INTRODUCTION
Meningiomas represent the most common intracranial extra-axial neoplasm7). The term “multiple meningioma” is applied to a condition where at least two tumors are present at different sites in a patient with no signs of neurofibromatosis1). With an aging population and increased neuroimaging studies, more cases of multiple meningiomas are being identified. Recent large-scale studies report an incidence of multiple meningiomas as high as 19% among patients with meningioma8,9). However, since there is no established standard treatment for multiple meningioma, the choice of surgical removal, radiotherapy, observation, etc., is left to the individual neurosurgeons and neuro-oncologists. Also, Multiple meningiomas with different subtypes and World Health Organization (WHO) grades are very rare and the related literature is limited to case series and case reports10,14). The authors present a rare case of multiple meningiomas consisting of different subtypes and grades, where gross total removal (GTR) was achieved with a single surgery.
CASE REPORT
An 80-year-old male was transferred to a tertiary hospital due to abruptly impaired cognition. He was unable to recognize his close relatives. Initial computed tomography scans revealed a discernible mass in the left frontal lobe (Fig. 1A) and cerebral edema in the left temporal lobe (Fig. 1B). After ruling out stroke or other causes, brain magnetic resonance imaging identified a small (1.8 x 1.5 cm) well-defined dural-based enhancing mass at the left frontal base (Fig. 2A), and another larger (4.0 x 3.6 cm) well-defined dural-based enhancing mass at the left temporal base with peritumoral edema. The temporal mass showed higher signal intensity than the frontal mass on contrast-enhanced T1-weighted sequences (Fig. 2B). An elective surgery was planned using stereotactic navigational guidance after considering surgical accessibility. A frontotemporal craniotomy was performed, retracting the frontal and temporal lobes to expose both masses adequately. The temporal lobe mass was greyish, friable, highly vascular, and removed piecemeal with meticulous bleeding control. The frontal lobe mass was harder and easily distinguished from surrounding tissue, so en bloc removal was possible. GTR was achieved for both tumors (Fig. 3). Histopathological examination (Fig. 4) identified both masses as meningiomas, but with different WHO grade and subtypes. The temporal mass was identified as atypical subtype (WHO grade 2) and the frontal mass was identified as transitional subtype (WHO grade 1). The patient reported improved cognition after the surgery. No complications and no sign of recurrence were reported during 1-year follow-up visits of 3-month intervals (Fig. 5).
DISCUSSION
"Multiple meningioma" was defined by Cushing and Eisehardt1) to describe the occurrences of multiple tumors in the absence of neurofibromatosis or acoustic neuromas. This term applies when at least two spatially separated meningiomas are present or more than two occupy distinct regions.
With increasing use of neuroimaging, meningiomas are estimated to occur in up to 1% of the population12). The incidence of multiple meningiomas, were generally reported to occur in only 1% to 10% of the meningioma population4,13), but a recent large-scale study by Ramos-Fresnedo et al.9) reported incidence as high as 19%, which indicates that the true incidence is actually higher than the traditional beliefs. Moreover, the existence of multiple lesions is shown to be associated with decreased overall survival and progression-free survival8,9), when compared to solitary meningioma.
Multiple meningiomas are more common in women, and observed cases report a higher female-to-male ratio (3.5F:1M) than solitary meningioma patients (2F:1M). This female preponderance might be attributed to higher progesterone expression identified in these tumors4,11). Also, one series outlined association of prior radiation history and multiple lesions (1 in 5 patients), and lack of such association in solitary lesions11).
Multiple meningiomas usually show uniform histology, and WHO grade 1 is predominantly reported in multiple and solitary meningioma. Only one-third of multiple meningiomas display simultaneous occurrence of different histological grades6). The combination of atypical subtype grouped with other WHO grade 1 subtypes are even rarer. Two hypotheses for this formation include independent tumor generation or cloning/migration from a common origin through meninges5).
There is no established gold standard treatment for multiple meningioma. It should be tailored specifically to each patient as in cases of solitary meningiomas3). Treatment strategies usually include surveillance, surgery, and radiation therapy including gamma knife radiosurgery. A comprehensive therapeutic approach that accounts for various factors, such as the patient’s age, underlying disease and co-morbidities, symptoms and neurologic deficits, potential risk and benefits of surgery, tumor count and locations is needed. One should not forget that multiple treatments might be required over patients’ courses2). In our case, despite the patient’s advanced age, tumors’ location and surgical accessibility allowed for a single craniotomy achieving GTR of the both tumors.
CONCLUSION
Multiple meningioma is considered rare but may have a higher incidence than many surgeons expect based on recent data. Although more evidence is required for the establishment of a gold-standard treatment method, especially in patients with different histological malignancy grades, single surgical removal without recurrence or complications is possible in selected patients.