Congenital restrictive strabismus associated with anomalous orbital structures: MRI findings and clinical characteristics.

PURPOSE To evaluate and classify the magnetic resonance imaging (MRI) features of anomalous orbital structures (AOS) and correlate these findings with clinical manifestations. DESIGN Retrospective, observational case series. METHODS The detailed clinical data from 35 patients diagnosed with congenital restrictive strabismus and AOS were retrospectively reviewed between July 2010 and October 2024. All patients underwent brain stem and intraorbital MRI. MAIN OUTCOME MEASURES The morphological features of AOS, extraocular muscles (EOMs), and ocular motor nerves were examined. RESULTS This retrospective study included 35 cases (21 males and 14 females). The mean ± SEM age was 6.9 ± 0.8 years (range: 2-22 years). Sixteen patients had right-eye involvement, and 19 had left-eye involvement. AOS were categorized into three types: Type 1, discrete anomalous bands extending from the rectus muscles to the posterior sclera (25.7%), with the inferior rectus (IR) being the most affected; Type 2 refers to anomalous connections observed between the extraocular muscles (EOMs) (65.7%), often occurring in the area between the superior rectus (SR) and medial rectus (MR); Type 3, abnormal connection between the posterior sclera and the surrounding optic nerve sheath and extending to the equatorial region of the globe (8.6%). Varying degrees of restricted eye movements and strabismus were observed in all patients. Most patients also exhibited amblyopia and eyelid malposition in the affected eye. CONCLUSIONS Discrete anomalous bands most commonly involve the IR, while abnormal EOM connections primarily occur between the SR and MR. Eyelid malposition could suggests the possible presence of AOS.