Ultrasound measurement of the horizontal external eye muscles in patients with thyroid disease. Is orbital involvement associated with thyroid autoantibodies?

Abstract

Purpose: To describe ophthalmic findings with emphasis on exophthalmometry and ultrasonic assessment of extraocular eye muscle diameter in a consecutive group of females with Graves' disease (GD), compared with healthy controls and patients with other thyroid diseases. We also investigated the relationship with biochemical markers of thyroid autoimmunity such as TSH receptor antibodies (TRAb) and anti-thyroid peroxidase antibodies (anti-TPO).

Methods: Seventy adult women (age 26-74 years) with various types of thyroid disease consecutively entered the study at a tertiary referral center for thyroid-associated ophthalmopathy (TAO). Twenty-three had long-standing GD with TAO. Clinically, TAO was mainly absent in 22 with newly diagnosed GD and in seven with relapse of GD. Nine with Hashimoto's thyrolditis and nine with multinodular goiter were included for comparison and 18 healthy females served as controls. A full ophthalmic status included B-scan ultrasonic assessment of the four horizontal rectus muscle thicknesses, and a clinical NOSPECS score was attempted for each.

Results and conclusions: Besides higher NOSPECS scores, the TAO subgroup had higher exophthalmometry and muscle thickness. The GD groups without significant TAO also scored higher in these ratings compared to controls. Hertel recordings, NOSPECS and muscle thicknesses were all correlated in GD but showed no correlation to thyroid antibodies (TRAb and anti-TPO). Thus, the muscle thickness did not correlate with thyroid autoimmune activity. Nevertheless, we found extraocular muscle assessment useful since a) thicker muscles were usually found in patients with GD, with or without evidence of TAO, and b) other space-occupying orbital lesions could be excluded, thereby reducing the need for the more elaborate imaging techniques (CT, MRI, etc.).