Magnetic resonance imaging (MRI) in Duane retraction syndrome

Purpose: To study the magnetic resonance imaging (MRI) findings in Duane retraction syndrome (DRS). Materials and Methods: In this case–control study, 16 consecutive cases of Duane syndrome underwent MRI of the brain and orbit, after informed consent. MRI (fast imaging enhancing state acquisition) was done with special focus on pontomedullary junction to look for the status of abducens nerve and associated abnormalities along with quasi-coronal sections of orbit to estimate thickness and cross sectional area of horizontal extra-ocular muscles (EOMs). Thickness and cross-sectional area of EOMs were compared to the contralateral side and to age-matched controls. Results: Of 16 cases, 14 had DRS Type I, and 2 had DRS Type II. MRI revealed absent abducens nerve on the ipsilesional side in 12 out of 14 in DRS I, whereas two DRS II patients revealed intact abducens nerve on the affected side. Thickness and cross-sectional area of the horizontal recti was statistically comparable to the contralateral side and age-matched controls. Conclusions: All the DRS patients in study had structurally normal horizontal recti muscles, whereas 12 out of 14 of DRS-I patients had an absent abducens nerve on MRI