Optimizing muscle biopsy for the diagnosis of mitochondrial myopathy

To establish a reliable technique for harvesting the orbicularis oculi muscle to facilitate diagnosis of chronic progressive external ophthalmoplegia, a mitochondrial myopathy.

In this retrospective observational case series, 10 patients clinically suspected to have chronic progressive external ophthalmoplegia underwent surgery for upper eyelid ptosis. A protocol for orbicularis biopsy was developed. Initial cases of levator muscle biopsy yielded inadequate, unorientated skeletal muscle with significant contraction artifact that prevented the study of morphologic features. To improve yield and quality, orbicularis oculi muscle biopsy was performed in the later patients following a standard muscle biopsy protocol used for limb muscles. This involved suturing a third of the muscle on a wooden stick, to keep it at isometric length. The specimen was sent fresh in saline-moistened gauze to the pathologist who then divided the muscle for various studies.

The biopsies of orbicularis muscle performed using this protocol resulted in adequate skeletal muscle with an acceptable level of artifact. Mitochondrial myopathy was diagnosed in 9 of 10 cases.

The orbicularis oculi muscle is a good source of skeletal muscle for investigating muscle disorders, and it is easily collected during blepharoplasty or ptosis surgery. This has avoided the need for a standard proximal limb muscle biopsy, thereby reducing morbidity and cost to the patients.