"Orbiting around" the orbital myositis: clinical features, differential diagnosis and therapy

Orbital myositis (OM) is a rare disease whose clinical heterogeneity and different treatment options represent a diagnostic and therapeutic challenge. We aim to review the state of knowledge on OM, also describing a cohort of patients diagnosed in our centre, to highlight some remarkable clinical features. A literature review was conducted in PubMed and Medline databases. The herein described cohort is composed of seven OM patients, diagnosed according to clinical, laboratory and neuroradiological features, whose clinical data were retrospectively analysed. OM is a non-infectious, inflammatory process primarily involving extraocular eye-muscles. It typically presents as an acute to sub-acute, painful ophthalmoplegia with signs of ocular inflammation, but atypical cases without pain or with a chronic progression have been described. The wide range of OM mimicking diseases make a prompt diagnosis challenging but orbit MRI provides valuable clues for differential diagnosis. Timely treatment is greatly important as OM promptly responds to steroids; nevertheless, partial recovery or relapses often occur. In refractory, recurrent or steroid-intolerant cases other therapeutic options (radiotherapy, immunosuppressants, immunoglobulins) can be adopted, but the most effective therapeutic management is yet to be established. In this review, we provide a detailed clinical description of OM, considering the main differential diagnoses and suggesting the most useful investigations. In light of the currently available data on therapy efficacy, we propose a therapeutic algorithm that may guide neurologists in OM patients' management.