Ultrasound-Guided Mechanical High-Intensity Focused Ultrasound (Histotripsy) Through an Acoustically Permeable Polyolefin-Based Cranioplasty Device.

INTRODUCTION: Histotripsy is a non-thermal focused ultrasound therapy in development for the non-invasive ablation of cancerous tumors. Intracranial histotripsy has been limited by significant pressure attenuation through the skull, requiring large, complex array transducers to overcome this effect. OBJECTIVE: Recently, a biocompatible, polyolefin-based cranioplasty device was developed to allow ultrasound (US) transmission into the intracranial space with minimal distortion. In this study, we investigated the in vitro feasibility of applying US-guided histotripsy procedures across the prosthesis. METHODS: Pressure waveforms and beam profiles were collected for singleand multi-element histotripsy transducers. Then, high-speed optical images of the bubble cloud with and without the prosthesis were collected in water and tissue-mimicking agarose gel phantoms. Finally, red blood cell (RBC) tissue phantom and excised brain tissue experiments were completed to test the ablative efficacy across the prosthesis. RESULTS: Single element tests revealed increased pressure loss with increasing transducer frequency and increasing transducer-to-prosthesis angle. Array transducer measurements at 1 MHz showed average pressure losses of >50% across the prosthesis. Aberration correction recovered up to 18% of the pressure lost, and high-speed optical imaging in water, agarose gels, and RBC phantoms demonstrated that histotripsy bubble clouds could be generated across the prosthesis at pulse repetition frequencies of 50-500 Hz. Histologic analysis revealed a complete breakdown of brain tissue treated across the prosthesis. Conclusion & Significance: Overall, the results of this study demonstrate that the cranial prosthesis may be used as an acoustic window through which intracranial histotripsy can be applied under US guidance without the need for large transcranial array transducers.

Natural History of Traumatic Encephaloceles: A Systematic Literature Review.

Encephaloceles rarely develop following traumatic skull fractures. Given their low incidence, the clinical presentations and management strategies of these lesions are confined to case reports and limited case series. A systematic literature review was performed using PubMed, Ovid, and Web of Science databases to identify relevant articles using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A total of 37 articles met inclusion criteria, including the case presented herein. These articles reported 52 traumatic encephaloceles. Mean patient age was 25.3 years (range 6 mo-66 y) with a male predominance (63%, 33/52). The most common bony defects resulting in encephalocele formation were the orbital roof (52%, 27/52), ethmoid (35%, 18/52), and sphenoid (10%, 5/52). Mean time from traumatic injury to initial presentation was 21.3 months (range 0 d-36 y) with a bimodal distribution split between immediately following the traumatic injury (57%, 26/46) or in a delayed manner (43%, 20/46). Common presentations of orbital roof, frontonasal, and temporal bone encephaloceles were exophthalmos (85%, 23/27), cerebrospinal fluid rhinorrhea (71%, 17/24), and hearing loss (100%, 4/4), respectively. Operative approach, repair technique, and materials used for encephalocele reduction were highly variable. Surgical intervention afforded definitive symptomatic improvement or resolution in the majority of cases (89%, 42/47). Clinical outcomes did not differ between orbital, frontonasal, or temporal bone encephaloceles ( P =0.438). Traumatic encephaloceles are a rare entity with diverse presenting symptomatology dependent upon the location of fracture dehiscence. Surgical intervention affords symptomatic improvement in the majority of cases irrespective of encephalocele location, time to presentation, or operative approach.

Noninvasive Low-Intensity Focused Ultrasound Mediates Tissue Protection following Ischemic Stroke.

Objective and Impact Statement. This study examined the efficacy and safety of pulsed, low-intensity focused ultrasound (LIFU) and determined its ability to provide neuroprotection in a murine permanent middle cerebral artery occlusion (pMCAO) model. Introduction. Focused ultrasound (FUS) has emerged as a new therapeutic strategy for the treatment of ischemic stroke; however, its nonthrombolytic properties remain ill-defined. Therefore, we examined how LIFU influenced neuroprotection and vascular changes following stroke. Due to the critical role of leptomeningeal anastomoses or pial collateral vessels, in cerebral blood flow restoration and tissue protection following ischemic stroke, we also investigated their growth and remodeling. Methods. Mice were exposed to transcranial LIFU (fundamental frequency: 1.1 MHz, sonication duration: 300 ms, interstimulus interval: 3 s, pulse repetition frequency: 1 kHz, duty cycle per pulse: 50%, and peak negative pressure: -2.0 MPa) for 30 minutes following induction of pMCAO and then evaluated for infarct volume, blood-brain barrier (BBB) disruption, and pial collateral remodeling at 24 hrs post-pMCAO. Results. We found significant neuroprotection in mice exposed to LIFU compared to mock treatment. These findings correlated with a reduced area of IgG deposition in the cerebral cortex, suggesting attenuation of BBB breakdown under LIFU conditions. We also observed increased diameter of CD31-postive microvessels in the ischemic cortex. We observed no significant difference in pial collateral vessel size between FUS and mock treatment at 24 hrs post-pMCAO. Conclusion. Our data suggests that therapeutic use of LIFU may induce protection through microvascular remodeling that is not related to its thrombolytic activity.