Asymmetric thyroid eye disease

The purpose of this study was to evaluate asymmetric thyroid eye disease (TED) using an objective, radiological-based definition of asymmetry.

We conducted a retrospective study on TED patients with computed tomography (CT) orbits. Demographic, biochemical, and clinical presentation data were collected. Extraocular muscle volumes were determined by manually segmenting the muscles in consecutive slices. The extraocular muscle volumes were summed in the right and left orbits. Asymmetry was defined by a ratio of ≥1.4 between the total muscle volumes of both orbits. Unilateral disease was present if there was no muscle enlargement in the opposite orbit. Hertel exophthalmometry was performed on participants, and the difference between the right and left globe protrusion was compared.

Fifteen out of 100 patients had asymmetric disease, of which 9 had unilateral disease. The mean age of participants was 55 ± 15 years, and 66 were female. No correlation was found between asymmetry and age, sex, thyroid status, or hormone levels. The exophthalmos difference was significantly greater in asymmetric orbits compared to nonasymmetric orbits. A cutoff of 2.75 mm for the exophthalmos difference gave a sensitivity of 0.87, specificity of 0.79, and an area under the curve of 0.83 for identifying radiologically defined asymmetric TED.

There is currently no universally accepted definition for asymmetric TED. Current definitions rely on differences in clinical signs and symptoms between orbits which are unreliable. We present a cohort of asymmetric TED defined using an objective radiological marker of extraocular muscle volumes from CT scans.