Origami-inspired soft fluidic actuation for minimally invasive large-area electrocorticography.

Electrocorticography is an established neural interfacing technique wherein an array of electrodes enables large-area recording from the cortical surface. Electrocorticography is commonly used for seizure mapping however the implantation of large-area electrocorticography arrays is a highly invasive procedure, requiring a craniotomy larger than the implant area to place the device. In this work, flexible thin-film electrode arrays are combined with concepts from soft robotics, to realize a large-area electrocorticography device that can change shape via integrated fluidic actuators. We show that the 32-electrode device can be packaged using origami-inspired folding into a compressed state and implanted through a small burr-hole craniotomy, then expanded on the surface of the brain for large-area cortical coverage. The implantation, expansion, and recording functionality of the device is confirmed in-vitro and in porcine in-vivo models. The integration of shape actuation into neural implants provides a clinically viable pathway to realize large-area neural interfaces via minimally invasive surgical techniques.

Complete encasement of the radial nerve by a giant lipoma: illustrative case.

BACKGROUND: Among the spectrum of adipose lesions associated with peripheral nerves, complete circumferential encasement of the nerve by the lesion is a very rare entity. The authors report the first case of a giant lipoma that completely and circumferentially encased the radial nerve. OBSERVATIONS: A 57-year-old woman presented with a large left-arm mass that she had noticed over a year following significant weight loss. She had hypersensitivity and dysesthesias in the left posterior arm but no weakness or other symptoms. Magnetic resonance imaging of the left upper limb demonstrated a large lipoma completely encasing the radial nerve, originating at the level of the spiral grove proximally and extending distally to the lateral epicondyle. The lesion was completely resected at surgery with total preservation of radial nerve function. LESSONS: Lipomas encasing peripheral nerves can be difficult to manage while preserving function. This case adds to the intriguing spectrum of adipose lesions associated with peripheral nerves. https://thejns.org/doi/10.3171/CASE24148.

The paraneurium and the tumefactive appearance of peripheral nerve neurolymphomatosis: illustrative case.

BACKGROUND: Peripheral neurolymphomatosis (NL) is an often-misdiagnosed condition characterized by lymphomatous infiltration within the peripheral nerves. Its rarity and complexity frequently result in delayed diagnosis and suboptimal patient outcomes. This study aims to elucidate the role of the paraneurium (circumneurium) in NL, emphasizing its diagnostic and therapeutic significance. OBSERVATIONS: A 72-year-old man presented with lesions on his right lower eyelid. Initial diagnostics were inconclusive until an excisional biopsy confirmed extranodal marginal zone lymphoma. Following a complete metabolic response to rituximab treatment, the patient relapsed 14 months later with progressive lymphoma and bilateral sciatic nerve involvement, as confirmed by positron emission tomography-computed tomography and magnetic resonance imaging. LESSONS: This paper underscores the critical role of the paraneurium in NL, enhancing understanding of its pathophysiology. Integrating advanced imaging techniques have proved essential in accurately identifying neurolymphomatous involvement within the paraneurium. This study paves the way for more effective management strategies in NL and similar conditions, focusing on improving patient care and outcomes.

Thoracic Outlet Syndrome Part II: Consensus on the Management of Neurogenic Thoracic Outlet Syndrome by the European Association of Neurosurgical Societies' Section of Peripheral Nerve Surgery.

BACKGROUND: In the first part of this report, the European Association of Neurosurgical Societies' section of peripheral nerve surgery presented a systematic literature review and consensus statements on anatomy, classification, and diagnosis of thoracic outlet syndrome (TOS) along with a subclassification system of neurogenic TOS (nTOS). Because of the lack of level 1 evidence, especially regarding the management of nTOS, we now add a consensus statement on nTOS treatment among experienced neurosurgeons. OBJECTIVE: To document consensus and controversy on nTOS management, with emphasis on timing and types of surgical and nonsurgical nTOS treatment, and to support patient counseling and clinical decision-making within the neurosurgical community. METHODS: The literature available on PubMed/MEDLINE was systematically searched on February 13, 2021, and yielded 2853 results. Screening and classification of abstracts was performed. In an online meeting that was held on December 16, 2021, 14 recommendations on nTOS management were developed and refined in a group process according to the Delphi consensus method. RESULTS: Five RCTs reported on management strategies in nTOS. Three prospective observational studies present outcomes after therapeutic interventions. Fourteen statements on nonsurgical nTOS treatment, timing, and type of surgical therapy were developed. Within our expert group, the agreement rate was high with a mean of 97.8% (± 0.04) for each statement, ranging between 86.7% and 100%. CONCLUSION: Our work may help to improve clinical decision-making among the neurosurgical community and may guide nonspecialized or inexperienced neurosurgeons with initial patient management before patient referral to a specialized center.

X-Ray Markers for Thin Film Implants.

Implantable electronic medical devices are used in functional mapping of the brain before surgery and to deliver neuromodulation for the treatment of neurological and neuropsychiatric disorders. Their electrode arrays are assembled by hand, and this leads to bulky form factors with limited flexibility and low electrode counts. Thin film implants, made using microfabrication techniques, are emerging as an attractive alternative, as they offer dramatically improved conformability and enable high density recording and stimulation. A major limitation of these devices, however, is that they are invisible to fluoroscopy, the most common method used to monitor the insertion of implantable electrodes. Here, the development of mechanically flexible X-ray markers using bismuth- and barium-infused elastomers is reported. Their X-ray attenuation properties in human cadavers are explored and it is shown that they are biocompatible in cell cultures. It is further shown that they do not distort magnetic resonance imaging images and their integration with thin film implants is demonstrated. This work removes a key barrier for the adoption of thin film implants in brain mapping and in neuromodulation.

Prevention of the foreign body response to implantable medical devices by inflammasome inhibition.

SignificanceImplantable electronic medical devices (IEMDs) are used for some clinical applications, representing an exciting prospect for the transformative treatment of intractable conditions such Parkinson's disease, deafness, and paralysis. The use of IEMDs is limited at the moment because, over time, a foreign body reaction (FBR) develops at the device-neural interface such that ultimately the IEMD fails and needs to be removed. Here, we show that macrophage nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome activity drives the FBR in a nerve injury model yet integration of an NLRP3 inhibitor into the device prevents FBR while allowing full healing of damaged neural tissue to occur.

Far Lateral Approaches: C1 Meningioma With Vertebral Artery Involvement: 3-Dimensional Operative Video.

Tumors around the cervicomedullary junction are rare and constitute 5% of spinal tumors and 1% of cranial tumors. The approach to these lesions is difficult because of the close proximity of the medulla and cervical spinal cord, lower cranial nerves, and vertebral artery (VA) as well as the complex articulation between occipital condyle, C1 and C2. Cervicomedullary junction meningiomas are commonly classified based on their origin in relation to the dentate ligament, but the relationship to the VA typically plays an important role in deciding the surgical approach. For lesions located dorsal to the dentate ligament and not involving the VA, a midline approach is typically sufficient. However, when the VA is involved a far lateral approach is preferred as it offers better access to the V4 segment. We describe a case of a 55-yr-old man who presented with accessory nerve palsy and mild upper motor neuron signs and was found to have a C1 meningioma encasing and narrowing the VA at the V3/V4 segment. Informed consent was obtained. The patient was treated with a right far lateral approach with limited condylectomy to gain access to the V4 segment. We described the steps used for safe resection of the tumor around the VA from distal to proximal. We demonstrate the relationship of the tumor to the VA and the need to completely skeletonize the VA to achieve a gross total resection. We supplement the discussion with a 3D surgical video.

Far Lateral Approaches: Far Lateral Approach With Minimal Condylectomy for C2 Schwannoma: 3-Dimensional Operative Video.

Upper cervical schwannomas are rare lesions and together with meningiomas constitute around 5% of spinal tumors. The approach to these lesions is difficult because of the close proximity of the medulla and cervical spinal cord, lower cranial nerves, and the vertebral artery. Schwannomas in the upper cervical area typically arise from the dorsal roots and are located posterior to the dentate ligament. Nevertheless, a far lateral approach is often required for these lesions because of their lateral extent through the neural foramen and the proximity of both the V3 and V4 segments of the vertebral artery. With these lesions, an extensive condylectomy is rarely required. We present a case of a 40-yr-old woman who presented with an 8-mo history of deteriorating mobility and feeling of heaviness in the lower limbs with a further acute deterioration 1 wk before admission. She had a dissociated sensory loss and myelopathy in keeping with a partial hemicord syndrome. Imaging revealed a right-sided C2 intradural lesion extending through the C2 foramen in keeping with a C2 schwannoma. The patient was counseled on the treatment options, and informed consent for surgery was obtained. We describe a right-sided far lateral approach with minimal condylectomy for gross total resection of this lesion. We demonstrate the relationship of the tumor with the C2 nerve root, the spinal accessory nerve, and the cervical cord. We supplement the discussion with a 3D surgical video.

Far Lateral Approaches: Dural Arteriovenous Fistulae at the Hypoglossal Canal: 3-Dimensional Operative Video.

Cognard type V dural arteriovenous fistulae (dAVF) are typically located at the foramen magnum. Their presentation often mimics that of cervical myelopathy, and they can be easily misdiagnosed even if spinal vascular imaging is undertaken. Treatment typically involves endovascular embolization or surgery when embolization is not possible. We describe a case of a 67-yr-old man who presented with progressive symptoms of cervical myelopathy with a significant reduced ambulation and upper motor neuron signs. Imaging disclosed upper cervical cord edema, and angiography confirmed a Cognard type V dAVF with drainage into the perimedullary and spinal venous system. The dAVF was supplied by the hypoglossal division of the ascending pharyngeal artery. Endovascular treatment was believed to pose a risk of ischemic injury to the hypoglossal nerve, and therefore, surgery was offered. Informed consent was obtained. A far lateral approach was used to access the fistulous point. We describe the relevant vascular anatomy and the benefits of the far lateral approach for this lesion. We also demonstrate a tailored inferior condylectomy to gain access to the intracranial part of the hypoglossal canal, where the draining vein is expected to be found. We supplement the discussion with a 3D surgical video.

Surgical Resection of an Arteriovenous Malformation of the Orbital Surface of the Frontal Lobe with Olfactory Tract Preservation: 2-Dimensional Operative Video.

Medial orbitofrontal area arteriovenous malformations (AVMs) are located in the noneloquent cortex and typically drain superficially into Sylvian veins or the superior sagittal sinus, making them favorable for surgical treatment. However, while typically supplied by pial/cortical branches of the anterior cerebral artery (ACA), they can incorporate the recurrent artery of Heubner and other ACA perforators on their way to the anterior perforated substance located just posterior. We present a case of a 30-year-old female admitted with sudden collapse and intraventricular hemorrhage from a ruptured medial orbitofrontal area AVM. She was admitted to the intensive care unit and an external ventricular drain was placed to treat acute hydrocephalus. Catheter angiography demonstrated an AVM located just anteromedial to the termination of the internal carotid artery with a compact nidus and an associated intranidal flow aneurysm. Arterial supply originated from the orbitofrontal artery off the ACA, with medial lenticulostriates seen coursing past the nidus. Additional supply from the recurrent artery of Heubner could not be excluded. However, a hypodensity in the inferior frontal lobe seen on the presentation computed tomography scan was suggestive of a prior orbitofrontal infarct and thus cortical, rather than perforator, supply. In our practice, treatment of ruptured AVMs is dictated by the patients' clinical recovery and associated high-risk features (e.g., flow aneurysms). In this case, despite the presence of a flow aneurysm, treatment was delayed 18 days due to slow neurologic recovery and family preference. The patient remained in the intensive care unit under close neurologic observation. She was extubated on day 10, and the external ventricular drain was removed on day 12 after confirming resolution of intraventricular hemorrhage. Preoperatively the patient recovered to a Glasgow Coma Scale score of 15. Risks of treatment were discussed, and informed consent was obtained. The patient was treated using a standard pterional craniotomy. We describe the anatomic location of the lesion in the medial orbitofrontal area, the relationship to the olfactory tract and olfactory stria. We demonstrate olfactory tract dissection from its arachnoid cistern between the orbitofrontal lobe and gyrus rectus in order to access the lesion. Indocyanine green angiography is used to help surgical dissection and for quality control at the end of the procedure. We do not perform intraoperative angiography routinely; however, it can be a useful adjunct in deep and/or eloquent locations, which are difficult to image using videoangiography. Nevertheless, in the absence of intraoperative angiography close dissection directly over the nidus on the eloquent side ensures preservation of functional brain. We describe the microsurgical techniques of surgical treatment of AVMs, in particular the "cone" dissection technique of the AVM in order to allow identification of all feeding vessels and tracing "en passant" vessels from proximal to distal, as well as the use of intraoperative videoangiography to elucidate the nidus morphology and immediate postoperative quality control (Video 1, available at https://drive.google.com/file/d/1IXuLg84MwyMek1_Z1f1n7qssLThimvdx/view?usp=sharing).

Electronics with shape actuation for minimally invasive spinal cord stimulation.

Spinal cord stimulation is one of the oldest and most established neuromodulation therapies. However, today, clinicians need to choose between bulky paddle-type devices, requiring invasive surgery under general anesthetic, and percutaneous lead-type devices, which can be implanted via simple needle puncture under local anesthetic but offer clinical drawbacks when compared with paddle devices. By applying photo- and soft lithography fabrication, we have developed a device that features thin, flexible electronics and integrated fluidic channels. This device can be rolled up into the shape of a standard percutaneous needle then implanted on the site of interest before being expanded in situ, unfurling into its paddle-type conformation. The device and implantation procedure have been validated in vitro and on human cadaver models. This device paves the way for shape-changing bioelectronic devices that offer a large footprint for sensing or stimulation but are implanted in patients percutaneously in a minimally invasive fashion.

When Bio Meets Technology: Biohybrid Neural Interfaces.

The development of electronics capable of interfacing with the nervous system is a rapidly advancing field with applications in basic science and clinical translation. Devices containing arrays of electrodes can be used in the study of cells grown in culture or can be implanted into damaged or dysfunctional tissue to restore normal function. While devices are typically designed and used exclusively for one of these two purposes, there have been increasing efforts in developing implantable electrode arrays capable of housing cultured cells, referred to as biohybrid implants. Once implanted, the cells within these implants integrate into the tissue, serving as a mediator of the electrode-tissue interface. This biological component offers unique advantages to these implant designs, providing better tissue integration and potentially long-term stability. Herein, an overview of current research into biohybrid devices, as well as the historical background that led to their development are provided, based on the host anatomical location for which they are designed (CNS, PNS, or special senses). Finally, a summary of the key challenges of this technology and potential future research directions are presented.

Microsurgical Resection of a Common Peroneal Nerve Schwannoma: A 3-Dimensional Operative Video.

Peripheral nerve sheath tumors are benign entities that manifest with pain or neurological deficits from mass effect. Treatment is mostly surgical, however, the aggressiveness of treatment needs to be carefully considered with respect to preserving function. We present a case of a 62-year-old male with a 2-year history of left lower extremity pain radiating toward the dorsolateral foot. There was a tender and palpable mass in the lateral popliteal fossa with imaging consistent with Schwannoma of the common peroneal nerve. The patient was counseled for surgery and informed consent was obtained. Microsurgical resection was undertaken and gross total resection was achieved without compromise of function. We demonstrate the placement of neurophysiological monitoring electrodes in all 3 compartment of the calf as well as the use of stimulation to identify a nonfunctioning area for entering the nerve sheath. Anatomy of the popliteal fossa and microsurgical technique for resection of nerve sheath tumors are discussed. When dealing with these pathologies, it is important to use intraoperative neurophysiology as well as careful technique in order to achieve maximal resection without compromising neurological function.

Clinical Experience and Results of Microsurgical Resection of Arterioveonous Malformation in the Presence of Space-Occupying Intracerebral Hematoma.

BACKGROUND: Management of ruptured arteriovenous malformations (AVMs) with a mass-producing intracerebral hematoma (ICH) represents a surgical dilemma. OBJECTIVE: To evaluate the clinical outcome and obliteration rates of microsurgical resection of AVM when performed concomitantly with evacuation of an associated space-occupying ICH. METHODS: Data of patients with AVM were collected prospectively. Cases were identified in which an AVM was resected and an associated space-occupying ICH was evacuated at the same time, and divided into "group 1," in which the surgery was performed acutely within 48 h of presentation (secondary to elevated intracranial pressure); and "group 2," in which selected patients were operated upon in the presence of a liquefying ICH in the "subacute" stage. Clinical outcomes were assessed using the modified Rankin Scale, with a score of 0 to 2 considered a good outcome. Obliteration rates were assessed using postoperative angiography. RESULTS: From 2001 to 2015, 131 patients underwent microsurgical resection of an AVM, of which 65 cases were included. In "group 1" (n = 21; Spetzler-Ponce class A = 13, class B = 5, and class C = 3), 11 of 21 (52%) had a good outcome and in 18 of 19 (95%) of those who had a postoperative angiogram the AVMs were completely obliterated. In "group 2" (n = 44; Spetzler-Ponce class A = 33, class B = 9, and class C = 2), 31 of 44 (93%) had a good outcome and 42 of 44 (95%) were obliterated with a single procedure. For supratentorial AVMs, the ICH cavity was utilized to provide an operative trajectory to a deep AVM in 11 cases, and in 26 cases the ICH cavity was deep to the AVM and hence facilitated the deep dissection of the nidus. CONCLUSION: In selected patients the presence of a liquefying ICH cavity may facilitate the resection of AVMs when performed in the subacute stage resulting in a good neurological outcome and high obliteration rate.

The Effect of 3-Dimensional Simulation on Neurosurgical Skill Acquisition and Surgical Performance: A Review of the Literature.

OBJECTIVE: In recent years, 3-dimensional (3D) simulation of neurosurgical procedures has become increasingly popular as an addition to training programmes. However, there remains little objective evidence of its effectiveness in improving live surgical skill. This review analysed the current literature in 3D neurosurgical simulation, highlighting remaining gaps in the evidence base for improvement in surgical performance and suggests useful future research directions. DESIGN: An electronic search of the databases was conducted to identify studies investigating 3D virtual reality (VR) simulation for various types of neurosurgery. Eligible studies were those that used a combination of metrics to measure neurosurgical skill acquisition on a simulation trainer. Studies were excluded if they did not measure skill acquisition against a set of metrics or if they assessed skills that were not used in neurosurgical practice. This was not a systematic review however, the data extracted was tabulated to allow comparison between studies RESULTS: This study revealed that the average overall quality of the included studies was moderate. Only one study assessed outcomes in live surgery, while most other studies assessed outcomes on a simulator using a variety of metrics. CONCLUSIONS: It is concluded that in its current state, the evidence for 3D simulation suggests it as a useful supplement to training programmes but more evidence is needed of improvement in surgical performance to warrant large-scale investment in this technology.

External Immobilization of Odontoid Fractures: A Systematic Review to Compare the Halo and Hard Collar.

BACKGROUND: The aim of this systematic review was to compare the halo and hard collar in the management of adult odontoid fractures. METHODS: Systematic and independent searches on MEDLINE (PubMed) and the Cochrane Database of Systematic Reviews. Inclusion criteria included studies 1) with clinical outcomes, 2) in adults (18 years of age or order), 3) with odontoid fractures, 4) with patients immobilized using a halo or hard collar, and 5) in multiple (more than 5) patients. Treatment failure rates were calculated as the proportion requiring operative intervention. RESULTS: There were 714 cases included, who were managed in a halo (60%) or collar (40%). The mean age was 66 years (range, 18-96 years). Type 2 odontoid fractures were the most common (83%). There was no significant difference in failure rates between the halo and collar in patients with type 2 odontoid fractures (P = 0.111). This was also true in elderly (older than 65 years of age) patients (P = 0.802). The collar had a higher failure rate in type 3 odontoid fractures, though numbers were small (P = 0.035). Fibrous malunion occurred in 56 patients, and only 7% failed. There was only 1 case of neurological deterioration. Although mortality rates were similar between the collar and halo (P = 0.173), the halo was associated with a significantly higher complication rate (P < 0.001). CONCLUSIONS: For the most common clinical scenario, the halo and collar have similar failure rates, such that the higher morbidity associated with the halo may not be justified, especially in elderly patients. Malunion usually represents a stable clinical outcome, and surgery is rarely required. Prospective randomized studies are needed to more definitively compare the devices.

Proposal for establishment of the UK Cranial Reconstruction Registry (UKCRR).

BACKGROUND: The increasing utilisation of decompressive craniectomy for traumatic brain injury and stroke has led to an increase in the number of cranioplasties undertaken. Cranioplasty is also undertaken following excision of tumours originating from or invading the skull vault, removal of bone flaps due to post-operative infection, and decompressive craniectomy for the management of rarer causes of brain oedema and/or refractory intracranial hypertension. The existing literature which mainly consists of single-centre, retrospective studies, shows a significant variation in practice patterns and a wide range of morbidity. There also exists a need to measure the outcome as perceived by the patients themselves with patient reported outcome measures (PROMs; functional outcome, quality of life, satisfaction with cosmesis). In the UK, the concept of long-term surveillance of neurosurgical implants is well established with the UK shunt registry. Based on this background, we propose to establish the UK Cranial Reconstruction Registry (UKCRR). AIM: The overarching aim of the UKCRR is to collect high-quality data about cranioplasties undertaken across the UK and Ireland in order to improve outcomes for patients. METHODS: Any patient undergoing reconstruction of the skull vault with autologous bone, titanium, or synthetic material in participating units will be eligible for inclusion. Data will be submitted directly by participating units to the Outcome Registry Intervention and Operation Network secure platform. A Steering Committee will be responsible for overseeing the strategic direction and running of the UKCRR. OUTCOME MEASURES: These will include re-operation due to a cranioplasty-related issue, surgical site infection, re-admission due to a cranioplasty-related issue, unplanned post-operative escalation of care, adverse events, length of stay in admitting unit, destination at discharge from admitting unit, mortality at discharge from admitting unit, neurological status and PROMs during routine follow-up. CONCLUSION: The UKCRR will be an important pillar in the ongoing efforts to optimise the outcomes of patients undergoing cranioplasty.