title: MRI shows thickening and altered diffusion in the median and ulnar nerves in multifocal motor neuropathy.
abstract: OBJECTIVE
  To study disease mechanisms in multifocal motor neuropathy (MMN) with magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) of the median and ulnar nerves.
  
  
  METHODS
  We enrolled ten MMN patients, ten patients with amyotrophic lateral sclerosis (ALS) and ten healthy controls (HCs). Patients underwent MRI (in a prone position) and nerve conduction studies. DTI and fat-suppressed T2-weighted scans of the forearms were performed on a 3.0T MRI scanner. Fibre tractography of the median and ulnar nerves was performed to extract diffusion parameters: fractional anisotropy (FA), mean (MD), axial (AD) and radial (RD) diffusivity. Cross-sectional areas (CSA) were measured on T2-weighted scans.
  
  
  RESULTS
  Forty-five out of 60 arms were included in the analysis. AD was significantly lower in MMN patients (2.20 ± 0.12 × 10-3mm2/s) compared to ALS patients (2.31 ± 0.17 × 10-3mm2/s; p < 0.05) and HCs (2.31± 0.17 × 10-3mm2/s; p < 0.05). Segmental analysis showed significant restriction of AD, RD and MD (p < 0.005) in the proximal third of the nerves. CSA was significantly larger in MMN patients compared to ALS patients and HCs (p < 0.01).
  
  
  CONCLUSIONS
  Thickening of nerves is compatible with changes in the myelin sheath structure, whereas lowered AD values suggest axonal dysfunction. These findings suggest that myelin and axons are diffusely involved in MMN pathogenesis.
  
  
  CONCLUSIONS
  • Diffusion magnetic resonance imaging provides quantitative information about multifocal motor neuropathy (MMN). • Diffusion tensor imaging allows non-invasive evaluation of the forearm nerves in MMN. • Nerve thickening and lowered diffusion parameters suggests myelin and axonal changes. • This study can help to provide insight into pathological mechanisms of MMN.
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands. w.haakma@umcutrecht.nl.|Department of Forensic Medicine and Comparative Medicine Lab, Aarhus University, Aarhus, Denmark. w.haakma@umcutrecht.nl.
authors.forename: Wieke
authors.identifier: http://orcid.org/0000-0003-1586-885X
authors.initials: W
authors.lastname: Haakma
authors.affiliation: Brain Centre Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Bas A
authors.initials: BA
authors.lastname: Jongbloed
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: Froeling
authors.affiliation: Brain Centre Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: H Stephan
authors.initials: HS
authors.lastname: Goedee
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Clemens
authors.initials: C
authors.lastname: Bos
authors.affiliation: Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Alexander
authors.initials: A
authors.lastname: Leemans
authors.affiliation: Brain Centre Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Leonard H
authors.initials: LH
authors.lastname: van den Berg
authors.affiliation: Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Hendrikse
authors.affiliation: Brain Centre Rudolf Magnus, Department of Neurology and Neurosurgery, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: W Ludo
authors.initials: WL
authors.lastname: van der Pol
mesh_terms: D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000000981:diagnostic imaging / Q000503:physiopathology; D016880:Anisotropy; D016022:Case-Control Studies; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D056324:Diffusion Tensor Imaging / Q000379:methods; D005260:Female; D005542:Forearm / Q000294:innervation; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008475:Median Nerve / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008875:Middle Aged; D016472:Motor Neuron Disease / Q000000981:diagnostic imaging* / Q000503:physiopathology; D009431:Neural Conduction / Q000502:physiology; D014459:Ulnar Nerve / Q000000981:diagnostic imaging* / Q000503:physiopathology
keywords: Amyotrophic lateral sclerosis; Diffusion tensor imaging; Magnetic resonance imaging; Median and ulnar nerve; Multifocal motor neuropathy