Graves Ophthalmopathy: The Bony Orbit in Optic Neuropathy, Its Apical Angular Capacity, and Impact on Prediction of Risk

• Published in: American journal of neuroradiology : AJNR Vol. 30; no. 3; pp. 597 - 602
• Main Authors: Chan, L.-L, Tan, H.-E, Fook-Chong, S, Teo, T.-H, Lim, L.-H, Seah, L.-L
• Format: Journal Article
• Language: English
• Published: Oak Brook, IL Am Soc Neuroradiology 01-03-2009; American Society of Neuroradiology
• Subjects: Adult; Aged; Biological and medical sciences; Female; Graves Ophthalmopathy - diagnostic imaging; Graves Ophthalmopathy - epidemiology; Head & Neck; Humans; Investigative techniques, diagnostic techniques (general aspects); Logistic Models; Male; Medical sciences; Middle Aged; Multivariate Analysis; Nervous system; Oculomotor Muscles - diagnostic imaging; Optic Nerve - diagnostic imaging; Optic Nerve Diseases - diagnostic imaging; Optic Nerve Diseases - epidemiology; Orbit - diagnostic imaging; Predictive Value of Tests; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Risk Factors; Sensitivity and Specificity; Severity of Illness Index; Tomography, X-Ray Computed; Endocrinopathy; Immunopathology; Nervous system diseases; Radiodiagnosis; Hyperthyroidism; Thyroid diseases; Risk factor; Prediction; Graves disease; Autoimmune disease; Neuropathy; Orbit (eye)
• ISSN: 0195-6108; 1936-959X
• DOI: 10.3174/ajnr.A1413

Optic neuropathy (ON), a serious complication of Graves ophthalmopathy, is often subclinical and masked by symptoms of orbitopathy. We examined herein bony and soft-tissue CT features associated with ON, including an angular assessment of orbital apex capacity, and their usefulness in the risk prediction of ON.
The CT scans of 41 patients with Graves ophthalmopathy (17 men, 24 women; mean age, 49.1 years) clinically diagnosed with (19 patients, 32 orbits) or without ON were evaluated by 2 independent raters. Quantitative linear and angular measurements of the orbital structures and bony walls and categoric scores of apical crowding and intracranial fat prolapse were assessed on a clinical workstation. Inter- and intrarater variability of these features was determined. The CT features of the 2 patient groups were compared, and multivariate logistic regression analysis was performed to evaluate the predictive features of ON.
Bony orbital angles (P < .005), length of the lateral orbital wall (P < .05), muscular diameters (P < .0005), muscular bulk of the medial rectus muscle relative to the bony orbit (P < .05), and apical crowding (P < .0005) were associated with clinical ON. Stepwise multivariate logistic regression analysis revealed the muscle diameter index and medial and lateral wall angles to be independent predictors. Combining these in a single multivariate equation yielded sensitivity, specificity, and positive and negative predictive values of 73%, 90%, 82%, and 85%, respectively.
Orbital wall angles, especially the medial wall, and muscular enlargement are independent risk predictors.