SELECTIVE DORSAL ROOT BLOCKADE USING SPINAL ENDOSCOPY AND ELECTRO-PHYSIOLOGY

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1) We developed a method of accurately identifying the dorsal roots for the corresponding afferent nerves.:We used an endoscope with an external diameter of 1.8 mm. Goats were anesthetized and mechanically ventilated. After small laminectomy on lower thoracic vertebrae, we inserted this endoscope into subarachnoid space and observed structures in the space. Then we inserted an eight polar catheter-type electrode into the visualized space to record evoked potentials. The each pole could be distinguished by marks. Using endoscopy, we tried to determine the spatial relationship between these poles and dorsal root. We chose the neighboring pairs of poles sequentially from the tip of catheter for bipolar recording. We inserted electrodes into Th11 or Th12 intercostal nerves. We obtained sequential recordings of potentials from dorsal surface of the cord evoked by stimulating each intercostal nerve. With the endoscope, we could determine the spatial relationship between the recording electrode and dorsal roots. Shapes of evoked potentials changed characteristically according to the relative position between roots and poles. By combining endoscopy with the electro-physiological technique, we could identify the dorsal roots for the corresponding afferent nerves using the recording electrode as a cue.2) We applied blockade on the roots under endoscopic view and evaluated the selectivity of the blockade.:Under endoscopic view, we applied a dose of 3 ml, 0.3 ml and 0.05 ml of 3% lidocaine solution on the dorsal root regarded as Th1 1. We obtained sequential recordings of evoked potentials after blockade and tried to determine the effects of blockade. We could determine the extension of blockade by obtaining sequential recordings of evoked potentials changing the site of stimulation and recording. We could also evaluate the selectivity of the blockade using this technique. This method can provide a useful tool for selective dorsal root blockade.