Intraoperative Neuromonitoring in Patients with Intradural Extramedullary Spinal Cord Tumor: A Single-Center Case Series.

BACKGROUND: Intradural extramedullary spinal cord tumors (ID-EMSCT) make up 40% of all spinal neoplasms. Resection of these tumors is mostly conducted using intraoperative neuromonitoring (IONM). However, the literature shows heterogenous data on its added value for ID-EMSCT. The aim of this study is to define sensitivity and specificity of IONM in ID-EMSCT resection and to study possible correlations between preoperative, intraoperative, and postoperative variables and neurologic outcomes after ID-EMSCT resection. METHODS: Data of patients undergoing ID-EMSCT surgeries with IONM from January 2012 until July 2019 were examined. Using neurologic status 6 weeks and 1 year postoperatively, sensitivity and specificity for IONM were calculated. IONM test results and neurologic outcomes were paired to preoperative, intraoperative, and postoperative parameters. RESULTS: Data of 78 patients were analyzed. 6 weeks postoperatively, 14.10% of patients had worse neurologic status, decreasing to 9.84% 1 year postoperatively. Multimodal IONM showed a sensitivity of 0.73 (95% confidence interval [CI], 0.39-0.94) and a specificity of 0.78 (95% CI, 0.66-0.87) after 6 weeks, and a sensitivity of 1.00 (95% CI, 0.54-1.00) and a specificity of 0.71 (95% CI, 0.57-0.82) after 1 year. CONCLUSIONS: IONM yielded high to perfect sensitivity and high specificity. However, IONM signals did not always determine the extent of resection, and false-positive results did not always result in incomplete tumor resections, because of surgeons overruling IONM. Therefore, IONM cannot fully replace clinical judgment and other perioperative information.

Intraoperative Neuromonitoring in Patients with Intramedullary Spinal Cord Tumor: A Systematic Review, Meta-Analysis, and Case Series.

BACKGROUND: Intramedullary spinal cord tumors (IMSCT) comprise the least common types of spinal neoplasms; surgery is mostly conducted with intraoperative neuromonitoring (IONM). However, although IONM is widely used to prevent neurologic damage and many single-center studies have been reported, the added value, in terms of overall sensitivity and specificity, of different monitoring techniques used in IMSCT surgery remains to be clearly defined. OBJECTIVE: To summarize and review the reported evidence on the use of IONM in IMSCT surgery, including our own case series (n = 75 patients). METHODS: We systematically searched the literature published from January 2000 to February 2018. Articles included patients with IMSCT who underwent surgery with neuromonitoring. We estimated the sensitivity, specificity, 95% confidence interval (CI), positive likelihood ratio, and negative likelihood ratio. RESULTS: Of 1385 eligible articles, 31 were included in the systematic review. Fifteen of these articles were used for a meta-analysis, complemented with our own case series. All neuromonitoring modalities showed acceptable but not optimal test characteristics. For the indications used in the different studies, the motor evoked potentials approach showed the highest sensitivity (0.838; 95% CI, 0.703-0.919) and the best specificity (0.829; 95% CI, 0.668-0.921) for detecting neuronal injury. In our own case series, the extent of resection was significantly smaller in the false-positive group than in the true-negative group (P = 0.045). CONCLUSIONS: IONM showed high but not perfect sensitivity and specificity. IONM prevents neurologic damage but can also limit the extent of tumor resection. Prospective studies will have to define the definitive value of IONM.

Nociceptive stimulation induces expression of Arc/Arg3.1 in the spinal cord with a preference for neurons containing enkephalin.

BACKGROUND: In pain processing, long term synaptic changes play an important role, especially during chronic pain. The immediate early gene Arc/Arg3.1 has been widely implicated in mediating long-term plasticity in telencephalic regions, such as the hippocampus and cortex. Accordingly, Arc/Arg3.1 knockout (KO) mice show a deficit in long-term memory consolidation. Here, we identify expression of Arc/Arg3.1 in the rat spinal cord using immunohistochemistry and in situ hybridization following pain stimuli. RESULTS: We found that Arc/Arg3.1 is not present in naïve or vehicle treated animals, and is de novo expressed in dorsal horn neurons after nociceptive stimulation. Expression of Arc/Arg3.1 was induced in an intensity dependent manner in neurons that were located in laminae I (14%) and II (85%) of the spinal dorsal horn. Intrathecal injection of brain derived neurotrophic factor (BDNF) also induced expression of Arc/Arg3.1. Furthermore, 90% of Arc/Arg3.1 expressing neurons also contained the activity marker c-Fos, which was expressed more abundantly. Preproenkephalin mRNA was found in the majority (68%) of the Arc/Arg3.1 expressing neurons, while NK-1 was found in only 19% and GAD67 mRNA in 3.6%. Finally, pain behavior in Arc/Arg3.1 KO mice was not significantly different from their wild type littermates after application of formalin or after induction of chronic inflammatory pain. CONCLUSIONS: We conclude that Arc/Arg3.1 is preferentially expressed in spinal enkephalinergic neurons after nociceptive stimulation. Therefore, our data suggest that Arc/Arg3.1 dependent long term synaptic changes in spinal pain transmission are a feature of anti-nociceptive, i.e. enkephalinergic, rather than pro-nociceptive neurons.