title: Hirayama disease is a pure spinal motor neuron disorder--a combined DTI and transcranial magnetic stimulation study.
abstract: Hirayama disease (HirD) is a juvenile spinal muscular atrophy predominantly affecting young men with an initially progressive course followed by a stable plateau within several years. It is a matter of debate whether HirD is a widespread motor neuron or more focal cervical cord disease. Whether the supraspinal pathways of the corticospinal tract (CST) are also affected has not been studied systematically. We analyzed CST integrity in seven HirD patients and 11 controls of similar age and gender using diffusion tensor imaging at a 1.5-T scanner and central motor conduction time (CMCT) using transcranial magnetic stimulation. The apparent diffusion coefficient, fractional anisotropy, and axial and radial diffusivity coefficients were determined bilaterally at four representative CST levels and along the whole CST using a probabilistic fiber tracking approach. There were no differences between the initially affected and the contralateral side in HirD patients and no difference between HirD patients and controls for both the ROI-based and the whole CST analyses. Radial diffusivity of the CST was positively correlated with years of disease progression in HirD patients. CMCT was normal in HirD patients. Combined anatomical and functional measurements established normal integrity of the supraspinal CST in HirD patients lending support to the notion that HirD is a pure spinal motor neuron disorder.
authors.affiliation: Department of Psychiatry, Memory Clinic, University Hospital Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany. k.boelmans@uke.uni-hamburg.de
authors.forename: Kai
authors.initials: K
authors.lastname: Boelmans
authors.forename: Jörn
authors.initials: J
authors.lastname: Kaufmann
authors.forename: Sophie
authors.initials: S
authors.lastname: Schmelzer
authors.forename: Stefan
authors.initials: S
authors.lastname: Vielhaber
authors.forename: Malte
authors.initials: M
authors.lastname: Kornhuber
authors.forename: Alexander
authors.initials: A
authors.lastname: Münchau
authors.forename: Stephan
authors.initials: S
authors.lastname: Zierz
authors.forename: Charly
authors.initials: C
authors.lastname: Gaul
mesh_terms: D000293:Adolescent; D000328:Adult; D056324:Diffusion Tensor Imaging; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D016472:Motor Neuron Disease / Q000503:physiopathology*; D009046:Motor Neurons / Q000473:pathology; D009431:Neural Conduction / Q000502:physiology; D011712:Pyramidal Tracts / Q000473:pathology; D013116:Spinal Cord / Q000473:pathology*; D014897:Spinal Muscular Atrophies of Childhood / Q000175:diagnosis*; D018709:Statistics, Nonparametric; D050781:Transcranial Magnetic Stimulation; D055815:Young Adult