title: Motor and somatosensory abnormalities are significant etiological factors for adolescent idiopathic scoliosis.
abstract: OBJECTIVE
  In adolescent idiopathic scoliosis (AIS), we explore the role of lateralized motor and somatosensory abnormalities as a possible etiological factor.
  
  
  METHODS
  Intraoperative transcranial electrical stimulation was performed in 15 AIS and 14 adult degenerative scoliosis (ADS) patients. Inter-side motor output balance (MOB) by comparing the ratios of right to left motor evoked potentials (MEP) amplitudes, and inter-side motor output excitability (MOE) computed with MEP amplitude, was determined separately for both patients groups. For somatosensory evoked potentials (SSEP), peak to peak P37 amplitudes from right and left lower limb SSEP and inter-side P37 amplitude ratios were obtained.
  
  
  RESULTS
  Inter-side MOB was significantly asymmetric in AIS patients, contributed mainly by inter-side MOB changes in the upper than the lower limbs. Inter-side MOE comparisons of ipsilateral and contralateral MEP amplitudes were significantly different between AIS and ADS patients. Mean upper limb MEP amplitudes were significantly reduced in AIS patients. Amplitude of the right upper limb MEPs were positively correlated with inter-side MEP ratio. AIS patients show larger mean MEP amplitudes on the same side as the scoliotic curve. Overall, no correlation of Cobb's angle or total levels of scoliosis involvement with inter-side MOB and MOE parameters was found. Inter-side SSEP ratios were significantly higher in AIS patients.
  
  
  CONCLUSIONS
  Primary dysfunctional and distributed motor output contributing to abnormalities of inter-side MOB and MOE changes involving the upper limbs is evident in AIS. Simultaneous but independent somatosensory and motor observations seen these patients suggest a central mechanism as an etiological factor.
authors.affiliation: National Neuroscience Institute, Singapore General Hospital, Singapore; Duke-NUS Graduate Medical School, Singapore. Electronic address: gnrlyl@sgh.com.sg.
authors.forename: Y L
authors.initials: YL
authors.lastname: Lo
authors.affiliation: Department of Neurology, Singapore General Hospital, Singapore.
authors.forename: A
authors.initials: A
authors.lastname: Teo
authors.affiliation: Department of Neurology, Singapore General Hospital, Singapore.
authors.forename: Y E
authors.initials: YE
authors.lastname: Tan
authors.affiliation: Department of Clinical Research, Singapore General Hospital, Singapore.
authors.forename: S
authors.initials: S
authors.lastname: Fook-Chong
authors.affiliation: Department of Orthopedic Surgery, Singapore General Hospital, Singapore.
authors.forename: C M
authors.initials: CM
authors.lastname: Guo
authors.affiliation: Department of Orthopedic Surgery, Singapore General Hospital, Singapore.
authors.forename: W M
authors.initials: WM
authors.lastname: Yue
authors.affiliation: Department of Orthopedic Surgery, Singapore General Hospital, Singapore.
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Orthopedic Surgery, Singapore General Hospital, Singapore.
authors.forename: S B
authors.initials: SB
authors.lastname: Tan
authors.affiliation: Department of Prosthetics and Orthotics, Queen Elizabeth Hospital, Hong Kong.
authors.forename: H W M
authors.initials: HW
authors.lastname: Lee
authors.affiliation: Department of Neurology, Singapore General Hospital, Singapore.
authors.forename: Y F
authors.initials: YF
authors.lastname: Dan
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D000069280:Electrocorticography; D004569:Electroencephalography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D012600:Scoliosis / Q000150:complications*; D012678:Sensation Disorders / Q000209:etiology*; D013223:Statistics as Topic; D065908:Transcranial Direct Current Stimulation; D055815:Young Adult
keywords: Adolescent idiopathic scoliosis; Intraoperative; Motor evoked potential; Sensorimotor integration; Somatosensory evoked potential; Transcranial electrical stimulation