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Neuroradiology Case of the Week

Case 95

Ramon deGuzman, MD, PL Westesson, MD, PhD, DDS,
Sven Ekholm, MD, PhD, and Sidhur Kathuria, MD

Clinical Presentation: The patient is an 80-year-old female presenting with confusion, aphasia, left-sided weakness and facial droop. MRI of the head showed an acute right thalamic infarct. However an incidental finding was noted.

Radiological Findings: Initial head CT showed a slightly hyperdense lesion at the mid-subfrontal region exerting minimal mass effect on the medial aspects of both frontal lobes. It appears to be in an extraaxial location. No associated calcifications are noted.
     Head MRI showed a 2.5 cm. extra-axial mass at the mid-subfrontal region broadly based along the dura. It is isointense to gray matter on TIWI and shows homogeneous enhancement on post-contrast study. It is hyperintense on FLAIR images and shows a lobulated contour. The underlying paranasal sinuses are clear and there is no evidence of bone destruction.

Diagnosis: Olfactory groove meningioma

Clinical Discussion:  These are meningiomas that arise in the olfactory groove over the cribriform plate and frontosphenoid suture and are usually bilateral over the roof of the orbit. Headache, visual changes or anosmia could be the presenting symptom/s of such olfactory groove lesions. They can project backward towards the sella, and if large can affect vision by pressure on the optic nerve and chiasm.
     They comprise approximately 10% of intracranial meningiomas, and 15% extend into the ethmoid sinuses.

Neuroimaging Discussion: Olfactory groove meningiomas exhibit the usual MRI characteristics of meningiomas in the other intracranial locations. They also have a characteristic angiographic feature which shows a spoke-wheel configuration of vessels supplying the meningioma with displacement of other vascular structures, particularly the anterior cerebral arteries. Blood supply is usually from the anterior and posterior ethmoidal arteries, anterior branches of the middle meningeal artery, and the meningeal branches of the ophthalmic artery.

References:

1. The Encyclopaedia of Medical Imaging, Volume VI:1
2. A. Welge-Luessen et al. Journal of Neurology Neurosurgery Psychiatry 2001; 70:218-221
3. S. Hentschel et al. Neurosurg Focus 2003; 14:1-5.