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Neuroradiology Case of the Month

August 2001

Clinical Presentation: A 60-year-old male presents with sinus congestion, cough, and sinusitis. He has a history of myelodysplastic syndrome and an allogenic bone marrow transplant one year prior.

Initial Radiographic Findings: Non-contrast facial CT reveals an intraorbital mass within the right orbit and several smaller masses in the left orbit (Figs. 1 & 2).

Figure 1. Initial coronal facial CT reveals bilateral intraorbital masses, medial to the optic globes.

Figure 2. The left mass measures 11mm x 8mm coronal and 10mm AP. There is a conglomerate of smaller masses in the left orbit, the largest of which measures 6mm x 6mm coronal and 5mm AP.

Differential Diagnosis: The differential diagnosis for an intraorbital mass in a patient with this history include leukemic chloroma, hemangioma, pseudotumor, and orbital venous varix.

Leukemic chloromas are infiltrative masses composed of immature granulocytes. They can spread hematogenously to involve the CNS, meninges, and subarachnoid space. They can present as infiltrative soft tissue masses on CT. On MRI, they are usually iso- or hyperintense to cerebral tissue and enhance considerably after Gd-DTPA contrast administration.

Hemangiomas are often well-circumscribed, homogenous, ovoid and highly dense masses which have variable enhancement on CT. They are isointense to muscle on T1 weighted MRI and hyperintense on T2-weighted MRI.

Pseudotumor is an inflammatory intraorbital lesion that occurs in multiple forms that include myositic, scleral, and retrobulbar masses. Lesions are bilateral in 15% of cases. On CT, there is enhancing soft tissue thickening. On T1-weighted MRI the lesions are isointense to muscle. On T2-weighted images, they are isointense to fat.

Intraorbital venous varices are rare venous malformations of the orbit and can be either congenital or acquired. Primary lesions are either congenital or present soon after birth, whereas secondary varicies are caused by intracranial or orbital AVM's or carotid cavernous fistulas. In either case there may be intermittent exophthalmos associated with the Valsalva maneuver or with coughing. On CT, varices are seen as enlarged, dilated tortuous intraconal vascular channels which are distensible with Valsalva maneuver and densely enhance. On MRI these lesions may demonstrate flow effects depending on flow velocity within the channels.

T2-weighted MRI obtained within 24 hours after CT demonstrates interval decrease in size of the lesions (Fig. 3).

Figure 3. Non-contrast CT (left image) demonstrates the 11mm x 8mm x10mm right intraorbital lesion. T2-weighted MRI (right image) demonstrates the same right intraorbital lesion, now measuring 6mm x 7mm x 4mm.

These findings are pathognomonic for bilateral intraorbital venous varices. The interval decrease in lesion size can be accounted for by the "hanging head" sequence during supine coronal facial CT protocol (figure 4). This protocol, applied to CT but not to MRI, increases intracranial venous pressure by placing the patient’s head below his body, similar to a Trendelenberg position. This results in distension of intraorbital venous varices. This venous distension is also reproducible by valsalva and jugular compression.

Figure 4. The "hanging head" sequence during supine coronal facial CT.

Intraorbital venous varices are a common cause of retrobulbar hemorrhage. Although often an asymptomatic incidental finding, they may present as proptosis, diplopia, and orbital pain, usually intermittent. Treatment may involve surgery or embolization if the preferred conservative approach fails.

Additional Images:

Figure 5. Noncontrast facial CT.

Figure 6. T1-weighted MRI.

Figure 7. T2-weighted MRI.

Diagnosis: These images also demonstrate that the patient did in fact have pansinusitis, which was the indication for his initial facial CT

References:

1. Bilaniuk LT. Orbital vascular lesions. Role of imaging. Radiologic Clinics of North America 37(1):169-83, xi, 1999 Jan
2. Edelman RR, Hesselink JR, Zlatkin MB. Clinical Magnetic Resonance Imaging, 2nd edition, W.B. Saunders Company, Philadelphia, 1996.
3. Hammerschlag SB, Hesselink JR, Weber AL. Computed Tomography of the Eye and Orbit. Appleton-Century-Crofts, New York, 1983.
4. Roden DT, Savino PJ, Zimmerman RA. Magnetic resonance imaging in orbital diagnosis. Radiol Clin North Am 26:535, 1988.