Impulsivity Relates to Relative Preservation of Mesolimbic Connectivity in Patients with Parkinson Disease.

IntroductionThe relationship between Parkinson Disease (PD) pathology, dopamine replacement therapy (DRT), and impulse control disorder (ICD) development is still incompletely understood. Given the sensorimotor-lateral substantia nigra (SN) selective degeneration associated with PD, we posit that a relative sparing of the limbic-medial SN in the context of DRT drives impulsive, reward-seeking behavior in PD patients with recent history of severe impulsivity.MethodsImpulsive and control participants were selected from a consecutive list of PD patients receiving pre-operative deep brain stimulation (DBS) planning scans including 3T structural MRI and 64 direction diffusion tensor imaging (DTI). Using previously identified substantia nigra (SN) subsegment network connectivity profiles to develop classification targets, split-hemisphere target-based SN segmentation with probabilistic tractography was performed. The relative subsegment volumes and strength of connectivity between the SN and the limbic, associative, and motor network targets were compared.ResultsOur results show that there is greater probability of connectivity between the SN and limbic network targets relative to motor and associative network targets in PD patients with recent history of severe impulsivity as compared to PD patients without impulsivity (P = 0.0075). We did not observe relative volumetric subsegment differences across groups.ConclusionFirstly, our results suggest that fine-grained, atlas-derived classification targets may be used in PD to parcellate and classify functionally distinct subsegments of the SN, with the apparent preservation of previously reported topographical limbic-medial SN, associative-ventral SN, and sensorimotor-lateral SN orientation. We suggest that relative, as opposed to absolute, degeneration amongst SN-associated dopaminergic networks relates to the impulsivity phenotype in PD

Technical Report: Durable efficacy of an endoscope-assisted syringo-panventriculoatrial shunt for concurrent hydrocephalus and syrinx

The management of syringomyelia in association with hydrocephalus can be a challenging pathology to treat with durable results. We present a durable treatment of a patient with symptomatic, idiopathic hydrocephalus, Chiari type I malformation, and syringomyelia with an endoscope-assisted placement of a single syringo-panventricular multiperforated shunt catheter via a transfrontal transaqueductal approach with simultaneous endoscopic third ventriculostomy (ETV). We discuss the technical details required for this single-shunt approach to a complex pathology, and indications for appropriate use of this novel approach in experienced hands. The patient rapidly improved radiographically and symptomatically, with a functioning shunt twelve years postoperatively. For surgeons well-versed in endoscopic techniques, this approach can be safe, durable, and obviate the need for an otherwise complex shunting system with multiple catheters, or a more traditional invasive craniovertebral decompression, in a patient with idiopathic hydrocephalus and a syrinx

Propofol-induced loss of consciousness is associated with a decrease in thalamocortical connectivity in humans.

Although the molecular effects of many anaesthetics have been well characterized, a network-level explanation for how these changes lead to loss of consciousness remains unclear. Studies using electroencephalography have characterized changes in neural oscillations in the cortex at specific frequency bands during propofol-induced anaesthesia and modelling work suggests these changes result from changes in thalamocortical functional connectivity. However, it is unclear if the neurophysiological changes seen at the cortex are due to enhanced or disrupted thalamocortical communication. Direct recordings from these sites during anaesthesia that could be used to confirm such models are rare. We recorded local field potentials from the ventral intermediate nucleus of the thalamus and electrocorticography signals from the ipsilateral sensorimotor cortex in 10 patients undergoing deep brain stimulation surgery. Signals were acquired during induction of propofol anaesthesia while subjects were resting. After confirming direct structural connectivity between the thalamus and the cortical recording site, we investigated propofol-associated changes in thalamic and cortical local power as well as thalamocortical functional connectivity, as measured with coherence, debiased weighted phase lag index, and phase amplitude coupling. Propofol anaesthesia resulted in local power increases at α frequencies (8-12 Hz) across both thalamic and cortical areas. At sensorimotor cortices, there was a broadband power increase (12-100 Hz), while the power of this same broad frequency band was suppressed within the thalamus. Despite the increase in local α power both within the thalamus and cortex, thalamocortical coherence and debiased weighted phase lag index in the α/low β frequencies (8-16 Hz, which was present in the awake state) significantly decreased with propofol administration (P < 0.05, two group test of coherence). Likewise, propofol administration resulted in decreased phase amplitude coupling between the phase of α/low β in the thalamus and the amplitude of broadband gamma (50-200 Hz) in the cortex (P = 0.031, Wilcoxon signed-rank test). We also report phase amplitude coupling between the phase of slow wave oscillations (0.1-1 Hz) and amplitude of broadband frequencies (8-200 Hz) within the cortex and across thalamocortical connections, during anaesthesia, both following a peak-max pattern. While confirming α-power increases with propofol administration both in thalamus and cortex, we observed decreased thalamocortical connectivity, contradicting models that suggest increasing cortical low frequency power is necessarily related to increased thalamocortical coherence but in support of the theory that propofol-induced loss of consciousness is associated with disrupted thalamocortical communication

Democratizing Access to Neurosurgical Medical Education: National Efforts in a Medical Student Training Camp During Coronavirus Disease 2019.

BackgroundNational medical student surveys amidst the coronavirus disease 2019 (COVID-19)-driven subinternship cancellations have demonstrated the need for supplemental, standardized subspecialty medical education, mentorship, and career planning nationally. We have presented the first live, cross-institutional virtual medical student subspecialty training camp to deliver standardized neurosurgical educational content to medical students during the COVID-19 pandemic, and its results on medical student anxiety and perceptions of neurosurgery.MethodsThe online training camp used a video conferencing platform that was open to all medical students. A post-training camp survey was administered.ResultsA total of 305 medical students registered for the event from 107 unique U.S. medical schools. Of the 305 medical students, 108 reported intending to apply to neurosurgery residency in 2021. The top medical student objectives for the training camp were program networking and mentorship. Of the 305 participants, 121 (39.7%) completed the post-training survey. Of the respondents, 65.0% reported improved neurosurgical knowledge, 79.8% reported decreased anxiety about subinternships and interviews, 82.5% reported increased enthusiasm about neurosurgery, and 100% desired a future annual virtual training camp because of the increased accessibility and decreased cost. This was especially important for students at institutions without home subspecialty programs and those with financial burdens.ConclusionsCOVID-19-driven innovations in medical education have accelerated changes that may have long been necessary. This virtual structure improved resource usage and scalability compared with in-person training, maintained social distancing, and democratized access to standardized, specialized content not often available through traditional medical curricula. Even as a supplement to in-person events, the virtual training camp model could be implemented by national medical societies, which might significantly increase medical students' preparedness for, and education in, neurosurgery and other subspecialties

Democratizing Access to Neurosurgical Medical Education: National Efforts in a Medical Student Training Camp During Coronavirus Disease 2019.

BackgroundNational medical student surveys amidst the coronavirus disease 2019 (COVID-19)-driven subinternship cancellations have demonstrated the need for supplemental, standardized subspecialty medical education, mentorship, and career planning nationally. We have presented the first live, cross-institutional virtual medical student subspecialty training camp to deliver standardized neurosurgical educational content to medical students during the COVID-19 pandemic, and its results on medical student anxiety and perceptions of neurosurgery.MethodsThe online training camp used a video conferencing platform that was open to all medical students. A post-training camp survey was administered.ResultsA total of 305 medical students registered for the event from 107 unique U.S. medical schools. Of the 305 medical students, 108 reported intending to apply to neurosurgery residency in 2021. The top medical student objectives for the training camp were program networking and mentorship. Of the 305 participants, 121 (39.7%) completed the post-training survey. Of the respondents, 65.0% reported improved neurosurgical knowledge, 79.8% reported decreased anxiety about subinternships and interviews, 82.5% reported increased enthusiasm about neurosurgery, and 100% desired a future annual virtual training camp because of the increased accessibility and decreased cost. This was especially important for students at institutions without home subspecialty programs and those with financial burdens.ConclusionsCOVID-19-driven innovations in medical education have accelerated changes that may have long been necessary. This virtual structure improved resource usage and scalability compared with in-person training, maintained social distancing, and democratized access to standardized, specialized content not often available through traditional medical curricula. Even as a supplement to in-person events, the virtual training camp model could be implemented by national medical societies, which might significantly increase medical students' preparedness for, and education in, neurosurgery and other subspecialties

Impulsivity Relates to Relative Preservation of Mesolimbic Connectivity in Patients with Parkinson Disease.

IntroductionThe relationship between Parkinson Disease (PD) pathology, dopamine replacement therapy (DRT), and impulse control disorder (ICD) development is still incompletely understood. Given the sensorimotor-lateral substantia nigra (SN) selective degeneration associated with PD, we posit that a relative sparing of the limbic-medial SN in the context of DRT drives impulsive, reward-seeking behavior in PD patients with recent history of severe impulsivity.MethodsImpulsive and control participants were selected from a consecutive list of PD patients receiving pre-operative deep brain stimulation (DBS) planning scans including 3T structural MRI and 64 direction diffusion tensor imaging (DTI). Using previously identified substantia nigra (SN) subsegment network connectivity profiles to develop classification targets, split-hemisphere target-based SN segmentation with probabilistic tractography was performed. The relative subsegment volumes and strength of connectivity between the SN and the limbic, associative, and motor network targets were compared.ResultsOur results show that there is greater probability of connectivity between the SN and limbic network targets relative to motor and associative network targets in PD patients with recent history of severe impulsivity as compared to PD patients without impulsivity (P = 0.0075). We did not observe relative volumetric subsegment differences across groups.ConclusionFirstly, our results suggest that fine-grained, atlas-derived classification targets may be used in PD to parcellate and classify functionally distinct subsegments of the SN, with the apparent preservation of previously reported topographical limbic-medial SN, associative-ventral SN, and sensorimotor-lateral SN orientation. We suggest that relative, as opposed to absolute, degeneration amongst SN-associated dopaminergic networks relates to the impulsivity phenotype in PD