Answer for BIR CoW 18 Aug 2024
Thyroid ophthalmopathy
Findings
Bilateral extra ocular muscles appears symmetrically bulky and is largely confined to the muscle belly with relative sparing of tendons. Bilateral proptosis noted. Symmetrical hyperintensity noted involving bilateral extra ocular muscles On contrast- the thickened muscle belly shows homogenous intense enhancement.
Discussion
Thyroid-associated ophthalmopathy or thyroid eye disease, is the most common cause of proptosis in adults and is most frequently associated with Graves disease. On imaging, it is characterized by bilateral and symmetrical enlargement of the extraocular muscle bellies. Radiographic features 1.Exophthalmos 2.Extraocular muscle enlargement Characteristic order of muscle involvement- inferior rectus, medial rectus,superior rectus,lateral rectus. Bilateral (~90%) and symmetric (~70%) involvement is typical. The anterior tendon is typically spared (although it can be involved in acute cases), with the swelling largely confined to the muscle belly this appearance is often referred to as "coke bottle" in nature (Coca-Cola bottle sign) MRI Findings include T1: isointense to the other facial muscles, or fatty infiltration T2: increased signal intensity may be seen due to the inflammatory process T1 C+ (Gd): enhancement may be present 3.Increase in retro-ocular orbital fat 4.The greater the extraocular muscle bulk (especially medial rectus bulk nearer to the apex) and the longer and narrower the bony orbit, the more crowded the orbital apex will become. Apical crowding could result in optic neuropathy due to optic nerve compression . A Barrett's index of ≥60% is highly suggestive of optic neuropathy . Other rarer signs include enlargement of the lacrimal glands (lymphocytic infiltration) chemosis anterior displacement of the orbital septum
References:
Ozgen A & Ariyurek M. Normative Measurements of Orbital Structures Using CT. AJR Am J Roentgenol. 1998;170(4):1093-6. doi:10.2214/ajr.170.4.9530066 - Pubmed Nugent R, Belkin R, Neigel J et al. Graves Orbitopathy: Correlation of CT and Clinical Findings. Radiology. 1990;177(3):675-82. doi:10.1148/radiology.177.3.2243967 - Pubmed John Robert Haaga. CT and MRI of the Whole Body. (2009) ISBN: 9780323053754 - Google Books Davies M & Dolman P. Levator Muscle Enlargement in Thyroid Eye Disease-Related Upper Eyelid Retraction. Ophthalmic Plast Reconstr Surg. 2017;33(1):35-9. doi:10.1097/IOP.0000000000000633 - Pubmed Monteiro M, Gonçalves A, Silva C, Moura J, Ribeiro C, Gebrim E. Diagnostic Ability of Barrett's Index to Detect Dysthyroid Optic Neuropathy Using Multidetector Computed Tomography. Clinics (Sao Paulo). 2008;63(3):301-6. doi:10.1590/s1807-59322008000300003 - Pubmed
Findings
Bilateral extra ocular muscles appears symmetrically bulky and is largely confined to the muscle belly with relative sparing of tendons. Bilateral proptosis noted. Symmetrical hyperintensity noted involving bilateral extra ocular muscles On contrast- the thickened muscle belly shows homogenous intense enhancement.
Discussion
Thyroid-associated ophthalmopathy or thyroid eye disease, is the most common cause of proptosis in adults and is most frequently associated with Graves disease. On imaging, it is characterized by bilateral and symmetrical enlargement of the extraocular muscle bellies. Radiographic features 1.Exophthalmos 2.Extraocular muscle enlargement Characteristic order of muscle involvement- inferior rectus, medial rectus,superior rectus,lateral rectus. Bilateral (~90%) and symmetric (~70%) involvement is typical. The anterior tendon is typically spared (although it can be involved in acute cases), with the swelling largely confined to the muscle belly this appearance is often referred to as "coke bottle" in nature (Coca-Cola bottle sign) MRI Findings include T1: isointense to the other facial muscles, or fatty infiltration T2: increased signal intensity may be seen due to the inflammatory process T1 C+ (Gd): enhancement may be present 3.Increase in retro-ocular orbital fat 4.The greater the extraocular muscle bulk (especially medial rectus bulk nearer to the apex) and the longer and narrower the bony orbit, the more crowded the orbital apex will become. Apical crowding could result in optic neuropathy due to optic nerve compression . A Barrett's index of ≥60% is highly suggestive of optic neuropathy . Other rarer signs include enlargement of the lacrimal glands (lymphocytic infiltration) chemosis anterior displacement of the orbital septum
References:
Ozgen A & Ariyurek M. Normative Measurements of Orbital Structures Using CT. AJR Am J Roentgenol. 1998;170(4):1093-6. doi:10.2214/ajr.170.4.9530066 - Pubmed Nugent R, Belkin R, Neigel J et al. Graves Orbitopathy: Correlation of CT and Clinical Findings. Radiology. 1990;177(3):675-82. doi:10.1148/radiology.177.3.2243967 - Pubmed John Robert Haaga. CT and MRI of the Whole Body. (2009) ISBN: 9780323053754 - Google Books Davies M & Dolman P. Levator Muscle Enlargement in Thyroid Eye Disease-Related Upper Eyelid Retraction. Ophthalmic Plast Reconstr Surg. 2017;33(1):35-9. doi:10.1097/IOP.0000000000000633 - Pubmed Monteiro M, Gonçalves A, Silva C, Moura J, Ribeiro C, Gebrim E. Diagnostic Ability of Barrett's Index to Detect Dysthyroid Optic Neuropathy Using Multidetector Computed Tomography. Clinics (Sao Paulo). 2008;63(3):301-6. doi:10.1590/s1807-59322008000300003 - Pubmed
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!