Planum sphenoidale meningioma
Neurosurgery Department, University General Hospital of Alicante, Foundation for the Promotion of Health and Biomedical Research in the Valencian Region (FISABIO), Alicante, Spain
Planum sphenoidale meningiomas are anterior cranial fossa meningiomas, overlying the area of the cribriform plate of the ethmoid bone, sphenofrontal suture, and planum sphenoidale.
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.
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.
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).
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).
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.
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).
12 planum/jugum sphenoidale meningioma 13).
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).
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.