Electrophysiological sensory demyelination in typical chronic inflammatory demyelinating polyneuropathy

Background: The presence of electrophysiological demyelination of sensory nerves is not routinely assessed in the evaluation of suspected chronic inflammatory demyelinating polyneuropathy (CIDP). Whether this can be useful is unknown. Methods: We compared, using surface recording techniques, in 19 patients with typical CIDP and 26 controls with distal large fibre sensory axonal neuropathy, the forearm median sensory conductions, sensory nerve action potential (SNAP) amplitudes and durations and sensory nerve conduction velocities (SNCVs) of median, radial and sural nerves. Results: Median nerve sensory conduction block (SCB) across the forearm was greater in CIDP patients than in controls (P = 0.005). SNAP durations were longer in CIDP patients for median (P = 0.001) and sural nerves (P = 0.004). Receiver operating characteristic (ROC) curves provided sensitive (>40%) and specific (>95%) cut‐offs for median nerve SCB as well as median and sural SNAP durations. SNCVs were significantly slower for median and sural nerves in CIDP patients, but ROC curves did not demonstrate cut‐offs with useful sensitivities/specificities. Median SCB or prolonged median SNAP duration or prolonged sural SNAP duration offered a sensitivity of 73.7% for CIDP and specificity of 96.2%. Used as additional parameters, they improved diagnostic sensitivity of the American Academy of Neurology (AAN) criteria for CIDP of 1991, from 42.1% to 78.9% in this population, with preserved specificity of 100%. Discussion: Sensory electrophysiological demyelination is present and may be diagnostically useful in typical CIDP. SCB detection and SNAP duration prolongation appear to represent more useful markers of demyelination than SNCV reduction.     

The dropped head syndrome with chronic inflammatory demyelinating polyneuropathy

The dropped head syndrome occurs in a variety of neuromuscular disorders. We present a woman with chronic inflammatory demyelinating polyneuropathy who developed this syndrome, likely reflecting severe demyelination of nerves to cervical paraspinal muscles. © 1994 John Wiley & Sons, Inc.     

Clinical and electrophysiological parameters distinguishing acute‐onset chronic inflammatory demyelinating polyneuropathy from acute inflammatory demyelinating polyneuropathy

Up to 16% of chronic inflammatory demyelinating polyneuropathy (CIDP) patients may present acutely. We performed a retrospective chart review on 30 acute inflammatory demyelinating polyneuropathy (AIDP) and 15 acute‐onset CIDP (A‐CIDP) patients looking for any clinical or electrophysiological parameters that might differentiate AIDP from acutely presenting CIDP. A‐CIDP patients were significantly more likely to have prominent sensory signs. They were significantly less likely to have autonomic nervous system involvement, facial weakness, a preceding infectious illness, or need for mechanical ventilation. With regard to electrophysiological features, neither sural‐sparing pattern, sensory ratio >1, nor the presence of A‐waves was different between the two groups. This study suggests that patients presenting acutely with a demyelinating polyneuropathy and the aforementioned clinical features should be closely monitored as they may be more likely to have CIDP at follow‐up. Muscle Nerve, 2010     

Dispersion of the distal compound muscle action potential in chronic inflammatory demyelinating polyneuropathy and carpal tunnel syndrome

Median neuropathy at the wrist can confound the electrodiagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP), since both conditions can prolong median distal motor latency. Dispersion of the distal CMAP (DCMAP) has recently emerged as a potentially useful adjunct in the electrodiagnosis of CIDP, with good specificity in distinguishing CIDP from certain axon-loss disorders. However, it is uncertain whether focal compression neuropathies produce dispersion of the DCMAP in a manner similar to CIDP. In this study we compared median DCMAP duration in 27 patients with CIDP and 86 with carpal tunnel syndrome, using 39 patients with non-neuropathic musculoskeletal pain syndromes as electrophysiologic controls. We found that, in contrast to CIDP, dispersion of the median DCMAP is uncommon, even in advanced carpal tunnel syndrome, being seen in only 8 of 103 (7.8%) hands. Although the pathophysiologic reasons for a differential effect of focal compression-mediated demyelination and multifocal immune-mediated demyelination (CIDP) on DCMAP duration are uncertain, our findings suggest that the presence of dispersion of the median DCMAP may prove useful in distinguishing immune-mediated demyelination from compression neuropathy alone.     

Restless legs syndrome and polyneuropathy.

Restless legs syndrome (RLS), diagnosed according to the International RLS Study Group criteria, was investigated in 97 consecutive patients with polyneuropathy and found in 29 patients. RLS patients were more often women (22 of 29 vs. 33 of 68; P = 0.015), mainly with sensory neuropathy of small fiber type (15 of 29 vs. 16 of 68; P = 0.009). Changes of sensory action potentials were significantly less severe in RLS patients. In the RLS group, acquired neuropathies, and in particular dysimmune neuropathies, were significantly more frequent (27/29 vs. 46/68; P = 0.009). Thus, RLS is frequent in acquired polyneuropathy of sensory type and mild entity, mainly in women.     

Case of the month: Isaacs' syndrome associated with chronic inflammatory demyelinating polyneuropathy

We report the first case of Isaacs' syndrome in which an inflammatory demyelinating neuropathy was documented histologically. For 9 months, the patient developed slowly progressive weakness, muscle spasms and stiffness, fasciculations, and myokymia in the arms, which were unmodified by sleep. Nerve conduction studies showed multifocal motor conduction block, abnormal dispersion phenomenon, and abnormal sensory and mixed nerve conduction. Needle electromyogram showed continuous motor unit potentials at rest with bursts of rapid-firing discharges which were unaffected by spinal anesthesia but diminished by peripheral nerve block and completely abolished by local curarization. Sural nerve biopsy demonstrated an inflammatory demyelinating neuropathy. Muscle cramping, twitching, and stiffness responded to phenytoin. The patient's weakness gradually responded to prednisone and azathioprine. Over a 17-year period, the patient had three relapses which were well-controlled with prednisone and azathioprine. At this time, the patient is symptom-free without any medication. © 1996 John Wiley & Sons, Inc.     

A European multicentre reappraisal of distal compound muscle action potential duration in chronic inflammatory demyelinating polyneuropathy

Background: The electrodiagnostic value of distal compound muscle action potential duration (DCMAPD) has been studied rarely in chronic inflammatory demyelinating polyneuropathy (CIDP). Cut‐offs proposed have not been widely evaluated. The influence of low‐cut EMG filter settings ≤ 10 Hz as used in Europe is uncertain. Methods: We retrospectively reviewed records of 110 patients with typical, treatment‐responsive CIDP, from Leicester, U.K., Paris and Angers, France. All fulfilled revised European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) clinical and electrodiagnostic criteria for typical CIDP (2010), before consideration of DCMAPD prolongation. Results were compared with those of 110 controls with chronic sensory/sensory‐motor axonal neuropathy. We constructed receiver operating characteristic (ROC) curves for each nerve and derived cut‐offs for DCMAPD prolongation, offering specificity of ≥ 98% vs. controls. Results: DCMAPD was significantly greater in all nerves for CIDP patients, compared with controls (P < 0.001). ROC curves allowed derivation of cut‐offs of sensitivities ranging from 27.1% (ulnar nerve) to 60% (tibial nerve). Using these cut‐offs to define DCMAPD prolongation in any studied motor nerve offered a sensitivity of 69.1% for CIDP and specificity of 97.3% vs. controls. Conclusion: Cut‐offs for DCMAPD are dependent on EMG filter settings. DCMAPD prolongation in any motor nerve, using our derived cut‐offs, represents a sensitive and specific marker of CIDP in patients studied with EMG equipment with low‐cut filter settings ≤ 10 Hz. Appropriate use of this parameter appears an essential criterion to consider in assessing suspected CIDP, which may be helpful in limiting extensiveness and duration of electrophysiological testing, thereby reducing patient discomfort.     

Clinical heterogeneity in mild chronic inflammatory demyelinating polyneuropathy

We describe the clinical presentation, progression and electrodiagnostic features of three patients with a mild form of chronic inflammatory demyelinating polyneuropathy (CIDP). The unusually mild but also variable clinical picture was a cause of diagnostic uncertainty in all, but CIDP was eventually confirmed by extensive electrophysiological studies in each case, as well as by histology in one. Cerebrospinal fluid protein was raised in only one patient. Two patients were treated by intravenous immunoglobulins and both improved. Awareness of the existence of this relatively benign form of CIDP in its various presentations is essential as it can be functionally disabling, progress to more severe symptomatology, and as patients may benefit from immunomodulatory therapy.     

Myasthenia gravis and chronic inflammatory demyelinating polyneuropathy

We describe a patient with the previously unreported association of chronic inflammatory demyelinating polyneuropathy (CIDP) and myasthenia gravis (MG). Immunosuppressive treatment with azathioprine and prednisone achieved clinical and electrophysiological remission of MG and improvement of CIDP. As ophthalmoplegia occurs infrequently in CIDP, the possibility of MG should be considered when this sign is present in a patient with CIDP. Since current therapy with corticosteroids, plasma exchange and other immunomodulating agents is effective against both diseases, their association may be undereported.     

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.     

Dispersion of compound muscle action potential in hereditary neuropathies and chronic inflammatory demyelinating polyneuropathy

Distal compound muscle action potential (DCMAP) dispersion, defined as a DCMAP duration > or = 9 ms, and proximal-distal (P-D) CMAP dispersion are considered useful in the electrodiagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP). Distal and P-D CMAP dispersion have not been fully studied in hereditary neuropathies, and it is not known whether these measures distinguish hereditary from acquired demyelination. We compared DCMAP duration and P-D CMAP dispersion in 91 genetically characterized hereditary neuropathies and 33 subjects with CIDP. DCMAP dispersion was more frequent in nerves affected by CIDP (41.5%) than in Charcot-Marie-Tooth disease (CMT)1A (24.4%), CMT1B (7.4%), hereditary neuropathy with liability to pressure palsies (HNPP) (10.5%), or CMTX (9.8%). P-D CMAP dispersion was more frequent in CIDP (27.7% of nerves) than in hereditary neuropathies (16.3%) when applying American Academy of Neurology (AAN) criteria; however, its frequency was similar in CIDP and the hereditary neuropathies using the more restrictive criteria of the American Association of Neuromuscular and Electrodiagnostic Medicine (AANEM). Although dispersion is more common in CIDP than in the hereditary neuropathies, DCMAP and P-D dispersion occur in at least one motor nerve in a significant proportion of hereditary neuropathies, and cannot be used in isolation to distinguish acquired from hereditary demyelination.     

慢性炎性脱髓鞘性多发性神经病的治疗进展

慢性炎性脱髓鞘性多发性神经病（chronic inflammatory demyelinating polyradiculopathy,CIDP）是一种获得性的免疫介导的周围神经病.临床特征包括进展性或复发性的肢体无力、感觉缺失和腱反射消失等.     

Acute inflammatory demyelinating polyneuropathy: contribution of a dispersed distal compound muscle action potential to electrodiagnosis

Prolonged duration of the distal compound muscle action potential (DCMAP) ("DCMAP dispersion") is useful in the electrodiagnosis of chronic inflammatory demyelinating polyneuropathy (CIDP) with good specificity in distinguishing CIDP from amyotrophic lateral sclerosis (ALS) and diabetic polyneuropathy, but its role in the electrodiagnosis of acute inflammatory demyelinating polyneuropathy (AIDP) is unclear. This study addresses this issue by determining the optimal cutoff for DCMAP duration using receiver operating characteristic (ROC) analysis in 207 motor nerves from 53 clinically defined AIDP patients compared to 148 motor nerves from 55 ALS patients. We also determined whether the presence of DCMAP dispersion improves the sensitivity of four of the most sensitive published sets of electrodiagnostic criteria for AIDP. Using the ROC-derived optimal DCMAP duration cutoff of 8.5 ms, DCMAP dispersion was found in at least one motor nerve in 66% of subjects with AIDP compared to 9% of subjects with ALS. DCMAP dispersion improved the sensitivity of the four tested criteria sets to 76%-87% from 43%-77%. Moreover, of 13 AIDP patients who met none of the four published criteria sets, 5 (38%) had at least one dispersed DCMAP. These findings indicate that the presence of DCMAP dispersion adds electrodiagnostic sensitivity to the currently published criteria sets, while maintaining reasonably high specificity against a prototypical disorder of the primary motor neuron with axon loss.