Intraoperative neurophysiological monitoring during spinal surgery: technical review in open and minimally invasive approaches.

Neurophysiological monitoring is of undoubted value for the intraoperative safety of neurosurgical procedures. Widely developed and used for cranial surgery, it is equally as effective, though perhaps less commonly employed, for spinal pathology. The most frequently used techniques for intraoperative monitoring during spinal surgery include somatosensory evoked potentials (SSEPs), motor evoked potentials (MEPs) and electromyography, which can either be spontaneous free-running (sEMG) or triggered (tEMG). The knowledge of the benefits and limitations of each modality is essential in optimising the value of intraoperative monitoring during spinal procedures. This review will analyse the single techniques, their anatomical and physiological basis, their use in spinal surgery as reliable indicators of functional injury, their limits and their application to specific procedures in minimally invasive surgery, such as the lateral transpsoas access for interbody fusion and the divergent trajectory for cortico-pedicular screws. In these particular techniques, because of reduced visual exposure, neuromonitoring is indeed essential to exploit the full potential of minimally invasive surgery, while avoiding damage to nervous structures.

Effects of Levetiracetam and Lacosamide on survival and seizure control in IDH-wild type glioblastoma during temozolomide plus radiation adjuvant therapy.

Introduction: There are no clear indications for the best choice of anti-seizure medications to control brain tumor related epilepsy. In vitro studies have shown an antitumoral effect of Levetiracetam and Lacosamide on glioblastoma IDH-wild type. Research question: This study investigates whether the use of levetiracetam and/or lacosamide impacts survival rates. The secondary aim was to evaluate the efficacy of both ASMs in controlling seizures. Materials and methods: In this observational retrospective single-cohort study, patients underwent chemoradiation protocol after GBM surgery. They were grouped as follows: (1) use of levetiracetam, (2) use of lacosamide, (3) simultaneous use of levetiracetam and lacosamide, (4) no ASM usage. Survival curves were plotted using the Kaplan-Meier method coupled with a log-rank test for difference assesments. To evaluate the pharmacological efficacy of post-operative seizure control, a negative binomial regression was conducted. Results: The study included 272 patients, 174 of which underwent adjuvant chemoradiation treatment. Patients without ASM therapy had a non-significant longer median OS (compared to the other groups (log-rank = 0.37). The IRR of seizure relapse was 2.57 (p = 0.007) times higher in lacosamide users, and MGMT promoter methylation demonstrated a protective effect against postoperative seizure onset (p = 0.05), regardless of the aforementioned confounding factors. Discussion and conclusions: In patients diagnosed with GBM IDH-WT undergoing chemoradiation therapy, the use of levetiracetam or lacosamide for controlling BTRE does not seem to modify survival. Lacosamide users exhibited a higher IRR of postoperative seizures compared to levetiracetam users, and MGMT promoter methylation appears to be a protective factor.

Different aquaporin-4 expression in glioblastoma multiforme patients with and without seizures.

Aquaporin-4 (AQP-4), the most important water channel in the brain, is expressed by astrocyte end feet abutting microvessels. Altered expression levels of AQP-4 and redistribution of the protein throughout the membranes of cells found in glioblastoma multiforme (GBM) lead to development of the edema often found surrounding the tumor mass. Dysregulation of AQP-4 also occurs in hippocampal sclerosis and cortical dysplasia in patients with refractory partial epilepsy. This work reports on analysis of the relationship between AQP-4 expression and the incidence of epileptic seizures in patients with GBM. Immunohistochemical and polymerase chain reaction techniques were used to evaluate AQP-4 in biopsy specimens from 19 patients with GBM, 10 of who had a history of seizures before surgery. AQP-4 mRNA levels were identical in the two groups of patients, but AQP-4 expression was more frequently detected on the GBM membranes from specimens of patients with seizures than from individuals without (10 versus 2, P < 0.001). We conclude that reduced expression of cell surface AQP-4 is characteristic of GBM patients without seizures, likely attributable to a posttranslational mechanism.

Intraoperative neuromonitoring in thoracoscopic excision of brachial plexus schwannoma.

Mediastinal schwannoma arising from brachial plexus are rare, but their surgical treatment could be challenging with a minimally invasive approach, given their position. Furthermore, their proximity to brachial plexus nerve fibres raises the risk for postoperative upper limb deficits. A 72-year-old man presented mediastinal schwannoma arising from the T1 nerve root. Complete surgical excision was achieved via video-assisted thoracic surgery with the aid of intraoperative neuromonitoring, and no postoperative neurological deficit developed after the intervention. Using intraoperative neuromonitoring, radical minimally invasive surgical treatment can be safely achieved for mediastinal schwannoma arising from brachial plexus.

Management of Extramedullary Intradural Spinal Tumors: The Impact of Clinical Status, Intraoperative Neurophysiological Monitoring and Surgical Approach on Outcomes in a 12-Year Double-Center Experience.

Objective: Intradural Extramedullary (IDEM) tumors are usually treated with surgical excision. The aim of this study was to investigate the impact on clinical outcomes of pre-surgical clinical conditions, intraoperative neurophysiological monitoring (IONM), surgical access to the spinal canal, histology, degree of resection and intra/postoperative complications. Methods: This is a retrospective observational study analyzing data of patients suffering from IDEM tumors who underwent surgical treatment over a 12 year period in a double-center experience. Data were extracted from a prospectively maintained database and included: sex, age at diagnosis, clinical status according to the modified McCormick Scale (Grades I-V) at admission, discharge, and follow-up, tumor histology, type of surgical access to the spinal canal (bilateral laminectomy vs. monolateral laminectomy vs. laminoplasty), degree of surgical removal, use and type of IONM, occurrence and type of intraoperative complications, use of Ultrasonic Aspirator (CUSA), radiological follow-up. Results: A total number of 249 patients was included with a mean follow-up of 48.3 months. Gross total resection was achieved in 210 patients (84.3%) mostly in Schwannomas (45.2%) and Meningiomas (40.4%). IONM was performed in 162 procedures (65%) and D-wave was recorded in 64.2% of all cervical and thoracic locations (99 patients). The linear regression diagram for McCormick grades before and after surgery (follow-up) showed a correlation between preoperative and postoperative clinical status. A statistically significant correlation was found between absence of worsening of clinical condition at follow-up and use of IONM at follow-up (p = 0.01) but not at discharge. No associations were found between the choice of surgical approach and the extent of resection (p = 0.79), the presence of recurrence or residual tumor (p = 0.14) or CSF leakage (p = 0.25). The extent of resection was not associated with the use of IONM (p = 0.91) or CUSA (p = 0.19). Conclusion: A reliable prediction of clinical improvement could be made based on pre-operative clinical status. The use of IONM resulted in better clinical outcomes at follow-up (not at discharge), but no associations were found with the extent of resection. The use of minimally invasive approaches such as monolateral laminectomy showed to be effective and not associated with worse outcomes or increased complications.

Exploring the anatomy of negative motor areas (NMAs): Findings in awake surgery.

Positive motor responses have been used in neurosurgery for the identification of motor structures. With the term "negative motor responses" (NMRs) a complete inhibition of movement without loss of muscle tone or consciousness is meant. Papers already exist in the literature regarding cortical areas in which such NMRs are evoked, the so-called "negative motor areas" (NMAs), but their location and functional meaning are still poorly understood. This paper discusses the anatomy of the NMAs of the human brain, in light of our brain mapping experience. 21 patients underwent awake surgery and direct electrical stimulation (DES) was performed using bipolar electrodes. Excision was interrupted when functional responses were intraoperatively identified through DES. The labeled mapping sites were recorded by photography prior to and following tumor resection. Results depicting a probabilistic map of negative motor network anatomy were retrospectively analyzed. Our findings strongly support the fact that the precentral gyrus, classical site of the of the Primary Motor Areas, is also strongly involved in generating NMRs. The distribution of NMAs was noted not to be as rigid as previously described, ranging in different brain areas with a somatotopic arrangement. Presented anatomical results are consistent with the literature, but the exact functional meaning of NMAs and their subcortical connectivity is still far from being completely understood.

Inferior Fronto-Occipital fascicle anatomy in brain tumor surgeries: From anatomy lab to surgical theater.

The Inferior Fronto-Occipital fascicle (IFOF) is a multitasking white matter (WM) bundle bridging frontal, temporal, parietal and occipital lobe. Many papers describe its role in the physiology of language, attention and affective behavior but its anatomical components and cortical terminations remain unclear. We analyze the surgical anatomy of the IFOF in the light of our experience with awake surgery, anatomical dissection on 10 human adult hemispheres (Klingler method) and literature review. Dissecting the specimens from lateral to medial we can describe 3 segments: a vertical segment that runs along the frontal lobe; an horizontal segment that runs along frontal lobe; an horizontal segment that runs from the limen insulae, passes into to the temporal stem and arrives at the parietal and occipital lobes. We retrospectively analyzed also 23 awake surgeries. 2 responses were elicited at subcortical stimulation at the third segment of the IFOF; stimulation gave paraphasias on the first segment of the IFOF in one case. All IFOF responses were founded in the left hemisphere. Anatomical knowledge is the cornerstone of surgical orientation, it allows eloquent structures to be reached quickly and it is of primary importance in awake surgery to avoid patient fatigue with lack of concentration.

Glioma surgery: From preservation of motor skills to conservation of cognitive functions.

The first step of glioma treatment is surgery. Extent of resection (EOR) improves patient survival if surgery does not negatively impair a patient's neurological status. However, how surgery affects the patient's quality of life (QOL) has been less studied, especially as regards cognitive aspects. In our study, we retrospectively analyzed our cases with awake surgery. In all patients, surgical excision was stopped when active functions were intraoperatively identified. A neuropsychological assessment was performed both before and after surgery (5 days and 1 month after). Writing, motor speech, comprehension, expression, reading, pragmatics, attention, memory, problem solving and visuoperceptive functions were evaluated and scored with the NOMS scale. We found no differences in the median values of writing and motor speech, while there was a difference in the following variables: comprehension, expression, reading, pragmatics, attention, memory, problem solving and visuoperceptive functions. Moreover, the Dunn test did not show any difference between preoperative evaluation and evaluation performed 30 days after surgery regarding comprehension, expression, reading, pragmatics, attention, problem solving and visuoperceptive functions. However, there was a difference between preoperative and postoperative evaluation for memory. This retrospective study shows that awake surgery could be a reasonable possibility to preserve a patient's QOL achieving an EOR >82% of the Total Tumor Volume (Fluid-attenuated inversion recovery (FLAIR) hyperintense region in low-grade gliomas and enhancing nodules plus FLAIR hyperintense region in high-grade gliomas). In this series memory was the only aspect that had an impairment after surgery without a complete recovery at one month after surgery.