with or without medication; 50% versus 17%; p=0.11), and the less frequency of the presence of generalized symptoms (30% versus 75%; p<0.05). Thymectomy appears to be effective for late onset, non-thymomatous patients with generalized myasthenia gravis.

We describe a 50-year-old woman who developed chronic inflammatory demyelinating polyneuropathy ( CIDP) one year after onset of hemochromatosis. Electrodiagnostic studies showed evidence of multifocal demyelination. Marked hypergammaglobulinemia with positive anti-nuclear and anti-DNA antibodies was found. Corticosteroid treatment resulted in a significant lessening of neurological symptoms. This is the first case of CIDP with hemochromatosis. The association may be coincidental, but the altered immune system by hemochromatosis was possibly related to the development of CIDP in this patient.

Background: Little is known about long term prognosis and course after immune treatments in chronic inflammatory demyelinating polyneuropathy ( CIDP). Objective: To study long term outcomes and prognostic factors in patients with CIDP. Methods: Clinical and electrophysiological findings, responses to immune modulating treatments, and outcomes five years after the start of treatment were reviewed in 38 CIDP patients. Results: Patients were treated with corticosteroids (89%), immunoglobulin infusion (45%), or plasmapheresis (34%), and 58% received combined therapy. Five years after treatment was begun, 10 (26%) of the patients had complete remission ( lasting >2 years with normal nerve conduction studies), and 23 (61%) had partial remission ( able to walk) with ( 26%) or without ( 34%) immune treatments. The remaining five patients (13%) still had severe disability ( unable to walk) or treatment dependent relapses. Patients with complete remission more often had subacute onset, symmetrical symptoms, good response to initial corticosteroid treatment, and nerve conduction abnormalities predominant in the distal nerve terminals. In contrast, insidious onset, asymmetrical symptoms, and electrophysiological evidence of demyelination in the intermediate nerve segments were associated with refractoriness to treatment or treatment dependent relapse. Conclusions: The long term prognosis of CIDP patients was generally favourable, but 39% of patients still required immune treatments and 13% had severe disabilities. Mode of onset, distribution of symptoms, and electrophysiological characteristics may be prognostic factors for predicting a favourable outcome.

Polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes syndrome is a rare multisystem disorder. Overproduction of vascular endothelial growth factor (VEGF) by plasmocytoma could be responsible for the symptoms. The authors treated four patients with high-dose chemotherapy and autologous peripheral blood stem cell transplantation. Within 6 months, symptoms associated with rapid normalization of serum VEGF levels improved.

Objective: The pattern of abnormal median-normal sural sensory nerve action potential (SNAP) is frequently found in acute/chronic inflammatory demyelinating polyneuropathy (AIDP/CIDP), whereas sural/radial SNAP amplitude ratio is sensitive to detect dying-back degeneration. To investigate whether radial SNAP and its amplitude ratio to median or sural SNAP provide additional particular patterns of sensory nerve involvement. Methods: Superficial radial, median, and sural SNAPs were recorded in 63 normal subjects and in 132 patients with AIDP/CIDP (n=22), diabetic neuropathy (n=83), or other axonal polyneuropathy (n=27). Median/radial and sural/radial amplitude ratios were examined. Results: In normal subjects, median/radial ratio was 0.96 +/- 0.05 (mean +/- SEM), and sural/radial ratio was 0.50 +/- 0.03. Compared with normal controls, the median/radial ratio was lower in patients with AIDR/CIDP (0.64 +/- 0.11; P < 0.001) or diabetic neuropathy (0.75 +/- 0.04; P=0.08), but similar in those with other neuropathy (0.94 +/- 0. 10). The sural/radial ratio was higher in the AIDP/CIDP group (0.71 +/- 0.08; P=0.10), and lower in the diabetic (0.36 +/- 0.03; P < 0.001) and other axonal neuropathy groups (0.40 +/- 0.07; P=0.08). Conclusions: AIDP/CIDP is associated with a reduced median/radial ratio and increased sural/radial ratio, probably reflecting demyelination predominant in the distal nerve terminals. Diabetic neuropathy is characterized by decreases in both median/radial and sural/radial ratios, presumably due to coexistence of carpal tunnel pathology and dying-back degeneration. Significance: Comparison of multiple SNAP amplitudes provides information about characteristic distribution patterns of sensory nerve involvement in peripheral neuropathies. (c) 2005 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.