title: Cortical reorganization following neurotization:  a diffusion tensor imaging and functional magnetic resonance imaging study.
abstract: BACKGROUND
  Following successful intercostal-musculocutaneous nerve (ICN-MCN) neurotization for brachial plexus injuries (BPIs), patients initially show a synkinetic movement of elbow flexion during inspiration. Later they are able to flex the elbow, independent of respiratory activity.
  
  
  OBJECTIVE
  To demonstrate cortical reorganization following ICN-MCN coaptation in BPI through functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI).
  
  
  METHODS
  Thirty adult patients underwent ICN-MCN coaptation for BPI. The controls were age and sex matched. All patients had Sunderland 3 or 4 degree of injury. Patients underwent fMRI and DTI (pre- and postoperatively) with electromyography of the biceps. Maps of neural activity within the motor cortex were generated in the paralyzed and control arms and center of maximum activity was calculated. Fractional anisotropy and apparent diffusion coefficient were generated from fMRI and DTI over the motor cortex and comparison was made between the paralyzed and control arms.
  
  
  RESULTS
  Median deinnervation interval was 6 months. Seventeen patients improved from grade 0 to grade 3 or more. There was no significant difference between the coordinates for maximum activity, when the cortical activity following elbow flexion of the patients who improved was compared with the control arm activity. There was reduction in FA and ADC values in patients who have improved following surgery when compared to controls. Fractional anisotropy and apparent diffusion coefficient values of the postoperative patients revealed no significant difference from the controls or preoperative patients.
  
  
  CONCLUSIONS
  Cortical plasticity following ICN-MCN transfer in BPI does occur. There was no correlation between the degree of improvement either with the transposition of activity on the motor cortex from the chest to the elbow area, or the amount of activity on the motor cortex representing the elbow area.
authors.affiliation: Department of Neurosurgery, National Institute of Mental Health and Neurosciences, Bangalore, Karnataka, India.
authors.forename: Anilkumar Masalavada
authors.initials: AM
authors.lastname: Sokki
authors.forename: Dhananjaya Ishwar
authors.initials: DI
authors.lastname: Bhat
authors.forename: Bhagavatula Indira
authors.initials: BI
authors.lastname: Devi
mesh_terms: D000328:Adult; D020516:Brachial Plexus Neuropathies / Q000503:physiopathology* / Q000601:surgery*; D002540:Cerebral Cortex / Q000503:physiopathology*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016067:Nerve Transfer / Q000379:methods; D009473:Neuronal Plasticity; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D013497:Sural Nerve / Q000637:transplantation*; D016896:Treatment Outcome