The use of ultrasonography in the diagnosis of endocrine orbitopathy

Abstract

Patients with endocrine orbitopathy (Graves' disease) are often euthyroid when seen, up to half may have normal Werner suppression tests, and frequently have no known history of thyroid disease. Ultrasonography. especially using quantitative A-scan techniques. provides the simplest and most reliable means of diagnosing endocrine orbitopathy. Accurate and reproducible measurements can be made of rectus muscle thicknesses, as well as of the size of the subdural perineural space about the optic nerve. One hundred consecutive patients in whom the diagnosis of endocrine orbitopathy was made by diagnostic ophthalmic ultrasonography are herein considered.

While the clinical presentation may be unilateral, ultrasonography will demonstrate bilateral abnormalities (and, in fact. this is a necessary condition for making the diagnosis). These may occasionally be extremely subtle. perhaps consisting of no more than an otherwise inexplicable increase in the subdural perineural space about the retrobulbar optic nerves; while rectus muscle measurements. interocular differences in muscle measurements and orbital fat echo patterns remain within the 'normal' range of variation. Such essentially 'unilateral' clinical presentations may be difficult to distinguish from other entities, but careful ultrasonic examination, together with the clinical history and findings allow the correct diagnosis to be made in virtually all cases.

Computed tomography has often been misinterpreted (e.g. enlarged muscles have been thought to represent orbital tumor masses), is qualitative, and is an unnecessary procedure in the diagnosis of this disorder. Blood chemistries are unreliable as diagnostic aids, but are of value in guiding therapy in those patients with detectable chemical abnormalities. Quantitative A-scan ultrasonography is the benchmark test in establishing the diagnosis of endocrine orbitopathy in cases where the diagnosis is not clinically obvious.