The underlying pathology of congenital oculomotor nerve palsy has not been determined. A previous MRI study reported that only one out of three patients showed bilateral oculomotor nerve hypoplasia; the two remaining patients had subarachnoid oculomotor nerves of normal size.1 This variability suggests heterogeneity in the pathogenesis of congenital oculomotor nerve palsy. This report describes the use of MRI to verify the pathology of the extraocular muscles as well as the cranial nerves in three patients with congenital oculomotor nerve palsy. This study was undertaken following the tenets of the Declaration of Helsinki and received an approval from Institutional Review Board of Seoul National University Bundang Hospital.

Case 1

A 6-month-old girl presented with an inability to elevate the right eye. There was an intermittent exotropia of 20 dioptres (PD). Ductions and versions showed underaction of elevation, depression and adduction OD (fig 1A). MRI showed normal right and left oculomotor nerves and slightly atrophic right inferior rectus (fig …