Walsh & Hoyt: Mitochondrial Disorders Associated with External Ophthalmoplegia

CPEO is the most frequent manifestation of mitochondrial myopathies. Harding et al. reviewed the records of 60 patients with mitochondrial myopathy examined at the National Hospital, Queen Square, and found that 54 of the patients (90%) had ocular or oculomotor abnormalities and that CPEO was the presenting feature in about two thirds of the patients. CPEO may occur in association with a variety of myopathic and other disorders (e.g., Graves disease, myasthenia gravis, and brain stem glioma); this is simply a clinical sign and not a nosologic entity. Kearns-Sayre syndrome (KSS).