Visual Vignette

Abstract

Answer: Acromegaly causing EOM enlargement resulting in exophthalmos. Exophthalmos is defined as severe proptosis (>18 mm), measured from the interzygomatic line to the anterior surface of the globe (Fig. 2). A study of 324 acromegaly patients revealed that initial evaluation was initiated due to visual field deficits (5.7%) infrequently (1). The most common nonthyroid causes of EOM disease are inflammatory, vascular, or neoplastic in etiology (2). In a retrospective analysis of 60 patients with nonthyroid EOM enlargement, acromegaly comprised just 3% of the cohort (3). Exophthalmos in acromegaly may be secondary to the IGF-1 effect on the IGF-1 receptors in the EOMs and orbital fat. CT findings revealed bilateral, diffuse, and symmetric EOM enlargement, with the degree of expansion correlating to the duration of disease, rather than the elevation in IGF-1 levels (2). While the pattern of EOM involvement in acromegaly may resemble that of thyroid orbitopathy, the muscle size generally remains smaller without lymphocytic infiltration or interstitial edema on histopathology (2). Our patient presented with obvious bilateral exophthalmos secondary to EOM enlargement from acromegaly, in the absence of thyroid disease. The patient underwent transsphenoidal surgery and a craniotomy, followed by pituitary irradiation, and is currently on medical treatment for persistent acromegaly.