Clinical, neuroelectrophysiological and muscular pathological analysis of chronic progressive external ophthalmoplegia

The aim of the present study was to explore the clinical, neuroelectrophysiological and muscular pathological characteristics of chronic progressive external ophthalmoplegia (CPEO) and to improve the understanding of CPEO. Clinical manifestations, neuroelectrophysiology and pathological features of muscle biopsies from 12 patients with CPEO were retrospectively analyzed. The average age of onset for the 12 patients (6 males and 6 females) was 17.2 years. All patients had different degrees of blepharoptosis. A total of 11 patients experienced ocular dyskinesia, but diplopia was rare. Electrophysiological testing in 12 patients revealed abnormal changes in 6 patients, including 4 patients with a myogenic lesion, 1 patient with a neurogenic lesion, and 1 patient with mixed myogenic/neurogenic lesions. Two patients had slow sensory nerve conduction velocity. Muscle biopsies in 12 patients demonstrated ragged-red, irregular and broken fibers in 11 patients through Gomori trichrome and hematoxylin and eosin (H&E) staining, increased lipid levels in some muscle fibers in 4 patients through Οil Ρed O staining and abnormal distribution of type I and II muscle fibers in 3 patients through ATPase staining. Electron microscopy in 5 patients showed an increased number of mitochondria and abnormal mitochondrial aggregation between submucosa and myofibrils in 4 patients. These findings suggest that the possibility of CPEO should be considered if patients present with obvious extraocular muscle paralysis without diplopia. Furthermore, the identification of ragged-red fibers by Gomori trichrome and H&E staining of muscle biopsies from patients is an important basis for the diagnosis of CPEO.