Current approach to meningiomas of the medial sphenoid wing and the cavernous sinus
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.227292
Source of Support: None, Conflict of Interest: None
Since their initial description and classification by Harvey Cushing, meningiomas of the sphenoid wing have undergone further classifications based on the advances in imaging. Their treatment has also evolved considerably due to improved imaging techniques; embolization when safely feasible; the utilization of skull base approaches, particularly, orbital and orbito- zygomatic osteotomy, anterior clinoidectomy, and optic nerve decompression; improved techniques of vascular dissection under the microscope; improved methods of tumor removal including advances in micro-instruments, ultrasonic aspirators and lasers; bypass techniques to overcome the severe encasement of the carotid artery or its symptomatic occlusion; skull base repair techniques; and finally, the utilization of radiosurgery and fractionated radiotherapy.
Complete tumor resection with minimal deficits remains the goal of treatment in the majority of cases, with the best prospect of long-term, recurrence-free tumor control or cure. However, with regard to tumors involving the cavernous sinus, especially the ones that encase the internal carotid artery (ICA), or the ones that present with minimal symptoms, continued observation with periodic imaging, or radiosurgery, is mostly used. There are, however, tumors which defy these attempts at tumor control, with continued growth and symptoms. In such patients, a more radical tumor resection is warranted.
Sphenoid Wing Meningiomas
The classification of these tumors as shown below is most practical:
The senior author prefers a fronto- temporal craniotomy with a full orbitotomy, or a posterolateral orbitotomy, for these tumors. Depending on the extent of hyperostosis, the optic canal may be decompressed extradurally and intradurally. Anterior clinoidectomy is also done in a similar fashion, extra and/or intradurally. One must actively look for extensions of the sphenoid sinus around the optic nerve, and in particular, through the optic strut. If found, the opening should be closed with muscle and fascia to avoid a subsequent cerebrospinal fluid (CSF) leakage. Once the dura is opened, the Sylvian fissure is opened initially to identify the MCA, which is traced back through the tumor along the ICA. The optic nerve dural sheath must be opened to decompress it completely. The tumor is then debulked progressively and disconnected from its dural base. Removal of the lateral wall of the CS, and the decompression of cranial Nerves IIIrd, IVth and Vth is done at the end of tumor removal. Reconstruction is usually performed with a dural graft (water–tight closure is usually not possible), and adequate bony repair, compensating for any loss of bone, to prevent a functional and cosmetic deformity.
As the majority of this tumor is subdural, there is an arachnoidal plane between it and the arteries and nerves in most places, making their dissection possible (Case 1). In recurrent cases, however, the tumor may be adherent to or invading the arteries, making a bypass necessary for safe resection.
In rare cases, the brain may be invaded causing significant brain edema. Such patients may harbor more aggressive tumors. Sometimes, it is necessary to leave the bone flap in the bone bank, until the brain swelling subsides (Case 2).
Cavernous Sinus Meningiomas
The treatment of meningiomas involving the cavernous sinus (CS) has improved markedly due to anatomical knowledge of the structures in and around the CS, and advances in surgical techniques. However, the surgical approach to meningiomas in this space has evolved in the last ten years due to the favorable results of radiosurgery for small lesions in this area.
Meningiomas of the CS can be classified in three different ways: based on the site of origin of the tumor, virgin or recurrent, and the degree of encasement of the intracavernous ICA.
a) Virgin tumor arising primarily within the CS
b) Virgin tumor mainly based elsewhere but secondarily involving the CS (for example, from the petroclival area).
2) Meningioma recurrent after prior therapy such as microsurgery, or radiotherapy
3) Sekhar – Hirsch Classification:
Surgical Plan for Virgin Tumors
When surgical excision is chosen, the goals of surgery are to:
When this is not easily possible, tumor is left in this area. In all patients, the goal is to achieve the best functional and long-term outcomes.
Radiosurgery may be given to small, but symptomatic tumors, and residual tumors in young people (55 to 60 years of age), and growing tumors in patients older than 60 years of age. In patients older than 60 years, small tumor remnants left after microsurgical excision may be observed with periodic imaging to see if there is growth, or treated with upfront radiosurgery, according to the patient's wishes.
Tumors Recurrent after Prior Treatment
When a meningioma presents after prior treatment with a recurrence, it may be pathologically or biologically aggressive, or both. The patient usually has a non-functional eye, with complete or near-complete ophthalmoplegia. In such patients, the goal of the surgery is to save the patient's life, and to attempt a cure. The intracavernous ICA needs to be resected, and a replacement bypass is indicated in order to avoid a stroke.
The surgical resection is staged. In the first stage, the CS area is surgically exposed, a high flow extra- intracranial bypass is constructed, and the cavernous ICA is trapped. In the second stage, the entire CS tumor is resected, including an exenteration of orbital contents, if needed. At this stage, a skull base repair including a vascularized flap may also be needed.
Case 1: Sphenocavernous meningioma with ICA encasement
This 66-year old male patient developed the acute-onset, right facial and shoulder pain. Clinically, he was found to have right facial numbness with right optic neuropathy and inferior field cut. An MRI examination showed an extensive sphenocavernous tumor measuring 30 × 30 × 31 mm, with MCA and ICA encasement [Figure 1]. The tumor was resected completely by a right fronto- temporal craniotomy and orbitotomy. The tumor was found to be firm and vascular. MCA and ICA were dissected free of the tumor and the optic nerve was decompressed; oculomotor nerve was dissected subdurally and inter-durally into the CS, after the lateral wall of the CS was resected. Postoperatively, the patient recovered well and the visual field cut resolved.
Case 2: Middle and medial sphenoid wing meningioma with brain invasion
This 53-year old woman presented with severe headaches and blurred vision in the right eye for the last 6 months. MR imaging showed a large sphenoid wing tumor invading the brain with the involvement of lateral wall of the cavernous sinus [Figure 2]. Preoperative embolization of the middle meningeal artery was done to decrease the vascularity of tumor.
The tumor was approached through a frontotemporal craniotomy and posterolateral orbitotomy. A much-thickened bone of the anterior clinoid process and optic canal was noted; therefore, an intradural anterior clinoidectomy and optic nerve decompression were performed. Following this, the tumor was detached from the anterior and middle fossa dura mater. The tumor was extensively invading the frontal and temporal lobes; an anterior temporal branch of the MCA, in addition to intracavernous ICA branches, were feeding it. The tumor was removed completely. Postoperative MRI showed no residual tumor, and the patient recovered well. The pathology report was World Health Organisation (WHO) grade 1 meningioma but with rhabdoid features. Due to this histopathology, the patient is under close surveillance with periodic MRI imaging.
Case 3: Virgin meningioma, mostly intracavernous
This 62-year old man presented with diplopia and left eye ptosis of a two-year duration. An ophthalmologist saw the patient and then referred him to the senior author. Preoperative imaging showed an intensely homogeneously enhancing mass measuring 2.7 × 1.0 cm, abutting the left anterior clinoid process and involving the interior of the cavernous sinus with a dural tail that extended into into the medial part of left middle cranial fossa [Figure 3]. The tumor had grown considerably over a six-month period based on serial MRI scans.
He underwent a left frontotemporal craniotomy, orbital osteotomy, and optic nerve decompression followed by a total microsurgical resection of the tumor, including the cavernous sinus portion. We excised the intracavernous tumor by a superior approach. The patient did well postoperatively and returned to work, after the resolution of the transient third nerve palsy. Postoperative MRI showed a slight enhancement along the lateral cavernous sinus wall, but with no residual tumor.
Case 4: Petroclival meningioma with cavernous sinus invasion
This 37-year male presented with a six-month history of left facial pain and numbness along with IIIrd, IVth and VIth cranial nerve palsy. The patient had undergone craniospinal radiation for childhood leukemia. He had developed multiple intracranial tumors including a posterior fossa meningioma that had been resected previously.
The preoperative MRI showed a large, left petroclival meningioma. It also involved the internal auditory canal, the Meckel's cave, sella, and the cavernous sinus. It encased the left ICA and left posterior communicating arteries, and was compressing the midbrain. A cerebral angiogram showed bilateral ICA narrowing in the cavernous and paraclinoid segments; and, the tumor was being fed primarily from the right meningo-hypophyseal trunk, left middle meningeal, left accessory meningeal, and left ascending pharyngeal arteries [Figure 4].
The patient underwent a left temporal and retrosigmoid craniotomy, a mastoidectomy with a presigmoid petrosal approach; and the tumor was excised sub-totally. Resection was very difficult due to the hard tumor consistency and brainstem invasion. Tumor remnants were left behind, particularly in the Meckel's cave and cavernous sinus areas. During tumor resection, the superior cerebellar artery was lacerated, but was repaired with 10/0 nylon sutures. At a one-year follow up, the patient had recovered IIIrd and VIth cranial nerve functions completely, while numbness of the V2-3 segments was improving. The patient is fully independent with a slight tandem gait ataxia. We plan to treat the residual tumor with radiosurgery.
Case 5: Recurrent cavernous sinus meningioma after prior radiotherapy
This 46-year old woman presented with diplopia and left eye pain in 2002. Imaging revealed a sphenocavernous meningioma, and she underwent fractionated stereotactic radiosurgery. Follow-up scans at 2005, and 2006 showed progressive tumor growth and eventually the patient developed complete ophthalmoplegia and blindness in the left eye along with restricted jaw mobility.
When she was referred to us, her MRI showed a tumor extending into the left sphenoid sinus and orbit through the optic canal and superior orbital fissure, bowing out the left lateral wall of cavernous sinus with encasement and constriction of the left ICA. Angiogram showed severe left ICA stenosis and a poor collateral flow [Figure 5].
The patient underwent surgery in two stages. In the first stage, we performed a left frontotemporal craniotomy, orbital osteotomy along with optic nerve decompression. We then placed a radial artery bypass graft from the cervical external carotid artery to an M2 branch of the middle cerebral artery; and then a saphenous vein graft from the internal carotid artery to another M2 segment of the middle cerebral artery. We performed two bypasses due to the very poor collateral circulation.
In the second stage, the frontotemporal craniotomy was re-explored. We performed a gross total microsurgical resection of tumor, with reconstruction of the large opening into the sphenoid sinus with a vascularized pericranial flap, free graft of pericranium and abdominal fat graft. The patient did very well postoperatively, with no speech or memory problems or hemiparesis. Imaging three years after surgery suggested a small recurrence of the tumor in the pterygopalatine fossa, but outside the area of the previous resection. She has not had further treatment, but we are following her with periodic imaging.
[Figure 6] provides the algorithm for the management of cavernous sinus meningiomas and [Figure 7] provides the algorithm for the management of other benign and malignant lesions in the medial sphenoidal wing and cavernous sinus location.
Based on the genes and epigenetic mechanisms identified, new approaches involving antibodies are being tried at present for the treatment of meningiomas involving the CS. We are awaiting the results of these studies. Until these approaches bear fruit, surgical resection, and radiotherapy remain the mainstay of treatment for these tumors.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19], [Figure 20], [Figure 21], [Figure 22], [Figure 23], [Figure 24], [Figure 25], [Figure 26]