To evaluate the usefulness of imaging diagnosis in patients with atypical oculomotor abnormalities and paralytic strabismus.

The magnetic resonance imaging (MRI) or computed tomography (CT) of 3 patients with atypical Y pattern vertical incomitance and medial rectus (MR) paresis after MR impingement reduction and A pattern vertical incomitance were analyzed. High-resolution, surface coil MRI was used to obtain sets of contiguous, 2-mm thick quasi-coronal images in 9-cardinal gaze directions. Digital image analysis was used to evaluate the results.

MRI revealed lateral displacement of the superior rectus (SR) and inferior displacement of the lateral rectus (LR) during upper temporal gaze and inferior displacement of the LR during lateral gaze in patients with Y pattern vertical incomitance. In patients with MR paresis, the maximal surface area of MR cross section is in the image plane 10 mm posterior from the orbital center at primary gaze. The maximal surface area of MR cross section is in the image plane 22 mm posterior from the orbital center during medial gaze. Quasi-coronal images show that contraction tends to cause the plane of maximum cross-section to move posteriorly. Surgical treatment was avoided and observational treatment maintained. There is incyclotorsion of both extraocular muscles in patients with A pattern vertical incomitance and upslanted palpebral fissure.

Imaging diagnosis of pulley position and rectus muscle contractility is helpful for determining accurate diagnosis and treatment methods at atypical oculomotor abnormalities and paralytic strabismus.