Olfactory groove meningioma - huge

A large lesion, isointense to grey matter on T1 and slightly hyperintense on T2, centred in the anterior cranial fossa, measures 71 x 62 x 49 mm (trans x AP x CC). The lesion shows vivid homogeneous enhancement, with a central spoke-wheel of vessels seen arising from the floor of the anterior cranial fossa. The tumour effaces the frontal lobes, frontal horns of the lateral ventricles and the genu of the corpus callosum. There is extensive white matter T2/FLAIR high signal in the frontal lobes, consistent with oedema. The lesion wraps around the anterior falx, but is larger on the left than the right.

Enhancement in the roof of the left ethmoid sinuses, with loss of definition of the overlying cortex, is concerning of tumour invasion. Review of the CT shows possible permeative change in this region. The posteroinferior aspect of the tumour extends into pituitary fossa, abutting the medial aspects of both supraclinoid internal carotid arteries (ICA). The anterior carotid arteries (ACA) extend over the posterosuperior surface of the tumour for much of its extent, and are deviated to the right.

A 18 x 11 mm T2 hyperintense lesion at the left posterolateral aspect of the tumour suppresses on FLAIR, consistent with a cyst (such as a peritumoural arachnoid cyst).

Conclusion:

The large frontal meningioma appears to be left olfactory groove in origin, with extension into the pituitary fossa. There is possible invasion into the left ethmoid sinuses, and if clinical relevant fine slice bony CT may be useful to confirm this. There is close approximation of the tumour to both the supraclinoid ICAs and the ACAs.