Francesco Belotti

Modular Endoscopic Medial Maxillectomies: Quantitative Analysis of Surgical Exposure in a Preclinical Setting.

BACKGROUND The nomenclature adopted for endoscopic medial maxillectomies (EMMs) is exceedingly heterogeneous. The aim of this study was to objectively measure surgical exposure in a preclinical anatomic setting to validate a classification for modular EMMs. MATERIALS AND METHODS Computed tomography was used to scan 6 cadaver heads, and images were uploaded on dedicated software. A neuronavigation system was used to measure areas and volumes of surgical corridors during dissection. Differences of >10% of area exposed and >3 cm3 of volume were considered to define incremental types of EMM. Specific anatomic targets were assessed on the axial and sagittal planes. Influence of anatomic variants on surgical exposure was evaluated. RESULTS There were 4 types of EMMs (A-D), with a transseptal variant for each, identified. In the axial plane, type A exposed the vidian canal and foramen rotundum, type B exposed the foramen ovale and foramen spinosum, and transseptal type C or type D exposed the coronoid process. In the sagittal plane, type A exposed the vidian canal, and type B exposed the foramen ovale and styloid process. Transseptal type C exposed the pterygomaxillary fissure, and type D exposed the inferior border of the lateral pterygoid plate. The nasal floor limits the downward angle in transseptal approaches. The width of the piriform aperture independently influenced surgical volume of types B and C. CONCLUSIONS This modular classification of EMMs, based on quantitative analysis in a preclinical setting, should allow for better personalized preoperative surgical planning and provides standardization of nomenclature.

Quantitative comparison of cranial approaches in the anatomy laboratory: A neuronavigation based research method

AIM To describe the development and validation of a novel neuronavigation-based method, which allows the quantification of the anatomical features that define an approach, as well as real-time visualization of the surgical pyramid. METHODS The method was initially developed with commercially-available hardware for coordinate collection (a digitizer and a frameless navigation system) and software for volume rendering; dedicated neuronavigation software (ApproachViewer, part of GTx-UHN) was then developed. The accuracy of measurements and the possibility of volumetric rendering of surgical approaches simulated in a phantom were compared among three different methods and commercially-available radiological software. In the anatomy laboratory, ApproachViewer was applied to the comparative quantitative analysis of multiple neurosurgical approaches and was used by many surgeons who were untrained for the research method. RESULTS The accuracy of ApproachViewer is comparable to commercially-available radiological software. In the anatomy laboratory, the method appears versatile. The system can be easily used after brief training. ApproachViewer allows for real-time evaluation and comparison of surgical approaches, as well as post-dissection analyses of collected data. The accuracy of the method depends on the navigation registration: with a 1-2 mm registration error, it is adequate for evaluation and comparison of most neurosurgical approaches. CONCLUSION This new research method and software allows semi-automated visualization, quantification, and comparison of neurosurgical approaches in the anatomy laboratory.

The ethmoidal arteries: a cadaveric study based on cone beam computed tomography and endoscopic dissection

PurposeTo describe the anatomical variability of the ethmoidal arteries (EAs). To evaluate the reliability of cone beam computed tomography (CBCT) in preoperative assessment of EAs.MethodsFourteen cadaver heads underwent CBCT and endoscopic dissection. The following anatomical features were evaluated for anterior (AEA), middle (MEA), and posterior (PEA) EAs: presence, cranio-caudal position, antero-posterior position, and dehiscence of the bony canal. Accuracy of radiological assessment was calculated.Results AEA, MEA, and PEA were identified in 100, 28.6, and 100% of sides. They were caudal to the skull base in 60.7, 25, and 17.9%, respectively. CBCT showed a high accuracy in identifying these features. The antero-posterior position of EAs, which was highly variable, was correctly assessed by CBCT. A dehiscent bony canal of AEA, MEA, and PEA was found in 46.4, 12.5, and 28.6% of sides, respectively. Accuracy of CBCT in picking up this feature was poor but negative predictive value was high.Conclusions CBCT was adequate in identifying and localizing EAs. In addition, it can be used to exclude the presence of MEA and dehiscence of ethmoidal canals, whereas the accuracy in detecting these anatomic variants was low.

Persisting Embryonal Infundibular Recess (PEIR): Two Case Reports and Systematic Literature Review

Context The persisting embryonal infundibular recess (PEIR) is a rare anomaly of the floor of the third ventricle with a debated pathogenesis. It can be a cause of misdiagnosis in the case of cystic lesions of the sellar and suprasellar area. Objective To describe two recently evaluated cases and provide a systematic literature review. Evidence Acquisition and Case Descriptions PEIR has been previously reported in six adult patients. Because in some cases it was associated with hydrocephalus and/or empty sella, a possible role of altered intracranial pressure in PEIR formation has been postulated. We evaluated two female patients, aged 34 and 50 years, referred to the Pituitary Surgery Clinic of the University of Brescia with the diagnosis of a sellar cyst and craniopharyngioma, respectively. Endocrine screening and visual field testing were normal. No signs of hydrocephalus or empty sella, as well as other indirect signs of intracranial hypertension, were visible on MRI scans. After a multidisciplinary reevaluation, diagnosis of PEIR was made in both cases. Both patients are followed but have not developed any disturbance related to the PEIR in the following 18 months. Conclusions PEIR is a rare condition, probably unrecognized and the result of dysembriogenesis, which should be included in the differential diagnosis of cystic sellar lesions. Imaging features (funnel pituitary stalk and cyst in the sella) appear pathognomonic. A normal endocrine evaluation might help in the diagnosis and warrants conservative treatment.

The turbinal flap: an additional option for anterior skull base reconstruction. Cadaveric feasibility study and case report

Over the past decade, the treatment of complex intradural and extradural pathologies via expanded endonasal approaches has been made possible by progresses and refinements in skull base reconstruction techniques. The aim of this anatomic study is to describe a novel endonasal flap, the turbinal flap (TF), based on the middle and superior turbinate mucosa and pedicled on the ethmoidal arteries system.

The myloglossus in a human cadaver study: common or uncommon anatomical structure?

BACKGROUND Additional extrinsic muscles of the tongue are reported in literature and one of them is the myloglossus muscle (MGM). Since MGM is nowadays considered as anatomical variant, the aim of this study is to clarify some open questions by evaluating and describing the myloglossal anatomy (including both MGM and its ligamentous counterpart) during human cadaver dissections. MATERIALS AND METHODS Twenty-one regions (including masticator space, sublingual space and adjacent areas) were dissected and the presence and appearance of myloglossus were considered, together with its proximal and distal insertions, vascularisation and innervation. RESULTS The myloglossus was present in 61.9% of cases with muscular, ligamentous or mixed appearance and either bony or muscular insertion. Facial artery provided myloglossal vascularisation in the 84.62% and lingual artery in the 15.38%; innervation was granted by the trigeminal system (buccal nerve and mylohyoid nerve), sometimes (46.15%) with hypoglossal component. CONCLUSIONS These data suggest us to not consider myloglossus as a rare anatomical variant.

Symmetrical anatomical variant of the anterior belly of the digastric muscle: clinical implications.

The digastric muscle is an important surgical landmark. Several anatomical variants of the digastric muscle are reported in literature and, in particular, the presence of accessory anterior bellies of the muscle is not uncommon. Here, an unreported symmetrical variant of the digastric muscle was found during a dissection of the suprahyoid region. The dissection showed digastric muscles with an accessory anterior belly, which originated from the anterior belly of muscles in proximity and anteriorly to the intermediate tendon. The accessory bellies were fused together on the midline and were attached with a unique tendon to the inner surface of the mental symphysis. These muscles completely filled the submental triangle. This unreported anatomical variant could be considered an additional contribution to description of the anatomical variants of the digastric muscle, with several implications in head and neck pathology, diagnosis and surgery.

Transnasal Endoscopic and Lateral Approaches to the Clivus: A Quantitative Anatomic Study.

BACKGROUND Transnasal endoscopic approaches to the clivus have been established recently. Comparative analyses with classic lateral approaches are limited. In this study, we compared transnasal endoscopic and lateral approaches to the clivus, quantifying the exposure and working volume of each approach in the anatomy laboratory. METHODS High-resolution computed tomography scans were performed on 5 injected specimens (10 sides). In each specimen, transnasal endoscopic approaches (i.e., paraseptal, transrostral, extended transrostral, transethmoidal, and extended transclival without and with intradural hypophysiopexy) and lateral approaches (i.e., retrosigmoid, far-lateral, presigmoid retrolabyrinthine and translabyrinthine) to the clivus were performed. An optic neuronavigation system and dedicated software (ApproachViewer; Guided Therapeutics Program, University Health Network, Toronto, Ontario, Canada) were used to quantify the working volume and exposed clival area of each approach. Statistical evaluation was performed with the Kruskal-Wallis test and Steel-Dwass-Critchlow-Fligner post hoc test. RESULTS Endoscopic transnasal transclival approaches showed higher working volume and larger clival exposure compared with lateral approaches. Incremental volumetric values were evident for transnasal approaches; presigmoid approaches provided less working volume than retrosigmoid approaches. A transnasal transclival approach with hypophysiopexy provided significant exposure of the upper clivus (84.4%). The transrostral approach was the first transnasal approach providing satisfactory access to the midclivus (66%); retrosigmoid and far-lateral approaches provided exposure of approximately one half of the midclivus. The lower clivus was optimally exposed with endoscopic transclival approaches (83%), whereas access to this region was limited with lateral approaches. CONCLUSIONS This quantitative anatomic study shows that endoscopic transnasal approaches to the clivus provide a larger working volume and wider exposure of the clivus compared with lateral approaches.

Endoscopic Fenestration of a Giant Midline Arachnoid Cyst: 3-Dimensional Operative Video

Intracranial arachnoid cysts are benign developmental collections of cerebrospinal fluid that account for approximately 1% of intracranial masses. Endoscopic fenestration of intracranial arachnoid cysts is a well-known, relatively recent surgical option. This video shows the use of a high-definition 3-dimensional ventriculoscope for treatment of a giant midline arachnoid cyst. This 7-yr-old boy presented with a movement disorder of the head (ie, side-to-side bobbling of the head–bobble-head doll syndrome), at first considered a simple motor tic, 2 years before being evaluated in our clinic. No endocrine dysfunctions, visual disorders, or other neurological deficits were observed. Brain magnetic resonance imaging (MRI) documented a giant midline cyst, extending from the prepontine region to the corpus callosum, markedly displacing the pituitary stalk and chiasm anteriorly and the midbrain posteriorly. The patient was placed in a supine position with slight head flexion; a right paramedian frontal skin incision was made and a burr hole was performed at Kocher’s point to allow for an optimal trajectory. The cyst wall was reached with the aid of an introducer. The most superficial and lateral portion of the cyst capsule was coagulated and cut. The right choroid plexus and septal vein became evident. Once inside the cyst, the relevant anatomy, stretched by the giant cyst, could be recognized, including, posteriorly, the Watch now at https://academic.oup.com/ons/article-lookup/doi/10.1093/ons/ opx207

Morphological aspect of the superior wall of the cavernous sinus

The lateral wall of cavernous sinus (CS) is made of two distinct layers of dura: meningeal dura (the external one) and endosteal dura (internal one). On the other hand, some debates about the histomorphological aspects of the superior and medial wall of CS are present in literature (1-2). In this study we aimed to demonstrate the histomorphological features of the superior wall of CS during cadaver dissection studies. We considered only the sellar area, bounded anteriorly by the posterior margin of planum sphenoidale, antero-inferiorly by the antero-superior surface of sphenoid sinus, inferiorly by the superior surface of sphenoid sinus, posteriorly by dorsum sellae, laterally by the interclinoid ligament (preserving the medial wall of CS) and superiorly by diaphragma sellae. The samples were collected, decalcified, paraffin embedded and serial sections were finally processed for standard histomorphological staining. Sections of each sample were analyzed using optical light microscope equipped with a digital camera. Our results showed that the two layers separated themselves at the superior wall of CS: the meningeal layer continued as diaphragma sellae and the endosteal layer continued downward between the venous compartment and pituitary capsule. In addition, between these two layers it was possible to define an interdural pathway. These data should be considered in the evaluation of the rare, though possible, extension of pituitary adenomas in the interdural space, rather than into the cavernous sinus.