A Side Door to Meckel's Cave: Anatomic Feasibility Study for the Lateral Transorbital Approach.

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.

Pituitary macroadenoma: analysis of intercarotid artery distance compared to controls.

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.

Pituitary macroadenoma: analysis of intercarotid artery distance compared to controls / Macroadenoma de hipófise: análise da distância intercarotídea comparada a controles

ABSTRACT 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.

Morphometric analysis of the medial opticocarotid recess and its anatomical relations relevant to the transsphenoidal endoscopic endonasal approaches.

BACKGROUND: 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. METHODS: The morphometric relations of the MOCR with the surrounding structures were studied in 18 cadaveric specimens after endoscopic endonasal approach (EEA). RESULTS: 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. CONCLUSIONS: 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.

Predicting the presigmoid retrolabyrinthine space using a sigmoid sinus tomography classification: A cadaveric study.

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.