By Michael Rubin, MD
Professor of Clinical Neurology, Weill Cornell Medical College
Dr. Rubin reports he is a consultant for Merck Sharp & Dohme Corp.
MRI of the brachial plexus and/or lumbar plexus may be helpful in making a diagnosis of chronic inflammatory demyelinating polyradiculopathy in patients who do not meet the standard criteria. Imaging findings include increased signal intensity, nerve hypertrophy, and nerve contrast enhancement.
Fargeot G, Viala K, Theaudin M, et al. Diagnostic usefulness of plexus magnetic resonance imaging in chronic inflammatory demyelinating polyradiculopathy without electrodiagnostic criteria of demyelination. Eur J Neurol 2019;26:631-638.
Proximal and distal symptoms, motor more so than sensory, that are progressive over more than two months, with depressed deep tendon reflexes, elevated cerebrospinal fluid protein with normal cells, and nerve conduction studies demonstrating demyelinating neuropathy, support a clinical diagnosis of chronic inflammatory demyelinating polyradiculopathy (CIDP). Approximately 20% of patients with predominantly axonal loss, proximal demyelination, or primarily sensory involvement lack definite or probable electrodiagnostic criteria for CIDP. Might brachial or lumbosacral plexus magnetic resonance imaging (MRI) allow a diagnosis of CIDP to be made in these instances?
In this retrospective study, Fargeot et al reviewed all patients who underwent brachial or lumbosacral plexus MRI, or both, for possible CIDP at the Bicetre and Pitié-Salpêtrière University Hospitals in Paris, between January 2013 and June 2015. All patients met European Federation of Neurological Societies/Peripheral Nerve Society (EFNS/PNS) clinical criteria for CIDP and had undergone nerve conduction studies and needle electromyography, as well as one of either lumbar puncture, nerve biopsy, or somatosensory-evoked potential examination. Laboratory studies included complete blood count, fasting blood glucose, liver and renal function tests, folate and B12 levels, human immunodeficiency virus antibody, serum protein electrophoresis, and antiganglioside and anti-myelin-associated glycoprotein (anti-MAG) antibody determination. Exclusion criteria included patients with hereditary neuropathy, anti-MAG neuropathy, or motor neuropathy with conduction block. Interpretation of the MRI was performed by a neuroradiologist aware of the possibility of CIDP but blinded to all clinical data. The authors performed a statistical analysis using the Wilcoxon-Mann-Whitney test, with categorical variables compared with a chi-squared test, or Fisher’s exact test, where warranted. P < 0.05 was considered statistically significant.
Among 60 patients who underwent plexus MRI for suspected CIDP, four were excluded because of a diagnosis of motor neuropathy with conduction block or anti-MAG neuropathy made during the study period (n = 2 each). Another eight patients who did not undergo either lumbar puncture, nerve biopsy, or somatosensory-evoked potential examination were excluded. Among the 48 remaining patients, 38 did not meet definite EFNS/PNS electrodiagnostic criteria for CIDP, of which 22 (61%) were purely sensory, six (17%) had distal acquired demyelinating symmetric neuropathy, three each (8% each) had purely motor or focal neuropathy, and two (6%) had multifocal acquired demyelinating sensory and motor neuropathy (Lewis-Sumner syndrome).
Among 10 patients who met electrodiagnostic criteria for CIDP, plexus MRI was abnormal in eight patients (80%), demonstrating increased signal intensity on STIR (8/8), hypertrophy (8/8), and contrast enhancement (2/8). Among 38 patients without definite electrodiagnostic criteria for CIDP, plexus MRI was abnormal in 22 (58%), encompassing increased signal intensity on STIR in 22/22, hypertrophy in 20/22 (91%), and contrast enhancement in 8/22 (36%). MRI findings in these patients were more asymmetric and less diffuse than in patients who satisfied electrodiagnostic criteria for CIDP. Following plexus MRI, diagnosis was adjusted in 7/38 (18%) and allowed 7/24 (29%) to be classified as definite CIDP when used as a supportive criterion in conjunction with electrodiagnostic studies. Plexus MRI can be a valuable tool in the diagnosis of CIDP.
COMMENTARY
Following treatment for CIDP, determining objective patient improvement may be challenging where variation is minimal or fatigue predominates. Spina et al tested the 6-minute walk test (6MWT) among 42 CIDP patients to determine its sensitivity compared to other clinical outcome measures, including the modified version of the inflammatory neuropathy cause and treatment scale–sensory subscore, the Overall Neuropathy Limitation Scale, the Rasch-built overall disability scale, the modified Rankin Scale, and the Medical Research Council scale. Fatigue was analyzed by comparing first minute vs. the sixth minute velocity during the 6MWT. By using anchor and distribution-based approaches, the Minimal Clinically Important Difference Score (MCID), indicating meaningful clinical change required to consider a patient a responder, was calculated to be 20 meters. Using the 6MWT-MCID with other outcome measures, 74% of patients were identified as responders. Sensitivity of the 6MWT, which also captured fatigue-related changes, was 90%, compared to 77% for other measures. Routine assessment of CIDP patients should include the 6MWT, with MCID to identify responders to therapy set at 20 meters.
REFERENCE
- Spina E, Topa A, Iodice R, et al. Six-minute walk test is reliable and sensitive in detecting response to therapy in CIDP. J Neurol 2019;266:860-865.
