Orbicularis oculi muscle in chronic progressive external ophthalmoplegia.

Orbicularis oculi muscle biopsies were performed in 38 patients (ten with chronic progressive external ophthalmoplegia and 28 controls) to determine whether ragged red fibers were present and, if so, whether they were specific to progressive external ophthalmoplegia. To our knowledge, the orbicularis muscle has not been previously studied in this regard. Ragged red fibers were seen in the orbicularis oculi in patients with and without ophthalmoplegia, although they were more abundant in patients with ophthalmoplegia. The limb muscles of patients with ophthalmoplegia showed ragged red fibers. Electron microscopy demonstrated that these fibers contain either abnormal or increased numbers of normal mitochondria. Thus, the presence of ragged red fibers in the orbicularis oculi muscle is not limited to patients with chronic progressive external ophthalmoplegia, and the diagnosis of this disorder with ragged red fibers should be based on a combination of clinical and laboratory findings, including those from a limb muscle biopsy.