The evaluation of chronic progressive external ophthalmoplegia with computerized tomography

Chronic progressive external ophthalmoplegia is characterised by limitation of ocular motility in all directions of gaze and ptosis. Innervational or myogenic factors were claimed to be responsible for this motility disorder. The aim of this study was to investigate the extraocular muscles in CPEO with computerized tomography in an attempt to distinguish extraocular muscle morphology caused by this disorder from that occurring in normal individuals.

Eighteen orbits from 9 patients diagnosed with CPEO were included in the study. Axial and coronal scans were obtained for CT evaluation of extraocular muscles and the dimensions of extraocular muscles were measured. The control group consisted of 40 orbits belonging to 20 individuals and, the results were compared with a student's t test.

The thickness (the vertical dimension of vertical recti and the horizontal dimension of horizontal recti) of all rectus muscles was significantly decreased in comparison with the control group, whereas the width (the horizontal dimension of vertical recti and the vertical dimension of horizontal recti) was similar in both the diseased and normal orbits. In all the rectus muscles of the diseased orbits, the normal fusiform shape was lost and the muscles appeared as thin bands.

The differentiation of CPEO from other myogenic and neurogenic disorders may present difficulty, and a cluster of criteria are required for a final diagnosis. CT has proven to be a valuable tool in assessing extraocular muscles [1, 2]. In this study, an extreme atrophy of all rectus muscles was demonstrated by means of CT. This diagnostic method may consequently contribute to a proper diagnosis of CPEO.