There are more anatomical variants in heaven and earth, Horatio, than are dreamt of in our philosophy: the precaval left renal artery.

AIM: To describe the CT findings in eight patients with left-sided inferior vena cava (IVC) in whom the left renal artery presented a precaval course (pLRA). MATERIALS AND METHODS: We searched the teaching files of six radiology departments for patients with pLRAs. Eight patients were found, and the available imaging studies and clinical histories were reviewed. Associated vascular and renal anomalies were noted. RESULTS: No patient had been examined for problems related to the vascular anomaly found. Four had a double IVC and two a solitary left IVC; in all, the left-sided IVCs had hemiazygos continuation. One patient had situs viscerum inversus. In one case, there was a left kidney in left iliac fossa. CONCLUSION: Although rare and probably overlooked, a pLRAs can be encountered in patients with situs viscerum inversus or presenting a left-sided IVC with hemiazygos continuation. These vessels can cause technical problems during surgery at the left renal hilum and should be specifically searched for in patients with vascular anomalies.

Minimally invasive techniques: full endoscopic inferior parietal lobule approach for an endoventricular removal of a left trigone meningioma grade I.

Intraventricular meningiomas are rare tumors, mainly localized in the lateral ventricle trigone. Several microscopic surgical approaches have been proposed according to the location of the tumors in the atrium. The authors present the case of a 68-year-old woman who had an increscent medically resistant headache with a left trigone meningioma. In the video, they demonstrate the four-hands surgical technique through a minimally invasive fully endoscopic retractor-less transcortical approach. They also discuss the background of these tumors and the technical nuances of the procedure, including the differences between an endoscopic surgical and a microsurgical one. The video can be found here: https://stream.cadmore.media/r10.3171/2023.1.FOCVID2296.

The Infratemporal Retro-Eustachian Transposition of the Temporoparietal Fascial Flap for Clival Reconstruction After Endoscopic Endonasal Approach: An Anatomic Conceptual Technique.

BACKGROUND: Reconstruction after endoscopic endonasal approaches is a key element. Lower clivus reconstruction is difficult and most of the times a pedicled flap is not available. As the complexity and the dimensions of the exposure increase, a reliable reconstruction technique becomes more and more important. OBJECTIVE: To describe the anatomic and technical nuances of the transposition of the temporoparietal fascial flap for lower clivus reconstruction. METHODS: A specific temporoparietal fascial flap (TPFF) design and tunneling technique has been studied using 4 head specimens, microscopic and endoscopic surgical techniques, and neuronavigation. RESULTS: The L-shaped flap offers several advantages. It can be tunneled directly toward the lower clivus passing through the infratemporal fossa. CONCLUSION: The infratemporal retro-eustachian transposition of an L-shaped TPFF provides a vascularized tissue virtually without dimension limits. This is the only technique that allows the flap to be tunneled directly in the lower clivus with the most vascular portion being at the bottom of the defect. Clinical validation is still required since more issues may become relevant in a real-surgery setting. Though, due to its possible complications, this methodology needs further testing and should not be attempted in less experienced hands.

Preoperative evaluation of bone quality and bone density using a novel CT/microCT-based hard-normal-soft classification system.

PURPOSE: To obtain more objective presurgical measurements of clinical interest, this study proposes a new method of measuring and classifying bone density. MATERIALS AND METHODS: The density of bovine bone blocks of different qualities was first measured in Hounsfield units (HU) using computed tomography (CT). Next, bone cylinders corresponding to each examined area were retrieved. Bone quality was then measured by both histomorphometric microCT and by subjective evaluation of bone quality during drilling. RESULTS: A statistically significant correlation was found between CT and microCT measurements. Based on this evidence, a new method of classifying bone density/quality into three classes of clinical interest was developed: hard/dense, normal, and soft (HNS). These statistical data also enabled the creation of a formula to convert ordinary CT values expressed in HU into bone volume percentages (BV%) to objectively measure bone density based on the HNS system. CONCLUSION: Stable implant placement depends upon measurements of bone quality/density that are site-specific, objective, and quantitative. To meet these standards, this paper reports an innovative method of classifying bone quality/density and then objectively measuring bone density based on this HNS classification system, using a simple, innovative mathematical formula that converts HU values into measurements of bone volume.

Fully endoscopic access and resection of hemorrhaged cavernous malformation of the posterior midbrain.

Cavernous malformations in the midbrain can be accessed via several safe entry zones. The accepted rule of thumb is to enter at the point where the lesion is visible at the surface of the brainstem to pass through as little normal brain tissue as possible. However, in some cases, in order to avoid critical neural structures, this rule may not apply. A different safe entry zone can be chosen. Our video presents a case of a ruptured cavernous malformation in the midbrain reaching its anterior surface which was successfully resected via a posterolateral route using the supracerebellar infratentorial approach. The video can be found here: https://youtu.be/j7VTqRO7qd4.

Two-Operator Endoscopic Resection of Left Cerebellopontine Angle Epidermoid.

Intracranial epidermoid cysts are developmental central nervous system abnormalities that arise from erroneous ectodermal inclusion during neural tube closure. Epidermoids are relatively common, representing 1% of all intracranial masses, and are particularly predominant in the cerebellopontine angle (CPA), where they are the third most prevalent diagnosis after schwannomas and meningiomas. Although small, asymptomatic, or incidental lesions may be safely observed, in the presence of symptomatic mass effect, epidermoid cysts typically require surgical resection. As shown in Video 1, we demonstrate the operating room setup and endoscopic resection of a left CPA epidermoid cyst through a retrosigmoid craniotomy. By use of a 2-surgeon 4-hands technique, the mass was dissected from the surrounding neurovascular structures, and a gross total removal was achieved with no postoperative neurologic deficits. Our video highlights the critical nuances pertinent to the fully endoscopic resection technique, with special attention to the relative restrictions of a small working corridor parallel to the tentorium and the petrous bone.

Chronic subdural hematoma pathophysiology: a unifying theory for a dynamic process.

Chronic subdural hematoma pathophysiology has been extensively studied and discussed. In the last decades, optic and electron microscope observations have successfully described its histopathology and the ultrastructure of internal membranes. Moreover, recent biochemical studies have identified a number of important pathways involved in its development and evolution. Our aim was to review recent literature regarding histopathology, ultrastructure and biochemichal pathways and supply a unifying theory about chronic subdural hematoma pathophysiology. The starting point of chronic subdural hematoma is a mechanical injury. The evolution of the pathology is due to the exclusive anatomy of the dura-arachnoid interface. This is a mechanically weak layer. Fibroblasts contained in this region produce an inflammatory reaction with neoangiogenesis and fibrinolysis. Biochemical pathways involved in these reactions is complex and could contain a number of pharmacological targets. The hematoma evolves in different stages thus recent outlooks consider chronic subdural hematoma as a dynamic process. One of the key points for a good outcome and a low recurrence rate may be the timing of the surgical treatment in relation of hematoma natural history. Surgery performed during active inflammatory stages may be less effective in terms of clinical outcome and recurrence rate.

Anterior and Posterior Ethmoidal Artery Ligation in Anterior Skull Base Meningiomas: A Review on Microsurgical Approaches.

OBJECTIVE: Anterior skull base neoplastic and vascular lesions can receive significant blood supply from the anterior and posterior ethmoidal artery. Although useful in preoperative embolization of middle meningeal artery branches, endovascular techniques for the occlusion of anterior ethmoidal artery expose the parent vessel, the ophthalmic artery, to possible embolic complications, which can cause loss of vision. When dealing with anterior fossa giant meningiomas, moreover, it is not always possible to gain direct intracranial access to anterior ethmoidal arteries because of dimensions and invasiveness of these neoplasms. The aim of this review is to illustrate the anterior and posterior ethmoidal artery anatomy and the microsurgical approaches for extracranial ligation. METHODS: We performed a literature review of the relevant microsurgical anatomy of these arteries; particular attention is given to anterior cranial fossa and medial orbital wall anatomy. RESULTS: Our research found two surgical sites of arterial occlusion that can be best exposed with five microsurgical approaches. CONCLUSIONS: A combination of different surgical and endovascular techniques before resection of hypervascular giant olfactory groove and planum sphenoidale meningiomas should always be considered. Microsurgical extracranial ligation of anterior and sometimes posterior ethmoidal arteries provides a safe and feasible option to limit blood loss during anterior skull base surgery.