Agosti, Edoardo

Abstract Introduction The development of endoscopic techniques has made endoscopic endonasal approaches (EEAs) to the anterior cranial fossa (ACF) increasingly popular. Still, the steps and nuances involved in the approach may be difficult to understand for trainees. Thus, we aim to didactically describe the EEAs to the ACF in an anatomically based, step-by-step manner with supplementary clinical cases. Methods Six cadaveric head specimens were dissected. Endoscopic endonasal Draf I, IIA, IIB, and III frontal sinusotomies, endoscopic endonasal superior ethmoidectomy, and endoscopic endonasal transcribriform and transplanum approaches were modularly performed. The specimens were photodocumented with endoscopic techniques. Results Draf I frontal sinusotomy started with the complete removal of the anteromedial portion of the agger nasi cell, exposing the medial orbital wall, cranial base, and anterior cribriform plate. Draf II frontal sinusotomy proceeded with the removal of the floor of the frontal sinus between the lamina papyracea and the middle turbinate (IIa), and the nasal septum (IIb) until the first olfactory filaments were exposed. Draf III proceeded by creating a superior septal window just below the floor of the frontal sinus. The bone of the ACF bounded by the limbus sphenoidale posteriorly, frontal sinus anteriorly, and the medial orbital walls bilaterally was removed; the cribriform plate was removed; and the crista galli was dissected free from the dural leaflets of the falx cerebri and removed. Conclusion We provide a step-by-step dissection describing basic surgical steps and anatomy of the EEAs to the ACF to facilitate the learning process for skull base surgery trainees.

AbstractBackgroundFor aggressive maxillary sinus and pterygopalatine fossa (PPF) tumors, an en‐bloc pterygomaxillectomy may be indicated.MethodsFive head specimens were used to study the feasibility of an en‐bloc pterygomaxillectomy. Eighty‐five non‐pathological CT scans were used to compare the superior edge of the inferior turbinate (IT) and the middle turbinate tail (MT) as landmarks for the pterygoid osteotomy.ResultsThrough a combined sublabial–subperiosteal incision and transoral route, a mid‐sagittal osteotomy through the hard palate and an axial osteotomy below the infraorbital foramen were performed. For the endoscopic pterygoid osteotomy, an infra‐vidian transpterygoid approach was performed, subsequently removing the pterygomaxillectomy en‐bloc. As landmarks, the osteotomies at the level of the MT tail and IT resected the pterygoid plates completely, but the IT osteotomy was further away from the vidian canal (7.5 vs. 6 mm).ConclusionsThe endoscopic‐assisted en‐bloc pterygomaxillectomy is feasible. The IT landmark is safe and ensures complete resection of the pterygoid plates.

Abstract Introduction The clival, paraclival, and craniocervical junction regions are challenging surgical targets. To approach these areas, endoscopic endonasal transclival approaches (EETCAs) and their extensions (far-medial approach and odontoidectomy) have gained popularity as they obviate manipulating and working between neurovascular structures. Although several cadaveric studies have further refined these contemporary approaches, few provide a detailed step-by-step description. Thus, we aim to didactically describe the steps of the EETCAs and their extensions for trainees. Methods Six formalin-fixed cadaveric head specimens were dissected. All specimens were latex-injected using a six-vessel technique. Endoscopic endonasal middle and inferior clivectomies, far-medial approaches, and odontoidectomy were performed. Results Using angled endoscopes and surgical instruments, an endoscopic endonasal midclivectomy and partial inferior clivectomy were performed without nasopharyngeal tissue disruption. To complete the inferior clivectomy, far-medial approach, and partially remove the anterior arch of C1 and odontoid process, anteroinferior transposition of the Eustachian–nasopharynx complex was required by transecting pterygosphenoidal fissure tissue, but incision in the nasopharynx was not necessary. Full exposure of the craniocervical junction necessitated bilateral sharp incision and additional inferior mobilization of the posterior nasopharynx. Unobstructed access to neurovascular anatomy of the ventral posterior fossa and craniocervical junction was provided. Conclusion EETCAs are a powerful tool for the skull-base surgeon as they offer a direct corridor to the ventral posterior fossa and craniocervical junction unobstructed by eloquent neurovasculature. To facilitate easier understanding of the EETCAs and their extensions for trainees, we described the anatomy and surgical nuances in a didactic and step-by-step fashion.

The anterior cranial fossa (ACF) is a complex anatomical region that can be affected by a broad spectrum of pathology. For the surgical treatment of these lesions, many approaches have been described, each of them with different scope and potential surgical complications, often associated with significant morbidity. Traditionally, tumors involving the ACF have been operated by transcranial approaches; however, in the last two decades, endoscopic endonasal approaches (EEAs) have been gaining popularity. In this work, the authors review and describe the anatomical aspects of the ACF and the technical nuances of transcranial and endoscopic approaches for tumors located in this region. Four approaches were performed in embalmed cadaveric specimens and the key steps were documented. Four illustrative cases of ACF tumors were selected to demonstrate the clinical application of anatomical and technical knowledge, which are essential in the preoperative decision-making process.

BACKGROUND: The dorsal brainstem and cerebellomesencephalic fissure are challenging surgical targets. To afford a preferentially craniocaudal trajectory to this region, the precuneal interhemispheric transtentorial approach (PCIT) has been proposed. OBJECTIVE: To didactically describe and compare exposures and anatomic indications of the supracerebellar infratentorial approach (SCIT) and PCIT to the cerebellomesencephalic fissure. METHODS: Nine formalin-fixed, latex-injected cadaveric head specimens were used to perform a midline SCIT and bilateral PCITs and measure the distance of each approach. Twenty-four formalin-fixed specimens were used to measure the distance from the most posterior cortical bridging vein entering the superior sagittal sinus to the calcarine sulcus and the torcula. Fifty-one magnetic resonance images were reviewed to calculate the angle of each approach. Three illustrative surgical cases were described. RESULTS: Mean distances from the brain or cerebellar surface to the operative target of the PCIT and SCIT were 7.1 cm (range: 5-7.7 cm) and 5.5 cm (range: 3.8-6.2 cm), respectively. The SCIT provided direct access to structures of the quadrigeminal cistern bilaterally. The PCIT provided access from the ipsilateral inferior colliculus to the ipsilateral infratrochlear zone. The PCIT's benefit was the direct access it provided to the cerebellomesencephalic fissure because of its superior to inferior trajectory. CONCLUSION: The PCIT is indicated for unilateral lesions of the cerebellomesencephalic fissure and dorsal brainstem that harbor a craniocaudal long axis and do not have a superior extension beyond the superior colliculi. The SCIT is beneficial for lesions that extend bilaterally, have an anteroposterior long axis, or involve the Galenic complex.