Romanian Neurosurgery (Sep 2010)
Posterior fossa meningiomas
Abstract
Aim: to identify the possible correlation between demographic data of the patients, site of tumor origin, and pathological characteristics of each subgroup of the posterior fossa meningiomas as the anatomical location of these tumors is a critical determinant of the operative approach that will be chosen. Materials and Methods: We analyzed medical records of 35 patients with posterior fossa meningiomas who underwent surgery between January 2005 and December 2009 at Neurosurgery Department, Iaşi. The analysis included: age and gender of the patients, tumor location, and pathologic findings. According to the anatomical relationship with posterior fossa structures, these 35 meningiomas were classified into 5 types: cerebellar convexity, cerebellopontine angle, petroclival, foramen magnum, and unclassified tumors. According to the classification scheme of WHO 2007 (19), all cases were classified into three histopathological groups: benign, atypical, and malignant meningiomas, and every histopathological subtype was noted. Results: Posterior fossa meningiomas have a 3.33:1 female-to-male ratio with a mean age of 51.6 years. 29 patients had anatomically distinct attachment to the dura of the 4 chosen compartments of the posterior fossa (cerebellar convexity – 14.28%, cerebellopontine angle – 48.57%, petroclival – 11.42%, and foramen magnum – 8.57%) and 6 patients (17.14%) had giant tumors with broad attachment in multiple areas of the posterior fossa. Grade I meningiomas encountered in majority of cases (82.85%), whereas grade II meningiomas were diagnosed in 11.42% of the operated case, and anaplastic meningiomas (grade III) accounted only 5.71%. The most common benign histological subtypes among posterior fossa meningiomas were fibrous (37.79%) and psamomatous (24.13%). Petroclival meningiomas accounted a higher incidence then that presented in other studies (11.42% of all posterior fossa meningiomas). The mean age for female patients was older (55 years) then in other studies. There were various benign histological subtypes (psammomatous, meningothelial, and secretory) and even an atypical one that was diagnosed in a male patient. Foramen magnum meningiomas affected only females with a mean age of 52.66 years. All tumors were benign (grade I) with psammomatous subtype being the most common histological subtype (66.66%). Cerebellar convexity meningiomas presented a female to male ratios of 4:1. Female patients were older (64.25 years) then the mean age of patients with posterior fossa meningiomas. In cerebellar convexity location, all meningiomas presented only benign histology (fibrous subtype, 100%) that made us thinking to a different tumorigenesis for this tumors comparative with other locations. Cerebellopontine angle meningiomas presented a strong preponderance of female patients (5:1). Though majority of cerebellopontine angle meningiomas had grade I of malignancy, they exhibited a large variety of histological subtypes. Conclusion: In our series, posterior fossa meningiomas are clearly various tumors in their histology and demographic data. We identified a significant association between age and gender of the patients, histology of posterior fossa meningiomas, and their site of origin.
