Aplasia of the inferior rectus muscle. A case report and review of the literature.

Purpose: The authors describe the clinical findings, results of preoperative radiologic studies, and results of surgery in a boy with congenital unilateral inferior rectus aplasia.

Methods: A 2-year-old boy is described who presented with a significant anomalous head posture, a large incomitant vertical deviation with marked deficit of depression of the left eye, and positive head-tilt test results. Preoperative magnetic resonance imaging (MRI) defined an absent inferior rectus muscle; computed tomography showed no evidence of a craniofacial syndrome. Full tendon inferior transposition of the horizontal rectus muscles was carried out on the affected eye.

Results: The compensatory head position was eliminated. The infraduction improved. The patient had a small left hypotropia after the healing phase.

Conclusions: To the authors' knowledge, this case is the first that used MRI to confirm preoperatively the isolated absence of an inferior rectus muscle. The MRI allowed effective surgical planning to correct the congenital abnormality.