Spheno-orbital meningioma

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Meningioma

General

• SOMs make up around 5% of intracranial meningiomas, but the numbers published in the literature are very much dependent on the exact definition of this group. SOMs are frequently indolent and do not require intervention if vision is preserved, are not growing, or severe visual compromise with optic atrophy has already been established. The major indications for surgery are potential or incipient optic nerve compromise, proptosis, or for cosmetic reasons. Although the extent of the tumour varies widely, they tend to be

Anatomy

• It is confined to the sphenoid bone with its greater wing forming a large part of the lateral orbital wall and extend to the floor of the middle fossa and its foraminae (rotundum, ovale, and spinosum) as well as the superior orbital fissure.

• This is located between the lesser and greater wing and is separated medially from the optic canal by the optic strut linking the ACP to the body of the sphenoid bone.

• The squamous temporal bone can also be involved.

• The soft tissue component can involve the intracranial compartment as well as the orbit and can grow down to the infratemporal fossa or deep to the temporalis muscle.

• The intracranial component is variable, ranging from an en plaque extension to a distinct intracranial mass. Image- guidance on bone window settings facilitates radical resection of involved bone (Marcus et al., 2013).

Nomenclature

• Sphenoid wing meningioma en plaque

• Pterional meningioma en plaque

• Hyperostosing meningioma of the sphenoid ridge

• Invading meningioma of the sphenoid ridge

Numbers

• 9% of all intracranial meningiomas.

• Middle age women

Pathology

• Originate: dura of the sphenoid wing,

• Extension:
• Dura
• Cavernous sinus
• Superior orbital fissure (SOF)
• Orbital apex
• Convexity dura
• Soft tissue growth
• Extracranial compartments, including the
• Orbit
• Infratemporal fossa
• Temporal fossa
• Bone involvement
• Anterior clinoid process
• Lesser sphenoid wing
• Orbital roof
• Lateral orbital wall
• Middle fossa base.
• Optic canal
• Paranasal sinuses

Clinical presentation

• Unilateral, nonpulsating, progressive proptosis (80 to 90%)





 
• Lesser degrees of proptosis can be best appreciated by observing the patient with the head tipped back.

• Optic neuropathy (27 to 80%)
• Decreased visual acuity,
• Loss of colour vision
• Constricted visual field with an enlarged scotoma

• Other cranial nerve (CN) deficits (20 to 25% )
• (CN III, IV, V, VI, and VIII)
• CN3 affected more than CN2

• Diplopia
• Due to
• Extraocular muscle restriction due to intraorbital tumor
• More common
• More likely to improve post op
• Secondary to neuropathy of the ocular motor nerves
• Less common
• When tumour invade
• Cavernous sinus
• SOF
• Orbital apex
• Annulus of Zinn
• Less likely to improve post op

Evaluation

Cranial nerve testing

Ophthalmological

• Examination of visual acuity

• Visual field

• Fundus examination

• Degree of proptosis (Hertel exophthalmometry)





• Vimeo

Radiology

CT

• Periosteal pattern of hyperostosis, surface irregularity of the hyperostotic bone, and remodelling of the orbital roof and sphenoid wing

MRI

• Tumor extension to the soft tissues and the dura

• MRI +C with fat-suppression techniques, best identifies soft tissue involvement of the orbital contents, the infratemporal fossa, and the temporalis muscle

Histopathology

• Most are grade 1

• Most are meningothelial variant.

Management

Observation

• Indicated without optic neuropathy

• Done with
• Cranial nerve testing
• Ophthalmological
• Examination of visual acuity
• Visual field,
• Degree of proptosis (Hertel exophthalmometry)
• MRI + C

Radiation therapy

• Indication
• Postoperative RT after evidence of clinical and radiographic evidence of recurrence
• As recurrence-free rates of 40 to 95% so not all pt require RT
• Radiographic observation, with judicious use of radiation therapy for proven recurrence or progression
• Soyuer et al
• 5-year progression free survival is significantly improved in patients who have had adjuvant radiotherapy for subtotally resected meningiomas when compared with those patients who have had subtotal resections without additional treatment.
• There was not, however, an overall survival advantage for those receiving immediate postoperative radiation.
• This significant finding indicates that delaying adjuvant radiation therapy does not compromise overall patient survival and may have the added benefit of delaying treatment-related toxicities

• Radiosurgical doses between 12 Gy and 18 Gy have been used to control skull base meningiomas

• Raw local tumor control rates between 80 and 100% have been reported in these studies

• The University of Pittsburgh experience with 972 patients reported tumor control rates of 93% at 5 years and 87% at 15 years using a median dose to the tumor margin of 13 Gy

Surgical resection

General

• Approach selected must allow access to the orbit and the middle fossa base for resection of the tumor-infiltrated bone and soft tissue.

• Decompression of the SOF, the optic canal, and the cavernous sinus should be possible, and brain retraction should be minimal.

• Complete resection, usually corresponding to a Simpson grade II resection
• Due to diffuse infiltrative nature of these tumors and the generally held philosophy of accepting a subtotal resection in the orbital apex, SOF, and cavernous sinus to preserve neural function.

Approaches

• Pterional

• Frontotemporal

• Transzygomatic

• Frontotemporal orbitozygomatic

• Frontotemporal-orbital

Positioning

• Supine with head rotation

Resection

Intracranial

• The stages of resection are extradural followed by intradural excision.

• CT and MRI coregistered stereotactic navigational data.
• Delineation of the extent of hyperostotic bone and dural involvement.

• Extradural stage
• A large frontotemporal or bicoronal skin incision is recommended to provide access
• Harvest pericranial tissue to repair the dural defect and the cranial base.
• Temporalis fascia is incised 2 cm above the “keyhole” region, from the superior temporal line to the root of the zygoma
• When infratemporal fossa exposure is required, a zygomatic osteotomy is performed, leaving the zygomatic arch attached to the masseter muscle
• Tumor-infiltrated temporalis muscle is excised.
• Tumor-infiltrated bone is removed with a high-speed cutting burr and rongeurs
• The aim is to decompress the optic canal and orbit whenever involved and this may require a ‘tailored’ clinoidectomy.
• All hyperostotic bone of the lesser sphenoid wing, middle fossa floor, lateral orbital wall, orbital roof, and anterior clinoid process is removed extradurally using a high-speed drill under magnification and constant irrigation.
• If more extensive dural or orbital exposure is necessary, a frontotemporal craniotomy can be elevated. If necessary, osteotomies of the orbital rims can be cut, and the supralateral orbital rim elevated, either separately or in continuity with the frontotemporal bone flap
• As the lesser sphenoid wing and anterior clinoid are removed, the optic canal and upper part of the SOF are opened.
• The foramen ovale and rotundum are opened as the floor of the hyperostotic middle fossa is removed

• Intradural stage
• Intradural tumor involvement is removed with sharp dissection and microscopic techniques
• Dural resection is extended to include the medial temporal dura of the lateral cavernous sinus wall if necessary
• Leave behind tumour in the cavernous sinus and SOF to prevent neurological complications
• Residual tumours in the orbital apex or involving the cavernous sinus may require radiation treatment if progressive.
• Once the intracranial portion of the tumour has been excised, attention is turned to the intraorbital involvement.

• Closure
• The dura is repaired with pericranium, temporalis fascia, or allograft material before the commencement of intraorbital tumour resection.

 

Intraorbital

• Tumor extension into the orbit is extraconal and extraperiorbital.

• This extent is removed when the bone of the lateral orbit is removed. When involved, the periorbita is resected, and intraorbital tumor invasion is removed. The lateral rectus can be tagged with a suture transconjunctivally at the beginning of the case to help identify the muscle once tumor resection has started.

• All intraorbital, extraconal tumor can be removed.

• Invasion into the orbital apex, annulus of Zinn, or SOF is left in place due to the high risk of injury to the cranial nerves

• Closure
• If the sphenoid or ethmoid sinuses are entered, these are obturated with autologous fat graft to prevent CSF leakage.
• If a periorbital defect is present, it is closed with locally harvested temporalis fascia
• The pericranial graft is then rotated over the orbit. This helps to compartmentalize the orbit from the intracranial space and to avoid adhesion of the orbital tissues to the dura.

 

Reconstruction

• Options for cranioplasty include polymethylmethacrylate, various commercially available bone cements, or commercially available prostheses

• Bony reconstruction of the orbital walls and sphenoid ridge is not necessary for achieving a good cosmetic result if the periorbita is intact or repaired
• DeMonte et al, demonstrated that as long as the periorbita is intact, or has been primarily repaired, isolated bone defects of the medial or lateral orbital walls do not need to be reconstructed

• If the superior or lateral orbital rim is removed, it can be reconstructed with split calvarial bone grafts or commercially available orbital prostheses

• Large defects of the orbital floor always need reconstruction, regardless of whether the periorbita is intact or repaired, to prevent hypoglobus or enophthalmos.

• The orbital and zygomatic osteotomies are fixated with low-profile cranial plating

• Remaining dead space from hyperostotic bone removal can be filled with autologous fat graft.

• If a temporal fossa defect exists, a cranioplasty is performed

Outcome

• Mortality rates
• Vary from 0 to 4%
• Reported mortality due to PE and carotid laceration

Neurological complications

• Temporary and permanent ptosis,

• Diplopia (neuropathic and restrictive),
• Most commonly reported postoperative cranial neuropathies are
• CN3
• CN4
• CN5

• Visual loss,

• Facial palsy,

• Hemiplegia

• Aphasia

• Diabetes insipidus

• Others
• Temporal hollowing,
• Orbital dystopia,
• Chemosis
• CSF leakage
• Meningitis
• Osteomyelitis
• Retroorbital hematoma
• Epidural hematoma
• Brain edema

Oncological

• Recurrence
• Due to
• Failure of early diagnosis of the tumor
• Inadequate surgical resection due to the complicated neurovascular anatomy of the orbit, cavernous sinus, and SOF;
• The failure to appreciate that hyperostotic bone is indeed part of the neoplastic process;
• The biological behavioral tendency of these tumors to insinuate themselves into the foramina, fissures, crevices, and interstices of the orbit, basal skull, and dura; and
• The apprehension of surgeons that they will produce iatrogenic morbidity or mortality associated with a too-radical tumor resection.
• Clinical features
• Most common clinical sign: Progressive proptosis.
• Most common cranial nerve deficit: Optic neuropathy
• Mirone et al
• 5% recurrence rate patients that had a complete resection
• 25% progression rate in patients with residual disease

Clinical features

• Proptosis
• Improvement in 77-100%
• Proptosis was reduced to an average value of 2.7 mm by reduction of globe protrusion of up to 11 mm.

• Visual Outcome
• Acuity
• Once vision has deteriorated to light perception only, it is unlikely that acuity will improve
• Mirone et al
• 73% improvement of visual acuity
• 7.3% worsened visual acuity
• Complete optic nerve decompression is key to improve and stabilize vision
• Ophthalmoplegia
• Improved in 50 to 68%
• Gradual improvement of ocular motor function over time;
• Complete improvement in 30% in 3 months
• Complete improvement in 90% in 9 months
• Double vision secondary to restricted movement of the extraocular muscles improves with orbital decompression.
• True CN III, IV, or VI deficits, these are less likely to improve after decompression.

Differential diagnosis

• Fibrous dysplasia, osteoma, osteoblastoma, Paget disease, hyperostosis frontalis interna, osteoblastic metastases, erythroid hyperplasia, and sarcoid