Utility of Multimodal Intraoperative Neuromonitoring for Excision of Filum Terminale Ependymoma in Close Proximity to Conus.

Myxopapillary ependymomas (MPEs) are well-circumscribed tumors arising mainly from the caudal neuraxis, i.e., conus medullaris (CM) and filum terminale (FT), commonly seen in adults with median age at presentation of 39 years.1 Owing to its partially aggressive clinical behavior involving cerebrospinal fluid dissemination and local recurrence, MPE is classified as grade 2 in the fifth edition of the World Health Organization Classification of Tumors of the Central Nervous System.2 Gross total resection without capsular violation is key, with subtotal resection being directly associated with local recurrence.3The FT has an intradural and extradural component. The intradural FT extends from the inferior tip of the CM to the coccyx.4 The intradural FT-CM junction is not demarcated, but rather a zone of transition, with neural tissue being incrementally replaced by fibrous tissue of filum, gradually converging to a pure non-neural FT.5 In intramedullary FT MPE in close proximity to the lower end of conus, achieving gross total resection presents a great challenge. Neuromonitoring is crucial to ensure preservation of vital CM functions. We present the case of a 33-year-old man with focal nocturnal back pain of 6 months' duration followed by bilateral lower limb deep boring pain. He had no neurological deficits. Preoperative magnetic resonance imaging revealed a T2 hyperintense, heterogeneous contrast-enhancing intradural extramedullary mass at L1. Video 1 highlights step-by-step en bloc excision of the FT MPE with technical nuances, including intraoperative neurophysiological monitoring. Triggered electromyography (EMG) was used to positively map the eloquent CM and identify the intradural FT-conus interface at the superior pole of the tumor, which was then carefully dissected under continuous bulbocavernosus reflex monitoring. Similarly, we confirmed non-neural intradural FT at the lower pole by negative mapping and resected the lesion en bloc with an adequate stump for clear margins. Free-run EMG monitored all the rootlets that adhered to or were in close proximity to the lesion, ensuring their integrity and an uneventful postoperative recovery. Figure 1 depicts the anatomical orientation of the lesion with surrounding neural structures. Histopathology confirmed MPE. En bloc resection with preservation of neurological function remains the mainstay of treatment for FT ependymoma. Understanding the transitional intradural FT-CM interface is essential, often precluding a clear filum stump superiorly while resecting MPE. Intraoperative neurophysiological monitoring is an indispensable adjunct to ensure safe en bloc resection. It is also theoretically possible to use tibial and pudendal sensory evoked potentials (SEPs) in this surgical procedure. However, the clinical utility of SEPs is limited in FT surgery compared with triggered EMG or transcranial motor evoked potentials because conventional SEPs from posterior tibial nerve of the lower extremity do not cover all the root levels at risk, and the change in SEPs cannot be immediately recognized (as SEPs are averaged responses, and there is always a time lag). We did not use pudendal SEPs in this study because SEPs may give information only on the sensory sacral pathway.6 Dermatomal SEPs may be helpful, but again, they provide only sensory information. Instead, we used triggered EMG for mapping the nerve roots and transcranial motor evoked potentials to monitor the motor tracts. Further, we used the bulbocavernosus reflex, an alternative and more precise technique to monitor both motor and sensory nervous pathways at the sacral root level. Moreover, SEPs are more difficult to monitor in very young children and are less relevant in guiding the surgical strategy. Thus, we used both mapping (triggered EMG) and monitoring (transcranial motor evoked potentials and bulbocavernosus reflex) techniques, which can preserve sensory and motor sacral roots in this surgical procedure.

Isolated Thoracic Spine Intramedullary Metastasis from Primary Ovarian Carcinoma: A Rare Case Report.

Ovarian carcinoma is one among the most commonly diagnosed cancer in women. Most commonly it metastasizes within peritoneal cavity by transcoelomic spread; distant metastasis to central nervous system through hematogenous spread is rare, and intramedullary spread is even rarer. Till date, only six reports have identified isolated intramedullary metastasis to spinal cord in a patient who were considered disease free on follow-up after treatment of primary disease; of which only two were in dorsal spine. The average time for diagnosis of intramedullary metastasis after diagnosis of primary disease was 26 months in previous reports. All were on regular follow-up, and clinicians were misleaded by normal CA-125 levels, and patients were considered disease free. This report is third in world literature case of isolated intramedullary dorsal spinal cord metastasis in a patient of primary ovarian carcinoma who was on follow-up with normal CA-125 levels and was treated with myelotomy and gross total resection of lesion + adjuvant chemotherapy and oral steroids. With our experience, we recommend keeping magnetic resonance imaging neuraxis to be done in follow-up of patients treated for high-grade ovarian carcinoma so that early diagnosis and prompt management can be given to patients that can improve their quality of life.

Utility and pitfalls of high field 3 tesla intraoperative MRI in neurosurgery: A single centre experience of 100 cases.

OBJECTIVE: In India, few centers are using 1.5 Tesla intraoperative MRI systems. We are using a 3 Tesla iMRI system. We share our initial experience of 3T iMRI in neurosurgical procedures with evaluation of its utility and pitfalls. METHODS: A prospective observational study conducted between August 2017 to July 2018 at Yashoda Hospital, Secunderabad. All patients undergoing iMRI guided resection of intracranial SOL were included. RESULTS: First 100 patients with various intracranial SOLs were included. The mean time required in shifting and image acquisition was 85.6 minutes in first 20 cases which was reduced to 37.4 minutes in next the next cases. Primary GTR was achieved in 44% cases, and residues were detected in 56%, secondary GTR was achieved in 37% cases, and surgery was discontinued in 19%. Maximum residues were detected in intraaxial sols and pituitary macroadenomas. No major iMRI associated complications were seen, minor issues involving transportation and minor contact burns were seen in 4 cases, insignificant anesthetic procedure related complications in 19 cases. CONCLUSION: As per our experience iMRI is an excellent tool to guide and improve the extent of safe resection by 37% in brain tumor surgeries. Good image quality, less time for image acquisition was observed advantages of 3T system. iMRI success depends on multidepartment coordinated teamwork and multiple iterations of the process to smoothen the workflow.