Chapter 6 Chronic Progressive External Ophthalmoplegia (CPEO)

A 55-year-old man was referred to our clinic for assessment of treatment-resistant myasthenia gravis. He presented to a community neurologist one year prior with a two-month history of ptosis and diplopia worse at the end of the day. Neurological examination showed a normal mental status, cranial nerve examination was positive for right greater than left ptosis, and ophthalmoparesis was limited to ∼15° in all directions with the up-gaze being more affected, mild bilateral hearing loss, and mild (4+/5) proximal muscle weakness. The remainder of the examination was normal, and the family history was negative. A single fiber electromyography was done and showed a significant increase in jitter. He was diagnosed with probable myasthenia gravis and started on pyridostigmine (60mgtid) with mild subjective improvement in the diplopia. One month later, he returned to the clinic with no further clinical improvement and complained of mild dysphagia for dry foods. His anti-acetylcholine receptor antibody test returned normal, as did a computed tomography scan of the chest (looking for thymoma). He was diagnosed with antibody-negative myasthenia gravis and started on azathioprine (150mg/d) in addition to the pyridostigmine. At follow-up six months later, there was still little improvement, and he was treated with intravenous immunoglobulin (1g/kg/q4weeks) for four months. When this treatment failed to improve the symptoms and he felt weaker going up stairs, he was sent for further assessment.