CHRONIC PROGRESSIVE EXTERNAL OPHTHALMOPLEGIA IN A HEREDO-ATAXIA: NEUROGENIC OR MYOGENIC?

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Abstract
A patients with Friedreich''s disease and chronic progressive external ophthalmoplegia (CPEO) was described. An investigation was performed into the nature of the ocular motor disorders, which clinically appeared to be supranuclear. The EMG [electromyogram] of the ocular muscles suggested myopathy. A specimen of ocular muscle was obtained by biopsy and examined by light microscopy and, for the 1st time, EM. Signs of mitochondrial myopathy were found alongside neurogenic features. Postmortem examination of the CNS confirmed the diagnosis of Friedreich''s disease with lesions of the motor cells in the anterior horn of the spinal cord. No evidence was found for a supranuclear or internuclear origin of the ocular palsies, but 20-30% of the neurons in nuclei III and IV were atrophic. Lesions of the non-medullated motor nerve fiber were also visible by EM. That the origin of the CPEO in this heredo-ataxia is neurogenic-nuclear was postulated on the grounds of the neuropathological and EM findings. Resemblances to the microscopic and submicroscopic appearance of many types of ocular myopathy and ophthalmoplegia-plus throw doubt on the myogenic character of these conditions. Possibly chronic, slowly progressive atrophy in the nuclear areas of the ocular motor nerves must in these cases also be held responsible for the CPEO. Perhaps Moebius''s Kern-Schwund theory may be revived after 85 yr.