Thyroid ophthalmopathy : CT

Case Report:40 yr old female known case of Thyroid disease with lids pain shows classical exopthalmos (distance nearly zero) belly enlargement of all extra ocular muscles with compression of superior opthalmic vein/ optic nerve at apex with increased retro orbital fat volume consistent with TAO (Thyorid associated opthalmopathy)

Teaching points by Dr MGK Murthy

1. Exact etiology not known , possibly TSH antibodies produce inflammatory response of the muscles due to shared antigens , and belly of the muscles show enlargement with inflammatory exudates, mucopolysaccarides and later collagen leading to fibrosis.

2. Sequence of involvement is IMSLOW (inferior/ medial/superior/ lateral/ obliques) with tendons spared

3. Exopthalmos measured by horizontal line joining the zygomatic bones tips in CT axials with post eye balls distance from this horizontal (Normal 10+/- 1.7mm)

4. Optic nerve at orbital apex(depends on the shape of orbit), superior opthalmic veins get compressed (latter leading to retro orbital fat volume increase)

5.Surpirisingly self limiting in majority of cases (<5yrs) . bilateral and symmetrical in 70%

6.Steroids/ other/ decompression may be needed

7. Though common with Graves disease, hashimotos Thyroiditis may be associated .

8. Thyroid abnormality may occur together, earlier or even later