Deep Brain Stimulation of Nucleus Basalis of Meynert improves learning in rat model of dementia.

Background: Deep brain stimulation (DBS) of the nucleus basalis of Meynert (NBM) has been preliminarily investigated as a potential treatment for dementia. The degeneration of NBM cholinergic neurons is a pathological feature of many forms of dementia. Although stimulation of the NBM has been demonstrated to improve learning, the ideal parameters for NBM stimulation have not been elucidated. This study assesses the differential effects of varying stimulation patterns and duration on learning in a dementia rat model. Methods: 192-IgG-saporin (or vehicle) was injected into the NBM to produce dementia in rats. Next, all rats underwent unilateral implantation of a DBS electrode in the NBM. The experimental groups consisted of i-normal, ii-untreated demented, and iii-demented rats receiving NBM DBS. The stimulation paradigms included testing different modes (tonic and burst) and durations (1-hr, 5-hrs, and 24-hrs/day) over 10 daily sessions. Memory was assessed pre- and post-stimulation using two established learning paradigms: novel object recognition (NOR) and auditory operant chamber learning. Results: Both normal and stimulated rats demonstrated improved performance in NOR and auditory learning as compared to the unstimulated demented group. The burst stimulation groups performed better than the tonic stimulated group. Increasing the daily stimulation duration to 24-hr did not further improve cognitive performance in an auditory recognition task and degraded the results on a NOR task as compared with 5-hr. Conclusion: The present findings suggest that naturalistic NBM burst DBS may offer a potential effective therapy for treating dementia and suggests potential strategies for the reevaluation of current human NBM stimulation paradigms.

Meningioma with holo-sagittal sinus involvement treated successfully with intrinsic sinus surgery: illustrative case.

BACKGROUND: This report describes an unusual meningioma with a large left frontal component and extensive growth within the sagittal sinus and its successful treatment with a staged approach: left frontal craniotomy followed by a sagittal craniotomy and intrinsic removal of the tumor from the sagittal sinus. OBSERVATIONS: A previously healthy 27-year-old presented with 6 months of progressively worsening bilateral headaches, visual changes, and nausea. On examination she had a left cranial nerve VI palsy and severe papilledema. Magnetic resonance imaging revealed a 5.1 × 3.8 × 4.1 cm homogenously enhancing left superior frontal parafalcine extra-axial mass with surrounding vasogenic edema and growth through the sagittal sinus extending just short of the torcula. LESSONS: This case report describes a fast-growing meningioma with a unique pattern of spread, growing through the sagittal sinus as if it were a conduit and resulting in complete occlusion of flow in the sinus. An important recognition in this case was that a robust parasagittal venous plexus had developed on either side of the falx cerebri with drainage to the inferior sagittal sinus. This collateral drainage pattern allowed for an extradural opening of the sagittal sinus from front to back and intrinsic resection of the tumor from the sinus with preservation of the lateral walls of the sinus.

Utility of GPI+VIM dual-lead deep brain stimulation for Parkinson's disease patients with significant residual tremor on medication.

OBJECTIVE: Randomized controlled trials have demonstrated that deep brain stimulation (DBS) of both the globus pallidus internus (GPI) and subthalamic nucleus (STN) for Parkinson's disease (PD) is superior to the best medical therapy. Tremor is particularly responsive to DBS, with reports of 70%-80% improvement. However, a small number of patients do not obtain the expected response with both STN and GPI targets. Indeed, the authors' patient population had a similar 81.2% tremor reduction with a 9.6% failure rate. In an analysis of these failures, they identified patients with preoperative on-medication tremor who subsequently received a GPI lead as a subpopulation at higher risk for inadequate tremor control. Thereafter, STN DBS was recommended for patients with on-medication tremor. However, for the patients with symptoms and comorbidities that favored GPI as the target, dual GPI and ventral intermediate nucleus of the thalamus (VIM) leads were proposed. This report details outcomes for those patients. METHODS: This is a retrospective review of patients with PD who met the criteria for and underwent simultaneous GPI+VIM DBS surgery from 2015 to 2020 and had available follow-up data. The preoperative Unified Parkinson's Disease Rating Scale scores were obtained with the study participants on and off their medication. Postoperatively, the GPI lead was kept on at baseline and scores were obtained with and without VIM stimulation. RESULTS: Thirteen PD patients with significant residual preoperative tremor on medication underwent simultaneous GPI+VIM DBS surgery (11 unilateral, 2 bilateral). A mean 90.6% (SD 15.0%) reduction in tremor scores was achieved with dual GPI+VIM stimulation compared to a 21.8% (SD 71.9%) reduction with GPI stimulation alone and a 30.9% (SD 37.8%) reduction with medication. Although rigidity and bradykinesia reductions were accomplished with just GPI stimulation, 13 of the 15 hemispheres required VIM stimulation to achieve excellent tremor control. CONCLUSIONS: GPI+VIM stimulation was required to adequately control tremor in all but 2 patients in this series, substantiating the authors' hypothesis that, in their population, medication-resistant tremor does not completely respond to GPI stimulation. Dual stimulation of the GPI and VIM proved to be an effective option for the patients who had symptoms and comorbidities that favored GPI as a target and had medication-resistant tremor.

A Consensus Study: Generational Differences in Neurosurgeons' Perception of Retirement and Practice Limits.

BACKGROUND: Concerns about the changing demographics in the United States and the aging of the neurosurgical workforce exist. Both the importance and inherent risk of surgical responsibilities suggest that thought be given to whether workloads should change later in surgeons' careers. We sought to assess current neurosurgeons' expectations concerning their late-stage careers. METHODS: A survey was sent to 3317 U.S. board-certified neurosurgeons. It was designed to assess surgeons' perceptions of call and operative responsibilities in the later stages of their careers. Statistical analyses were completed in R version 3.6.1, with an alpha set to 0.05. RESULTS: Six-hundred and fifty-nine neurosurgeons completed the questionnaire. Seventy-seven percent believed that the call burden should decrease later in practice, and 66% planned to decrease their own call burden later in their career. The most common age range for planned retirement was 65 to 69 years (36%), followed by 70+ years (33%). Most (67%) believed that there should not be a mandatory age to stop operating. More recent year of residency completion was negatively associated with the belief that call burden should decrease at older age groups and positively associated with support for a mandatory age to stop operating as well as an earlier retirement age. CONCLUSIONS: This study suggests that neurosurgeons have differing views on how workloads should change later in their careers. Younger neurosurgeons support an earlier decrease in workload or even a policy-mandated stop to operating after a certain age. These results may give insight into future trends and turnover in neurosurgery and provide a valuable tool to help practices anticipate workforce changes.