Correlation of clinical and demyelinating features in patients with neuropathy of otherwise unknown etiology.

PURPOSE: To correlate the electrodiagnostic and clinical features of patients with demyelinating abnormalities and neuropathy of otherwise unknown etiology. METHODS: We examined the records of patient with demyelinating abnormalities and no other cause for neuropathy that were evaluated in our electrophysiology laboratory over the course of a year, to correlate the clinical and electrodiagnostic features. RESULTS: Eight percent of all patients had one or more demyelinating abnormalities. Demyelinating features were significantly more numerous in generalized or asymmetric neuropathy than in distal polyneuropathy. The peroneal nerve was the most commonly affected in all phenotypes, and none of the patients with distal neuropathy had F-wave prolongation in the demyelinating range. CONCLUSIONS: The number and type of demyelinating abnormalities in patients with polyneuropathy vary with the clinical phenotype. The clinical presentation should be considered in developing or evaluating electrodiagnostic criteria for demyelinating neuropathies.

Effect of amplifier gain setting on distal motor latency in normal subjects and CTS patients.

OBJECTIVE: To determine normative cutoffs and sensitivities for median distal latency (MDL), median-thenar to ulnar-thenar latency difference (TTLD), and median-thenar to ulnar-hypothenar latency difference (THLD) at various amplifier gains for carpal tunnel syndrome (CTS) electrodiagnosis. A prior study utilized only an amplifier gain of 0.2 mV/division. METHODS: Abnormal cutoffs for MDL, TTLD and THLD were determined based on 34 control hands at gains of 0.2, 0.5, 1, 2, and 5 mV. Diagnostic sensitivities were determined for 50 patients (80 hands) with clinically and electrodiagnostically defined CTS. RESULTS: At a gain of 0.2 and 0.5 mV/division, abnormal cutoffs for MDL, THLD, and TTLD were: 3.7, 1.2, and 0.8 ms. At gains of 1, 2, and 5 mV the abnormal cutoffs were 4, 1.2, and 1 ms. The sensitivities at gains of 0.2, 0.5, 1, 2, and 5 mV for MDL, THLD, and TTLD were: 65, 66, 53, 57, 61/86, 83, 88, 86, 86/91, 91, 76, 73, 59. CONCLUSIONS: MDL and THLD sensitivities are gain-independent. THLD is substantially more sensitive than MDL at all gains. TTLD sensitivity is maximized with 0.2 and 0.5 mV gains. SIGNIFICANCE: TTLD and THLD increase diagnostic sensitivity with minimal additional effort. TTLD sensitivity is maximized with 0.2 or 0.5 mV gains. The electromyographer's preferred gain may be used.

Rituximab treatment of an IgM monoclonal autonomic and sensory neuropathy.

Rituximab, a monoclonal antibody against B-cell membrane marker CD-20, is an effective treatment for immunoglobulin M (IgM) monoclonal anti-myelin-associated glycoprotein (MAG) neuropathies. We report a patient with an autonomic and painful sensory neuropathy associated with an IgM lambda monoclonal gammopathy, responsive to rituximab. Treatment resulted in a decline in total IgM and improvement in the patient's painful neuropathy and dysautonomia. Rituximab may be an effective and tolerable treatment for autonomic and sensory neuropathy associated with IgM monoclonal gammopathy.

Characterization of neuropathies associated with elevated IgM serum levels.

BACKGROUND: In contrast to the IgM monoclonal gammopathies the neuropathy associated with polyclonal IgM gammopathy has not been well characterized. OBJECTIVE: To characterize the neuropathy in patients with elevated serum IgM. DESIGN: Retrospective review. SETTING: Academically based neuropathy center. PATIENTS: 45 patients with elevated quantitative immunoglobulin M were identified. MAIN OUTCOME MEASURES: Patients are described with regard to clinical phenotype, electrodiagnostic features of demyelination or focality, presence of IgM monoclonal gammopathy, and presence of autoantibody activity. RESULTS: Elevated IgM levels occurred in 45 (11.5%) of 391 patients. Of these, 24 (53%) had polyclonal gammopathy and 21 (47%) had an IgM monoclonal gammopathy. Anti-nerve antibodies occurred in 14/21 (67%) of patients with monoclonal gammopathy, as compared to 1/24 (4%) with polyclonal gammopathy. Clinically, most patients in all groups had a predominantly large fiber sensory neuropathy. Thirty patients underwent electrodiagnostic testing. Of these, 22/30 (73%) fulfilled at least one published criteria for CIDP, including 92% of the monoclonal gammopathy patients and 59% of the polyclonal gammopathy patients. Fifteen of the 30 patients had evidence of focality or multifocality, with 14 of these 15 showing evidence of demyelination. CONCLUSIONS: Monoclonal and polyclonal IgM patients have similar distributions of neuropathy phenotypes. Neuropathy in association with elevated serum IgM, with or without monoclonal gammopathy or autoantibody activity, is more likely to be demyelinating or multifocal. Serum quantitative IgM level and immunofixation in neuropathy patients may aid in identification of an immune mediated or a demyelinating component.

Multifocal acquired sensory and motor neuropathy: electrodiagnostic features.

The electrodiagnostic studies of 13 consecutive patients with multifocal sensory and motor neuropathy of unknown etiology were reviewed to determine whether they exhibit features of demyelination or axonal degeneration. The type and frequency of demyelinating features, fulfillment of electrodiagnostic criteria for chronic inflammatory demyelinating polyneuropathy (CIDP), and response to immunotherapy were noted. Of 13 patients, 11 had at least one electrodiagnostic feature of demyelination at presentation and 2 had none. Seventeen percent to 77% of the patients fulfilled at least one of the published electrodiagnostic CIDP criteria, depending on the criteria used, but the number of demyelinating features per patient was less than reported for unselected patients with CIDP. Patients with multifocal sensory and motor neuropathy had a similar percentage of nerves with partial conduction block or F-wave prolongation as reported for unselected CIDP, but a smaller percentage of nerves exhibiting prolonged distal compound muscle action potential duration, distal latency prolongation or slowed conduction velocities. All treated patients, including 2 who did not meet any CIDP criteria, had at least a moderate response to immunotherapy. The results indicate that a large majority of, but not all, patients with idiopathic multifocal sensory and motor neuropathies exhibit electrodiagnostic features of demyelination, although fewer than seen in classic CIDP.