Biomehanicke karakteristike tkiva kicmene mozdine - osnov za razvoj modifikovane tehnike DREZ operacije

Mechanical properties of the spinal cord tissue - biological basis for the development of the modality of the DREZ surgery lesioning technique Successful treatment of the chronic neurogenic pain of spinal cord and cauda equina injury origin remains a significant management problem. The mechanism of this pa-in phenomenon has been shown to be related to neurochemical changes that lead to the state of hypereactivity of the second order dorsal horn neurons. The DREZ surgery (Dorsal Root Entry Zone lesion), designed to destroy anatomy structures involved in pain generating thus interrupting the neurogenic pain mechanism, as a causative procedure in treating this chronic pain, has been performed by using different technical modalities: Radiofrequency (RF) coagulation technique, Laser, Ultrasound and Microsurgical DREZotomy technic. The purpose of the study was to assess the possibility for the establishment of the lesioning technique based on the natural difference in the mechanical properties between the white and gray cord substance. We experimentally determinate mechanical properties of the human cadaveric cord white versus gray tissue for the purpose of testing possibility of selective suction of the dorsal horn gray substance as a DREZ lesioning procedure. Based on the fact of the difference in tissue elasticity between white and gray cord substance we established a new and simple DREZ surgical lesioning technique that was tested on cadaver cord. For the purpose of testing and comparing the size and shape of the DREZ lesion achieved the DREZ surgery has been performed on cadaver cord by employing selective dorsal horn suction as a lesioning method. After the procedure cadaver cord underwent histological fixation and analysis of the DREZ lesions achieved. Our result revealed that the white cord substance with longitudinal fiber structure had four time higher dynamical viscosity than gray substance of local neuronal network structure (150 PaS versus 37,5 PaS) that provided possibility for the safe and selective suction of the gray substance of the dorsal horn. Technique includes incision of the dorsolateral sulcus according to Sindous Microsurgical DREZotomy technique than suction under visual control of the dorsal horn gray matter using sucker adopted from the lumbar puncture nidle. Operative experimental testing and hystological analysis confirmed expected size and shape of the DREZ lesion performed by dorsal horn suction as DREZ lesioning technique. The utility, selectivity and safety of this technique has been provided by the natural mechanical properties of the cord tissue itself. Application of the Dorsal horn suction as a DREZ lesioning in humans confirmed this technique as a safe and reliable DREZ lesioning method.

Current Status of the DREZ Operation: 1984

The DREZ operation was introduced in 1976 as a method to control deafferentation pain associated with brachial plexus injury. Since then, 250 DREZ operations have been done at Duke Medical Center. At present, the best results of pain relief occur in brachial and lumbosacral root avulsions, paraplegia, and postherpetic pain. Post-DREZ complications have been reduced by the introduction of new lesion techniques, including the recent use of the laser. The neural basis of deafferentation pain is still not solved, nor is the therapeutic effect of the DREZ lesion known.

Theoretical Aspects of Radiofrequency Lesions in the Dorsal Root Entry Zone

The history and physical principles of radiofrequency (rf) lesion making are reviewed. The advantages of the rf lesion method are presented, with emphasis on its importance in small, critical regions such as the dorsal root entry zone (DREZ). The evolution and specifications of a satisfactory DREZ rf electrode are described. DREZ lesion sizes for this electrode at specific electrode tip temperatures were experimentally determined in animals and were used as a guide to determine acceptable clinical lesioning parameters. Emphasis is placed on lesion temperature monitoring and on the stability of electrode penetration into the spinal cord to achieve consistent and safe results.