Craniovertebral Junction Instability after Oncological Resection: A Narrative Review.

The craniovertebral junction (CVJ) is a complex transition area between the skull and cervical spine. Pathologies such as chordoma, chondrosarcoma and aneurysmal bone cysts may be encountered in this anatomical area and may predispose individuals to joint instability. An adequate clinical and radiological assessment is mandatory to predict any postoperative instability and the need for fixation. There is no common consensus on the need for, timing and setting of craniovertebral fixation techniques after a craniovertebral oncological surgery. The aim of the present review is to summarize the anatomy, biomechanics and pathology of the craniovertebral junction and to describe the available surgical approaches to and considerations of joint instability after craniovertebral tumor resections. Although a one-size-fits-all approach cannot encompass the extremely challenging pathologies encountered in the CVJ area, including the possible mechanical instability that is a consequence of oncological resections, the optimal surgical strategy (anterior vs posterior vs posterolateral) tailored to the patient's needs can be assessed preoperatively in many instances. Preserving the intrinsic and extrinsic ligaments, principally the transverse ligament, and the bony structures, namely the C1 anterior arch and occipital condyle, ensures spinal stability in most of the cases. Conversely, in situations that require the removal of those structures, or in cases where they are disrupted by the tumor, a thorough clinical and radiological assessment is needed to timely detect any instability and to plan a surgical stabilization procedure. We hope that this review will help shed light on the current evidence and pave the way for future studies on this topic.

Understanding the Leakage Mechanisms and Breakdown Limits of Vertical GaN-on-Si p+n-n Diodes: The Road to Reliable Vertical MOSFETs.

This work investigates p+n-n GaN-on-Si vertical structures, through dedicated measurements and TCAD simulations, with the ultimate goal of identifying possible strategies for leakage and breakdown optimization. First, the dominant leakage processes were identified through temperature-dependent current-voltage characterization. Second, the breakdown voltage of the diodes was modelled through TCAD simulations based on the incomplete ionization of Mg in the p+ GaN layer. Finally, the developed simulation model was utilized to estimate the impact of varying the p-doping concentration on the design of breakdown voltage; while high p-doped structures are limited by the critical electric field at the interface, low p-doping designs need to contend with possible depletion of the entire p-GaN region and the consequent punch-through. A trade-off on the value of p-doping therefore exists to optimize the breakdown.

Posttraumatic Middle Meningeal Artery Pseudoaneurysm: Case Report and Review of the Literature.

BACKGROUND: Intracranial pseudoaneurysm is a rare entity, with few cases described in the literature, and is mostly associated with a history of traumatic brain injury. Traumatic aneurysms comprise <1% of all intracranial aneurysms. In particular, middle meningeal artery (MMA) aneurysms are uncommon and usually caused by a skull fracture in the temporal region. About 40 traumatic MMA aneurysms are reported in the literature, and only 28 nontraumatic aneurysms are reported, usually related to high-flow conditions. The behavior of these aneurysms is largely unknown: both spontaneous resolution and aneurysm growth, leading to subsequent rupture, have been reported. Surgical and endovascular management are feasible for MMA aneurysms; however, the criterion standard treatment is not defined. CASE DESCRIPTION: We report the case of a traumatic pseudoaneurysm of the right MMA treated with an endovascular approach and provide a review of the literature. CONCLUSIONS: Aneurysms of the MMA are a rare entity that must be taken into account in the setting of a traumatic brain injury or predisposing factors. The diagnosis and aggressive treatment are mandatory, preventing the devastating consequences of their rupture. Endovascular and surgical techniques are well defined and available, even though there is not a demonstrated superiority in any of them.

Rare Case of Dumbbell-Shaped Spinal Cavernous Hemangioma and Literature Review.

BACKGROUND: Spinal epidural cavernous hemangiomas are rare vascular malformations. Exceptionally, they present with dumbbell-shaped morphology. When they happen, it's mandatory to include their pathology in the differential diagnosis because of their similarity to schwannomas. CASE DESCRIPTION: We report the case of a 72-year-old woman with a dumbbell-shaped thoracic epidural cavernous hemangioma. A literature review of diagnostic features and current treatment options are also discussed. CONCLUSIONS: Surgery is safe and effective in both improving patient condition and preventing acute hemorrhage that can worsen the outcome, causing neurologic and potentially irreversible deficits. The favorable result we obtained in our patient suggests that surgery should be evaluated as the first option, even in patients with large epidural cavernous hemangiomas.

Translaminar Approach for Treatment of Hidden Zone Foraminal Lumbar Disc Herniations: Surgical Technique and Preoperative Selection of Patients with Long-Term Follow-Up.

BACKGROUND: Lumbar disc herniation is a common degenerative disease of the lumbar spine with a prevalence of 1%-3% in some population studies. In 10% of patients, there is a fragment migrated cranially in Macnab's "hidden zone." In selected cases, this fragment can be removed with a translaminar approach that was described in 1998. We provide a detailed description of the technical advantages and pitfalls of the translaminar approach in a consecutive series of 32 patients treated at our institution. METHODS: Patients were divided preoperatively and postoperatively into 5 classes based on the Oswestry Disability Index (ODI): class 1, ODI 0%-20% (minimal disability); class 2, 20%-40% (moderate disability); class 3, 40%-60% (severe disability); 60%-80% (crippled); 80%-100% (bedridden or disabling symptoms). RESULTS: Four (12.5%) patients were upgraded 1 ODI class after the operation; 6 (18.7%) patients were upgraded 2 classes, 8 (25%) patients were upgraded 3 classes, and 11 (34.4%) patients were upgraded 4 classes. In 3 (9.4%) patients, ODI class did not change after the operation. After surgery, 7 (21.9%) patients developed mild low back pain. Mean follow-up was 25 months. CONCLUSIONS: When performed by dedicated spinal neurosurgeons, the translaminar approach is safe and effective in patients with long-term follow-up. Most patients showed an improvement in ODI. Major pitfalls were related to surgical selection and the narrow working space.