title: Do longer necks predispose to Hirayama disease? A comparison with mimics and controls.
abstract: BACKGROUND
  Dynamic changes in cervical spine during flexion is a proposed mechanism for Hirayama disease [HD], a localized form of anterior horn cell disorder. Apparent shortening of dura as compared to vertebral column leading to dural shift on flexion is considered to be the primary mechanism in this hypothesis. Whether this disproportion is a result of short dura or longer cervical segment is not known and neck length has not been studied in HD. Also, all patients with segmental motor weakness and wasting of upper limbs do not show dural changes; hence comparative evaluation of HD and its mimics is important.
  
  
  METHODS
  Patients with segmental wasting and weakness limited to upper limbs were subjected to flexion MRI. A special pillow was designed to provide fixed flexion angle of 35°. Patients showing dural changes formed the HD group while rest formed the non-HD group [mimics]. Both groups were analyzed on clinical, electrophysiological and radiological parameters. Whole spine to neck ratio of patients in HD group was compared to the non-HD group and age matched controls.
  
  
  CONCLUSIONS
  Patients with HD had longer cervical segments as compared to the non-HD group and age matched controls [p=0.001]. The longer cervical segment, in combination with dural changes probably contributes to the pathophysiology of dynamic flexion hypothesis of HD and the onset around the growth spurt. Patients with HD had cold paresis and finger extensors were consistently weaker than flexors. Apart from longer necks, cold paresis and pattern of weakness may help to differentiate HD from its mimics.
authors.affiliation: Department of Neurology, Grant Medical College and Sir J. J. Group of Hospitals, Mumbai, India. Electronic address: khadilkarsatish@gmail.com.
authors.forename: Satish
authors.initials: S
authors.lastname: Khadilkar
authors.affiliation: Department of Neurology, Grant Medical College and Sir J. J. Group of Hospitals, Mumbai, India. Electronic address: bhagyadhan30@gmail.com.
authors.forename: Bhagyadhan
authors.initials: B
authors.lastname: Patel
authors.affiliation: Department of Neurology, Grant Medical College and Sir J. J. Group of Hospitals, Mumbai, India. Electronic address: drashishbhutada@gmail.com.
authors.forename: Ashish
authors.initials: A
authors.lastname: Bhutada
authors.affiliation: Department of Neurology, Grant Medical College and Sir J. J. Group of Hospitals, Mumbai, India. Electronic address: chtn.chaudhari@gmail.com.
authors.forename: Chetan
authors.initials: C
authors.lastname: Chaudhari
mesh_terms: D000293:Adolescent; D002574:Cervical Vertebrae / Q000473:pathology; D004198:Disease Susceptibility; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009333:Neck / Q000473:pathology*; D009334:Neck Muscles / Q000503:physiopathology; D009431:Neural Conduction / Q000502:physiology; D011446:Prospective Studies; D014897:Spinal Muscular Atrophies of Childhood / Q000473:pathology*; D018709:Statistics, Nonparametric; D055815:Young Adult