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Trochlear calcification

Posted Sat, 12/19/2009 - 05:46 by Norman Loberant

Images

Figure 1.

Figure 2.

Figure 3.

Clinical History:

29 year old women underwent CT for head trauma.

Findings:

1. Axial CT image, soft tissue window, superior orbital level. There is a small focus of high attenuation at the point of superior oblique muscle angulation.
2. Axial CT image, bone window, superior orbital level. A small linear calcification is visible.
3. CT coronal reconstruction, bone window, through anterior portion of orbits shows trochlear calcification in the superior medial aspect of left orbit.

Diagnosis:

Trochlear calcification in the left orbit – incidental finding on brain CT

Discussion:

The trochlea is a cartilaginous structure (U-shaped piece of fibro-cartilage) through which the superior oblique tendon and its sheath pass. It is attached to the frontal bone a few millimeters behind the orbital margin on the medial wall of the orbit. Calcification in this region may occur in adults as an aging-related normal variant (1). Its presence in patients younger than 40 years is strongly associated with diabetes (2).In the setting of trauma, trochlear calcification, especially asymmetric, may be confused with fracture or foreign body. Additionally, distinguishing between trochlear calcification and intraorbital foreign body is important in patients for whom MRI is planned.

References / Suggested Reading:

1. LeBedis CA, Sakai O. Nontraumatic orbital conditions: diagnosis with CT and MRI imaging in the emergent setting. Radiographics 2008, 28:1741-1753.
2. Hart BL, Spar JA, Orrison WW Jr. Calcification of the trochlear apparatus
of the orbit: CT appearance and association with diabetes and age.
Am J Roentgenol 1992, 159: 1291-1294.

3. Internet reference for anatomy: http://www.missionforvisionusa.org/anatomy/2006/03/extraocular-muscles.html

Author

Anna Chernihovsky, Norman Loberant,MD

Department of Radiology, Western Galilee Hospital, Nahariya, Israel