Marieke van Rosmalen

Reliability of brachial plexus MRI in chronic inflammatory neuropathies 47 3 RESULTS Subjects We identified 36 patients with a chronic inflammatory neuropathy (CIDP = 19, MMN = 17) and 14 disease controls (motor neuron disease = 4, Hirayama disease = 3, ulnar neuropathy = 1, neurogenic thoracic outlet syndrome = 1, polyneuropathy in Sjögren’s disease = 1, brachial plexopathy caused by alcohol abuse = 1, cervical myelopathy = 1, lumbar polyradiculopathy = 1, chronic idiopathic axonal polyneuropathy = 1). Patient characteristics are summarized in Table 3.1 . Data was acquired for 26 subjects by using 1.5T MRI scanners and for 24 subjects by using 3.0T MRI scanners. Table 3.1 Patient characteristics Patient characteristics Inflammatory neuropathy Controls Level of significance Total CIDP MMN Total Number of subjects 36 19 17 14 Age, years (SD) 59.7 (14.9) 69.9 (9.0) 48.3 (11.7) 55.2 (16.5) NS Male (%) 26 (72%) 12 (63%) 14 (82%) 7 (50%) NS Disease duration, months (SD) 43.3 (47.7) 45.0 (48.7) 41.5 (48.0) 39.1 (37.0) NS Abbreviations: CIDP = Chronic inflammatory demyelinating polyneuropathy; MMN = Multifocal motor neuropathy; SD = standard deviation; NS = not significant. Age and disease duration are mean (SD). Inter-rater variability Raters agreed in 26 of 50 (52%) brachial plexus images when using three categories for abnormality ( Table 3.2 ). Using the dichotomy normal – abnormal (i.e. category 1 versus categories 2 and 3) raters agreed in 36 of 50 (72%) cases. Kappa coefficient was 0.44 (SE 0.13, 95% CI 0.19 – 0.67, p = 0.002). Kappa coefficients for both methods indicate a minimal to weak level of agreement between raters. In 15 of 50 (30%) cases rater 1 scored “possible nerve thickening” while rater 2 scored “no nerve thickening” or “definite nerve thickening”. Discrepancies between raters seem therefore to be caused mostly by the appreciation and distinction of subtle abnormalities ( Figure 3.2 ). Sensitivity was 61% and 75% and specificity was 79% and 86% for rater 1 and 2 respectively. Area under the curve was 0.698 (95% CI 0.539 – 0.858) for rater 1 and 0.804 (95% CI 0.667 – 0.940) for rater 2 ( Figure 3.3 ).