Resection of a Sphenoid Wing Meningioma

Abstract

Sphenoid wing meningiomas are typically benign, slow-growing tumors that may be identified incidentally on imaging or due to a symptomatic presentation from compression of a nearby structure. Located along the sphenoid wing, these tumors may infiltrate or compress the optic nerve, oculomotor nerve, cavernous sinus, or internal carotid artery, causing neurologic deficits such as visual disturbances, headache, paresis, and diplopia. Surgical resection is considered the first-line treatment for a symptomatic meningioma, but is often challenging due to tumor proximity to these critical neurovascular structures. The most important prognostic factor for recurrence is the completeness of the surgical removal of the tumor, but this goal must be adapted to preserve neurologic function based on individual tumor location and invasion. Here we present a case of a 43-year-old patient diagnosed with a sphenoid wing meningioma after presenting with episodic difficulty speaking and aura-like symptoms who underwent total neurosurgical resection of the tumor via craniotomy.

Keywords

meningioma; sphenoid wing; surgical management; skull base tumors; craniotomy

Case Overview

Meningiomas are the most common benign brain tumors and account for approximately 20% of all primary intracranial tumors.^1,2 Around 15–20% of meningiomas originate from the sphenoid wing, and meningiomas are also the most common tumors of this region.^3,2 TheyMeningiomas are typically slow-growing tumors that arise from arachnoid cap cells found between the brain and skull, along the spinal cord, and within the ventricles.^1,5 They are most commonly found in middle-aged individuals but can occur at any age, and are often identified incidentally on imaging. Only about 25% of meningiomas are symptomatic, resulting from compression of a nearby structure.¹

Sphenoid wing meningiomas are typically classified both by morphology and location. Morphology criteria by the World Health Organization categorizes meningiomas into three groups: grade I is benign, grade II is borderline, and grade III is malignant. 90% of meningiomas are grade I, and less than 3% are grade III.^2,5 Sphenoid wing meningiomas are also often classified based on their location along the sphenoid wing, either lateral, medial, or spheno-orbital (en plaque).³ En plaque meningiomas are sheet-like lesions that infiltrate the dura and sometimes invade the adjacent bone.^3,6 These criteria are used to guide treatment selection, and location categorization is often associated with the presenting symptoms. Treatment strategies for meningiomas include observation, radiation alone, or surgical resection with or without radiation. Surgical resection of sphenoid wing meningiomas is typically the main curative approach but is challenging due to its proximity to critical neurovascular structures, including but not limited to the optic nerve, oculomotor nerve, and internal carotid artery.^3,5 Here we discuss a case of a left-sided sphenoid wing meningioma treated by neurosurgical resection via craniotomy.

This is a 43-year-old patient that presented with episodes of speech arrest and aura-like symptoms for 4 weeks. Other symptoms may have included visual impairment, orbital pain, headaches, mental status changes, paresis, or other cranial neuropathies depending on the extent of tumor invasion and areas of compression.^1,3,4 

Physical exam findings may include visual field deficits, dysphasia, or other neurologic abnormalities depending on the structures affected by the tumor.³ In addition to a thorough history and physical exam with attention to the symptoms listed above, MRI is indicated for diagnosis and tumor identification. This patient underwent MRI, which showed the presence of a left-sided sphenoid wing meningioma. If surgery is indicated, CT may be used to determine if the tumor is invading the bone and to help navigate the tumor area during surgery.³

Treatment for sphenoid wing meningiomas often depends on symptomatology, size, location, and presence of bone invasion. In general, neurosurgical resection is the mainstay of treatment for symptomatic sphenoid wing meningiomas.³ If small, asymptomatic tumors are found incidentally on imaging, observation may be considered. Meningiomas are generally slow-growing tumors, and watchful waiting may be employed for patients who prefer to defer treatment. 

In addition, if the tumor is only causing ocular symptoms, such as visual failure through compression of the optic nerve, alternative procedures may be indicated to relieve the compression. For example, endoscopic transnasal orbital decompression has been used to successfully relieve the optic neuropathy.⁴ This option is less invasive than full neurosurgical resection but is not curative and requires continuous monitoring for potential tumor growth. 

Meningiomas have also been treated with radiotherapy techniques, including stereotactic radiosurgery, which involves the delivery of large single doses of radiation to the target in the hopes of reducing tumor size.^7,8 Stereotactic radiosurgery is considered as an option for small, asymptomatic tumors, but the proximity of the sphenoid wing to highly radiosensitive structures like the optic nerves often prohibits its use for meningiomas in this location.³

Goals of treatment for symptomatic sphenoid wing meningiomas include the resolution of associated symptoms and improvement of quality of life. Full surgical resection of the tumor is a curative treatment option that aims to eliminate the source of symptom development and prevent any further progression.^3,5 As described above, other surgical approaches may be less invasive with a focus on symptomatic relief, but they may not be curative. 

Contraindications to surgical resection of sphenoid wing meningiomas are often related to the extent of tumor invasion into the central nervous system, cavernous sinus, orbits, or internal carotid artery. While the vast majority of sphenoid wing meningiomas are benign, a malignant tumor may present with more aggressive invasion of these local structures.⁹

Here we present the case of a 43-year-old patient with a left-sided sphenoid wing meningioma. The patient was experiencing episodes of difficulty speaking and aura-like disturbances, and therefore elected to undergo surgical resection of the tumor. The tumor was exposed using a pterional, or frontotemporal, craniotomy. Microsurgical techniques were used to locate tumor borders, devascularize, and remove the tumor. A wire mesh was inserted to line the residual cavity in the brain, and the bone flap was refixed to the skull to close the craniotomy. Overall, the procedure went very well without any complications. 

Surgery is the first-line treatment for symptomatic sphenoid wing meningiomas.^3,10 The goal of this operation should always be the total resection of the meningioma at first surgery, while also preserving surrounding neurovascular structures and their function.^10,11 The indication for surgery should always be tailored to the specific patient based on their age, extent of tumor involvement, tumor behavior over time, and neurologic status. The most important prognostic factor for disease recurrence is the completeness of the surgical removal of the tumor; therefore, this is the chief objective.^10–13

The Simpson scale is used to predict the risk of meningioma recurrence following tumor resection.^3,10,12 This operation completed a Simpson grade 2 resection, which indicates complete tumor resection with coagulation of dural attachment. This predicts a 10-year tumor recurrence of 19%. For the total removal of the tumor, including the site of attachment, or Simpson grade 1, there is an estimated 9% recurrence.^3,10 The goal of surgery is to achieve a Simpson grade 1 or 2 resection with total removal of the tumor in order to minimize the risk of recurrence. Grade 3 resection is a complete resection but without dural coagulation and raises the recurrence risk to 29%. Grade 4 is subtotal resection with a 10-year recurrence predicted at 40%.³ If the tumor does recur, it is likely to be within 5 years of surgery.¹⁰  

The sphenoid wing extends from the anterior clinoid process to the pterion, and sphenoid wing meningiomas may develop anywhere across this area. Sphenoid wing meningiomas are often categorized based on their location along the sphenoid wing as each group raises specific surgical problems. Cushing and Eisenhardt were the first to create a system to classify meningiomas in this way, and numerous modifications have been made over time in order to better understand the natural history, and predict outcomes and recurrence.^2,11,14,15 

Lateral and middle sphenoid wing meningiomas are generally more accessible during surgery. Therefore, they are easier to resect; however, they pose a challenge following surgery since they commonly involve the bone, which leads to increased rates of recurrence.¹⁰ At the other end, medial sphenoid wing meningiomas often present as more challenging to resect due to their close relationship with important neurovascular structures such as the oculomotor and optic nerves, the internal carotid artery and its branches, and the cavernous sinus.^10,11,13,15 These neurovascular structures can not only make the procedure more difficult but also limit the extent of resection, which impacts recurrence. When the tumor infiltrates the cavernous sinus, Nakamura et al. reported that only 14.5% of these tumors were able to be completely resected, compared with 92.3% total resection for non-infiltrative tumors.^15,16 In addition, tumor infiltration of bony structures such as the optic canal, orbit, and superior orbital fissure, or hyperostosis of adjacent bone is associated with less optimal long-term outcomes and increased tumor recurrence.^13,15 

Clinical features of sphenoid wing meningiomas are also often based on the location of the tumor along the sphenoid wing, and their presentations are usually due to the compression of a nearby structure.¹ Visual impairment is the most common preoperative neurologic deficit.¹³ Meningiomas located on the medial part of the sphenoid wing are often associated with visual disturbances due to their proximity to the optic nerve.^2, 4 Orbital and cavernous sinus invasion may cause diplopia or exophthalmos. Other sign and symptoms associated with a meningioma may include seizures, headaches, and cognitive impairment.^1, 3, 10

When surgical resection of the meningioma is planned, the preoperative workup focuses heavily on mapping the tumor’s involvement with surrounding neurovascular structures. Pirotte and Brotchi emphasize that a preoperative workup for a sphenoid wing meningioma resection requires MR angiography and venography to depict the tumor’s vascularity, a CT scan with bony windows to check for involvement, and a multiplanar gadolinium-enhanced MRI to assess the tumor boundaries and invasion of the dura.^10, 15 If the tumor receives its blood supply only from branches of the external carotid artery system, then the preoperative embolization of these branches is indicated.^2, 10 Surgical exposure and strategy must be tailored to each case individually based on the specific location of the meningioma to avoid both neurologic damage and suboptimal removal.^{5, 10, 11, 15} 

Postoperative monitoring is required in the intensive care unit for a minimum of 24 hours following surgery. Steroids are given starting 48 hours before the operation and are continued and tapered postoperatively as needed depending on the level of cerebral edema.¹⁰ Postoperative CT is recommended within a few hours of surgery to monitor for postoperative hematoma or pneumocephalus.^10, 15 Patients should be monitored for a change in mental status or acute onset of neurologic symptoms. 

Mortality and morbidity associated with surgical resection of sphenoid wing meningiomas have significantly decreased over the last three decades due to the advances made in the field of neurosurgery, especially in the areas of neuroimaging, cranial base approaches, and microsurgical techniques.¹⁵ However, these risks are still significant, especially for medial sphenoid wing meningiomas due to their proximity to the critical neurovascular structures discussed previously.^15, 17 Complication rates are higher with medial sphenoid wing meningiomas than with those that are lateral and middle.¹⁰ Just as the most common preoperative deficits are ocular symptoms, the most common postoperative complications involve the orbital structures. These include visual loss, oculomotor nerve palsy, and diplopia.^{10, 11, 13, 15} Other new postoperative neurologic deficits may include hemiparesis and aphasia.^10, 11 While some of these outcomes may be permanent, it is important to consider that many new deficits that appear following surgery may be caused by postoperative edema and are, therefore, likely transient.¹¹ More severe complications requiring further acute management may include hemorrhage, bone infection, cerebrospinal fluid fistula leading to meningitis, and vascular injury.^10, 15 In order to avoid these complications, extreme care must be taken when dissecting the nearby neurovascular structures, including the oculomotor and optic nerves, and branches of the internal carotid artery. Brain retraction may cause an array of neurologic deficits, and a retractor should never be used on the optic nerve. To avoid the creation of a cerebrospinal fluid fistula, the dural closure and suturing must be watertight.¹⁰

Patients are generally monitored for recurrence with MRI for a few years after resection. If a tumor were to recur, it would likely happen within 5 years of surgery.^10,15

Disclosures

Nothing to disclose.

Statement of Consent

The patient referred to in this video article has given their informed consent to be filmed and is aware that information and images will be published online.