A MAGNETIC-RESONANCE-IMAGING STUDY OF HORIZONTAL RECTUS MUSCLE PALSIES

The assessment of extraocular muscle function is usually performed ind irectly by an examination of ocular motility. We have utilized magneti c resonance imaging, in both cine and static modes, to directly observ e the contractility behavior of the extraocular muscles. This noninvas ive technique was applied to the study of patients with horizontal rec tus muscle palsies. In all cases, the palsied muscle was of a smaller diameter than its normal counterpart. This size differential was noted in all fields of gaze. Additional studies are required to determine t he relative contributions of denervation atrophy and loss of tonus to this diminution of muscle size.