Marieke van Rosmalen

Diagnostic value of quantitative assessment of brachial plexus MRI in chronic inflammatory neuropathies 57 4 INTRODUCTION Chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN) are rare disorders that often respond to treatment. Diagnostic criteria have been developed to distinguish CIDP and MMN from more common neuropathies and motor neuron disorders that rely on sets of typical clinical combined with specific electrodiagnostic features. 1,2 Diagnosing CIDP or MMN remains challenging when nerve conduction studies (NCS) do not meet the required electrodiagnostic criteria. 2,3 Nerve imaging by means of qualitative MRI is recommended in diagnostic guidelines for cases without NCS abnormalities. MRI of the brachial plexus and cervical nerve roots shows nerve root thickening and increased T2 signal intensity in 45-57% of patients. 4–7 These abnormalities have therefore been included as a supportive criterium in the diagnostic criteria for CIDP and MMN. 1,2 However, qualitative assessments showed low interrater reliability. 8,9 In contrast, a quantitative assessment of nerve ultrasound showed excellent test characteristics for the detection of inflammatory neuropathies. 10–13 This suggests that quantification of MRI abnormalities may improve its diagnostic value. Therefore, the aim of our study is to systematically assess nerve root sizes on MRI of the brachial plexus and cervical nerve roots in a large cohort of patients with chronic inflammatory neuropathies and relevant disease controls. Using these data, we investigated interrater reliability and the diagnostic value of MRI in addition to NCS and nerve ultrasound. METHODS Study design We performed a cross-sectional study in prevalent and incident patients with CIDP and MMN, and clinically relevant controls (i.e. amyotrophic lateral sclerosis ALS) or progressive muscular atrophy (PMA)). We used a standardized protocol to systematically assess cervical nerve root sizes, determined their diagnostic value and reproducibility and developed a risk chart including objective cut-off values for abnormality. Patients and clinical data All prevalent and incident patients with an established diagnosis of CIDP or MMN, visiting our neuromuscular outpatient clinic at the University Medical Center Utrecht (UMCU), were eligible for inclusion. We used previously published diagnostic criteria for CIDP and MMN, in short for CIDP we used the diagnostic criteria as defined in the EFNS/PNS guideline and for MMN we used the Utrecht criteria. 1,2 As disease controls, we enrolled a random sample of patients with motor neuron