title: TMS neuro-cardiovascular coupling in vascular compression cranial neuropathy.
abstract: BACKGROUND
  Neurovascular compression (NVC) may cause cranial mononeuropathy but lacks a definitive diagnostic investigation. We hypothesized that the arterial pressure wave (APW) would interact at the neurovascular interface in NVC to inhibit transmission of transcranial magnetic stimulation (TMS) stimuli to affected muscles.
  
  
  METHODS
  We report a novel neurophysiological method coupling cardiovascular physiology with TMS. The electrocardiogram (ECG) and arterial pressure wave (APW) were coupled to triggering of cortical TMS in a patient with NVC-induced spinal accessory (CNXI) mononeuropathy. Outcome measures included motor evoked potential (MEP) amplitudes and firing probabilities of normal and affected trapezieus (TPZ). Values at intervals in proximity to the APW (40/80/120/160 ms) were compared to baseline (800 ms) using ANOVA and student t-test.
  
  
  RESULTS
  Electrocardiogram triggered TMS of CNXI pathways with 100% reliability. MEP amplitudes were decreased in proximity to the APW, particularly at 120 ms (0.21-0.04 mV versus 0.39 +/- 0.10 mV, p=0.003). TPZ firing probabilities were similarly inhibited (43.8% versus 88.2%, p=0.009). No effect of APW proximity was observed on the unaffected side (p=0.868). Procedures were well tolerated.
  
  
  CONCLUSIONS
  Vascular compression causes CNXI mononeuropathy. Transcranial magnetic stimulation-cardiovascular coupling may evaluate neurovascular junction interactions and non-invasively diagnose NVC.
authors.affiliation: Division of Neurology, Alberta Children's Hospital, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Adam
authors.initials: A
authors.lastname: Kirton
authors.forename: Carolyn
authors.initials: C
authors.lastname: Gunraj
authors.forename: Robert
authors.initials: R
authors.lastname: Chen
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001794:Blood Pressure / Q000502:physiology; D002319:Cardiovascular System / Q000503:physiopathology*; D003389:Cranial Nerve Diseases / Q000150:complications / Q000175:diagnosis*; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D019054:Evoked Potentials, Motor / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D016491:Peripheral Vascular Diseases / Q000150:complications / Q000175:diagnosis*; D011930:Reaction Time / Q000502:physiology; D013997:Time Factors; D050781:Transcranial Magnetic Stimulation