Marieke van Rosmalen

Reliability of brachial plexus MRI in chronic inflammatory neuropathies 45 3 INTRODUCTION Magnetic resonance imaging (MRI) of the brachial plexus can be helpful to diagnose inflammatory neuropathies such as chronic inflammatory demyelinating polyneuropathy (CIDP) and multifocal motor neuropathy (MMN). The diagnostic challenge in CIDP and MMN is to distinguish these disorders from those that do not respond to immunomodulatory treatment. Diagnostic criteria for CIDPandMMNprimarily rely on clinical phenotype and specific nerve conduction study (NCS) abnormalities. 1,2 Brachial plexus MRI can be of diagnostic value when NCS is inconclusive despite high clinical suspicion. Magnetic imaging abnormalities associated with CIDP and MMN are thickening of roots, plexus and nerves, often combined with T2 hyperintensity. 3–5 Previous MRI studies were exclusively qualitative and lacked clear definitions of abnormality. 6–8 To clarify the value of brachial plexus MRI in the diagnostic workup of inflammatory neuropathies, we assessed interrater variability. METHODS Study design We performed an interrater study in a retrospective cohort of patients with CIDP andMMN and controls. Subjects Patients aged 18 to 85 years with CIDP andMMN according to the European Federation of Neurological Societies/Peripheral Nerve Society criteria 1,2 , who were seen at the University Medical Center (UMC) Utrecht and who underwent brachial plexus MRI between September 2016 and September 2018 were selected for this study. Brachial plexus MRI from patients with other causes of peripheral motor deficits were used as controls. Clinical data We obtained clinical data from electronic patient records, including age, sex and time from onset of symptoms to diagnosis in months, defined as disease duration. All patients gave informed consent. This study was approved by the Medical Ethical Committee of the UMC Utrecht. MRI protocol and assessment Brachial plexusMRI was performed for diagnostic purposes andwas reassessed for this study. Scans were performed on 1.5 and 3.0 Tesla (T) scanners (Philips, Best, the Netherlands). TheMRI protocol consisted of a fat-suppressed coronal 3D T2-weigthed short-tau inversion recovery (STIR) with the following parameters: field of view = 250*320*170 mm 3 , matrix size = 208*269, voxel size = 0.6*0.6*1mm 3 , echo time = 259 ms, repetition time = 2200 ms, turbo spin echo factor = 95, acquisition time = 06:16 minutes. In postprocessing, a coronal slab maximum intensity projection (MIP) was created.