The tumors are usually bilateral based on their midline origin, although they can also be unilateral.
A universally accepted classification system predicting surgical risk and outcome is still lacking.
Planum sphenoidale meningiomas account for 5-10% of all intracranial meningiomas.
They are typically slow-growing tumors, explaining why some patients remain asymptomatic and, therefore, un-diagnosed for extended periods of time. The ensuing growth of the extra-axial neoplasm can cause displacement of the optic apparatus resulting in visual disturbances. It is, therefore, imperative that patient undergoes formal neuro-ophthalmological testing before any surgical intervention. A headache, although present in many patients with this neoplasm, is a non-specific finding.
Delay in the diagnosis of meningiomas of the tuberculum sellae and planum sphenoidale is detrimental to the patient in terms of visual recovery, morbidity and mortality. Early accurate diagnosis of these tumors is possible through the use of neuroimaging which is recommended for all patients with unexplained impairment of vision 2).
Neuroimaging characteristics on CT include a homogenously and avidly contrast-enhancing, extra-axial mass, with a well-defined border and broad dural attachment and/or dural tail. The tumor is associated with moderate circumferential edema and mass effect. There may be an area of central calcification within the tumour and hyperostosis of adjacent bony structures may be evident.
On MRI, the meningioma appears hypo to isointense on T1-weighted imaging and possesses variable signal intensity on T2-weighted images. Gadolinium MR imaging demonstrates intense homogeneous or heterogeneous-enhancement of the tumor, with well-circumscribed margins.
Tuberculum sellae meningiomas are located not only on the limited surface between the prechiasmatic sulcus and diaphragma sellae, but also on the limbus sphenoidalis, chiasmatic sulcus and diaphragma sellae.
Planum sphenoidale meningiomas are located more anterior and in proximity of the olfactory groove location.
A 45-year-old gentleman who presented with signs of raised intracranial hypertension, secondary optic atrophy and a contrast-enhancing mass arising from the planum sphenoidale. Postoperatively, mass was diagnosed as aspergilloma on histopathology and culture. Despite antifungal treatment, patient could not be saved due to large artery infarcts in the immediate postoperative period 3).
Hemangioblastomas are rarely seen in the suprasellar region, arising from the optic apparatus or pituitary stalk, mimicking meningiomas on the preoperative MRI scan. They may be suspected in the presence of large flow voids and the absence of a dural tail. Intraoperatively, the extreme vascularity and compressibility of the tumour with no dural attachment should alert the surgeon to the diagnosis. A complete resection with preservation of vision may be successfully attempted because of the well-demarcated tumour-nerve interface 4).
Two cases of intracranial leiomyosarcoma revealed a mass at the left cavernous sinus involving prepontine cistern in one case and two lesions in the other case showing masses with dural based appearance at the region of the planum sphenoidale and the posterior aspect of the falx cerebri which mimiced a meningioma. The leiomyosarcoma should be included in the differential diagnosis of extra-axial CNS lesions in HIV-infected patients 5).
Adenoid cystic carcinoma (ACC) is rarely encountered by the neurosurgeon; however it should always be considered in the differential diagnosis of skull base tumors. Interdisciplinary surgical approaches represent the major advance in the treatment of these complex neoplasms 6).
Midline anterior skull base lesions are becoming amenable for total surgical excision with minimal morbidities and mortalities. Most preferred surgical routes are the subfrontal approach and the pterional approach 7).
Small and midsize olfactory groove, planum sphenoidale, and tuberculum sellae meningiomas can be removed via an endonasal endoscopic approach, an alternative option to the transcranial microsurgical approach. The choice of approach depends on tumor size and location, involvement of important neurovascular structures, and, most importantly, the surgeon's preference and experience. In most meningiomas, the endonasal approach has no advantage compared with the transcranial approach. Disadvantages of the endonasal approach are the discomfort after surgery and the prolonged recovery phase because of the nasal morbidity, which requires intensive nasal care. Compared with the eyebrow approach, the trauma to the nasal cavity, paranasal sinuses, and skull base is greater, and the risk of cerebrospinal fluid leak is higher 8).
A combination of different surgical and endovascular techniques before resection of hypervascular giant planum sphenoidale meningiomas should always be considered. Microsurgical extracranial ligation of anterior and sometimes posterior ethmoidal arteries provides a safe and feasible option to limit blood loss during anterior skull base surgery 9).
Like most meningiomas, meningiomas of the anterior cranial base are typically benign and potentially curable. Thus, the extent of surgical resection is the most important predictor of recurrence.
Despite the benign pathology, their recurrence rates 10 years after surgical resection have ranged from 10 to 41%.
These high rates have been attributed to the difficulty in removing the tumor cells that invade the base of skull and paranasal sinuses.
It is well known that it is difficult to remove the planum sphenoidale without damaging the optic nerves. The visual outcome after this operation has been unacceptable in such tumors, especially in large ones.
Mortazavi et al., conducted a retrospective review of the patients who between 2005 and March 2015 underwent a craniotomy or endoscopic surgery for the resection of meningiomas involving the suprasellar region. Operative nuances of a modified frontotemporal craniotomy and orbital osteotomy technique for meningioma removal and reconstruction are described.
Twenty-seven patients were found to have tumors arising mainly from the planum sphenoidale or the tuberculum sellae; 25 underwent frontotemporal craniotomy and tumor removal with orbital osteotomy and bilateral optic canal decompression, and 2 patients underwent endonasal transphenoidal resection. The most common presenting symptom was visual disturbance (77%). Vision improved in 90% of those who presented with visual decline, and there was no permanent visual deterioration. Cerebrospinal fluid leak occurred in one of the 25 cranial cases (4%) and in 1 of 2 transphenoidal cases (50%), and in both cases it resolved with treatment. There was no surgical mortality.
An orbitotomy and early decompression of the involved optic canal are important for achieving gross total resection, maximizing visual improvement, and avoiding recurrence. The visual outcomes were excellent. A new classification system that can allow the comparison of different series and approaches and indicate cases that are more suitable for an endoscopic transsphenoidal approach is presented 10).
In patients treated with endonasal endoscopic meningioma surgery. Sughrue et al., believe that very low rates of morbidity can be achieved in carefully selected patients, thus avoiding brain manipulation 11).
7 PSMs (23.3%) of midline anterior skull base meningiomas 12).
12 planum/jugum sphenoidale meningioma 13).
Zygourakis et al., retrospectively identified 44 patients with planum/olfactory meningiomas treated at our institution from 1996 to 2006. We used univariate and multivariate regression models to analyze the effect of several magnetic resonance imaging characteristics (tumor volume, distance to optic chiasm, anterior cerebral artery encasement, paranasal sinus invasion, and sellar invasion) on preoperative symptoms and postoperative outcomes, including complication rate and tumor recurrence.
Only brain tumor volume (>42 cm(3)), but not distance to the optic chiasm, is independently associated with an increased likelihood of preoperative visual symptoms. Tumors with nasal sinus invasion are significantly more likely to cause postoperative surgical complications, and tumors with anterior cerebral artery encasement are associated with a greater likelihood of both postoperative complications and tumor recurrence.
Tumors larger than 3.4 cm in diameter and those whose posterior edge is within 6-8 mm of the optic chiasm should be recommended for early surgical intervention. In terms of predicting surgical complications, nasal sinus invasion and anterior cerebral artery encasement are associated with greater-risk profiles when surgery becomes necessary. Thus, it is prudent to take these specific variables into consideration when advising patients about the risks of observation and surgery for olfactory/planum meningiomas 14).
Perera et al., retrospectively reviewed the clinical records of 17 patients with planum sphenoidale meningiomas who were admitted between 2004 and 2011. Patients had formal visual assessments (including Humphrey’s visual field testing) pre- and postoperatively.
The mean age at presentation was 62.3 years; there were 11 women and 6 men. The meningiomas ranged in diameter from 17 mm to 70 mm (mean diameter 37.2 mm). Twelve of the patients had neurosurgical intervention (seven of these had a pterional approach, three had a bicoronal frontal approach, and two had the tumor resected via the transglabellar frontal approach). Histological analysis showed nine of the cases were WHO grade I and the remaining three were grade II.
Ten of the patients demonstrated improvement in their visual acuity assessment, and four of the patients had no demonstrable visual impairment preoperatively.
Conclusions: Prevention of visual deterioration and/or improvement of visual function remain benefits that could be attained by resection of planum sphenoidale meningioma. Pre- and postoperative formal ophthalmological assessments should be an integral component in the management of these tumors.
A review propounds a strategy to secure visual acuity through operation. A total of eight cases are summarized. In five midline symmetrical meningiomas, the tumors compressed the nerves at the portion of the optic chiasma, causing a typical bitemporal hemianopsia. Four large tumors were resected by the frontobasal interhemispheric approach to minimize the intraoperative damage to the optic chiasma, and a small one was removed by the pterional approach. Visual disturbances were recovered immediately after the operation in all cases without any surgical complications. Three meningiomas were attached to the lateral part of the planum sphenoidale or tuberculum sellae. Although the sizes were relatively small in all cases, they caused ipsilateral severe visual loss by direct compression to optic nerves. MRI and three-dimensional CT angiography showed the tumor extension into the optic canal. The ipsilateral pterional approach was selected in these cases. To avoid additional nerve damage, we tried to reduce the tension of nerves which were compressed by the tumors. Uede et al., removed the anterior clinoid process and opened the optic canal before surgical manipulation of the tumor. In two cases, tumors severely compressed the optic nerves from the medial side, and nerves were stretched laterally. Great care was required to separate the optic nerves from tumors in those two cases. In contrast, the resection seemed to be very easy in one of the cases where the optic nerve was displaced infero-medially. Visual symptoms were improved in all cases, although one case became worse temporarily. Although planum sphenoidale and tuberculum sellae meningiomas are still troublesome, appropriate preoperative management would allow us to expect an excellent visual outcome. Especially, selection of the surgical approach should be based on the anatomical analysis of the nerve displacement 15).
In this article 105 cases of meningiomas of the planum sphenoidale and tuberculum sellae are reviewed. In only five cases was the diagnosis made within three months of the onset of the symptoms 16).
Meningiomas of the tuberculum sellae and planum sphenoidale. A review of 83 cases 17).
Coincidental pituitary adenoma and planum sphenoidale meningioma mimicking a single tumor 18).
A 60-year-old male presented with complaints of dizziness, which worsened with fatigue and a sense his balance was 'off'. Initial physical examination was negative and the laboratory testing was unremarkable. Within weeks, the patient developed bilateral visual field defects. MRI revealed an extra-axial mass which extended into the pituitary fossa and caused compression of the pituitary gland. The pituitary stalk was displaced posteriorly and the optic chiasm was compressed with displacement superiorly and posteriorly. The patient underwent a surgical resection. Diabetes insipidus developed postoperatively requiring a vasopressin drip. He also developed hypopituitarism after the resection with hypothyroidism, hypoadrenalism and hypogonadism. The patient requires testosterone, levothyroxine and hydrocortisone replacement and has mild residual bitemporal hemianopsia 19).
A previously healthy 31-year-old man presented with an extremely rare case of small meningioma associated with cerebral infarction preceded by recurrent transient ischemic attacks manifesting as a 3-day history of recurrent and transient weakness of the left lower limb lasting several minutes for each episode. The symptoms became persistent and complete on the following day. Magnetic resonance imaging revealed acute cerebral infarction in the right frontal lobe and a 20 mm diameter tumor in the planum sphenoidale encasing the right anterior cerebral artery. Cerebral angiography demonstrated occlusion of the right A(2) portion. The patient underwent surgery and the tumor was gross totally removed. The histological diagnosis was meningothelial meningioma. Cases of meningioma causing cerebral infarction are very rare, but the possibility should be considered even if the tumor is small 20).
A 66-year-old woman who developed a planum sphenoidale meningioma. Histologically, the tumor was composed of meningothelial cells arranged in fascicles and whorls, typical of a well-differentiated meningioma. Many tumor cells contained round intracytoplasmic eosinophilic inclusions that were periodic acid Schiff-negative and red on Masson trichrome. The inclusions were immunopositive for vimentin, and were immunonegative for epithelial membrane antigen, smooth muscle actin, desmin and type IV collagen. Ultrastructural examination showed the inclusions were composed of round to oval, well-demarcated, non-membrane-bound, osmiophilic granular material. The inclusions within this tumor had histochemical, immunohistochemical and ultrastructural properties not described in other reported meningiomas with eosinophilic granular or granulofilamentous inclusions 21).