Anterior Clinoidal Meningiomas: Meningeal Anatomical Considerations and Surgical Implications

Anterolateral Routes to the Skull Base-The Frontotemporal Approaches and Exposure of the Sellar and Parasellar Regions

Surgical approaches to the sellar and parasellar regions are highly challenging due to the densely packed nature of the traversing neurovasculature. The frontotemporal-orbitozygomatic approach offers a wide angle of exposure for the management of lesions involving the cavernous sinus, parasellar region, upper clivus, and adjacent neurovascular structures. It combines the pterional approach with different osteotomies that remove the superior and lateral walls of the orbit and zygomatic arch. Extradural exposure and preparation of the periclinoid region, whether as initial preparation for a combined intraextradural approach to deep-seated skull base targets or as the main avenue of surgical exposure, can substantially enlarge surgical corridors and minimize the need for brain retraction in this very confined microsurgical space. We provide a stepwise description of how we perform the fronto-orbitozygomatic approach and an associated series of surgical maneuvers and techniques that can be utilized in a variety of anterior and anterolateral approaches, either alone or in combination, to tailor exposure to a given lesion. These techniques are not limited to traditional skull base approaches and represent a valuable addition to every neurosurgeon's armamentarium as enhancements to common surgical approaches.

The factors influencing postoperative efficacy of anterior clinoidal meningioma treatment and an analysis of best-suited surgical strategies

Objective

To explore the influence of the type of anterior clinoidal meningioma on surgical strategy planning, surgical approach selection, and postoperative efficacy.

Patients and methods

We conducted a retrospective analysis of the clinical data of 63 cases, including data on visual function, extent of tumor resection, and postoperative follow-up. Grade I and II approaches were selected according to the type of tumor. A univariate analysis of the factors influencing the extent of tumor resection, postoperative visual function, and postoperative relapse and complications was conducted.

Results

Simpson Grade I–II total resection was seen in 48 cases (76.2%), with an overall relapse/progression rate of 12.7%. The tumor type and texture and the relationship between the tumors and adjacent structures were the main factors influencing total tumor resection (P < 0.01). The overall postoperative visual acuity improvement, stabilization rate, and deterioration rate were 76.2, 15.9, and 7.9%, respectively. Postoperative visual acuity level was significantly correlated with preoperative visual acuity level and tumor type (P < 0.01).

Conclusions

Determining the type of tumor at a preoperative level and whether the optic canal and cavernous sinus are invaded can aid in the planning of detailed individualized surgical strategies.

Complete Removal of Bilateral Clinoidal Meningiomas Through a Pterional Approach: 3-Dimensional Operative Video

Surgical removal of anterior clinoidal meningiomas remains a challenge because of its complicated relationship with surrounding vascular and neural structures.1-3  This is a 39-yr-old female, with headaches, neurofibromatosis type 2, and history of 3 previous brain surgeries. The patient gave the consent to use the images and surgical video. In the imaging control, the growth of bilateral anterior clinoidal meningiomas was observed.  A right pterional approach and extradural anterior clinoidectomy was performed, and a complete resection of bilateral clinoidal meningiomas was achieved obtaining a Simpson scale resection grade 1.  The patient evolved without neurological deficits after the surgery, and the postoperative magnetic resonance imaging (MRI) evidenced a complete bilateral resection of the clinoidal meningiomas.  Clinoidal meningiomas are the unique subset of tumors because of their close proximity to neurovascular structures and can be safely excised with minimal morbidity and mortality using microsurgical techniques.3-5 In rare cases of bilateral anterior clinoidal meningiomas such as the case presented, we recommend detailed neuroimaging analysis and consider the possibility to resect both in a single approach.

Stereotactic radiosurgery for clinoid meningiomas: a multi-institutional study

PURPOSE

Resection of clinoid meningiomas can be associated with significant morbidity. Experience with stereotactic radiosurgery (SRS) for clinoid meningiomas remains limited. We studied the safety and effectiveness of SRS for clinoid meningiomas.

METHODS

From twelve institutions participating in the International Radiosurgery Research Foundation, we pooled patients treated with SRS for radiologically suspected or histologically confirmed WHO grade I clinoid meningiomas.

RESULTS

Two hundred seven patients (median age: 56 years) underwent SRS for clinoid meningiomas. Median treatment volume was 8.02 cm³, and 87% of tumors were immediately adjacent to the optic apparatus. The median tumor prescription dose was 12 Gy, and the median maximal dose to the anterior optic apparatus was 8.5 Gy. During a median post-SRS imaging follow-up of 51.1 months, 7% of patients experienced tumor progression. Greater margin SRS dose (HR = 0.700, p = 0.007) and pre-SRS radiotherapy (HR = 0.004, p < 0.001) were independent predictors of better tumor control. During median visual follow-up of 48 months, visual function declined in 8% of patients. Pre-SRS visual deficit (HR = 2.938, p = 0.048) and maximal radiation dose to the optic apparatus of ≥ 10 Gy (HR = 11.297, p = 0.02) independently predicted greater risk of post-SRS visual decline. Four patients experienced new post-SRS cranial nerve V neuropathy.

CONCLUSIONS

SRS allows durable control of clinoid meningiomas and visual preservation in the majority of patients. Greater radiosurgical prescription dose is associated with better tumor control. Radiation dose to the optic apparatus of ≥ 10 Gy and visual impairment before the SRS increase risk of visual deterioration.

Invasive Corridor of Clivus Extension in Pituitary Adenoma: Bony Anatomic Consideration, Surgical Outcome and Technical Nuances

Background

It is well known that the clivus is composed of abundant cancellous bone and is often invaded by pituitary adenoma (PA), but the range of these cancellous bone corridors is unknown. In addition, we found that PA with clivus invasion is sometimes accompanied by petrous apex invasion, so we speculated that the petrous apex tumor originated from the clivus cancellous bone corridor. The aim of this study was to test this hypothesis by investigating the bony anatomy associated with PA with clival invasion and its clinical significance.

Methods

Twenty-two cadaveric heads were used in the anatomical study to research the bony architecture of the clivus and petrous apex, including six injected specimens for microsurgical dissection and sixteen cadavers for epoxy sheet plastination. The surgical videos and outcomes of PA with clival invasion in our single center were also retrospectively reviewed.

Results

The hypoglossal canal and internal acoustic meatus are composed of bone canals surrounded by cortical bone. The cancellous corridor within clivus starts from the sellar or sphenoid sinus floor and extends downward, bypassing the hypoglossal canal and finally reaching the occipital condyle and the medial edge of the jugular foramen. Interestingly, we found that the cancellous bone of the clivus was connected with that of the petrous apex through petroclival fissure extending to the medial margin of the internal acoustic meatus instead of a separating cortical bone between them as it should be. It is satisfactory that the anatomical outcomes of the cancellous corridor and the path of PA with clival invasion observed intraoperatively are completely consistent. In the retrospective cohort of 49 PA patients, the clival component was completely resected in 44 (89.8%), and only five (10.2%) patients in the early-stage had partial residual cases in the inferior clivus.

Conclusion

The petrous apex invasion of PA is caused by the tumor invading the clivus and crossing the petroclival fissure along the cancellous bone corridor. PA invade the clivus along the cancellous bone corridor and can also cross the hypoglossal canal to the occipital condyle. This clival invasion pattern presented here deepens our understanding of the invasive characteristics of PA.

Endoscopic endonasal surgery for anterior cranial fossa meningiomas

Meningiomas along the anterior skull base arise from the midline but have historically been resected via open cranial approaches with lateral to medial trajectories. The endoscopic endonasal approach (EEA) offers a direct, inferomedial approach which has demonstrated several superior qualities for their resection. These meningiomas include tuberculum sellae, planum sphenoidale, and olfactory groove meningiomas. While early gross total resection (GTR) was lower than open approaches, EEA has currently achieved comparable rates of GTR and significantly improved postoperative visual outcomes. Rate of cerebrospinal fluid (CSF) leak was one of the early complicating features preventing widespread use of EEA. However, CSF leak rates have dramatically fallen into a tolerable range with introduction of the vascularized nasoseptal flap. Olfactory groove meningiomas often present with anosmia which is persistent after endonasal approach. Rates of other complications have proven similar between EEA and open approaches and include: vascular injury, infection, morbidity, and mortality. With the appropriate team and experience, EEA for anterior skull base meningiomas is increasingly becoming the standard for resection of these lesions. However, there are certain anatomic considerations, patient features, and other aspects which may favor the open approach over EEA, and vice versa; these must be carefully and judiciously evaluated preoperatively. Overall, resection and recurrence rates are comparable, complication rates fall within a very acceptable range, and patients experience superior cosmesis and improved visual outcome with this approach.