Ultrasonic evidence of inflammatory thickening and fluid collection within the retrobulbar fascia: the T sign.

A case of nonfebrile and nonpyogenic but inflammatory exophthalmos in a 60-year-old woman is presented in illustration of a diagnostic enigma which has previously eluded physical and roentgen examination. With painful limitation of rotation, a less than satisfactory diagnosis of tenonitis or, less commonly, orbital pseudotumor usually has been made. The convenient assistance of contact (nonimmersion) B-scan ultrasound gives objective evidence of fluid within Tenon's space and communicating into the vaginal spaces beneath the optic nerve sheath appearing as homogeneous and echolucent areas. Concurrently there is thickening of the posterior bulbar complex and muscle sheaths evidenced by increased echo density. A definitive finding as the echolucent "T sign" lends substantial and specific basis for clinical management. Rapid improvement in exophthalmos, rotations, and discomfort following oral steroids (without antibiotics) further supports the etiologic concept of both noninfectious and nonendocrine ophthalmopathy. The T sign is suggested as a specific finding, rather than an artifact, differentiating this exophthalmos from neoplastic invasion or thyroidopathy.