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Malignancies of the sinonasal region and ventral skull base include a varied group of uncommon tumors that are a challenge to treat. These malignancies, with few exceptions, often present late because of their insidious growth and bland symptomatology. As with malignancies of other sites, the primary goal in surgical management is complete resection with negative margins. This presents a unique surgical challenge in that these lesions lie within a region of densely populated anatomic real estate. This fact reinforces the importance of complete preoperative work-up and a sound anatomic understanding. This article discusses key anatomic regions and their importance from an endonasal perspective.

Background In the last decade, endoscopic skull base surgery has significantly developed and generated a plethora of techniques and approaches for access to the cranial ventral floor. However, the exploration for the least-aggressive, maximally efficient approach continues. Objective To describe in detail an anatomical study, along with the technical nuances of a novel endoscopic approach to Meckel's Cave (MC) using a lateral transorbital (LTO) route. Methods Eighteen orbits of injected cadaveric specimens were operated on, using an endoscopic LTO approach to MC, middle cranial fossa, and paramedian skull base preserving the orbital rim. Surgical navigation and an after-the-fact infratemporal craniectomy were utilized to identify the limits of the approach. Results Following a transorbital approach opening a trapezoid window at the superolateral aspect (average 166.7 mm 2 ), a middle fossa "peeling" and full visualization of MC was accomplished with no difficulties in all specimens. The entire approach was performed extradurally without the need to expose the temporal lobe. Conclusion In a cadaveric model, the endoscopic LTO approach affords a direct route to access MC. Its main advantage is that it is minimally disruptive in nature, less brain retraction is required, and it reaches the middle fossa in an anterolateral perspective. It also requires no manipulation of the temporalis muscle, limited cosmetic incision, and rapid recovery. It seems a viable alternative to traditional approaches for lesions lateral to the cranial nerves at the cavernous sinus and MC, that is, schwannomas. Clinical utilization of this approach will challenge its efficacy and identify limitations.

OBJECTIVEPituitary adenomas may extend into the parapeduncular space by invading through the roof of the cavernous sinus. Currently, a transcranial approach is the preferred choice, with or without the combination of an endonasal approach. In this paper the authors present a novel surgical approach that takes advantage of the natural corridor provided by the tumor to further open the oculomotor triangle and resect tumor extension into the parapeduncular space.METHODSSix injected specimens were used to demonstrate in detail the surgical anatomy related to the approach. Four cases in which the proposed approach was used were retrospectively reviewed.RESULTSFrom a technical perspective, the first step involves accessing the superior compartment of the cavernous sinus. The interclinoid ligament should be identified and the dura forming the oculomotor triangle exposed. The oculomotor dural opening may be then extended posteriorly toward the posterior petroclinoidal ligament and inferolaterally toward the anterior petroclinoidal ligament. The oculomotor nerve should then be identified; in this series it was displaced superomedially in all 4 cases. The posterior communicating artery should also be identified to avoid its injury. In all 4 cases, the tumor invading the parapeduncular space was completely removed. There were no vascular injuries and only 1 patient had a partial oculomotor nerve palsy that completely resolved in 2 weeks.CONCLUSIONSThe endoscopic endonasal transoculomotor approach is an original alternative for removal of tumor extension into the parapeduncular space in a single procedure. The surgical corridor is increased by opening the dura of the oculomotor triangle and by working below and lateral to the cisternal segment of the oculomotor nerve.

Background The McConnell's capsular arteries (MCCA) were first described in 1953. They consist of medial branches of the cavernous internal carotid artery (ICA) and are divided in anterior and inferior capsular arteries. Objective To highlight the anatomy of the MCCA and its importance in the surgical treatment of tuberculum sellae and planum sphenoidale tumors through an endoscopic endonasal approach. Methods Ten cadaveric specimens fixed in formalin and perfused with colored silicone were dissected. Standard endoscopic endonasal transsphenoidal approach to the sellar region was performed. The MCCA were identified and still images were captured for further analysis. We report 1 case to illustrate the importance of the MCCA. Results The anterior capsular artery, which originates from the anteromedial aspect of the anterior loop of the cavernous ICA and reaches the suprasellar space, was present in 70% of the specimens with no difference between the right and left sides. The anterior capsular artery plays an important role in the vascularization of tuberculum sellae meningiomas. The inferior capsular artery originates from the inferomedial aspect of the cavernous ICA, at its horizontal portion, and reaches the floor and anterior wall of the sella where it anastomoses to branches of the inferior hypophyseal artery. Conclusion The MCCA are key structures when performing an endoscopic endonasal approach for tumors of the sellar and suprasellar regions.

Objective To evaluate the intercarotid distance (ICD) of patients with pituitary macroadenoma and compare to heatlhy controls. Method We retrospectively reviewed contrast-enhanced MRI images from twenty consecutive patients diagnosed with non-functioning pituitary macroadenoma, measured the ICD at two different levels (petrous segment – ICD1 and horizontal cavernous segment – ICD2) and compared to twenty paired controls. Results There was no statistically significant difference of the mean ICD1 between the groups and subgroups. For the ICD2 there was statistically significant difference between the case and controls. However, there was no significant difference between the patients with smaller adenomas and the controls. In contrast, the patients with giant adenomas showed statistically significantly higher ICD2 than the controls. Conclusion The ICD at the horizontal segment of the cavernous carotid tends to be wider in patients with giant pituitary adenomas than in healthy individuals or patients with smaller adenomas. RESUMO Objetivo Avaliar a distância intercarotídea (DIC) de pacientes com macroadenoma de hipófise e comparar com controles saudáveis. Método Foram analisados retrospectivamente imagens de ressonância magnética com contraste de vinte pacientes consecutivos com diagnóstico de macroadenoma hipofisário não-funcionante, medidas as DIC em dois níveis diferentes (segmento petroso – DIC1 e segmento cavernoso horizontal – DIC2) e comparados com vinte controles pareados. Resultados Não houve diferença estatisticamente significativa da DIC1 média entre os grupos e subgrupos. Para a DIC2 houve diferença estatisticamente significativa entre os casos e controles. No entanto, não houve diferença significativa entre os doentes com adenomas menores e os controles. Entretanto, os pacientes com adenomas gigantes tiveram estatisticamente significativamente DIC2 que os controlos. Conclusão A DIC no segmento horizontal da carótida cavernoso, tende a ser mais larga em doentes com adenomas hipofisários gigantes do que em indivíduos saudáveis ou de pacientes com adenomas menores.

The medial opticocarotid recess (MOCR) is located in the posterior wall of the sphenoid sinus, medial to the junction of the optic canal (OC) and the carotid prominence (CP). There is controversy in the literature in relation to the presence of the MOCR and its constancy, which is relevant when approaching the skull base through an endoscopic route. The morphometric relations of the MOCR with the surrounding structures were studied in 18 cadaveric specimens after endoscopic endonasal approach (EEA). The distance between both MOCR was 11.06 ± 1.14 mm; the distance between the MOCR and the lateral opticocarotid (LOCR) recess was 5.56 ± 0.85 mm; the distance between the MOCR and the suprasellar recess was 3.72 ± 0.49 mm; the angle between the MOCR plane and the OC 13.32 ± 2.30°; the angle between the MOCR plane and the CP 13.50 ± 2.68° and; the angle between the OC and the CP 26.81 ± 4.26°. All measurements showed low variability, with low standard deviation and interquartile range. No relations were found between any of the measurements. The MOCR may be used as a reference point for precise location of structures during EEA. Objective measurements may be especially useful in cases with distorted sphenoid bone anatomy.

Background: The presigmoid retrolabyrinthine space is characterized by a widely variable size. The main structure involved in this large variability is the sigmoid sinus. Few studies have attempted to establish a reliable classification of sigmoid sinus to predict the presigmoid retrolabyrinthine space. We used tomographic mapping of human cadaver temporal bones to classify the position of sigmoid sinus and performed a cadaveric study to assess the validity of a novel classification in predicting the presigmoid retrolabyrinthine space. Methods: Ten human cadaver temporal bones were randomly selected and subjected to fine-cut computed tomography scanning to classify the position of sigmoid sinus using a reference line. The specimens were classified into medial and lateral groups and each specimen was then subjected to mastoidectomy. The groups were compared using quantitative and qualitative analysis. Results: The medial group showed a larger distance between the sigmoid sinus and the external auditory canal and a shallower lateral semicircular canal. In the lateral group, the mastoidectomy was more demanding, and the Trautmann's triangle was typically narrower and often “hidden” medially to the sigmoid sinus. Conclusions: The tomographic classification proposed in this study predicts, in a cadaveric model, the presigmoid retrolabyrinthine space. It may help the surgeon select the best approach to reach the petroclival region and lead to safer neurological and otological surgeries.

Background: Pneumocephalus is defined as the presence of air within the intracranial vault. A common complication of head trauma and surgery, pneumocephalus is usually related to ventricular shunts, craniotomies, and surgery in the sitting position. Tension (symptomatic) pneumoventricle is a rare entity associated with significant clinical morbidity. Case Description: We report an unusual case of a 15‑year‑old girl with tension pneumoventricle developed shortly after removal of a choroid plexus papilloma of the fourth ventricle by a midline suboccipital approach while in the sitting position. Conclusion: The presence of a cerebrospinal fluid (CSF) diversion system that causes a decrease in intracranial pressure and the existence of a craniodural defect with or without an obvious CSF leak may be the cause of tension pneumoventricule. According to our present understanding, this is the first report of this peculiar complication of fourth ventricular surgery. We discuss clinical manifestations, surgical management, contributing factors, and mechanisms involved in the pathogenesis of tension pneumoventricle.

Background: Primitive neuroectodermal tumor (PNET) is a malignant neoplasm that generally arises from bone and soft tissues, with predilection for young adults. This neural crest origin tumors share biologic and histologic features with Ewing's sarcoma (ES). Case Description: We present a case of a 22-year-old woman with history of severe progressive neck pain, without radiation, associated with paresthesia in the right arm, and palpable right posterior cervical mass. Neurological examination showed increased reflexes in all four limbs, bilateral Hoffman's sign, right Babinski's sign, and right hemi-hypoesthesia. Neuroimaging revealed a right posterior cervical lesion with heterogeneous contrast enhancement extending to the neural foramina of the atlas and axis. Patient underwent microsurgical removal of the lesion, and histopathological and immunohistochemical analysis confirmed the diagnosis of peripheral primitive PNET (pPNET). The patient had adjuvant treatment with radiotherapy and chemotherapy. After twelve months, neuroimaging showed no signs of tumor regrowth and the patient had no neurological deficits. However, three months later, the patient developed hydrocephalus and cerebrospinal fluid (CSF) was positive for neoplastic cells. No other treatment was administered and the patient died. Conclusion: pPNET is a rare malignant tumor with poor prognosis, although promising results with multimodal treatment-surgery, radiotherapy, and chemotherapy. Diagnosis requires immunohistochemical analysis, with identification of neuronal differentiation markers.