Role of muscle biopsy in diagnosis of extraocular muscles enlargement

Purpose To study the role of muscle biopsy in patients with enlarged extraocular muscles. Methods A retrospective review of 31 patients who underwent biopsy for extraocular muscle enlargement. Characteristics, including signs, symptoms, imaging findings, and histopathological assessment were examined. Results Chronic inflammatory disorders represented the most common cause of the muscle enlargement followed by malignancy/metastasis. Multiple muscle involvement was more consistent with benign diseases, whereas single muscle involvement was more consistent with malignant causes. Positive predictive value of muscle biopsy was 0.52 for determining a specific cause of the muscle enlargement. Conclusions Muscle biopsy is the standard for diagnosis in patients with extraocular muscle enlargement. This diagnostic test should be performed in every case of non-resolving muscle enlargement, with a specific diagnosis being made in over half of cases.