Teaching Case

A 30-year-old female patient presented to the Emergency Department (ED) with a six-week history of right eye pain, diplopia on lateral gaze, and proptosis. She had reported progressive onset of symptoms over the past 12 months. Her only previous medical issue was asthma. Haematological and biochemical results were all normal.

Non-contrast CT orbits were undertaken to evaluate for intraconal or extraconal masses or collection.  Findings demonstrated poorly marginated diffuse right greater sphenoid wing cortical thickening, resulting in mass effect on the lateral rectus muscle.  Post-contrast CT orbits did not show lesional or soft-tissue enhancement. A CT thorax/abdomen/pelvis was undertaken to exclude a primary malignancy.

MRI orbits pre-and post-contrast demonstrated low-signal thickening of the right greater sphenoid wing with lesional and adjacent dural enhancement on post-contrast sequences.

Meningiomas are tumours that arise from arachnoidal meningothelial cells [1]. They are usually slow growing, and greater than 90% are benign [2]. The incidence increases with age, with a female to male ratio of 2:1 [3].

Primary intraosseous meningiomas (IOM) represent part of a rare spectrum of meningioma subtype termed extradural meningiomas, and comprise less than 2% of cases [4-6]. Clinical presentation of IOMs occurs due to mass effect with calvarial convexity lesions most commonly presenting as a palpable lump on the scalp. Cranial nerve deficits occur secondary to mass effect with skull base IOMs.  Temporal bone IOMs can result in sensorineural hearing loss. Those at the sphenoid ridge, as in our case, tend to present with visual disturbances such as diplopia and proptosis [5].

Non-contrast CT imaging can identify conventional dural-based meningiomas as a well-circumscribed, smoothly marginated mass abutting the dura. Calcification is seen in 20-25% of cases. Meningiomas enhance homogeneously post-IV-contrast greater than 90% of the time [6].

On MRI, conventional meningiomas are well-delineated extra-axial masses with broad dural base. T1-weighted imaging typically shows isointense to grey matter 60-90% of the time [7]. Gadolinium-enhanced contrast T1-weighted shows homogenous enhancement in 85% of cases. Fluid-attenuation inversion recovery sequences (FLAIR) may demonstrate adjacent parenchymal oedema. A dural tail appears in 65% of meningiomas. This feature is not specific for meningiomas but is highly suggestive.

Ilica et al (2014) correlated CT and MRI imaging features with WHO histologic classification in 65 cases of IOM [8]. They showed that the sphenoid ridge was the most common location of IOMs at 53% (n=35) of the time, and that all the cases of IOMs at the sphenoid ridge were WHO grade-1 (benign). The second most common location was the calvarial convexity at 33% (n=22). They found that IOMs can present as osteosclerotic lesions (68%), osteolytic (8%), or a mixture of both (24%). On CT imaging in low-grade IOMs, osteosclerosis with bony expansion is most commonly observed. Factors suggesting a higher-grade tumour include location at the calvarial convexity or non-sphenoidal skull base lesion, or the presence of radial spiculations on CT and adjacent osteosclerosis/osteolysis [8]. Management depends on location, but may involve osteotomy if symptomatic. There is no consensus on adjuvant radiation therapy or chemotherapy [9, 10].

As our patient’s eye pain persisted she underwent tumour-debulking surgery. Histopathology confirmed primary intraosseous meningioma, meningothelial type, WHO grade-1.

Written informed patient consent for publication has been obtained.