Detection of Spinal Cord Injury during Thoracoabdominal Aortic Aneurysm Surgery Using Multi-channel Superconducting Quantum Interference Device

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The main purpose of the current project was to test superconducting quantum interference device (SQUID), for detecting the spinal cord conduction and for predicting spinal cord ischemia. (1) Development of SQUID system for spinal cord study (at Hiroshima University) : Detection of spinal cord action magnetic field using one-channel SQUID failed. The limitation of the performance of the one-channel device was the profound cause of this failure. (2) Spinal cord ischemia model : Ischemia was induced in adult dogs by cross-clamping the thoracic aorta for 60 min.On April, 2002, we started to research using high performance 71-channel SQUID at NTT Docomo Multimedia Laboratories (Yokosuka, Japan). This multi-channel device has given results as follows. (3) Measurement of the peripheral compound nerve action magnetic field (CAF) and its spatial analysis : We succeeded in measuring the CAF of the human median and ulnar nerves. Nerve conduction was visualized by means of magnetography. (4) Magne … More tic analysis of ischemia-induced nerve conduction impairment : We succeeded in recording ischemic- changes of the median nerve conduction with magnetic study. Twenty -minute fore-arm ischemia was induced with the pneumatic tourniquet placing around the upper arm. The amplitude of the CAF of the median nerve significantly increased at 5 min after the initiation of ischemia, and it gradually decreased and almost completely disappeared at 20 min. Magnetographic evaluation also showed characteristic findings during early period of ischemia. (5) Development of multi -channel SQUID system for spinal cord study : A)-Spinal cord action magnetic field in rabbit ; We succeeded in visualization of ascending spinal cord conduction only in the lumbar area with magnetic study. B)-Dog study ; We failed to recording magnetic field of the canine cord because of insufficient sensor sensitivity. If this trouble is solved, we will apply an ischemia protocol for testing the current multi-channel device to detect spinal cord ischemia. Less