Background: Surgery for intracranial meningioma is either relatively simple or extremely difficult based heavily on tumor consistency.

Objective: To examine the average diffusion constant from apparent diffusion coefficient (ADC), acquired from routine magnetic resonance imaging (MRI), whether it can reliably predict consistency of intracranial meningioma. The secondary objective is to find out if tumor consistency correlate with its histopathology.

Material and Method: Prospectively collected data between July 2009 and July 2011, including demographic, radiographic, intra-operative findings, and histopathology, was evaluated. Eligible patients must have had pre-operative conventional MRI obtained at Faculty of Medicine Ramathibodi Hospital, with calculated average diffusion constant from ADC. All of the included patients’ meningioma resection as well as histopathology were performed at our institute. During each surgical resection, unaware of the MRI interpretation, the operating neurosurgeon classified each meningioma as having soft, firm, or hard consistency. Pathology of 2007 WHO grade I vs. II, tumors was independently reported by neuropathologist without knowledge of pre-operative radiographic and intra-operative tumor consistency.

Results: Fifty-eight patients with intracranial meningioma met the inclusion criteria. The average ADC values amongst soft, firm, and hard consistency tumors were not statistically different (p = 0.82). As for WHO grades, neither the T2 weighted images (T2W) intensity nor the average ADC value showed differences between grade I and grade II meningioma (p = 0.84 and p = 0.31 respectively). The only significant correlation was observed between hyperintensity signal on T2W and high proportion of soft consistency tumors (p = 0.001). In addition, meningiomas with soft consistency were more commonly associated with WHO grade II histopathology (p = 0.01).

Conclusion: Although theoretically sound, average ADC did not reliably predict consistency of intracranial meningioma. Nevertheless, tumors with soft consistency often exhibited hyperintensity signal on T2W and were frequently associated with WHO grade II. This adds to prior studies reiterating similar findings. Neurosurgeons should utilize such information to prepare well before performing intracranial meningioma surgery.

Keywords: Meningioma, MRI, Consistency, DWI, Apparent diffusion coefficient, ADC, T2W