1271. Defining the somatotopy of the human spinothalamic tract: CT-guided mapping and physiologic responses in patients undergoing percutaneous cervical cordotomy

Award: First Place Pain Eposter Award

Authors: Christopher Michael Honey, MD; C Michael Honey, MD; Zurab Ivanishvili, MD; Christopher Honey; Manraj Heran, MD (Winnipeg, Canada)

Introduction: The location of the human spinothalamic tract (STT) in the anterolateral spinal cord has been known for over a century.The exact nature of the neuronal fiber lamination within the STT, however, remains controversial. Neurosurgeons continue to describe two very different models of somatotopic organization of the STT: medial-to-lateraland anterior-to-posterior lamination. We present a novel description of the somatotopy of the human cervical spinothalamic tract utilizing in vivo macrostimulation-induced pain/temperature sensation during percutaneous cervical cordotomy with concurrent CT imaging of the electrode tip location. Methods: Patients undergoing CT-guided percutaneous cervical cordotomy to alleviate contralateral medication-refractory cancer pain were included in this study. During the operation, a Rosomoff electrode was inserted percutaneously into the STT under local anesthetic. Patient responses to electrical stimulation (0.01–0.1 V, 50 Hz, 1 ms) were recorded and the electrode location for each response documented with a contemporaneous CT scan. Results: A total of 64 data points were available for analysis with simultaneous clinical responses (n=41 positive and n=23 negative) and CT documented electrode tip location.Clinically the patients did well. Maximal daily pain on the contralateral side was significantly reduced (p<0.001, paired t-test) from a pre-operative average of 9.3 ± 0.5 (mean ± standard deviation measured on a visual analog scale) to 0.5 ± 1.2 on the first post-operative day.In our cohort of patients, the STT from the lower limb region was located superficially and posteriorly in the anterolateral quadrant of the cervical cord with the STT from the upper limb region surrounding it primarily anteriorly and medially (deep). Conclusion: The somatotopic organization of the human STT was elucidated for the first time using in vivo macrostimulation and contemporaneous CT imaging during cordotomy, adding a small but fundamental piece of knowledge to our understanding of human neuroanatomy.