Magnetic Resonance Imaging (MRI) Demonstrates Abnormal Cyclotorsion of the Rectus Extraocular Muscle (EOM) Pulleys During Head Tilt in Superior Oblique Palsy (SOP)

Abstract

Introduction: Head tilt testing is fundamental to the clinical diagnosis of SOP. We employed MRI to study head tilt effects on EOM pulleys in SOP. Methods: Five patients with unilateral SOP and 10 controls underwent contrast-enhanced, surface coil orbital MRI in 90-degree right and left head tilts. EOM paths were determined from 2-mm-thickness, quasi-coronal MRI by analysis of cross-sections in normalized, oculocentric coordinates. SOP was confirmed by SO atrophy on MRI. Results: Rectus pulley arrays of nonpalsied orbits in both controls and patients with SOP incyclorotated when the orbits were tilted up relative to down (P< 0.025).