Background: The standard of care is to utilize intraoperative neurophysiological monitoring (IOM) of triggered electromyography (tEMG) during posterior lumbosacral instrumented-fusion surgery. IOM should theoretically signal misplacement of S1 screws into the neural L5–S1 foramen or spinal canal, utilizing screw stimulation, and recording of the lower limb muscles and the anal sphincter. Here, we evaluated when and whether anterolateral S1 screw malposition could be detected by IOM/tEMG during open posterior lumbosacral instrumented fusion surgery. Methods: tEMG, somatosensory-evoked potential (SSEP), and transcranial electrical motor-evoked potential (TcMEP) data were retrospectively reviewed from 2015 to 2017 during open posterior lumbosacral instrumented fusions. We utilized screw stimulation alert thresholds of <14 mA (tEMG) and recorded from the lower extremity muscles and anal sphincter. Furthermore, all patients underwent routine postoperative computed tomography (CT) scans to confirm the screw location. Results: There were 106 S1 screws placed in 54 patients: 52 bilateral and 2 unilateral. In 6 patients (11.1%), 7 screws (6.6%) registered at low tEMG thresholds. In 1 patient, the postoperative CT scan documented external malposition of the screw despite no intraoperative IOM/tEMG alert. When S1 misplaced screws were stimulated, the most sensitive muscle was the tibialis anterior; the sensitivity of the IOM/tEMG was 87.5%, the specificity was 97.9%, the positive predictive value was 77.8%, and the negative predictive value was 98.9%. TcMEP and SSEP did not change during any of the operations. Notably, no patient developed a new neurological deficit. Conclusion: Anterolateral S1 screw malposition can be detected accurately utilizing IOM/tEMG stimulation of screws. When alerts occur, they can largely be corrected by partially backing out the screw (e.g., a few turns) and/ or changing the screw trajectory.

Background: Surgery of thickened-fibrolipoma filum terminale (FT) is performed routinely and without conflict but is not a risk-free surgical procedure. Intraoperative neurophysiological monitoring with mapping techniques can help to certify the FT before sectioning. However, a tailored surgical approach to cauda equina and a low threshold of surrounding nerve roots can confuse the final surgical decision. The aim is to demonstrate the usefulness of this double methodology for FT certification. Methods: A prospective study collected and reviewed retrospectively, from 2015 to 2018, 40 patients undergoing an FT surgery section were included in the study. After opening the dura mater and under the microscope, the cauda equina mapping is performed and the recording of muscles of the lower limbs and the external anal sphincter. In addition, a high-intensity stimulation of constant current of an isolated FT for a short period of time and in a dry surgical field, obtaining a bilateral-polyradicular-symmetrical response of cauda equina nerve roots. Results: Traditional motor mapping identified FT in 65% (26/40) of patients. Although, 35% (14/40) of the patients still have low-intensity stimuli response (<1 mA) of a muscle, especially anal sphincter. When this happens, the optimization of the dissection around FT is performed. After that, 25% (10/40) of the patients still having a muscle response in spite of seem isolated FT. Increasing the stimulation intensity up to 20 mA evoked a cauda equina response in all cases. No postoperative neurological impairment was observed in this series. Conclusion: This proposed methodology accurately confirms the FT so that it can be safely found and cut. The Double Neurophysiological Certification improves the gap of the traditional mapping techniques of cauda equina and can be used in a variety of more complex surgeries in this area.

Thoracic pedicle screws placement remains being a challenge despite modern technologies available. To assess neural integrity during these surgeries, intraoperative neurophysiological monitoring (IOM) is indicated. Motor-evoked potentials (MEP) and somatosensory-evoked potentials (SSEP) give valuable information regarding spinal cord function, and pedicle screws stimulation could evaluate medial malpositioning. However, the accuracy of thoracic pedicle screws stimulation is still controversial, using single-pulse stimulation, recording from intercostal and abdominal muscles, and with high false-positive rate.

We report the case of a patient who presented a pineal tumor. A partial resection was performed. The biopsy showed a glioneuroma rosette forming tumor, considered as WHO grade I. The patient was observed for 13 months and experienced significant tumor growth. Radiotherapy was performed. Instead of scarce evidence of the topic and treatment modalities in this type of tumors; radiotherapy was performed. The patient has been stable and asymptomatic.Keywords: pineal, tumor, partial, resection, radiotherapy IntroducationThe rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle tumor of the glioneuronal family (Komori, 2002). The clinical presentation, natural history, and treatment response of these tumors has been unclear as there are no significant series of a sizeable population with long-term follow-up (Solis, 2011;Marhold, 2008). Classically, has been described as WHO I grade neoplasms with indolent biologic behaviour. The optimal management is surgical resection, mainly in symptomatic patients cases where tumor is causing mass effect over neighboring structures (Zhang, 2013). Adjuvant treatments are supported by few data and their role is unknown. We present the case of a rosette forming glioneuroma tumor with aggressive behavior that doubled size after 16 months of follow up after partial resection achieving decompression of neural structures. Case ReportThe present case refers to a previously healthy 48 years old woman who began with mild headache for 2 weeks. Brain MRI showed an expansive cystic-solid heterogeneous contrast enhancement mass of 2,4 cm in the pineal region with mass effect over mesencephalon and cuadrigeminal plate. Tumor markers, including beta-human chorionic gonadotropin, and alpha-fetoprotein were not significantly elevated in both the cerebrospinal fluid (CSF). A partial resection of the tumor by endoscopic approach and III cisternoventriculostomy was approached because of thalamic invasion.The tumor specimen was analyzed by pathology department of Universidad de Concepcion and the case was consulted to neuropathologists of the MD Anderson cancer center. The final biopsy report was Rosette forming glioneuronal tumor, Ki67 negative, GFAP positive. The patient was evaluated then by an interdisciplinary oncology committee (neurosurgery, radiation oncology, pathology and medical oncology) and the management decision based on the evidence reported was observation, mainly due to the indolent behavior reported in the literature.

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