Human reflexes are simple motor responses that are automatically elicited by various sensory inputs. These reflexes can provide valuable insights into the functioning of the nervous system, particularly the brainstem and spinal cord. Reflexes involving the brainstem, such as the blink reflex, laryngeal adductor reflex, trigeminal hypoglossal reflex, and masseter H reflex, offer immediate information about the cranial-nerve functionality and the overall state of the brainstem. Similarly, spinal reflexes such as the H reflex of the soleus muscle, posterior root muscle reflexes, and sacral reflexes provide crucial information about the functionality of the spinal cord and peripheral nerves. One of the critical benefits of reflex monitoring is that it can provide continuous feedback without disrupting the surgical process due to no movement being induced in the surgical field. These reflexes can be monitored in real time during surgical procedures to assess the integrity of the nervous system and detect potential neurological damage. It is particularly noteworthy that the reflexes provide motor and sensory information on the functional integrity of nerve fibers and nuclei. This article describes the current techniques used for monitoring various human reflexes and their clinical significance in surgery. We also address important methodological considerations and their impact on surgical safety and patient outcomes. Utilizing these methodologies has the potential to advance or even revolutionize the field of intraoperative continuous monitoring, ultimately leading to improved surgical outcomes and enhanced patient care.

Brain tumour surgery in visual eloquent areas poses significant challenges to neurosurgeons and has reported inconsistent results. This is a single-centre prospective cohort study of patients admitted for asleep surgery of intra-axial lesions in visual eloquent areas. Demographic and clinical information, data from tractography and visual evoked potentials (VEPs) monitoring were recorded and correlated with visual outcomes. Thirty-nine patients were included (20 females, 19 males; mean age 52.51 ± 14.08 years). Diffuse intrinsic glioma was noted in 61.54% of patients. There was even distribution between the temporal, occipital and parietal lobes, while 55.26% were right hemispheric lesions. Postoperatively, 74.4% remained stable in terms of visual function, 23.1% deteriorated and 2.6% improved. The tumour infiltration of the optic radiation on tractography was significantly related to the visual field deficit after surgery (p = 0.016). Higher N75 (p = 0.036) and P100 (p = 0.023) amplitudes at closure on direct cortical VEP recordings were associated with no new postoperative visual deficit. A threshold of 40% deterioration of the N75 (p = 0.035) and P100 (p = 0.020) amplitudes correlated with a risk of visual field deterioration. To conclude, direct cortical VEP recordings demonstrated a strong correlation with visual outcomes, contrary to transcranial recordings. Invasion of the optic radiation is related to worse visual field outcomes.

Background/Objectives: 5-aminulevulinic acid (5-ALA)-guided surgery for high-grade gliomas remains a challenge in neuro-oncological surgery. Inconsistent fluorescence visualisation, subjective quantification and false negatives due to blood, haemostatic agents or optical impediments from the external light source are some of the limitations of the present technology. Methods: The preliminary results from this single-centre retrospective study are presented from the first 35 patients operated upon with the novel Nico Myriad Spectra System©. The microdebrider (Myriad) with an additional in situ light system (Spectra) can alternately provide white and blue light (405 nm) to within 15 mm of the tissue surface to enhance the morphology of the anatomical structures and the fluorescence of the pathological tissues. Results: A total of 35 patients were operated upon with this new technology. Eight patients (22.85%) underwent tubular retractor-assisted minimally invasive parafascicular surgery (tr-MIPS). The majority had high-grade gliomas (68.57%). Fluorescence was identified in 30 cases (85.71%), with residual fluorescence in 11 (36.66%). The main applications were better white–blue light alternation and visualisation during tr-MIPS, increase in the extent of resection at the border of the cavity, identification of satellite lesions in multifocal pathology, the differentiation between radionecrosis and tumour recurrence in redo surgery and the demarcation between normal ependyma versus pathological ependyma in tumours infiltrating the subventricular zone. Conclusions: This proof-of-concept study confirms that the novel in situ light-source delivery technology integrated with the usual intraoperative armamentarium provides a spatially, functionally and oncologically informed framework for glioblastoma surgery. It allows for the enhancement of the morphology of anatomical structures and the fluorescence of pathological tissues, increasing the extent of resection and, possibly, the prognosis for patients with high-grade gliomas.

Background and objectives: Recently, reduction of transcallosal inhibition by contralateral navigated repetitive transcranial magnetic stimulation (nrTMS) improved neurorehabilitation of glioma patients with new postoperative paresis. This multicentric study examines the effect of postoperative nrTMS in brain tumor patients to treat surgery-related upper extremity paresis. Methods: This is a secondary analysis of two randomized and three one-arm studies in brain tumor patients with new/progressive postoperative paresis. Patients underwent either low frequency contralesional nrTMS or sham stimulation followed by physiotherapy. Outcome was assessed on postoperative day 1, 7, and after 3 months using British Medical Research Council score (BMRC), Fugl-Meyer assessment (FMA), Karnofsky Performance Scale (KPS) and National Institutes of Health Stroke Scale (NIHSS). Results: A total of 135 patients (mean age of 53.8 years, 60 women) were included, of whom 51 patients were treated in RCTs (30 treatment group, 21 sham group) and 84 in prospective, single-arm studies. Linear mixed models showed an advantage for the treatment group for the BMRC (7 days: OR 3.28; 95%CI: 1.08–9.99; 3 months: OR 2.03, 95%CI: 0.65–6.39) and KPS (7 days: mean difference (MD) 11, 95%CI: 2–19; 3 months: MD 11, 95%CI: 2–20), less pronounced for the FMA (7 days: MD 0.28, 95%CI: -0.34-0.9; 3 months: MD 0.14, 95%CI: -0.52-0.81). A stronger treatment effect was evident with proven ischemia on the postoperative MRI. To observe an improvement by at least one grade at 3 months, the number needed to treat (NNT) for the entire cohort is 4 (BMRC) and 3 patients (KPS), respectively. Conclusion: Our multicenter data confirm the positive treatment effect of nrTMS to reduce transcallosal inhibition with a considerably low NNT - especially if caused by ischemia.

Background/Objectives: The purpose of this study was to investigate preoperative interhemispheric differences of the FAT in relation to the onset of postoperative SMA syndrome. Methods: This was a single-center retrospective analysis of patients who underwent surgical resection of diffuse gliomas involving the SMA between 2018 and 2022. Inclusion criteria were availability of preoperative and postoperative Magnetic Resonance Imaging, no previous surgery, and no neurological deficits at presentation. Diffusion-weighted data were processed by spherical deconvolution (SD) and diffusion tensor imaging tractography algorithms, and TrackVis was used to dissect the FAT of both hemispheres. The FAT data were analyzed for correlation with postoperative SMA syndrome onset. Results: N = 25 cases were included in the study, among which n = 23 had preoperative bilaterally identifiable FAT by SD. N = 12 developed an SMA syndrome, 6 demonstrated a motor-only syndrome, 4 had a verbal-only syndrome, and 2 had mixed verbal and motor features. The SMA syndrome incidence was significantly more frequent in lower-grade gliomas (p = 0.005). On the tumor side, the FAT identified by SD was smaller than the contralateral (mean volume 6.53 cm³ and 13.33 cm³, respectively, p < 0.001). In the 6 cases that developed a verbal SMA syndrome, a normalized FAT volume asymmetry (FAT-VA) demonstrated an asymmetry shifted towards the non-dominant side (mean FAT-VA = −0.68), while the cases with no postoperative verbal impairment had opposite asymmetry towards the dominant side (mean FAT-VA = 0.42, p = 0.010). Conclusions: Preoperative interhemispheric FAT volume asymmetry estimated according to functional dominance can predict postoperative onset of verbal SMA syndrome, with proportionally smaller FAT on the affected dominant hemisphere.