Assessment of inflammation in idiopathic orbital myositis with fat-suppressed T2-weighted magnetic resonance imaging

PURPOSE: To evaluate the inflammation in idiopathic orbital myositis by fat-suppressed T2-weighted magnetic resonance imaging (MRI). DESIGN: Observational case series. METHODS: The inflammation in nine patients with orbital myositis was evaluated with fat-suppressed T2-weighted MRI within three weeks of onset. Patients were mainly treated with steroid pulse therapy and followed to the acute improvement or chronic ocular motility restriction phases. RESULTS: Each patient was found to have localized inflammations in the extraocular muscles or associated fascial structures. Of the five patients with acute improvement, none had inflammation of the extraocular muscles, whereas the four patients with chronic ocular motility restriction had inflammation of the extraocular muscles. CONCLUSION: These results suggest that acute or chronic pattern in orbital myositis is correlated with the localized inflammation. The inflammation in the extraocular muscles may be one of the factors that lead to the chronic ocular motility restriction.