Continuous neural control of a bionic limb restores biomimetic gait after amputation.

For centuries scientists and technologists have sought artificial leg replacements that fully capture the versatility of their intact biological counterparts. However, biological gait requires coordinated volitional and reflexive motor control by complex afferent and efferent neural interplay, making its neuroprosthetic emulation challenging after limb amputation. Here we hypothesize that continuous neural control of a bionic limb can restore biomimetic gait after below-knee amputation when residual muscle afferents are augmented. To test this hypothesis, we present a neuroprosthetic interface consisting of surgically connected, agonist-antagonist muscles including muscle-sensing electrodes. In a cohort of seven leg amputees, the interface is shown to augment residual muscle afferents by 18% of biologically intact values. Compared with a matched amputee cohort without the afferent augmentation, the maximum neuroprosthetic walking speed is increased by 41%, enabling equivalent peak speeds to persons without leg amputation. Further, this level of afferent augmentation enables biomimetic adaptation to various walking speeds and real-world environments, including slopes, stairs and obstructed pathways. Our results suggest that even a small augmentation of residual muscle afferents restores biomimetic gait under continuous neuromodulation in individuals with leg amputation.

Congenitally Fused Cervical Spine Is Associated With Adjacent-Level Degeneration in the Absence of Cervical Spine Surgery.

BACKGROUND: Cervical fusion surgery is associated with adjacent-level degeneration, but surgical and technical factors are difficult to dissociate from the mechanical effects of the fusion itself. OBJECTIVE: To determine the effect of fusion on adjacent-level degeneration in unoperated patients using a cohort of patients with congenitally fused cervical vertebrae. METHODS: We identified 96 patients with incidental single-level cervical congenital fusion on computed tomography imaging. We compared these patients to an age-matched control cohort of 80 patients without congenital fusion. We quantified adjacent-level degeneration through direct measurements of intervertebral disk parameters as well as the validated Kellgren & Lawrence classification scale for cervical disk degeneration. Ordinal logistic regression and 2-way analysis of variance testing were performed to correlate extent of degeneration with the congenitally fused segment. RESULTS: Nine hundred fifty-five motion segments were analyzed. The numbers of patients with C2-3, C3-4, C4-5, C5-6, and C6-7 congenitally fused segments were 47, 11, 11, 17, and 9, respectively. We found that patients with congenital fusion at C4-C5 and C5-C6 had a significantly greater extent of degeneration at adjacent levels compared with the degree of degeneration at the same levels in control patients and in patients with congenital fusion at other cervical levels, even while controlling for expected degeneration and age. CONCLUSION: Taken together, our data suggest that congenitally fused cervical spinal segments at C4-C5 and C5-C6 are associated with adjacent-level degeneration independent of fixation instrumentation. This study design removes surgical factors that might contribute to adjacent-level degeneration.

Predicting Discharge Disposition Following Meningioma Resection Using a Multi-Institutional Natural Language Processing Model.

BACKGROUND: Machine learning (ML)-based predictive models are increasingly common in neurosurgery, but typically require large databases of discrete variables for training. Natural language processing (NLP) can extract meaningful data from unstructured text. OBJECTIVE: To present an NLP model that predicts nonhome discharge and a point-of-care implementation. METHODS: We retrospectively collected age, preoperative notes, and radiology reports from 595 adults who underwent meningioma resection in an academic center from 1995 to 2015. A total of 32 algorithms were trained with the data; the 3 best performing algorithms were combined to form an ensemble. Predictive ability, assessed by area under the receiver operating characteristic curve (AUC) and calibration, was compared to a previously published model utilizing 52 neurosurgeon-selected variables. We then built a multi-institutional model by incorporating notes from 693 patients at another center into algorithm training. Permutation importance was used to analyze the relative importance of each input to model performance. Word clouds and non-negative matrix factorization were used to analyze predictive features of text. RESULTS: The single-institution NLP model predicted nonhome discharge with AUC of 0.80 (95% CI = 0.74-0.86) on internal and 0.76 on holdout validation compared to AUC of 0.77 (95% CI = 0.73-0.81) and 0.74 for the 52-variable ensemble. The multi-institutional model performed similarly well with AUC = 0.78 (95% CI = 0.74-0.81) on internal and 0.76 on holdout validation. Preoperative notes most influenced predictions. The model is available at http://nlp-home.insds.org. CONCLUSION: ML and NLP are underutilized in neurosurgery. Here, we construct a multi-institutional NLP model that predicts nonhome discharge.

Multidisciplinary approaches to complication reduction in complex spine surgery: a systematic review.

BACKGROUND CONTEXT: Complex spine surgery carries a high complication rate that can produce suboptimal outcomes for patients undergoing these extensive operations. However, multidisciplinary pathways introduced at multiple institutions have demonstrated a promising potential toward reducing the burden of complications in patients being treated for spinal deformities. To date, there has been no effort to systematically collate the multidisciplinary approaches in use at various institutions. PURPOSE: The present study aims to determine effective multidisciplinary strategies for reducing the complication rate in complex spine surgery by analyzing existing institutional multidisciplinary approaches and delineating common themes across multiple practice settings. STUDY DESIGN: Systematic review. METHODS: We followed guidelines established under the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The studies reported on data from PubMed, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Web of Science and Cochrane. We included articles that described either approaches to, or results from, the implementation of multidisciplinary paradigms during the preoperative, perioperative, and postoperative phases of care for patients undergoing complex spine surgery. We excluded studies that only targeted one complication unless such an approach was in coordination with more extensive multidisciplinary planning at the same institution. RESULTS: A total of 406 unique articles were identified. Following an initial determination based on title and abstract, 22 articles met criteria for full-text review, and 10 met the inclusion criteria to be included in the review. Key aspects of multidisciplinary approaches to complex spine surgery included extensive preoperative workup and interdisciplinary conferencing, intraoperative communication and monitoring, and postoperative floor management and discharge planning. These strategies produced decreases in surgical duration and complication rates. CONCLUSIONS: This study represents the first to systematically analyze multidisciplinary approaches to reduce complications in complex spine surgery. This review provides a roadmap toward reducing the elevated complication rate for patients undergoing complex spine surgery.

Myopericytoma at the Craniocervical Junction: Clinicopathological Report and Review of a Rare Perivascular Neoplasm.

BACKGROUND AND IMPORTANCE: Myopericytoma is an emerging class of neoplasm originating from the perivascular myoid cellular environment, previously classified as a variant of hemangiopericytoma. Most reported myopericytomas are found in soft tissues of the extremities; however, infrequent cases are described involving the central nervous system. Intracranial myopericytoma remains rare. Here, we describe the first report of myopericytoma occurring at the cervicomedullary junction in close proximity to the vertebral artery, mimicking a vascular lesion. CLINICAL PRESENTATION: A 64-yr-old woman presented with radiating neck pain. Magnetic resonance imaging revealed a well-circumscribed enhancing lesion adjacent to the vertebral artery-accessory nerve complex. She underwent a far lateral craniotomy and cervical laminectomy to obtain proximal vertebral artery control and adequate exposure of the lesion, which appeared most consistent with neoplasm at surgery. Histopathology revealed a grade I myopericytoma. A gross total resection was achieved, and the patient has no evidence of recurrence 3 yr after surgery. CONCLUSION: Tumors of perivascular origin include hemangiopericytoma, glomus tumor, myofibroma, and myopericytoma and are uncommon lesions intracranially. Consideration of and distinction among these perivascular tumors is critically important, as they each have distinct clinical behaviors and management. Myopericytoma can mimic other neoplastic and cerebrovascular pathologies, but it most commonly has a benign course and can be surgically cured if a gross total resection can be achieved. Rarer myopericytoma variants that adopt a more malignant course have been described, and ongoing molecular studies may identify mutations or activated signaling pathways that can be targeted to offer chemotherapeutic options in the future.

Long-Term Visual Memory and Its Role in Learning Suppression.

Long-term memory is a core aspect of human learning that permits a wide range of skills and behaviors often important for survival. While this core ability has been broadly observed for procedural and declarative memory, whether similar mechanisms subserve basic sensory or perceptual processes remains unclear. Here, we use a visual learning paradigm to show that training humans to search for common visual features in the environment leads to a persistent improvement in performance over consecutive days but, surprisingly, suppresses the subsequent ability to learn similar visual features. This suppression is reversed if the memory is prevented from consolidating, while still permitting the ability to learn multiple visual features simultaneously. These findings reveal a memory mechanism that may enable salient sensory patterns to persist in memory over prolonged durations, but which also functions to prevent false-positive detection by proactively suppressing new learning.

Decoding unconstrained arm movements in primates using high-density electrocorticography signals for brain-machine interface use.

Motor deficit is among the most debilitating aspects of injury to the central nervous system. Despite ongoing progress in brain-machine interface (BMI) development and in the functional electrical stimulation of muscles and nerves, little is understood about how neural signals in the brain may be used to potentially control movement in one's own unconstrained paralyzed limb. We recorded from high-density electrocorticography (ECoG) electrode arrays in the ventral premotor cortex (PMv) of a rhesus macaque and used real-time motion tracking techniques to correlate spatial-temporal changes in neural activity with arm movements made towards objects in three-dimensional space at millisecond precision. We found that neural activity from a small number of electrodes within the PMv can be used to accurately predict reach-return movement onset and directionality. Also, whereas higher gamma frequency field activity was more predictive about movement direction during performance, mid-band (beta and low gamma) activity was more predictive of movement prior to onset. We speculate these dual spatiotemporal signals may be used to optimize both planning and execution of movement during natural reaching, with prospective relevance to the future development of neural prosthetics aimed at restoring motor control over one's own paralyzed limb.

Intradural spinal arachnoid cyst resection: implications of duraplasty in a large case series.

OBJECTIVE Optimal diagnosis and management strategies for intradural spinal arachnoid cysts (SACs) are still unresolved given the rare nature of this entity, with few large case series and virtually no statistical analyses of patient characteristics in the literature. Here, the authors studied a large patient cohort with these lesions to determine whether pre- or postoperative attributes could be used to aid in either diagnosis or prognosis. METHODS A chart review was completed at a single institution for the period from 2002 to 2016 to determine the preoperative characteristics and postoperative outcomes of 21 patients with exclusively intradural SACs. Patients were assessed for symptoms such as weakness, pain, sensory changes, bowel and/or bladder dysfunction, and gait changes. Postoperatively, patients were analyzed for symptom improvement, complication occurrence, and duration of follow-up. RESULTS Approximately two-thirds of the patients in this series had developed SACs idiopathically, and the mean duration of symptoms prior to diagnosis was 15 months among all patients. A slight majority (57%) underwent CT myelography in the course of diagnosis, and a quarter of the patients had a syrinx. There was a statistically significant association between location of the SAC and number of presenting signs and symptoms; that is, patients with cysts in the lumbosacral region had more symptoms than those with cysts at the cervical or thoracic levels (p = 0.031). Overall, outcomes were largely positive, with approximately 60%-70% of patients experiencing postoperative improvement in symptoms, with motor weakness showing the highest response rate (71%) and pain symptoms the least likely to subside (50%). In the cohort with preoperative pain, those who had undergone expansile duraplasty were significantly more likely to experience relief of their pain symptoms (p = 0.028), which may have been a result of the superior restoration of cerebrospinal fluid pathways allowing for more adequate reduction in compression. CONCLUSIONS In this large case series on intradural SACs, new light has been shed on aspects of both pre- and postoperative care for patients with these rare lesions. Specifically, the authors revealed that lumbosacral intradural SACs may be associated with a higher disease burden and that patients who undergo expansile duraplasty may have an increased likelihood of experiencing postoperative pain relief.

Rapid Neurological Recovery Following Partial Surgical Resection of Spinal Glioblastoma Multiforme in a Pediatric Patient Presenting With Complete Paraplegia.

Pediatric spinal cord glioblastoma multiforme is a rare entity with a poor prognosis often presenting with lower extremity weakness or paralysis. Previous literature suggests that aggressive surgical resection may provide overall survival benefit; however, there is limited concurrent analysis demonstrating neurological recovery following surgical resection. We report the case of a 9-year-old boy who presented with complete paraplegia and regained the ability to ambulate independently following subtotal surgical resection, radiation, and chemotherapy. The case demonstrates the balance between meaningful neurological recovery and overall survival when deciding on the extent of resection in cases of pediatric spinal glioblastoma multiforme.

Initial Experience with High-Definition Camera-On-a-Chip Flexible Endoscopy for Intraventricular Neurosurgery.

OBJECTIVE: The usefulness of existing neuroendoscopes has been limited by either decreased range of motion or suboptimal image resolution. The flexible high-definition chip-camera endoscope has emerged as a potential solution to the shortcomings of available instruments by combining superior flexibility and image quality in order to better operate within spatially constrained intraventricular operations. CASE DESCRIPTION: Here we describe a 36-year-old woman who presented with hydrocephalus caused by an obstructive mass arising from the tectum. A high-definition camera-on-a-chip flexible neuroendoscope was used to sample the tectal mass after a traditional neuroendoscope was used to perform a third ventriculostomy. CONCLUSIONS: As demonstrated by this initial experience, the use of high-definition camera-on-a-chip flexible endoscopy may provide enhanced intraoperative visualization and application for intraventricular neurosurgery.