Congenital Superior Oblique Palsy and Trochlear Nerve Absence: A Clinical and Radiological Study

Abstract

To evaluate patients with congenital superior oblique palsy (SOP) by classifying them according to their magnetic resonance imaging (MRI) findings and cross-comparing the clinical characteristics of each group. Retrospective, observational study. Ninety-seven consecutive patients diagnosed with congenital SOP. Medical records of patients who demonstrated typical signs of congenital SOP were reviewed. The presence or absence of the trochlear nerve was visualized with thin-section high-resolution MRI of the cranial nerves. Presence of the trochlear nerve and superior oblique (SO) muscle hypoplasia on MRI, age at the onset of symptoms or signs, ocular motility examination results, objective ocular torsion, and surgical outcomes. Of the 97 patients with congenital SOP, 73% of patients were identified with an ipsilateral absent trochlear nerve and variable degree of SO muscle hypoplasia (absent group), whereas the remaining 27% had a normal trochlear nerve and normal symmetric SO muscle (present group). Patients with an absent trochlear nerve showed more frequent head tilt (P = 0.030) that was manifest at an earlier onset before 1 year of age (P<0.001). Patients with a normal trochlear nerve had a more prominent overelevation in adduction (P = 0.008) and more frequently were associated with dissociated vertical deviation (DVD; P = 0.025). Congenital SOP patients without a trochlear nerve had a hypoplastic SO muscle and frequently manifested head tilt at an earlier age, whereas patients with a normal trochlear nerve showed prominent overelevation in adduction and frequent DVD. The author(s) have no proprietary or commercial interest in any materials discussed in this article.