29 Orbital Masses Not Involving the Optic Nerve

CLINICAL IMAGAGINGAN ATLAS OF DIFFERENTIAL DAIGNOSIS

EISENBERG

DR. Muhammad Bin Zulfiqar PGR-FCPS III SIMS/SHL

• Fig SK 29-1 Cavernous hemangioma. Contrast-enhanced CT scan shows a typical homogeneous enhancing intraconal mass.47

• Fig SK 29-2 Cavernous hemangioma. (A) Precontrast axial T1-weighted MR image shows a focal intraconal mass surrounding the right optic nerve. There is mild proptosis. This condition did not alter the patient's visual acuity. (B) Corresponding postcontrast fat-suppressed T1-weighted image shows that the lesion becomes intensely enhanced.6

• Fig SK 29-3 Retinoblastoma. (A) Axial CT scan shows a large calcified mass in the right eye. The posterior sclera is thick, implying invasion by tumor. (B) Axial noncontrast scan of a different patient shows the hyperdense tumor that fills most of the vitreous chamber and contains a small focus of calcification. The eye is enlarged. In both cases, there is no tumor extension outside of the globe.6

• Fig SK 29-4 Melanoma. (A) Coronal (surface coil) noncontrast T1-weighted image shows the bright melanoma (M) with retinal effusions (arrows). (B) Coronal T2-weighted scan shows the tumor (M) to be dark. The effusions blend with the bright vitreous. (C) Axial postcontrast T1-weighted image with fat suppression shows the enhancing melanoma (arrow).6

• Fig SK 29-5 Orbital varix. T2-weighted MRI scan shows round, hyperintense mass compatible with surgically proved orbital varix (V).48

• Fig SK 29-6 Orbital pseudotumor. (A) Axial enhanced CT scan shows a typical poorly defined intraconal mass on the right with marked proptosis.48 (B) Less common appearance of a focal pseudotumor, predominantly extraconal, in the inferolateral aspect of the right orbit associated with mild proptosis.48 (C) Proton-density MR scan shows an ill-defined region of relatively low signal intensity behind the globe.

• Fig SK 29-7 Orbital subperiosteal abscess. CT scan shows proptosis of left eye with subperiosteal abscess (open arrow). Note air bubble (arrowhead) within abscess and swollen left medial rectus muscle (white arrow).48

• Fig SK 29-8 Mucocele. (A) CT scan shows benign expansion of bone by a sharply marginated, lucent, nonenhanced ethmoid mass that has extended into the medial aspect of the right orbit by eroding the lamina papyracea.48 (B) In another patient, a T1-weighted MR image shows an expansile, hyperintense abnormality of the anterior ethmoids bilaterally that is greater on the right (arrows).49 (C) T2-weighted MR image shows greater signal hyperintensity in the mucocele (arrows) and involvement of the lower right frontal sinus.49

• Fig SK 29-9 Meningioma. MR image shows a large mass virtually isointense to brain that arose from the planum sphenoidale and extended into the posterior aspect of the orbit (arrows).

• Fig SK 29-10 Adenoid cystic carcinoma. MR scan shows an ill-defined mass (arrow) invading the lateral rectus muscle and breaking through the lateral wall of the orbit.47

• Fig SK 29-11 Hematogenous metastasis. Well-circumscribed retrobulbar mass (arrow).

• Fig SK 29-12 Lacrimal gland tumor. (A) Coronal and (B) axial MR scans show the mass in the superolateral aspect of the right orbit (arrows).

• Fig SK 29-13 Dermoid cyst. A fat-fluid level (arrows) is seen in this well-defined extraconal lesion on (A) T1-weighted and (B) T2-weighted MR images. The artifact in the right orbit (curved arrow) is due to cosmetics.47

• Fig SK 29-14 Lymphoma. Ill-defined enlargement of the medial rectus muscle (arrow) that typically has low signal on T1-weighted images (A) and high signal on T2-weighted images (B).47