Clinical spectrum of chronic acquired demyelinating polyneuropathies

A number of presentations of chronic demyelinating polyneuropathy have been identified, each distinguished by its phenotypic pattern. In addition to classic chronic inflammatory demyelinating polyneuropathy (CIDP), which is characterized clinically by symmetric proximal and distal weakness and sensory loss, several regional variants can be recognized: multifocal motor neuropathy (MMN: asymmetric and pure motor), multifocal acquired demyelinating sensory and motor (MADSAM) neuropathy (asymmetric, sensory, and motor), and distal acquired demyelinating symmetric (DADS) neuropathy (symmetric, distal, sensory, and motor). There are also temporal, pathological, and disease-associated variants. This review describes a clinical scheme for approaching the chronic acquired demyelinating polyneuropathies that leads to a rational use of supportive laboratory studies and treatment options. In addition, we propose new diagnostic criteria for CIDP that more accurately reflect current clinical practice.     

Distal acquired demyelinating symmetric neuropathy

OBJECTIVE: To characterize an acquired, symmetric, demyelinating neuropathic variant with distal sensory or sensorimotor features. BACKGROUND: Classic chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) patients have prominent proximal and distal weakness. However, chronic demyelinating neuropathies may present with different phenotypes. An approach that distinguishes these disorders primarily according to the pattern of weakness may be useful to the clinician. METHODS: A total of 53 patients with acquired symmetric demyelinating polyneuropathies were classified primarily according to the pattern of the neuropathy and secondarily according to the presence and type of monoclonal protein (M-protein) in this retrospective review. The authors distinguished between patients with distal sensory or sensorimotor involvement, designated as distal acquired demyelinating symmetric (DADS) neuropathy, from those with proximal and distal weakness, who were designated as CIDP. RESULTS: M-proteins were present in 22% of patients with CIDP. There were no features that distinguished clearly between CIDP patients with or without an M-protein, and nearly all of these patients responded to immunomodulating therapy. In contrast, nearly two-thirds of the patients with DADS neuropathy had immunoglobulin M (IgM) kappa monoclonal gammopathies, and this specific combination predicted a poor response to immunomodulating therapy. Antimyelin-associated glycoprotein (anti-MAG) antibodies were present in 67% of these patients. CONCLUSION: Distinguishing acquired demyelinating neuropathies by phenotype can often predict the presence of IgM kappa M-proteins, anti-MAG antibodies, and responses to immunomodulating therapy.     

Distal acquired demyelinating symmetric polyneuropathy progressing to classic chronic inflammatory demyelinating polyneuropathy and response to fludarabine and cyclophosphamide

Introduction: Distal acquired demyelinating symmetric polyneuropathy (DADS) is proposed as a distinct entity from classic chronic inflammatory demyelinating polyneuropathy (CIDP). Methods: We report a 58‐year‐old woman with DADS that progressed to a severe case of classic CIDP. Results: She had distal numbness and paresthesias, minimal distal weakness and impaired vibratory sensation. She had anti‐MAG antibodies, negative Western blot, and lacked a monoclonal gammopathy. There were prolonged distal motor latencies. She remained stable for 6 years until developing proximal and distal weakness. Nerve conduction studies showed multiple conduction blocks. She developed quadriparesis despite first‐line treatment for CIDP. She was started on cyclophosphamide and fludarabine. Twenty‐five months after receiving chemotherapy, she had only mild signs of neuropathy off all immunotherapy. Conclusions: DADS may progress to classic CIDP and is unlikely to be a separate disorder. Fludarabine and cyclophosphamide may be effective for refractory CIDP. Muscle Nerve, 2013     

Chronic polyneuropathies in Vest-Agder, Norway

Epidemiological data on chronic polyneuropathies, especially inflammatory types, is limited. The purpose of this study was to examine the spectrum of causes and estimated prevalence of various polyneuropathy types in Vest‐Agder, and to examine the clinical features of the Vest‐Agder population of chronic inflammatory demyelinating polyneuropathy (CIDP). In Vest‐Agder county (population of 155 464), polyneuropathy patients are registered in a database and followed prospectively. We did a measure of the database on October 31 1999. A total of 192 patients were registered. The prevalence for chronic inflammatory demyelinating polyneuropathy (CIDP) was 7.7 per 100 000 population. The course was relapsing in five of fifteen patients, progressive in four patients and slowly progressive in six of fifteen patients. Two of the fifteen patients had pure sensory symptoms. The mean Rankin disability score was 3.4 at maximal deficit and 2.1 at last follow‐up. The prevalence of paraproteinemic polyneuropathy was 5.1 per 100 000 population. None of the patients with paraproteinemic polyneuropathy were worse than slightly disabled (disability score ≤ 2). The prevalences for other polyneuropathies were as follows: polyneuropathy and RA, 1.3; polyneuropathy and Sjögren's syndrome or sicca complex, 4.5 (polyneuropathy was the presenting symptom in five of seven patients); sarcoidosis 1.9; polyneuropathy and chronic Lyme, 0.6; paraneoplastic polyneuropathy, 1.9; diabetic polyneuropathy 23.2; vitamin deficiency, 5.1; alcoholic and toxic polyneuropathy, 19.9; hereditary polyneuropathy, 14.8. Cryptogenic polyneuropathies made up 26% of all polyneuropathies. The mean disability score was 2.0 (SD 1.1). In conclusion, prevalence of CIDP was significantly higher than previously reported, and the prognosis was good in the majority of patients. Patients with paraproteinemic polyneuropathy were not severely disabled. Polyneuropathy was the presenting symptom in the majority of patients with Sjögren's syndrome or sicca complex.     

Chronic inflammatory demyelinating polyradiculoneuropathy and variants: where we are and where we should go

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a chronic and often disabling sensory motor neuropathy postulated as caused by an immune attack against peripheral nerve myelin. In addition to a classic sensory–motor polyneuropathy, other phenotypes of CIDP have been described including the Lewis‐Sumner syndrome, distal acquired demyelinating symmetric (DADS) neuropathy, pure motor CIDP, pure sensory CIDP including chronic immune sensory polyradiculopathy (CISP), and focal CIDP. These phenotypes are currently considered to be variants of CIDP, even if the possibility that they represent different demyelinating neuropathies cannot be fully excluded considering differences in their response to therapy. Several data support the role of the immune system in the pathogenesis of CIDP even if the precise targets and actors (antibodies and lymphocytes) of this immune response remain uncertain. Recent studies have shown that the therapeutic response may differ in patients with peculiar clinical presentations supporting the hypothesis that different pathogenetic mechanisms may underlie the heterogeneity of CIDP. The majority of patients with CIDP show improvement after immune therapies including corticosteroids, plasma exchange, and high‐dose intravenous immunoglobulin (IVIg). It remains unclear why none of the other immune therapies that were reported to be variably effective in other immune disorders proved to be effective also in CIDP.     

Multifocal acquired demyelinating sensory and motor neuropathy: report of a case and review of the literature

Multifocal acquired demyelinating sensory and motor (MADSAM) neuropathy is characterized by an asymmetric multifocal pattern of motor and sensory loss, and conduction block and other features of demyelination in nerve conduction studies. MADSAM neuropathy needs to be differentiated from chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN). In classic CIDP, there are symmetric proximal and distal weakness, sensory deficit in both upper and lower extremities and reduced deep tendon reflex. In MMN, limb weakness without sensory loss is asymmetric in the distribution of individual peripheral nerves and the weakness typically begins in the distal upper extremities. We report one patient with chronic progression of asymmetric numbness and weakness in four extremities. MADSAM neuropathy was diagnosed after extensive clinical and laboratory evaluations. It is very important to distinguish between CIDP, MADSAM neuropathy, and MMN by clinical, laboratory, and histological features because of different effective therapeutic strategies.     

New trends in neuropathy practice: clinical approach to CIDP]

Our recent study showed that the overall prevalence of CIDP was estimated as 2.2 per 100,000 population in Aomori Prefecture, in Northan Honshu of Japan. In our series of more than 80 cases with CIDP, a chronic acquired inflammatory demyelinating polyneuropathy, nearly 30% showed clear laterality of weakness, and electrophysiologic laterality or multifocality was apparent in almost all cases. Nearly 90% of patients were able to walk without walking aids or other assistance. Sixty% showed distal dominant muscular weakness. In 12 patients with age of onset under 15, pes cavus deformity was seen in 5. Two thirds complained numbness in the extremities during progressive phase. Four cases initially showed severe sensory ataxia associated with motor conduction block. It should be, thus, reminded that clinical spectrum of CIDP is enormously wide: chronic acquired demyelinating multiple mononeuropathy showing asymmetric involvement (Lewis-Summer syndrome) should be put on one side of the clinical presentation of CIDP. Multifocal motor neuropathy (MMN) is, on the other hand, an unique syndrome mimicking amyotrophic lateral sclerosis (ALS). There may be, however, true association syndrome of CIDP and ALS presenting both peripheral nerve demyelination and pyramidal sign with progressive bulbar involvement. Recently, several atypical varieties of CIDP showing only one-limb involvement, upper limb weakness rather than lower limb power loss, or proximal weakness, etc ... have been reported in the literature. To realize such clinical variations of chronic acquired demyelinating neuropathy is important for early diagnosis and commencement of treatment of CIDP. Clinical guideline for suspicion of CIDP could be useful for general physicians and neurologists unfamiliar to peripheral neuropathies.     

Non‐anti‐MAG DADS neuropathy as a variant of CIDP: clinical,electrophysiological, laboratory features and response to treatment in 10 cases

Background and purpose: Some patients within the spectrum of chronic inflammatory demyelinating polyradiculoneuropathies (CIDP) have distal acquired demyelinating symmetric (DADS) neuropathy, usually associated with anti‐myelin‐associated‐glycoprotein (MAG) IgM monoclonal gammopathy. The aim of this retrospective study was to investigate patients with DADS neuropathy without anti‐MAG antibodies, and study their response to immunotherapy. Methods: Patients were selected on the basis of (i) ‘Definite CIDP’ according to the EFNS/PNS Guideline criteria, (ii) The presence of disproportionately prolonged motor latencies resulting in a terminal latency index (TLI) ≤0.25 in at least two motor nerves and (iii) The absence of anti‐MAG antibodies on ELISA. Response to immunotherapy was defined as persistent improvement by at least one point on the INCAT disability score. Results: Data from 146 CIDP patients were analysed, and 10 patients were included. Six had clinically pure sensory neuropathy, and four had sensorimotor neuropathy. Ataxia was present in nine patients, generalized areflexia in seven and postural tremor in two. Five of the 10 patients had abnormal sensory potentials only in the upper limbs. An associated condition was found in nine patients: two chronic lymphocytic leukaemias, four IgG monoclonal gammopathies (one associated with non‐Hodgkin’s lymphoma) and two IgM monoclonal gammopathies of unknown significance. Patients were mostly improved with intravenous immunoglobulin (IVIg), corticosteroids, plasma exchanges, or a combination thereof. Conclusion: DADS neuropathy without anti‐MAG antibodies is more likely to be considered a variant of CIDP. In addition, such patients should be systematically investigated for an associated haematological or immunological condition.     

Utility of somatosensory evoked potentials in chronic acquired demyelinating neuropathy

Chronic acquired demyelinating polyneuropathy (CADP) is a heterogeneous syndrome that may be classified into a number of subtypes. Somatosensory evoked potentials (SSEPs) assess proximal segments of sensory nerves, inadequately assessed by routine nerve conduction studies (NCSs). The aim of the present study was to determine the utility of SSEPs in diagnosing and classifying different CADP subtypes. Forty-seven patients with CADP were studied and classified in five groups based on conventional NCSs and SSEPs. Some patients in Group 1 were initially misdiagnosed as having either motor neuron disease or multifocal motor neuropathy due to normal sensory NCSs, but they exhibited abnormal tibial and median nerve SSEPs, as evidenced by marked prolongation or absence of peripheral potentials (N9-median nerve, and N20-tibial nerve). These were reclassified as having chronic inflammatory demyelinating neuropathy (CIDP). In CIDP patients (Group 2), SSEPs were abnormal, thereby confirming the presence of demyelination in the proximal peripheral nerves. Patients with distal acquired demyelinating neuropathy (DADS) (Group 3), as defined by conventional NCS, exhibited abnormal SSEPs when anti-MAG antibodies were present. Anti-MAG-negative DADS patients (Group 3) had normal SSEPs. In the pure sensory ataxic group (Group 4), SSEP studies disclosed poorly formed and delayed cortical potentials with absent lumbar (N20) potentials, thereby suggesting the presence of proximal demyelination. SSEPs were normal in the pure motor CIDP and multifocal motor neuropathy patients (MMN) (Group 5), thereby differentiating asymmetric forms of CIDP from MMN. These findings suggest that SSEPs may be an important complementary investigation to conventional NCSs in the diagnosis of CADP.     

The relative diagnostic sensitivity of different F-wave parameters in various polyneuropathies.

We studied F-wave minimum latency, persistence, and chronodispersion in the median and ulnar nerves of 70 controls and 75 patients with various polyneuropathies. Prolonged minimum latency was the most frequent F-wave abnormality in all groups of patients with polyneuropathy. The finding of decreased persistence or absence of F-responses was comparable in sensitivity to prolonged minimum latency in Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP), whereas chronodispersion had a comparable sensitivity only in CIDP. Decreased persistence of obtained F-responses, and the absence of F-responses in nerves with low compound muscle action potential amplitudes, were nonspecific findings. F-wave studies often provide useful additional information in the evaluation of patients suspected of having a polyneuropathy. In patients with axonal polyneuropathies, we found that F-wave studies are significantly more sensitive than standard motor conduction studies in identifying physiological abnormalities of motor axons. Furthermore, in a patient with an acquired polyneuropathy, the finding of markedly prolonged minimum latency, or the absence of F-responses in nerves with normal CMAP amplitude, is highly specific for the presence of demyelination.     

Polyneuropathy associated with IgG/IgA monoclonal gammopathy: a clinical and electrophysiological study of 15 cases

Peripheral neuropathy has been widely reported in patients with monoclonal gammopathy (MG), more frequently immunoglobulin M (IgM) or IgG than IgA. Nevertheless, it remains unclear whether this association has clinical or pathogenic relevance. In order to clarify the possible role of IgG/IgA MG in neuropathy, we studied the clinical and electrophysiological features of 15 consecutive patients with polyneuropathy and IgG/IgA-MG, and compared them to those of 40 patients with polyneuropathy associated with IgM-MG, previously reported. Nine middle-aged patients (60%) had a chronic progressive or relapsing demyelinating polyneuropathy (DP) that was clinically and electrophysiologically indistinguishable from classic chronic inflammatory demyelinating polyneuropathy (CIDP) and frequently responded to immunosuppressive treatments, both characteristics supporting a dysimmune process. Six older patients (40%) had a chronic axonal distal polyneuropathy similar to the so-called chronic cryptogenic sensory polyneuropathy: there was no clear relationship with the MG in these patients and the response to immunosuppressive treatments was poor. Several features allowed us to distinguish between polyneuropathies associated with IgG/IgA-MG (IgG/IgA-PN) considered together and polyneuropathies associated with IgM-MG (IgM-PN). In the first group, the proportion of patients with a predominantly sensory clinical picture (27%) was less than that in the second group (75%), and there were fewer changes in nerve conduction studies. In addition, we found that the nine patients with DP associated with IgG/IgA-MG (IgG/IgA-DP) differed from the 31 with DP associated with IgM-MG (IgM-DP): clinical and electrophysiological studies clearly showed that the demyelinating pattern was more heterogeneous in IgG/IgA-DP than in IgM-DP. The spectrum of polyneuropathies associated with IgG/IgA-MG is heterogeneous, including DP, which is similar to classic CIDP, and axonal polyneuropathy, in which the pathogenic role of the MG remains elusive. In addition, IgG/IgA-DP differ from IgM-DP on clinical and electrophysiological grounds, suggesting probable different physiopathological mechanisms.     

Cutaneous innervation in chronic inflammatory demyelinating polyneuropathy

The authors evaluated epidermal nerve density (END) and thermal thresholds in 18 patients with chronic inflammatory demyelinating polyneuropathy (CIDP). END of patients with CIDP were lower than those of controls (4.5 +/- 2.9 vs 10.5 +/- 3.9 fibers/mm, p < 0.001). Reduced END were associated with autonomic symptoms. Thermal thresholds of patients with CIDP were elevated (88.2% for warm stimuli and 70.6% for cold stimuli). Patients with CIDP have small-fiber sensory and autonomic neuropathies.     

Serum levels of tumor necrosis factor-alpha in chronic inflammatory demyelinating polyneuropathy

BACKGROUND: Activated macrophages and T lymphocytes may play a role in the pathogenesis of chronic inflammatory demyelinating polyneuropathy (CIDP). Both cell types secrete tumor necrosis factor-alpha (TNFalpha), which has toxic effects on myelin and endothelial cells. METHODS: The serum concentration of TNFalpha was measured by ELISA and compared with clinical and electrophysiological profiles in 20 patients with CIDP. RESULTS: An increased serum level of TNFalpha was detected in 5 (25%) patients and was associated with subacute progression, severe neurologic disabilities, and symmetric weakness involving proximal as well as distal muscles. TNFalpha levels increased during the active phase in this subgroup of patients. The levels of TNFalpha correlated with the severity of demyelinating conduction abnormalities in the intermediate as well as distal nerve segments, suggesting demyelination diffusely distributed along the nerves. CONCLUSION: Circulating TNFalpha increases during the active phase in a subgroup of CIDP patients and may play a role in the pathogenesis of demyelination and the breakdown of the blood-nerve barrier in CIDP.     

Clinimetric evaluation of a new overall disability scale in immune mediated polyneuropathies

OBJECTIVES: To determine the validity, reliability, and responsiveness of a new overall disability sum score in immune mediated polyneuropathies. METHODS: Three impairment measures (MRC sum score, sensory sum score, grip strength (Vigorimeter)) and three disability scales (an overall disability sum score (ODSS), Hughes' functional scale (f score), Rankin scale) were assessed in a cross sectional group of 113 clinically stable patients (83 with Guillain-Barré syndrome, 22 with chronic inflammatory demyelinating polyneuropathy (CIDP), eight with a gammopathy related polyneuropathy). The ODSS was also used serially in 20 patients with recently diagnosed Guillain-Barré syndrome (n = 7) or CIDP (n = 13) and changing clinical conditions. Multiple regression studies were performed to compare the impact of impairment disturbances (independent variables) on the various disability scales (dependent variable). RESULTS: Moderate to good construct validity (stable group: Spearman's rank test (absolute values), r = 0.41-0.79; longitudinal group: multiple correlation coefficient, R = 0.69-0.89; p < 0.006 for all associations) and reliability (intraclass correlation coefficient, R = 0.90-0.95; p < 0.0001) were demonstrated for the ODSS. Its SRM values were high (> 0.8), indicating good responsiveness. Impairment measures accounted for a higher variance proportion of the ODSS compared with the f score and Rankin (R = 0.64 v 0.56 and 0.45, respectively). CONCLUSIONS: All clinimetric requirements were met by the overall (arm and leg) disability sum score in immune mediated polyneuropathies. Its use is therefore suggested in evaluating immune mediated polyneuropathies.     

血清抗糖脂抗体在自身免疫性多发性周围神经病中的意义

目的 :探讨抗周围神经膜表面糖脂抗体在自身免疫介导的多发性周围神经病中的临床意义。方法 :ELISA法测定格林 巴利综合征和慢性炎性脱髓鞘性周围神经病患者血清中抗硫脂抗体和 7种节苷脂抗体 (GM1、GM2、GA1、GD1a、GD1b、GT1b和GQ1b)的阳性率。结果 :GBS和CIDP组患者抗硫脂抗体、抗GM1、GA1和GD1b抗体的阳性率显著高于非自身免疫性周围神经病组 (P <0 0 5 ) ;此两组患者间的抗体阳性率比较则无显著差异 ;GBS组内有眼 /咽肌麻痹的患者 (17例 )与无眼肌和 (或 )咽喉肌麻痹患者 (2 5例 )的节苷脂抗体阳性率也无显著差异。结论 :血清抗硫脂抗体和抗GM1抗体增高对自身免疫介导的多发性周围神经病患者有一定临床意义。     

Development of weakness in patients with chronic inflammatory demyelinating polyneuropathy and only sensory symptoms at presentation: A long-term follow-up study

This long-term follow-up study examined patients with chronic inflammatory demyelinating polyneuropathy (CIDP) and only sensory symptoms at first presentation, with emphasis on the development of motor symptoms and long-term disability. From all CIDP patients referred to our Department between 1987 and 1995, seven had only sensory symptoms at first clinical presentation. These were investigated according to a standard protocol, including a quantified clinical neurological examination and nerve conduction studies. The mean duration of the disease before weakness developed was 3.1 years, but varied considerably (0.8–6.3 years). At follow-up, weakness developed in five patients and persisted in three of them. Five patients were not seriously incapacitated by their disease (Rankin 1 or 2), four of them being in remission now and one showing a very slow progression of disease. Two patients were moderately disabled (Rankin 3); one had severe persistent sensory ataxia and only weakness during relapses and one had stepwise progression and moderate weakness. Motor nerve conduction studies revealed that the most notable worsening in the entire group of patients was a decrease in distal compound muscle action potential amplitudes, indicating the development of distal conduction block or axonal degeneration. These findings show that CIDP with only sensory symptoms is a transient clinical stage that precedes the appearance of weakness in about 70% of patients. The long-term prognosis does not differ from that of patients with CIDP who have weakness at the beginning of the disease. Received: 3 December 1998 Received in revised form: 17 May 1999 Accepted: 2 July 1999     

Immunotherapy‐responsive allodynia due to distal acquired demyelinating symmetric (DADS) neuropathy

Introduction: Distal acquired demyelinating symmetric (DADS) neuropathy is a distal variant of chronic inflammatory demyelinating polyradiculoneuropathy. It is characterized by chronic distal symmetric sensory or sensorimotor deficits. Sensory ataxia is a common clinical presentation. Nerve conduction studies typically show markedly prolonged distal motor latencies. Methods: We report 2 patients with chronic progressive generalized pain and fatigue, with normal neurological examinations except for allodynia. Results: Nerve conduction studies were typical of DADS neuropathy. Monoclonal protein studies were negative. Cerebrospinal fluid protein levels were elevated. Sural nerve biopsies revealed segmental demyelination and remyelination. One biopsy had marked endoneurial and epineurial lymphocytic infiltration. Immunomodulatory therapy alleviated the pain and fatigue and markedly improved distal motor latencies in both patients. Conclusions: DADS neuropathy can present with pain and a normal neurological examination apart from allodynia. Nerve conduction studies are necessary for diagnosis. These patients respond to immunotherapy better than typical DADS neuropathy patients with sensory ataxia. Muscle Nerve 54 : 973–977, 2016     

Individual attributes versus composite scores of nerve conduction abnormality: sensitivity,reproducibility, and concordance with impairment

Composite scores may be more sensitive and reproducible than single attributes of nerve conduction for detection of peripheral neuropathy, but this requires validation in large patient cohorts. Also, the concordance of individual attributes versus composite scores with clinical measures of severity has not been tested. Here, we study these issues in prospectively studied cohorts: diabetic patients from Rochester, Minnesota (RDNS; n = 396); chronic inflammatory demyelinating polyneuropathy (CIDP) patients (n = 55); and multifocal motor neuropathy (MMN) patients (n = 18). With specificity fixed at the 97.5 percentile, we found that, in generalized polyneuropathies (diabetic and CIDP), composite scores (especially ones including conduction velocity, distal latencies, and F-waves) of individual or multiple nerves tended to be more sensitive than individual attributes. By contrast, for multiple mononeuropathies, some individual attributes or composite scores of individual nerves were more sensitive than composite scores. In diabetic polyneuropathy, composite scores tended to be more reproducible than individual attributes of nerve conduction. Highly significant correlations were found between individual attributes or composite scores and neurologic impairment in diabetic polyneuropathy and in CIDP; in general, correlation coefficients were higher for composite scores. These correlations were higher for amplitudes than for conduction velocities or distal latencies. We conclude that, with the availability of microprocessors and normative databases, electromyographers may increasingly seek to express nerve conduction abnormality also as composite scores of individual or several nerves.     

Restless legs syndrome in chronic inflammatory demyelinating polyneuropathy

The prevalence of restless legs syndrome (RLS) is unknown in chronic inflammatory demyelinating polyneuropathy (CIDP). We prospectively studied 28 patients with CIDP. Prevalence of RLS in CIDP was ascertained by face‐to‐face interview using validated criteria and compared with that in 28 age‐ and gender‐matched controls. Eleven (39.3%) CIDP patients were diagnosed with RLS, compared with 2 (7.1%) controls (P < 0.01). A significant correlation was ascertained between presence of RLS and lower limb weakness, functional disability, and summated compound muscle action potential (CMAP). The prevalence of RLS in CIDP was significantly higher than in controls in our study population, approaching 40%. Screening for RLS in CIDP patients may be appropriate, particularly in those with weakness, disability, and motor axonal loss in the lower limbs. Our findings may otherwise suggest the existence of peripheral components to the pathophysiology of RLS in patients with CIDP. Muscle Nerve, 2010     

Utility of the distal compound muscle action potential duration for diagnosis of demyelinating neuropathies

To assess the significance of distal compound muscle action potential (CMAP) duration for diagnosis of demyelinating neuropathies, electrophysiologic data were reviewed from 471 subjects, including 145 normal controls, 60 patients with chronic inflammatory demyelinating polyneuropathy (CIDP), 205 with other neuropathy, and 61 with amyotrophic lateral sclerosis (ALS). The duration of distally evoked CMAP was measured in the median, ulnar, tibial, and peroneal nerves. Optimal cut-off values were calculated with receiver-operating characteristic (ROC) curves. In comparison of normal controls and CIDP patients, ROC analyses showed the sufficient area under the curves (82-93%). When the cut-off values in the detection of demyelination were determined as the point with 98% specificity vs. normal on the ROC curves (median, 6.6 ms; ulnar, 6.7 ms; peroneal, 7.6 ms; tibial, 8.8 ms), the sensitivity was 77% for CIDP, with a specificity of 90% vs. ALS and 95% vs. diabetic neuropathy. The distal CMAP duration is a useful index for the detection of distal demyelination. We suggest the above cut-off values for each nerve as one of the electrodiagnostic criteria for demyelinating neuropathies, preferentially affecting the distal nerve terminals, such as CIDP.