Filum terminale lipomas-the role of intraoperative neuromonitoring.

BACKGROUND: Filum terminale lipomas (FTL) represent a sub-type of spinal lipomas, where there is fatty infiltration of the filum. It becomes a surgical entity when it manifests as clinical or radiological tethered cord syndrome. Intraoperative neuromonitoring (IONM) has been suggested as a valuable tool in children for tethered cord surgeries. FTL is distinct and cannot be compared with complex tethered cord syndrome (TCS). Untethering an FTL is a relatively straightforward microsurgical exercise, usually based on anatomical findings. Neurological morbidity in FTL untethering is extremely low. The necessity of IONM in FTL has not been evaluated. The objective of this study was to identify the role of IONM in untethering an FTL METHODS: Available electronic data and case files were interrogated to identify children (0-18 years) who underwent an untethering of FTL between 2008 and 2019. We had a shift in our policy and tried to use IONM as often as possible in all tethered cord surgery from 2014. All children were categorised under 'IONM implemented' or 'no IONM' group. Outcomes analysed were as follows: (1) Clinical status on short-term and long-term follow-up, (2) alteration of surgical course by IONM and (3) complications specifically associated with IONM RESULTS: Among 80 children included in this study, IONM was implemented in 37 children and 43 children underwent untethering without IONM. 32.5% of children were 'syndromic'. Seventy-five percent of children were under age 3 years during surgery. Both groups (No IONM vs. IONM implemented) were well matched in most variables. Majority of 'no IONM' surgeries were performed prior to 2014. There was no neurological morbidity in the entire cohort. Mean duration of follow-up was 49.10 (± 33.67) months. Short-term and long-term clinical status remained stable in both cohorts. In 16 children, the filum was stimulated. Based on our protocol, majority had a negative response. One child showed a positive response, contradicted by thorough microscopic inspection. Despite a positive response, the filum was untethered. IONM was not associated with any complication in this study. CONCLUSION: FTL untethering is an inherently low-risk microsurgery in experienced hands with rarely reported neurological morbidity. IONM may not be required for all FTL and may be used more judiciously.

Intraoperative Neurophysiology for Optimization of Percutaneous Spinothalamic Cordotomy for Intractable Cancer Pain.

BACKGROUND: Percutaneous ablation of the cervical spinothalamic tract (STT) remains a therapeutic remedy for intractable cancer pain. However, it is accompanied by the risk of collateral damage to essential spinal cord circuitry, including the corticospinal tract (CST). Recent studies describe threshold-based mapping of the CST with the objective of motor bundle preservation during intramedullary spinal cord and supratentorial surgery. OBJECTIVE: To assess the possibility that application of spinal cord mapping using intraoperative neuromonitoring in percutaneous cordotomy procedures may aid in minimizing iatrogenic motor tract injury. METHODS: We retrospectively reviewed the files of 11 patients who underwent percutaneous cervical cordotomy for intractable oncological pain. We performed quantitative electromyogram (EMG) recordings to stimulation of the ablation needle prior to the STT-ablative stage. We compared evoked motor and sensory electrical thresholds, and the electrical span between them as a reliable method to confirm safe electrode location inside the STT. RESULTS: Quantified EMG data were collected in 11 patients suffering from intractable cancer pain. The threshold range for evoking motor activity was 0.3 to 1.2 V. Stimulation artifacts were detected from trapezius muscles even at the lowest stimulation intensity, while thenar muscles were found to be maximally sensitive and specific. The minimal stimulation intensity difference between the motor and the sensory threshold, set as "Δ-threshold," was 0.26 V, with no new motor deficit at 3 days or 1 month postoperatively. CONCLUSION: Selective STT ablation is an effective procedure for treating intractable pain. It can be aided by quantitative evoked EMG recordings, with tailored parameters and thresholds.

Incidence and impact of stroke following surgery for low-grade gliomas.

OBJECTIVE: Ischemic complications are a common cause of neurological deficits following low-grade glioma (LGG) surgeries. In this study, the authors evaluated the incidence, risk factors, and long-term implications of intraoperative ischemic events. METHODS: The authors retrospectively evaluated patients who had undergone resection of an LGG between 2013 and 2017. Analysis included pre- and postoperative demographic, clinical, radiological, and anesthetic data, as well as intraoperative neurophysiology data, overall survival, and functional and neurocognitive outcomes. RESULTS: Among the 82 patients included in the study, postoperative diffusion-weighted imaging showed evidence of acute ischemic strokes in 19 patients (23%), 13 of whom (68%) developed new neurological deficits. Infarcts were more common in recurrent and insular surgeries (p < 0.05). Survival was similar between the patients with and without infarcts. Immediately after surgery, 27% of the patients without infarcts and 58% of those with infarcts experienced motor deficits (p = 0.024), decreasing to 16% (p = 0.082) and 37% (p = 0.024), respectively, at 1 year. Neurocognitive functions before and 3 months after surgery were generally stable for the two groups, with the exception of a decline in verbal rhyming ability among patients with infarcts. Confusion during awake craniotomy was a strong predictor of the occurrence of an ischemic stroke. Mean arterial pressure at the beginning of surgery was significantly lower in the infarct group. CONCLUSIONS: Recurrent surgeries and insular tumor locations are risk factors for intraoperative strokes. Although they do not affect survival, these strokes negatively affect patient activity and performance status, mainly during the first 3 postoperative months, with gradual functional improvement over 1 year. Several intraoperative parameters may suggest the impending development of an infarct.