Successful Surgical Outcomes in Medial Rectus Muscle Injury Manifesting as Strabismus and Mimicking Medial Rectus Loss from MRI Findings

Abstract

Introduction: Although rare, damage to the medial rectus muscle can be a serious and life-altering consequence of FESS, often presenting significant difficulties in both diagnosis and treatment. In one instance, a 53-year-old female patient reported a persistent outward deviation of her right eye that began following a sinus operation conducted a year prior. Visual acuity of the right eye was 4/60. Krimsky test showed 115 PDBI far, near upgaze and down gaze, 65 PDBI right gaze, >115 PDBI left gaze, with restriction of ocular motility of the right eye. MRI revealed detachment of the right musculus rectus medialis from its insertion in the right bulbus oculi by +/- 0.9cm posteromedially, causing abduction of the right bulbus oculi laterally. FDT examination did not find any restriction. Discussion: Following FESS, limitations in eye movement can result either from the entrapment of an extraocular muscle in a bony defect or from disruption of the muscle’s blood supply or innervation. In this particular case, the preserved but significantly weakened and non-functional medial rectus tendon suggests that neurovascular compromise is the most plausible cause, leading to impaired inward movement of the eye. To restore proper ocular alignment, surgical intervention for strabismus may be necessary. While clinical evaluation and imaging techniques offer valuable insights into the cause of outward eye deviation after FESS, definitive diagnosis may ultimately depend on findings during surgical assessment.