Deep brain stimulation (DBS) of nucleus basalis of Meynert (NBM) is currently being evaluated as a potential therapy to improve memory and overall cognitive function in dementia. Although, the animal literature has demonstrated robust improvement in cognitive functions, phase 1 trial results in humans have not been as clear-cut. We hypothesize that this may reflect differences in electrode location within the NBM, type and timing of stimulation, and the lack of a biomarker for determining the stimulation’s effectiveness in real time. In this article, we propose a methodology to address these issues in an effort to effectively interface with this powerful cognitive nucleus for the treatment of dementia. Specifically, we propose the use of diffusion tensor imaging to identify the nucleus and its tracts, quantitative electroencephalography (QEEG) to identify the physiologic response to stimulation during programming, and investigation of stimulation parameters that incorporate the phase locking and cross frequency coupling of gamma and slower oscillations characteristic of the NBM’s innate physiology. We propose that modulating the baseline gamma burst stimulation frequency, specifically with a slower rhythm such as theta or delta will pose more effective coupling between NBM and different cortical regions involved in many learning processes.

New anticoagulant and antiplatelet medications have been approved and are prescribed with increased frequency. Intracranial hemorrhage is associated with the use of these medications. Therefore, neurosurgeons need to be aware of these new medications, how they are different from their predecessors, and the strategies for the urgent reversal of their effects. Utilization of intraluminal stents by endovascular neurosurgeons has resulted in the need to have a thorough understanding of antiplatelet agents. Increased use of dabigatran, rivaroxaban, and apixaban as oral anticoagulants for the treatment of atrial fibrillation and acute deep venous thrombosis has increased despite the lack of known antidotes to these medications.

The stereotactic frame has served as the gold standard apparatus for accurate and precise targeting of deep brain structures since 1947. Despite passing the test of time, the stereotactic frame has several limitations from the perspective of both neurosurgeons and patients. Therefore, there was a need to develop a frameless system that had equivalent accuracy and reliability to the frame. This need was met with 3 commercially available frameless stereotactic systems designed specifically for deep brain stimulation surgery: Nexframe, STarFix, and ClearPoint. Over the past decade, the frameless and frame-based systems have been extensively investigated by numerous studies and found to be equivalent in experimental and clinical accuracy as well as in clinical outcomes. This chapter summarizes the findings of those studies along with the discussion of sources of stereotactic errors. The procedural aspects, advantages, and disadvantages of each frameless system are reviewed. Frameless stereotaxy is a safe, accurate, and effective technique for functional stereotactic approaches and provides a viable alternative to the frame-based systems.

Background Vagal nerve stimulation (VNS) is approved therapy for the treatment of intractable epilepsy. The stimulation of either nerve, left or right, is effective. However, due to the anatomic and physiological effects of cardiac innervation, the right vagus nerve is typically avoided in order to minimize the risk of cardiac bradyarrhythmias. The location of the VNS lead contacts on the nerve can also have an effect, namely, more distally placed contacts have been associated with lower risk of cardiac arrhythmias, presumably by avoiding vagal cervical cardiac branches; however, our case demonstrates reproducible asystole despite left sided, distal VNS lead placement. Case presentation We report a 28-year-old male patient with pharmacoresistant generalized clonic-tonic seizures. The VNS therapy with 1.5 mA output and 16% duty cycle drastically reduced his seizure burden for several years. The breakthrough seizures along with stabbing pain episodes at the implantable pulse generator (IPG) site have prompted the VNS lead revision surgery with new lead contacts placed more caudally than the old contacts. However, the intraoperative device interrogation with 1 mA output resulted in immediate asystole for the duration of stimulation and it was reproducible until the output was decreased to 0.675 mA. Conclusions Our case highlights the possibility of new severe cardiac bradyarrhythmias following surgical VNS lead replacements even in patients without preoperatively known clinical side effects. We suggest preoperative electrocardiography and cardiology consultation for detected abnormalities for all patients undergoing new VNS implantations, as well as revision surgeries for VNS malfunctions. Intraoperatively, the surgeon and anesthesia team should be vigilant of cardiac rhythms and prepared for the immediate management.

Background: Accurate segmentation and calculation of total brain volume (BV) and intracranial volume (ICV) (further-volumetry) may serve various clinical tasks and research studies in neuroscience. Manual segmentation is extremely time consuming. There is a relative lack of published broad recommendations and comparisons of tools for automated volumetry, especially for users without expertise in computer science, for settings with limited resources, and when neuroimaging quality is suboptimal due to clinical circumstances.Our objective is to decrease the barrier to entry for research and clinical groups to perform volumetric cranial imaging analysis using free and reliable software tools.Methods: Automated volumetry from computed tomography (CT)/magnetic resonance imaging (MRI) scans was accomplished using 3D Slicer (v. 4.11.0), FreeSurfer (v. 7.1.1), and volBrain (v. 1.0) in a cohort of 39 patients with ischemic middle cerebral artery territory brain infarcts in the acute stage. Visual inspection for accuracy was also performed. Statistical analysis included coefficient of determination (R 2 ) and Bland-Altman (B-A) plots. A multifaceted comparison between 3D Slicer, FreeSurfer, and volBrain from practical user perspective was performed to compile a list of distinguishing features.Results: BV: FreeSurfer, 3D Slicer, and volBrain provide similar estimations when high quality T1-MRI scans with 1 mm slices (3D scans) are available, whereas 3 mm and thicker slices (2D scans) introduce a dispersion in results. ICV: the most accurate volumetry is provided by 3D Slicer using CT scans. volBrain uses T1-MRIs and also provides good results which agree with 3D Slicer. Both of these methods may be more trustworthy than T1 MRI-derived FreeSurfer calculations.Conclusions: All three studied tools of automated intracranial and brain volumetry-3D Slicer, FreeSurfer, and volBrain-are free, reliable, require no complex programming, but still have certain limitations and significant differences. Based on our investigation findings, the readers should be able to select the right volumetry tool and neuroimaging study, and then follow provided step-by-step instructions to accomplish specific volumetry tasks.

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INTRODUCTION Diffuse leptomeningeal glioneural tumor (DLGT) is a very rare central nervous tumor that has no standard of care for its treatment. This report illustrates a case of DLGT with a unique presentation and a first description of multiple systemic metastasis. Case: 19 year-old male with personal history of hereditary multiple osteochondromas and recent covid-19 infection who on investigation of headaches, progressive cranio-neuropathies, and right-sided weakness was found to have vasospasms resulting in acute infarcts in multiple vascular areas, and diffuse leptomeningeal enhancement in the thoracic spine and cauda equina. Patient underwent meningeal biopsy, after 2 months of first symptoms, which revealed DLGT per two different neuro-oncology centers. Course of disease was complicated with hydrocephalus needing shunt placement soon after diagnosis. Craniospinal radiation concurrent with temozolomide was started one month from diagnosis. Patient developed pancytopenia and chemotherapy was stop in the first weeks during radiation therapy. Metastatic disease to bone marrow was diagnosed in the second adjuvant temozolomide cycle through biopsy. One week after, on investigation of pleural effusion, lung metastasis were discovered on pleural cytology and thoracic computer tomography. Liquid biopsy showed non-actionable mutations on PIK3CA, BRAF and KRAS. Chemotherapy with carboplatin and vincristine was started with markedly improvement of pancytopenia and pleural effusions leading to cessation of frequent transfusions and auxiliary oxygen. Vincristine dose was decreased due to painful neuropathy and tinnitus. At the end of endovenous chemotherapy, worsening of disease was found with metastasis to muscles of the face and brain parenchyma. Patient was then enrolled in hospice, dying weeks after. CONCLUSION DLGT should be considered in the differential diagnosis of vasospasm. DLGT is a primary central nervous system that can metastasize to other organs. Although no standard of care is yet identified, chemotherapy with vincristine and carboplatin can be offered to systemic metastatic disease.

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