Walsh & Hoyt: Anomalies of Extraocular Muscle Location

An abnormal insertion of an extraocular muscle is occasionally responsible for ocular motor dysfunction. In its mildest form, this may simply occur as a bifid insertion of the medial, lateral, or superior rectus muscles. The insertions of the superior and inferior oblique muscles vary widely, so it is often difficult to state when they are truly abnormal. Nevertheless, in some patients, the insertions of one or the other of these muscles are clearly abnormal. For example, the superior oblique tendon may insert on the undersurface of the superior rectus muscle, or the inferior oblique tendon may be attached to the lateral rectus muscle. The insertions of the four rectus muscles are much less variable, and thus abnormal insertions are more easily recognized. Strebel described monozygotic twins with fusion of the tendons of the superior and medial recti. Abnormal insertions of extraocular muscles, like agenesis of the muscles, often occur in children with craniostenosis.