Clinical History
A 40-year-old female patient evaluated for disturbances in visuospatial processing. Both conventional and advanced MRI was performed.
Imaging Findings
A case of meningioma, evaluated with both conventional and advanced MRI techniques. The conventional MR Imaging protocol included transverse non-enhanced T1 and T2 weighted sequences as well as Fluid attenuation inversion recovery (FLAIR) and contrast-enhanced T1 weighted sequences. The findings were indicative of a typical meningioma.
A single-shot-echoplanar (with fat supression) DWI in tree b-values (0, 500, 100mm2/sec) Apparent Diffusion Coefficient (ADC) maps were generated and the ADC was calculated by region of interest (ROI) measurements. A diffusion weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping, perfusion weighted imaging (PWI) with cerebral blood volume (CBV) mapping, MRI venography (MRV), spectroscopy and functional MRI (fMRI) were performed. The signal intensity of the meningioma were similar to the brain parenchyma at T1 (Fig. 1) and increased compared to brain parenchyma at T2 (Fig. 2). Minimal perifocal oedema was observed. After contrast medium enhancement the lesion demonstrated intense enhancement (Fig. 1). Τ2* star sequence was negative for hemorrhagic or calcification foci. At DWI the signal intensity was increased with low signal intensity at ADC map (Fig. 3) and mean ADC value 0.8. Increased CBV values (Fig. 4) observed at PWI (with characteristic contrast enhancement curve (mother in law sign). Infiltration of the superior saggital sinus with lumen stenosis at the adhesion point was demonstrated at MRV (Fig. 5) Spectroscopy (Fig. 6) showed increased choline and alanine levels, and decreased NAA levels. The findings were indicative of an atypical meningioma.
The diagnosis was confirmed histopathologically (Fig. 7)
Discussion
Although conventional MR imaging is adequate for characterization of typical forms of meningioma, the technique may not be sufficient for characterization of the more atypical forms of meningioma and differential diagnosis from its mimics. In such cases advanced MRI techniques are important supplemental means in the diagnosis of meningiomas.
Diffussion –weighted Imaging (DWI) may allow the cellularity of meningiomas to be graded noninvasively because cells constitute a relative barrier to water diffusion, compared with extracellular space. More cellular tumour would show increased signal intensity at DWI with low apparent diffusion coefficient (ADC) values at ADC map. Atypical meningiomas demonstrate increased signal intensity at DWI with very low signal intensity at ADC maps, and extremely low ADC values indicative of marked diffusion, with exception the cystic or necrotic part of the lesion which has increased ADC values. On the other hand typical meningiomas demonstrate variable signal intensity at DWI with increased signal intensity at ADC map and increased ADC values, with exception the calcified psammomatous bodies that form irregular calcified mass with decreased ADC values.The degree of angiogenesis is a key determinant of malignant potential in brain tumor. Although the conventional MRI with gadolininium contrast is useful for the detection and characterization of the tumour, the enhancement reflects the disruption of blood brain barrier rather than the vascularity. Perfusion weighted imaging, offers the quantitative estimation of cerebral blood volume that reflects the underlying microvasculature and angiogenesis. Given the correlation of microvessel density and tumor grade and further correlation between microvessel density and CBV, higher grade meningioma have higher CBV values. Signal intensity-time curve of typical meningioma displays immediate leakage of contrast media due to absence of blood brain barrier which is characteristic for extra-axial tumors, followed by partial and slow recovery of signal intensity known as “mother in law” sign, it comes early stays late. Magnetic resonance venography (MRV) evaluates the possible sinus involvement. Magnetic resonance spectroscopy (MRS) shows increased alanine levels with peak ranges from 1.3-1.15 ppm. NAA and Cr levels are virtually zero. The spectra from meningioma may show lipids. Functional MRI (fMRI) serves as preoperative map. Surgery with complete removal of the tumour, including the site of dural attachment, is the treatment of choice. Predicting histological nature meningiomas would aid in treatment planning. Chemotherapeutic regiments and radiotherapy protocols may be applied or preoperative embolization may be commonly used to reduce intraoperative blood loss.
Differential Diagnosis List
Atypical menigioma (grade II) with neoplastic meningothelial cells
Final Diagnosis
Atypical menigioma (grade II) with neoplastic meningothelial cells
