Exploring optimal microscopic keyhole access to the skull base: an anatomical evaluation of transciliary supraorbital and transpalpebral orbitofrontal craniotomy approaches.

PURPOSE: The past two decades have witnessed the rise of keyhole microscopic minimally invasive surgeries, including the transciliary supraorbital approach (TCA) and transpalpebral approach (TPA), commonly known as the transorbital approach. This study aims to elucidate the nuances, specific indications, and advantages of each approach. METHODS: A series of dissections were conducted on five formalin-fixed, alcohol-preserved cadaver heads. The TCA was performed on one side, and the TPA on the other. Virtual measurements of working angles for both approaches were recorded. Additionally, three clinical cases were presented to illustrate the practical application of the techniques. RESULTS: For TCA, the craniotomy dimensions were 1.7 cm x 2.5 cm (Cranial-Caudal (CC) x Lateral-Lateral (LL)), while for TPA, they measured 2.1 cm x 2.9 cm (CC x LL). The measurements of anterior clinoid processes (ACP) were obtained and compared between approaches. In the TCA, the mean ipsilateral ACP measurement was 62 mm (Range: 61 -63 mm), and the mean contralateral ACP measurement was 71.2 mm (Range: 70 -72 mm). In TPA, these measurements were 47.8 mm (Range: 47 -49 mm) and 62.8 mm (Range: 62 -64 mm), respectively. TCA exhibited an average cranial-caudal angle of 14.9°, while TPA demonstrated an average of 8.3°. CONCLUSION: The anterior cranial fossa was better exposed by a TCA, which also featured shorter operative times, enhanced midline visualization, and a quicker learning curve. Conversely, the middle fossa was better exposed by a TPA, making it an excellent option for middle fossa pathologies, including those in the anterior temporal lobe. After sphenoid bone wing drilling, the TPA offers superior visualization from the lateral to the medial aspect and enhances the CC angle. Additionally, the TPA reduces the risk of postoperative frontalis palsy based on anatomic landmarks. However, the TPA requires a greater cranial osteotomy, and due to unfamiliarity with eyelid anatomy, the learning curve for most neurosurgeons is lengthier for this procedure.

Letter to the Editor: "Exploring optimal microscopic keyhole access to the skull base: an anatomical evaluation of transciliary supraorbital and transpalpebral orbitofrontal craniotomy approaches".

This letter to the editor examines the recent comparative study by Santos et al. (2024) on transciliary supraorbital (TCA) and transpalpebral (TPA) approaches for skull base access. The original article offers valuable insights into the anatomical distinctions and potential clinical applications of each approach. The letter praises the methodical analysis presented in the study while proposing future directions incorporating advanced imaging technologies and expanded clinical trials to enhance surgical precision and outcomes. Additionally, it suggests integrating longitudinal studies to evaluate patient outcomes, thereby refining the procedural choice based on specific clinical scenarios.

Supraorbital transciliary approach as primary route to fronto-basal high grade glioma resection with 5-Aminolevulinic Acid use: Technical note.

BACKGROUND: Gliomas are diffuse intra-axial lesions, which can be accessed by multiple surgical corridors for a same location depending on the surgeon's preference. 5-Aminolevulinic Acid use facilitates the extend of resection in case of high-grade gliomas, especially when differentiating normal brain from tumor periphery is challenging. METHODS: Complete resection of glioblastoma via a supraorbital transciliary approach with 5-Aminolevulinic Acid use was performed without any complications, as demonstrated on postoperative MRI. RESULTS: Patient was discharged on the third postoperative day. Wound follow-up shows good cosmetic result. Patient underwent concomitant chemo-radiation (Temozolomide- 60Gy) and adjuvant chemotherapy (Temozolomide). No tumor recurrence was noted at six months follow-up. CONCLUSION: In selected cases, supraorbital transciliary approach could be proposed as primary approach as it provides the advantage of full control over all the vasculo-nervous structures at skull base without the necessity of protective brain retractor use while the 5-Aminolevulinic Acid use allows a gross total resection.

Supraorbital Keyhole Craniotomy via Eyebrow Incision: A Systematic Review and Meta-Analysis.

BACKGROUND: Supraorbital eyebrow keyhole craniotomy is a minimally invasive alternative to a frontotemporal craniotomy and is often used for tumor resection and aneurysm clipping. The purpose of this study is to provide a contemporary review on the outcomes related to this approach and to determine whether they vary with the type of pathology and the addition of an endoscope. METHODS: PubMed, Embase, and Scopus databases were systematically searched, and results were reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. For the meta-analysis portion, the DerSimonian-Laird random effects model was used. RESULTS: A total of 2629 manuscripts were identified. of those, 124 studies (8241 surgical cases) met the inclusion criteria. Mean total complication rate was 26.7 ± 25.7% and the mean approach-related mortality rate was 1.3 ± 2.8%. Technical success, defined as gross total tumor resection or complete aneurysm clipping, was achieved in 83.6 ± 21.5% of the cases. Vascular pathologies were associated with greater technical success, lower total complications, and longer length of hospital stay compared with tumor cases (P < 0.05 for all). For vascular cases, addition of the endoscope yielded lower technical success (P = 0.001) and lower complication rate (P = 0.041). The use of the endoscope for tumor pathologies did not affect technical success, complications, mortality, length of hospital stay, operative time, or reoperation rate (P > 0.05). CONCLUSIONS: The supraorbital craniotomy via an eyebrow incision is a feasible minimally invasive approach with an overall high technical success rate for both vascular and tumor pathologies.

Surgical Limitations of the Microscopic Transciliary Supraorbital Keyhole Approach to the Anterior and Middle Skull Base.

BACKGROUND: The microscopic transciliary SupraOrbital keyhole (mtSO) approach has been used for a wide variety of anterior and middle fossa pathologies, including aneurysms, meningiomas, craniopharyngiomas, and other skull-base tumors. Several clinical series have proven its efficacy and safety, but detailed anatomical demarcations of the anterior and middle cranial base exposure are lacking. Our aim was to define the surgical limitations of the mtSO approach to the ipsilateral and contralateral anterior and middle skull base. METHODS: Five cadaveric specimens (10 sides) were studied with image guidance to illustrate the limits of the surgical exposure. In addition, 30 dry skulls were used to measure the working distances between the craniotomy and key bony landmarks of the mtSO approach. RESULTS: Surgical exposure at the anterior skull base covered the area between the medial half of the contra- and the medial two-thirds of the ipsilateral sphenoid wing including both optic nerves and interoptic space. The anterior limit at the midline was the sphenoethmoidal suture. Ipsilateral anterior clinoidectomy permitted exposure of the superior orbital fissure, which defined the anteromedial limit at the middle fossa, whereas the anterolateral limit was defined by the ophthalmic branch of the trigeminal nerve. Moreover, the posteromedial and posterolateral limits were the posterior clinoid process and the petrous ridge, respectively. CONCLUSIONS: Our findings define the surgical limitations of the mtSO approach for the treatment of anterior and middle cranial base pathologies. These limits can be reliably identified on imaging studies allowing assessment of exposure to guide preoperative case selection.

Combined Simultaneous Multiportal Approach via Minimally Invasive Transciliary and Endoscopic Endonasal Approaches for Tumors Invading Both the Skull Base and the Sinonasal Area.

BACKGROUND: A combined transcranial and transfacial approach has long been the gold standard for surgical management of large tumors with sinonasal and skull base involvement. The extended endoscopic endonasal approach for such pathologies has its advantages, but it has flaws as well, such as anatomic limitations and more ponderous skull base reconstruction and thus higher risk of postoperative complications. Our primary technique for surgical treatment of these pathologies has been a combination of transfacial and minimally invasive transciliary supraorbital keyhole approaches. With the aim to further minimize invasiveness, potential complications, and unsatisfactory aesthetic outcomes during surgical treatment of large tumors invading both the sinonasal area and the skull base, we abandoned the transfacial approach and simultaneously combined the transciliary supraorbital keyhole approach with the endoscopic endonasal approach. METHODS: The well-known microscope-assisted minimally invasive approach via a transciliary supraorbital keyhole craniotomy was combined with the endoscopic endonasal approach. RESULTS: Six patients with different histologic types of tumors affecting the sinonasal area and the skull base were operated on. The mean operative time was 3 hours, there were no unexpected intraoperative or postoperative complications, and total tumor removal was achieved in each patient. None of the patients experienced complications associated with the surgery during follow-up. CONCLUSIONS: Our combined simultaneous multiportal approach enables total tumor eradication with reduced operative time and is associated with minimal intraoperative and postoperative complications, low mortality rate, and excellent cosmetic results.

The Transpalpebral Versus the Transciliary Variant of the Supraorbital Keyhole Approach: Anatomic Concepts for Aneurysm Surgery.

BACKGROUND: The supraorbital craniotomy (SOC) is classically performed through a skin incision in the patient's eyebrow. A variant with a skin incision in the patient's eyelid has become increasingly popular in recent years. OBJECTIVE: To compare the transpalpebral and the transciliary variants of the SOC with regard to their potential role in aneurysm surgery. METHODS: We carried out cadaveric dissections and virtual craniotomies on computerized tomography datasets. The skin incision, the craniotomy location and size, the working angles, and the achievable exposure of neurovascular structures were assessed and compared for both variants of the SOC. RESULTS: The skin incision measured 4 cm for the transpalpebral and 3 cm for the transciliary variant. The skin could be retracted 1.5 cm upward from the lower edge of the orbital rim with the transpalpebral and 2.5 cm upward with the transciliary variant. The craniotomy size was 2.5 × 1.5 cm for both variants, given that the transpalpebral variant included an orbital osteotomy. The bony opening in the transpalpebral variant was 1 cm more caudal; this restricted the craniocaudal working angles and, thereby, limited the achievable exposure of neurovascular structures in the paraclinoid area and along the sphenoid ridge. CONCLUSION: If the orbital rim and the anterior aspect of the orbital roof are removed, then the transpalpebral variant of the SOC enables a bony opening that is just as large as that of the transciliary variant. Nonetheless, the more caudal location of the bony opening alters the available working angles and may impede exposure of key structures during aneurysm surgery.

A Review of the Literature on the Transciliary Supraorbital Keyhole Approach.

BACKGROUND: Conventional craniotomy approaches involve substantial soft tissue manipulation that can cause complications. The transciliary supraorbital keyhole approach was developed to avoid these complications. The aim of this review is to evaluate the safety and the effectiveness of the transciliary supraorbital keyhole approach. METHODS: We searched the PubMed/Medline database for full-text publications from 1996 onward containing data on 100 or more cases of aneurysm clipping or tumor resection by the transciliary supraorbital keyhole approach. The primary outcome was the incidence of approach-related complications. The secondary outcomes were the aneurysm occlusion rate and the extent of tumor resection. RESULTS: Eight publications met the eligibility criteria. All publications were of the retrospective case-series or case-cohort type without any independent assessment of outcomes. The risk of bias at the individual study level may thus have influenced any conclusions drawn from the overall study population, which included 2783 patients with 3085 lesions (2508 aneurysms and 577 tumors). Approach-related complications included 3.3% cerebrospinal fluid collection or leak, 4.3% permanent and 1.6% temporary supraorbital hypesthesia, 2.9% permanent and 1% temporary facial nerve palsy, and 1% wound healing disturbance or wound infection. Complete aneurysm clipping was achieved in 97% of cases. Complete tumor resection in 90% of cases. The overall surgical revision rate was 2.5%. The esthetic outcome was typically reported as highly acceptable. CONCLUSIONS: This approach may represent a safe, effective, and less invasive alternative to conventional craniotomies in experienced hands and for a well-selected subset of patients. However, higher-level evidence is needed to confirm this hypothesis.