Presentation2, radiological imaging of intra cranial meningioma.

Health&medicine.

1. Radiological Imaging of Intra-cranial Meningioma. Dr/ ABD ALLAH NAZEER. MD.

2. Meningiomas are relatively common extra-axial primary neoplasms and are found in any area of the central nervous system (CNS) but are most common over the cerebral convexities or at the cranial base. The incidence of intracranial meningiomas increases with each decade of life and peaks in the 60-69 year age group among men and in the 70-79 year age group among women. They are rare in children and young adults. Meningiomas are categorized by the World Health Organization (WHO) into three grades that reflect increasing histological anaplasia and portend increasingly aggressive tumor behavior with greater risk of recurrence.     Risk factors  Established risk factors for the development of meningiomas include deletion in neurofibromatosis type 2 gene, ionizing radiation, head injury. The NF2 gene is thought to be the primary target, with mutation and/or deletion constituting an early tumorigenic event in 50% to 80% of sporadic and the majority of NF2-associated meningiomas. It has been demonstrated that approximately two thirds of all meningiomas express progesterone receptors on their cell membranes, occurring more frequently in female patients however, the role of sex hormones in the genesis of meningiomas is yet not clarified 

3. Common sites of intracranial meningiomas. 

4. Schematic drawing show common sites of intracranial meningiomas.

5. Radiographic features In addition to histological variants, many of which have 'atypical' imaging appearances, a number of 'special examples' of meningiomas are best discussed separately. These include: burnt out meningioma cystic meningiomas intraosseous meningioma intraventricular meningioma optic nerve sheath meningioma radiation-induced meningioma The remainder of this section focuses on more typical imaging appearances of run-of-the-mill meningiomas. Plain radiograph Plain films no longer have a role in the diagnosis or management of meningiomas. Historically a number of features were observed, including: Enlarged meningeal artery grooves. Hyperostosis or lytic regions. Calcification. Displacement of calcified pineal gland/choroid plexus due to mass effect.

6. CT CT is often the first modality employed to investigate neurological signs or symptoms, and often is the modality which detects an incidental lesion: non-contrast CT 60% slightly hyperdense to normal brain, the rest are more isodense 20-30% have some calcification post-contrast CT 72% brightly and homogeneously contrast enhance Malignant or cystic variants demonstrate more heterogeneity/less intense enhancement. Hyperostosis (5%) Typical for meningiomas that abut the base of the skull need to distinguish reactive hyperostosis from: direct skull vault invasion by adjacent meningioma primary intraosseous meningioma enlargement of the paranasal sinuses (pneumosinus dilatans) has also been suggested to be associated with anterior cranial fossa meningiomas lytic/destructive regions are seen particularly in higher grade tumours but should make one suspect alternative pathology (e.g. hemangiopericytoma or metastasis)

7. MR Signal characteristics T1- usually isointense to grey matter (60-90%). hypointense to grey matter (10-40%): particularly fibrous, psammomatous variants T1 C+ (Gd): usually intense and homogeneous enhancement T2- usually isointense to grey matter (~50%). hyperintense to grey matter (35-40%) usually correlates with a soft texture and hypervascular tumours seen in microcystic, secretory, cartilaginous (metaplastic) choroid and angiomatous variants hypointense to grey matter (10-15%): compared to grey matter and usually correlates with harder texture and more fibrous and calcified contents DWI/ADC: atypical and malignant subtypes may show greater than expected restricted diffusion although recent work suggests that this is not useful in prospectively predicting histological grade. MR spectroscopy: usually it does not play a significant role in diagnosis but can help distinguish meningiomas from mimics. Features include: Increase in alanine. Increased glutamine/glutamate Increased choline (Cho): cellular tumor Absent or significantly reduced N- acetylaspartate (NAA): non-neuronal origin Absent or significantly reduced creatine (Cr) MR perfusion: good correlation between volume transfer constant (k-trans) and histological grade ref

8. Angiography (DSA) Catheter angiography is rarely now of diagnostic use but rather is performed for preoperative embolization to reduce intraoperative blood loss and alleviate resection of a tumor. This is especially useful for skull base tumours, or those thought to be particularly vascular (e.g. microcystic variants or those with very large vessels). Particles are favored typically 7-9 days prior to surgery although there are not free of complication particularly one study showed a high prevalence of complications associated with particles smaller than 45–150 μm , so risks and benefits should be thoroughly assessed. Meningiomas can have a dual blood supply. The majority of tumours are predominantly supplied by meningeal vessels; these are responsible for the sunburst or spoke-wheel pattern observed on MRI/DSA. Some tumours also have a significant pial supply to the periphery of a tumor. A well known angiographic sign of meningiomas is the mother-in-law sign, in which the tumor contrast blush "comes early, stays late, and is very dense".

9. Olfactory Groove Meningioma.

10. Multimodal appearance in a case of a right clinoid meningioma (coronal T2 WI MRI, B-mode, color Doppler, ASG).

11. Sagittal (A and B) and axial (C and D) T2 weighted images demonstrate the different signal intensities of meningiomas. (A) hypointense, (B) isointense (C) hyperintense and (D) heterogeneous.

12. Grade III meningioma. Coronal post contrast T1 with fat sat (A), coronal CT reconstruction (B) and coronal T2 (C) images demonstrate a large meningioma with bone destruction and soft tissue invasion.

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