A comparison of computed tomography angiography and digital subtraction angiography for the diagnosis of penetrating cerebrovascular injury: a prospective multicenter study.

OBJECTIVE: In this research, the authors sought to characterize the incidence and extent of cerebrovascular lesions after penetrating brain injury in a civilian population and to compare the diagnostic value of head computed tomography angiography (CTA) and digital subtraction angiography (DSA) in their diagnosis. METHODS: This was a prospective multicenter cohort study of patients with penetrating brain injury due to any mechanism presenting at two academic medical centers over a 3-year period (May 2020 to May 2023). All patients underwent both CTA and DSA. The sensitivity and specificity of CTA was calculated, with DSA considered the gold standard. The number of DSA studies needed to identify a lesion requiring treatment that had not been identified on CTA was also calculated. RESULTS: A total of 73 patients were included in the study, 33 of whom had at least 1 penetrating cerebrovascular injury, for an incidence of 45.2%. The injuries included 13 pseudoaneurysms, 11 major arterial occlusions, 9 dural venous sinus occlusions, 8 dural arteriovenous fistulas, and 6 carotid cavernous fistulas. The sensitivity of CTA was 36.4%, and the specificity was 85.0%. Overall, 5.6 DSA studies were needed to identify a lesion requiring treatment that had not been identified with CTA. CONCLUSIONS: Cerebrovascular injury is common after penetrating brain injury, and CTA alone is insufficient to diagnosis these injuries. Patients with penetrating brain injuries should routinely undergo DSA.

Pediatric Cranial Vault and Skull Base Fractures.

Cranial vault and skull base fractures in children are distinctly different from those seen in adults. Pediatric skull fractures have the benefit of greater capacity to remodel; however, the developing pediatric brain and craniofacial skeleton present unique challenges to diagnosis, natural history, and management. This article discusses the role of surgical treatment of these fractures, its indications, and techniques.

High-Flow Bypass and Clip Trapping of a Giant Fusiform Middle Cerebral Artery (M1) Aneurysm: Technical Case Instruction.

BACKGROUND AND IMPORTANCE: Giant intracranial aneurysms have a poor natural history with mortality rates of 68% and 80% over 2-year and 5-year, respectively. Cerebral revascularization can provide flow preservation while treating complex aneurysms requiring parent artery sacrifice. In this report, we describe the microsurgical clip trapping and high-flow bypass revascularization for a giant middle cerebral artery (MCA) aneurysm. CLINICAL PRESENTATION: A 19-year-old man was diagnosed with a giant left MCA aneurysm after he suffered a left hemispheric capsular stroke 6 months ago. Since then, the patient recovered from the right hemiparesis and dysarthria with residual symptoms. Neuroimaging demonstrated a giant fusiform aneurysm encompassing the entire M1 segment. The bilobed aneurysm measured 37 × 16 × 15 mm. Endovascular treatment options included partial coiling of the aneurysm followed by deployment of flow-diverting stent spanning from the M2 branch-through the aneurysm neck-into the internal carotid artery. Because of the high risk of lenticulostriate artery stroke with endovascular treatment, the patient opted for microsurgical clip trapping and bypass. The patient consented to the procedure. High-flow bypass from internal carotid artery to M2 MCA was performed using radial artery graft, followed by aneurysm clip trapping using 3 clips. CONCLUSION: We demonstrate the successful microsurgical treatment for a complex case of giant M1 MCA aneurysm with fusiform morphology. High-flow revascularization using radial artery graft helped in achieving good clinical outcome with complete aneurysm occlusion with flow preservation despite the challenging morphology and location. Cerebral bypass continues to be a useful tool to tackle complex intracranial aneurysms.

Operative Technique and Complication Management in a Case of Giant Esthesioneuroblastoma Resected by a Combined Transcranial and Endonasal Endoscopic Approach: Technical Case Report.

BACKGROUND AND IMPORTANCE: Esthesioneuroblastoma (ENB) is a rare anterior skull base tumor derived from olfactory epithelium. There are very few operative videos in the literature demonstrating the surgical resection techniques for giant ENB because of their rarity and complexity. In this technical report, we demonstrate the microsurgical resection of a very large and complex high-grade ENB, initially deemed unresectable, through a bifrontal craniotomy and extended subfrontal approach combined with an endonasal endoscopic approach. CLINICAL PRESENTATION: A 34-year-old woman presented with headaches, nasal congestion, and bloody nasal drainage. MRI showed a large nasal cavity mass with extension into the anterior cranial fossa and bifrontal lobes. There was significant bifrontal edema causing headaches and abutting the optic nerves. Initial management with surgical resection was offered to the patient for local tumor control and to preserve her vision. A combined bifrontal craniotomy and endonasal transsphenoidal approach was used for resecting this giant tumor. After achieving gross total resection, we reconstructed the anterior skull base in layers. She developed several postoperative complications which were appropriately managed. CONCLUSION: We demonstrate the surgical resection of a giant ENB through a combined transcranial and endonasal endoscopic approach. We discuss the several postoperative complications in this complex case and the lessons learned.

Traumatic Pseudoaneurysm of the Occipital Artery Treated with Open Surgical Ligation: 2-Dimensional Operative Video.

Scalp pseudoaneurysms occur most commonly because of trauma and are often in the superficial temporal artery due to the lack of soft tissue coverage between skin and bone, making it more vulnerable anatomically.1,2 Pseudoaneurysms of the occipital artery (OA) also occur but are extremely rare.2-4 An 80-year-old man presented with scalp bleeding and a small left-sided posterior scalp laceration after a fall and head strike 10 days prior. He was admitted and during his 2-week hospital stay, the occipital laceration continued to rebleed (Video 1). He developed a 2-cm pulsatile ulcerative mass with central necrosis on the left nuchal ridge. Computed tomography angiography revealed an ovoid left occipital lesion measuring 1.3 × 2.5 × 2.3 cm with delayed contrast filling and partial thrombosis. The base of the lesion had dense contrast filling continuous with the OA, diagnostic of OA pseudoaneurysm. OA pseudoaneurysm may be treated endovascularly or surgically. While surgical resection is the most common treatment, minimally invasive techniques have been successfully done through direct injection of N-butyl cyanoacrylate or endovascular embolization. The clinical presentation of this case was unique because this patient had an ulcerated lesion with central necrosis overlying the pseudoaneurysm. Endovascular management alone would not address the open lesion, which is at high risk for infection. The risk of infection would increase after embolization of the occipital artery, causing further necrosis of the tissue.

Clinical Utility of Routine Postprocedural Computed Tomography of the Head Following Elective Neuroendovascular Interventions.

BACKGROUND: Little evidence supports acquisition of routine head imaging after uncomplicated elective neurosurgical procedures for patients with unchanged neurological examinations; however, imaging is still performed by some neurointerventionalists. We assessed the clinical utility of routine computed tomography of the head (CTH) following elective neuroendovascular interventions, including aneurysm coiling, aneurysm stent-assisted coiling, aneurysm flow diversion, arteriovenous malformation/fistula embolization, middle meningeal artery embolization for subdural hematoma, extracranial carotid artery stenting, and venous sinus stenting. METHODS: Retrospective chart review identified patients undergoing neuroendovascular intervention from 2011 to 2021 at our institution. Demographic, clinical, and radiographic variables, including presenting signs and symptoms, antiplatelets and/or anticoagulant medications, intraprocedural complications, postprocedural CTH findings, and postprocedural neurological examinations, were recorded. Association of clinical variables with an abnormal postprocedural CTH was assessed with univariate analysis. Patients with ruptured vascular pathology, preoperative embolizations, and missing postprocedural CTH images and/or reports were excluded. RESULTS: Of 509 procedures identified, 354 were eligible for analysis; 4.8% of patients (17/354) had abnormal findings on postprocedural CTH. Nine patients had intraprocedural complications or new postprocedural neurological deficits that would have prompted imaging regardless of institutional practice. None of the remaining 8 (2.3%) patients required additional procedures. New postprocedural neurological deficit was the only significant predictor of abnormal postprocedural CTH (odds ratio = 6.79; 95% confidence interval, 2.01-20.32; P = 0.0009). CONCLUSIONS: In a large cohort of patients undergoing elective neuroendovascular intervention, no patients were identified for whom routine postprocedural CTH alone meaningfully altered their clinical care. Routine CTH is not necessary after uncomplicated elective neuroendovascular interventions performed with careful postprocedural neurological assessment.

Short-term outcomes associated with temozolomide or PCV chemotherapy for 1p/19q-codeleted WHO grade 3 oligodendrogliomas: A national evaluation.

Background: The optimal chemotherapy regimen between temozolomide and procarbazine, lomustine, and vincristine (PCV) remains uncertain for WHO grade 3 oligodendroglioma (Olig3) patients. We therefore investigated this question using national data. Methods: Patients diagnosed with radiotherapy-treated 1p/19q-codeleted Olig3 between 2010 and 2018 were identified from the National Cancer Database. The overall survival (OS) associated with first-line single-agent temozolomide vs multi-agent PCV was estimated by Kaplan-Meier techniques and evaluated by multivariable Cox regression. Results: One thousand five hundred ninety-six radiotherapy-treated 1p/19q-codeleted Olig3 patients were identified: 88.6% (n = 1414) treated with temozolomide and 11.4% (n = 182) with PCV (from 5.4% in 2010 to 12.0% in 2018) in the first-line setting. The median follow-up was 35.5 months (interquartile range [IQR] 20.7-60.6 months) with 63.3% of patients alive at the time of analysis. There was a significant difference in unadjusted OS between temozolomide (5-year OS 58.9%, 95%CI: 55.6-62.0) and PCV (5-year OS 65.1%, 95%CI: 54.8-73.5; P = .04). However, a significant OS difference between temozolomide and PCV was not observed in the Cox regression analysis adjusted by age and extent of resection (PCV vs temozolomide HR 0.81, 95%CI: 0.59-1.11, P = .18). PCV was more frequently used for younger Olig3s but otherwise was not associated with patient's insurance status or care setting. Conclusions: In a national analysis of Olig3s, first-line PCV chemotherapy was associated with a slightly improved unadjusted short-term OS compared to temozolomide; but not following adjustment by patient age and extent of resection. There has been an increase in PCV utilization since 2010. These findings provide preliminary data while we await the definitive results from the CODEL trial.

Fixed, Dilated, and Conversing-Unreactive Pupil With Preserved Consciousness Indicating Acutely Rising Intracranial Pressure due to Traumatic Intraparenchymal Contusions: Case Report and Review of the Literature.

Patients with fixed and dilated pupils (FDPs) due to rising intracranial pressure (ICP) typically experience a deterioration in consciousness. We describe an exceptional case of a patient with bifrontal contusions who developed worsening edema and a unilaterally FDP while maintaining consciousness and the ability to communicate. A 58-year-old man with history of hypertension and diabetes mellitus type II presented after being assaulted, with bifrontal contusions and right frontal intraparenchymal hemorrhage. On hospital day 8, his right pupil became fixed (NPi 0) and dilated (4.8 mm). The patient was drowsy, arousable to tactile stimuli, answering questions, oriented to place and time, following commands on his right side, maintaining Glasgow Coma Scale of 14 (E4, V5, M6). He described complete loss of vision and could not identify objects or count fingers. His gaze was dysconjugate with impaired vertical excursion and inability to fully abduct to the right side. Corneal reflexes were intact bilaterally. Hypertonic saline and mannitol produced no improvement in his pupillary exam. Head computed tomography showed worsening midline shift and interval increase in subfalcine herniation related to increased peri-hematoma edema. We performed an emergent right-sided decompressive hemicraniectomy with durotomy and duraplasty. His pupil became reactive 5 hours after surgery. While FDP without deterioration of consciousness has been described due to traumatic subdural and epidural hematomas, we report this unusual constellation as a sign of rising ICP and impeding herniation due to intraparenchymal contusions, highlighting that any pupillary change warrants prompt work-up and intervention.

Somatic Mosaicism of a PDGFRB Activating Variant in Aneurysms of the Intracranial, Coronary, Aortic, and Radial Artery Vascular Beds.

Background Activating variants in platelet-derived growth factor receptor beta (PDGFRB), including a variant we have previously described (p.Tyr562Cys [g.149505130T>C [GRCh37/hg19]; c.1685A>G]), are associated with development of multiorgan pathology, including aneurysm formation. To investigate the association between the allele fraction genotype and histopathologic phenotype, we performed an expanded evaluation of post-mortem normal and aneurysmal tissue specimens from the previously published index patient. Methods and Results Following death due to diffuse subarachnoid hemorrhage in a patient with mosaic expression of the above PDGFRB variant, specimens from the intracranial, coronary, radial and aortic arteries were harvested. DNA was extracted and alternate allele fractions (AAF) of PDGFRB were determined using digital droplet PCR. Radiographic and histopathologic findings, together with genotype expression of PDGFRB were then correlated in aneurysmal tissue and compared to non-aneurysmal tissue. The PDGFRB variant was identified in the vertebral artery, basilar artery, and P1 segment aneurysms (AAF: 28.7%, 16.4%, and 17.8%, respectively). It was also identified in the coronary and radial artery aneurysms (AAF: 22.3% and 20.6%, respectively). In phenotypically normal intracranial and coronary artery tissues, the PDGFRB variant was not present. The PDGFRB variant was absent from lymphocyte DNA and normal tissue, confirming it to be a non-germline somatic variant. Primary cell cultures from a radial artery aneurysm localized the PDGFRB variant to CD31-, non-endothelial cells. Conclusions Constitutive expression of PDGFRB within the arterial wall is associated with the development of human fusiform aneurysms. The role of targeted therapy with tyrosine kinase inhibitors in fusiform aneurysms with PDGFRB mutations should be further studied.

Full Endoscopic Ligamentum Flavum Sparing Unilateral Laminotomy for Bilateral Recess Decompression: Surgical Technique and Clinical Results.

OBJECTIVE: Interlaminar endoscopic spine surgery has been introduced and utilized for lumbar lateral recess decompression. We modified this technique and utilized it for bilateral lateral recess stenoses without significant central stenosis. Here we present the surgical details and clinical outcome of ligamentum flavum sparing unilateral laminotomy for bilateral recess decompression (ULBRD). METHODS: Prospectively collected registry for full-endoscopic surgeries was reviewed retrospectively. One hundred eighty-two consecutive cases from a single center between September 2015 and March 2021 were reviewed and 57 of them whom underwent ULBRD were enrolled for analysis. Basic patient demographic data, perioperative details, surgeryrelated complications, and clinical outcome were reviewed. The detailed surgical technique is presented as well. RESULTS: Among the 57 patients enrolled, 37 were males while the other 20 were females. The mean age was 58.53 ± 14.51 years, and a bimodal age distribution at the age of mid-fifties and mid-sixties or older was noted. The later age-peak was related to coexistence of degenerative scoliosis. The average operative time per lamina was 70.34 ± 20.51 minutes and mean length of stay was 0.56 ± 0.85 days. Four perioperative complications were reported (7.0%) and the overall reoperation rate at the index level within 1 year was 8.8%. The preoperative back/leg visual analogue scale scores and functional outcome scales including EuroQol-5 dimension questionnaire, Oswestry Disability Index presented significant improvement immediately after surgery and were maintained until final follow-up. CONCLUSION: ULBRD for bilateral lateral recess stenoses without significant central stenosis resulted in good clinical outcomes with acceptably low perioperative complications rates. Sufficient decompression was achieved with the central ligamentum flavum being preserved.

The low utility of routine cranial imaging after pediatric shunt revision.

OBJECTIVE: Postoperative routine imaging is common after pediatric ventricular shunt revision, but the benefit of scanning in the absence of symptoms is questionable. In this study, the authors aimed to assess how often routine scanning results in a change in clinical management after shunt revision. METHODS: The records of a large, tertiary pediatric hospital were retrospectively reviewed for all consecutive cases of pediatric shunt revision between July 2013 and July 2018. Postoperative imaging was classified as routine (i.e., in the absence of symptoms, complications, or other direct indications) or nonroutine. Reinterventions within 30 days were assessed in these groups. RESULTS: Of 387 included shunt revisions performed in 232 patients, postoperative imaging was performed in 297 (77%), which was routine in 244 (63%) and nonroutine in 53 (14%). Ninety revisions (23%) underwent any shunt-related procedure after postoperative imaging, including shunt reprogramming (n = 35, 9%), shunt tap (n = 10, 3%), and a return to the operating room (OR; n = 58, 15%). Of the 244 cases receiving routine imaging, 241 did not undergo a change in clinical management solely based on routine imaging findings. The remaining 3 cases returned to the OR, accounting for 0.8% (95% CI 0.0%-1.7%) of all cases or 1.2% (95% CI 0.0%-2.6%) of cases that received routine imaging. Furthermore, 27 of 244 patients in this group returned to the OR for other reasons, namely complications (n = 12) or recurrent symptoms (n = 15); all arose after initial routine imaging. CONCLUSIONS: The authors found a low yield to routine imaging after pediatric shunt revision, with only 0.8% of cases undergoing a change in management based on routine imaging findings without corresponding clinical findings. Moreover, routine imaging without abnormal findings was no guarantee of an uneventful postoperative course. Clinical monitoring can be considered as an alternative in asymptomatic, uncomplicated patients.

Classification of glioblastoma versus primary central nervous system lymphoma using convolutional neural networks.

A subset of primary central nervous system lymphomas (PCNSL) are difficult to distinguish from glioblastoma multiforme (GBM) on magnetic resonance imaging (MRI). We developed a convolutional neural network (CNN) to distinguish these tumors on contrast-enhanced T1-weighted images. Preoperative brain tumor MRIs were retrospectively collected among 320 patients with either GBM (n = 160) and PCNSL (n = 160) from two academic institutions. The individual images from these MRIs consisted of a training set (n = 1894 GBM and 1245 PCNSL), a validation set (n = 339 GBM; 202 PCNSL), and a testing set (99 GBM and 108 PCNSL). Three CNNs using the EfficientNetB4 architecture were evaluated. To increase the size of the training set and minimize overfitting, random flips and changes to color were performed on the training set. Our transfer learning approach (with image augmentation and 292 epochs) yielded an AUC of 0.94 (95% CI: 0.91-0.97) for GBM and an AUC of 0.95 (95% CI: 0.92-0.98) for PCNL. In the second case (not augmented and 137 epochs), the images were augmented prior to training. The area under the curve for GBM was 0.92 (95% CI: 0.88-0.96) for GBM and an AUC of 0.94 (95% CI: 0.91-0.97) for PCNSL. For the last case (augmented, Gaussian noise and 238 epochs) the AUC for GBM was 0.93 (95% CI: 0.89-0.96) and an AUC 0.93 (95% CI = 0.89-0.96) for PCNSL. Even with a relatively small dataset, our transfer learning approach demonstrated CNNs may provide accurate diagnostic information to assist radiologists in distinguishing PCNSL and GBM.

3D Printed frames to enable reuse and improve the fit of N95 and KN95 respirators.

BACKGROUND: In response to supply shortages caused by the COVID-19 pandemic, N95 filtering facepiece respirators (FFRs or "masks"), which are typically single-use devices in healthcare settings, are routinely being used for prolonged periods and in some cases decontaminated under "reuse" and "extended use" policies. However, the reusability of N95 masks is limited by degradation of fit. Possible substitutes, such as KN95 masks meeting Chinese standards, frequently fail fit testing even when new. The purpose of this study was to develop an inexpensive frame for damaged and poorly fitting masks using readily available materials and 3D printing. RESULTS: An iterative design process yielded a mask frame consisting of two 3D printed side pieces, malleable wire links that users press against their face, and cut lengths of elastic material that go around the head to hold the frame and mask in place. Volunteers (n = 45; average BMI = 25.4), underwent qualitative fit testing with and without mask frames wearing one or more of four different brands of FFRs conforming to US N95 or Chinese KN95 standards. Masks passed qualitative fit testing in the absence of a frame at rates varying from 48 to 94 % (depending on mask model). For individuals who underwent testing using respirators with broken or defective straps, 80-100 % (average 85 %) passed fit testing with mask frames. Among individuals who failed fit testing with a KN95, ~ 50 % passed testing by using a frame. CONCLUSIONS: Our study suggests that mask frames can prolong the lifespan of N95 and KN95 masks by serving as a substitute for broken or defective bands without adversely affecting fit. Use of frames made it possible for ~ 73 % of the test population to achieve a good fit based on qualitative and quantitative testing criteria, approaching the 85-90 % success rate observed for intact N95 masks. Frames therefore represent a simple and inexpensive way of expanding access to PPE and extending their useful life. For clinicians and institutions interested in mask frames, designs and specifications are provided without restriction for use or modification. To ensure adequate performance in clinical settings, fit testing with user-specific masks and PanFab frames is required.

Expandable Versus Static Cages in Minimally Invasive Lumbar Interbody Fusion: A Systematic Review and Meta-Analysis.

BACKGROUND: Expandable cages for interbody fusion allow for in situ expansion optimizing fit while mitigating endplate damage. Studies comparing outcomes after using expandable or static cages have been conflicting. METHODS: This was a meta-analysis A systematic search was performed in accordance with the Preferred Reporting Items for Systemic Reviews and Meta-Analyses (PRISMA) guidelines identifying studies reporting outcomes among patients who underwent minimally invasive lumbar interbody fusion (MIS-LIF). RESULTS: Fourteen articles with 1129 patients met inclusion criteria. Compared with MIS-LIFs performed with static cages, those with expandable cages had a significantly lower incidence of graft subsidence (expandable: incidence 0.03, I2 22.50%; static: incidence 0.27, I2 51.03%, P interaction <0.001), length of hospital stay (expandable: mean difference [MD] 3.55 days, I2 97%; static: MD 7.1 days, I2 97%, P interaction <0.01), and a greater increase in disc height (expandable: MD -4.41 mm, I2 99.56%; static: MD -0.79 mm, I2 99.17%, P interaction = 0.02). There was no statistically significant difference among Oswestry Disability Index (expandable: MD -22.75, I2 98.17%; static: MD -17.11, I2 95.26%, P interaction = 0.15), fusion rate (expandable: incidence 0.94, I2 0%; static incidence 0.92, I2 0%, P interaction = 0.44), overall change in lumbar lordosis (expandable: MD 3.48 degrees, I2 59.29%; static: MD 3.67 degrees, I2 0.00%, P interaction 0.88), blood loss (expandable: MD 228.9 mL, I2 100%; static: MD 261.1 mL, I2 94%, P interaction = 0.69) and operative time (expandable: MD 184 minutes, I2 95.32%; static: MD 150.4 minutes, I2 91%, P interaction = 0.56). CONCLUSIONS: Expandable interbody cages in MIS-LIF were associated with a decrease in subsidence rate, operative time and greater in increase in disc height.

Long-term follow-up results of the SMART coil in the endovascular treatment of intracranial aneurysms.

BACKGROUND: The Penumbra SMART coil is a novel device that becomes progressively softer from its distal to proximal end to maximize coil packing and prevent microcatheter prolapse or coil migration. Here, we report a large series of patients detailing the long-term experience of a single institution using the SMART coil among patients with intracranial aneurysms (IAs). METHODS: Prospective data of 105 consecutive patients with 106 IAs treated using SMART coils was collected between March 2015 and July 2018. Clinical and angiographic data were analyzed. RESULTS: Forty-nine patients (46.7%) presented with subarachnoid hemorrhage and 16 (14.2%) had recurrent aneurysms. Two patients had minor intraprocedural ruptures and remained neurologically stable. One patient had a thromboembolic complication with progressive neurologic decline. There was only one case microcatheter prolapse related to placement of a stent before coiling. An initial post-treatment modified Raymond-Roy Occlusion Classification (mRROC) I or II closure was achieved in 56 (52.8%) aneurysms. The average time to last follow-up was 8.4 months at which 70 (81.4%) aneurysms had mRROC I or II occlusion and a major recurrence was seen in 5 (5.8%) patients. Thirteen (12.3%) aneurysms required re-treatment of which one aneurysm was clipped. CONCLUSIONS: The Penumbra SMART coil is safe and effective for the endovascular treatment of appropriately selected IAs. Additional studies at multiple centers comparing safety and efficacy profile over long-term periods to other mainstream coils are necessary.

Immune Therapy for Central Nervous System Metastasis.

Brain metastases lead to substantial morbidity and mortality among patients with advanced malignancies. Although treatment options have traditionally included largely palliative measures, studies of brain metastasis response to immunotherapy are promising. Immune checkpoint inhibitors have shown efficacy in studies of patients with melanoma, renal cell carcinoma, and lung cancer brain metastases. Patients with brain metastases are more frequently included in clinical trials, ushering in a new era in immunotherapy and management for patients with brain metastases. Gaining an understanding of the molecular determination for response to immunotherapies remains a major challenge and is an active area of future research.

Vascularized Muscle Flap to Reduce Wound Breakdown During Flexible Electrode-Mediated Functional Electrical Stimulation After Peripheral Nerve Injury.

The success of devices delivering functional electrical stimulation (FES) has been hindered by complications related to implants including skin breakdown and subsequent wound dehiscence. Our hypothesis was that a vascularized muscle flap along the dorsal surface of an epimysial electrode would prevent skin breakdown during FES therapy to treat atrophy of the gastrocnemius muscle during peripheral nerve injury. Resection of a tibial nerve segment with subsequent electrode implantation on the dorsal surfaces of the gastrocnemius muscle was performed on ten Lewis rats. In five rats, the biceps femoris (BF) muscle was dissected and placed along the dorsal surface of the electrode (Flap group). The other five animals did not undergo flap placement (No Flap group). All animals were treated with daily FES therapy for 2 weeks and degree of immune response and skin breakdown were evaluated. The postoperative course of one animal in the No Flap group was complicated by complete wound dehiscence requiring euthanasia of the animal on postoperative day 4. The remaining 4 No Flap animals showed evidence of ulceration at the implant by postoperative day 7. The 5 animals in the Flap group did not have ulcerative lesions. Excised tissue at postoperative day 14 examined by histology and in vivo Imaging System (IVIS) showed decreased implant-induced inflammation in the Flap group. Expression of specific markers for local foreign body response were also decreased in the Flap group.

3D Printed frames to enable reuse and improve the fit of N95 and KN95 respirators.

BACKGROUND: In response to supply shortages during the COVID-19 pandemic, N95 filtering facepiece respirators (FFRs or "masks"), which are typically single-use devices in healthcare settings, are routinely being used for prolonged periods and in some cases decontaminated under "reuse" and "extended use" policies. However, the reusability of N95 masks is often limited by degradation or breakage of elastic head bands and issues with mask fit after repeated use. The purpose of this study was to develop a frame for N95 masks, using readily available materials and 3D printing, which could replace defective or broken bands and improve fit. RESULTS: An iterative design process yielded a mask frame consisting of two 3D-printed side pieces, malleable wire links that users press against their face, and cut lengths of elastic material that go around the head to hold the frame and mask in place. Volunteers (n= 41; average BMI= 25.5), of whom 31 were women, underwent qualitative fit with and without mask frames and one or more of four different brands of FFRs conforming to US N95 or Chinese KN95 standards. Masks passed qualitative fit testing in the absence of a frame at rates varying from 48 - 92% (depending on mask model and tester). For individuals for whom a mask passed testing, 75-100% (average = 86%) also passed testing with a frame holding the mask in place. Among users for whom a mask failed in initial fit testing, 41% passed using a frame. Success varied with mask model and across individuals. CONCLUSIONS: The use of mask frames can prolong the lifespan of N95 and KN95 masks by serving as a substitute for broken or defective bands without adversely affecting fit. Frames also have the potential to improve fit for some individuals who cannot fit existing masks. Frames therefore represent a simple and inexpensive way of extending the life and utility of PPE in short supply. For clinicians and institutions interested in mask frames, designs and specifications are provided without restriction for use or modification. To ensure adequate performance in clinical settings, qualitative fit testing with user-specific masks and frames is required.

Flexible Multielectrode Array for Skeletal Muscle Conditioning, Acetylcholine Receptor Stabilization and Epimysial Recording After Critical Peripheral Nerve Injury.

Complete re-innervation after a traumatic injury severing a muscle's peripheral nerve may take years. During this time, the denervated muscle atrophies and loses acetylcholine receptors, a vital component of the neuromuscular junction, limiting functional recovery. One common clinical treatment for atrophy is electrical stimulation; however, epimysial electrodes currently used are bulky and often fail due to an excessive inflammatory response. Additionally, there remains a need for a device providing in vivo monitoring of neuromuscular regeneration and the maintenance of acetylcholine receptors. Here, an implantable, flexible microelectrode array (MEA) was developed that provides surface neuromuscular stimulation and recording during long-term denervation. Methods: The MEA uses a flexible polyimide elastomer and an array of gold-based microelectrodes featuring Peano curve motifs, which together maintain electrode flexibility. The devices were implanted along the denervated gastrocnemius muscles of 5 rats. These rats underwent therapeutic stimulation using the MEA daily beginning on post-operative day 2. Another 5 rats underwent tibial nerve resection without implantation of MEA. Tissues were harvested on post-operative day 14 and evaluated for quantification of acetylcholine receptors and muscle fiber area using immunofluorescence and histological staining. Results: The Young's modulus was 1.67 GPa, which is comparable to native tendon and muscle. The devices successfully recorded electromyogram data when implanted in rats. When compared to untreated denervated muscles, MEA therapy attenuated atrophy by maintaining larger muscle fiber cross-sectional areas (p < 0.05). Furthermore, the acetylcholine receptor areas were markedly larger with MEA treatment (p < 0.05). Conclusions: This proof-of-concept work successfully demonstrates the ability to combine conformability, tensile strength-enhancing metal micropatterning, electrical stimulation and recording into a functional implant for both epimysial stimulation and recording.