193 The Morphology of the Cod Dorsal Horn: Implications for Dorsal Root Entry Zone Surgery Using Suction of the Gray Substance as the Lesioning Method.

INTRODUCTION: Chronic neuropathic pain in traumatic paraplegia appears as the illness by itself, and it represents the unique treatment challenge. The dorsal horn, an anatomical structure involved in pain generating, has been recognized as a target for ablative dorsal root entry zone (DREZ) surgery. The dorsal horn suction technique as the DREZ lesioning method takes advantage of the natural difference in dynamical viscosity of the cord white vs gray matter to perform DREZ lesions by using the suction of the dorsal horn gray matter.

METHODS: The testing of the mechanical properties of the cord tissue were studied in the cadaveric specimens. In the period April 1997 to December 2015, 24 patients, 21 men and 3 women, with a mean age of 41 years (range, 24-69) were operated on using dorsal horn suction as the DREZ lesioning. NMR examination was done preoperatively to determine the morphology and position of the dorsal horn.

RESULTS: The white cord substance had 4 times higher dynamical viscosity in comparison with the dorsal horn gray substance (150 vs 37.5 Pa/s). Dorsal horn was most voluminous and just under the cord surface at the lumbar enlargement, while it was tiny, on the distance from the cord surface at the thoracic cord segments.

CONCLUSION: The lumbar enlargement, with most voluminous dorsal horn mass positioned just under the cord surface provides best anatomical condition for controllable and selective suctioning of the gray mass, while the thoracic cord with tiny and distant dorsal horn imposes technical difficulties for the procedure. The correlation between dorsal horn morphology, the feasibility of the suctioning technique, pain pattern, intensity, and the outcome of surgery are discussed.