Meningiomas arising from the PCP can compress the pituitary stalk anteriorly, the oculomotor nerve laterally or infero-laterally and encase the C1-C2 segment of the internal carotid artery (ICA) or its perforators and branches 1).
Clinical and radiological features or characteristics of posterior clinoid process (PCP) meningiomas have rarely been described because of their extreme scarcity and terminological confusion.
Geng et al. subdivided the dorsum sellae meningiomas into two groups
Type 1 (dorsum sellae, inferior third ventricle type)
Lesions in this region are primarily of two anatomic types:
Centrally placed meningiomas located between the two PCPs and arising from the dorsum sellae or upper clival region – which should be referred to as dorsum sellae meningioma or upper clivus meningiomas.
Eccentrically placed meningiomas centered on the PCP are true PCP meningiomas 9).
Takase et al., suggests that PCP meningioma may be characterized by the anterior displacement of internal carotid artery, and infero-laterally shifted posterior communicating artery, and homonymous hemianopsia, a distinctive clinical feature 10).
Hongo et al., report a case of an osteochondroma in the posterior clinoid process that occurred in a 43-year-old man with trochlear nerve palsy. Although the potential preoperative diagnoses based on computed tomography and magnetic resonance imaging included other intracranial tumors such as calcified meningioma, thallium-201 single-photon emission computed tomography effectively differentiated osteochondroma from those possibilities 11).
Strategies in the surgical intervention have not been well established. Moreover, the proximity to important neurovascular structures, including optic chiasm, internal carotid artery (ICA), pituitary stalk, and oculomotor nerve, can be difficult to predict preoperatively, making their surgical excision more challenging.
Differentiation between the dorsum sellae/upper clival meningiomas and the PCP meningiomas may have important implications in selecting the surgical approach 12). One of the key issues in PCP meningioma surgery is preservation of the optic nerve. Unlocking the optic nerve by anterior clinoidectomy and dissection, the falciform ligament is the important step to preserve vision for larger tumors 13).
Various surgical approaches have been described to approach the PCP to minimize complications, and to improve the extent of resection.
These include the extradural trancavernous-transellar approach described by Dolenc 14).
A frontotemporal or pterional approach, presigmoid transpetrosal approach, and a transzygomatic subtemporal approach 15).
In the frontotemporal and pterional approach, there is direct access to the tumor through the optico-carotid and carotico-oculomotor corridors, but the perforators, which are pushed anteriorly by the tumor, are at risk of injury or vasospasm. A two stage approach, combining retrosigmoid suboccipital corridor to devascularize the tumor, followed by total excision of the tumor by frontotemporal route, has also been described 16) 17).
The transzygomatic subtemporal approach is anatomically a good technique as it allows the dural attachment of the tumor to be coagulated first, followed by piecemeal tumor excision. However, temporal lobe retraction may be hazardous and occasional venous infarcts have been reported 18). The transcavernous approach described by Dolenc is also potentially hazardous for the cranial nerves and the ICA 19).
Complication with the perforators is also hazardous of these challenging surgeries than anterior clinoid region meningiomas for their specific neuroanatomical structures and might not be feasible to avoid even with additional techniques and critical monitoring. A combination and multi-staged-surgical approach can be options of tailor-made surgical strategy in cases with tumor adhesion to the perforators 20).
The tumor described by Nakamura et al. was anteriorly placed, arising from the upper clivus and should be labeled as dorsum sellae or upper clival meningioma 21).
Takase et al., report two surgical cases of PCP meningioma and discuss the appropriate assessment of preoperative features and surgical strategies with review of the literature 25).
Sodhi et al., describe a basal frontotemporo-orbito-zygomatic approach with splitting of the sylvian fissure to resect an eccentrically placed PCP meningioma.
The approach allowed access through the carotico-optic corridor, and between the carotid artery and the oculomotor nerve, as well as the anterior subtemporal approach. This provided an additional surgical trajectory allowing direct access to the PCP posterior to the perforating vessels without temporal lobe retraction.
A basal frontotemporo-orbito-zygomatic approach with splitting of the sylvian fissure is a safe approach to resect an eccentrically placed PCP meningioma 26).
Shukla et al. reported a patient as posterior clinoid meningioma, which was eccentric and centered over the PCP 27).