Successful Outcome of Two-Stage Strabismus Surgery in a Rare Case of Unilateral Möbius Syndrome: A Case Report.

Möbius syndrome (MBS) is a rare congenital disorder characterized by facial and abducens palsy which is usually bilateral and may involve multiple cranial nerves. Additional features, such as craniofacial anomalies, tongue malformations, and limb defects, may also be present. The etiology of this syndrome is not well established but the ischemic necrosis of the brainstem leading to hypoplasia of the cranial nerve nuclei is the supposed to be most likely one. MBS leads to a large angle esotropia along with bilateral limitation of abduction with delayed diagnosis, which is very challenging to correct with a single procedure. There are only a few reports illustrating the surgical outcome of strabismus in MBS. In this case report, we describe an unusual case of unilateral MBS who presented with large esotropia since childhood and was managed by two-stage strabismus surgery, including unilateral medial rectus (MR) muscle recession followed by vertical recti transposition. The final primary position alignment was satisfactory. Therefore, MR muscle recession alone is an effective first procedure of choice for mild-to-moderate esotropia in patients with MBS, whereas severe cases may further require the transposition of vertical recti. As it is a congenital condition, early surgical intervention may prevent amblyopia and provide an opportunity for the development of binocular single vision. Hence, prompt diagnosis and early surgical intervention are of utmost importance in these cases.