Teaching Case

A 9-month-old male patient, a full-term newborn with adequate birth weight, had prenatal exposure to misoprostol in the 3rd week of pregnancy. In follow-up by neuropediatric and ophthalmology due to right facial palsy and palsy of the VI cranial nerve. A contrasted brain MRI with emphasis on cranial nerves was obtained.

Contrast-enhanced brain MRI is obtained under general anaesthesia, with emphasis on the posterior fossa. There is absence of the nuclei of the VII cranial nerve, which configures the "horseshoe" shape of the 4th ventricle (Figure 1). Asymmetry of the left external rectus compared with the right (Figure 2A). In the volumetric T2 sequences of the posterior fossa, the facial nerves (cisternal and intracanalicular portion) and the absence of the VI cranial nerve are not identified (Figure 2B). The left sixth cranial nerve is absent in its cisternal portion (Figure 2B). Absence of the VII cranial nerve (Figure 3A). These findings and the symptoms confirm the diagnosis of Moebius syndrome due to exposure to misoprostol.

Moebius syndrome, also known as congenital facial diplegia, is a rare congenital pathology characterized by the absence of the nuclei of the abducens nerve [VI cranial nerve] and the facial nerve [VII cranial nerve] [1]. It is also associated with abnormalities in the extremities, chest wall, spinal cord, and soft tissues [2]. Ischemia of the midbrain during embryogenesis is the most accepted theory. The hypoxia of the dorsomedial aspect of the embryonic branches of the basilar artery are very vulnerable to hypoxic-ischemic injury. This probably explains the association between the use of misoprostol, which causes bleeding, and uterine contraction [3].

High-resolution cisternography sequences MRI, best demonstrate the absence or hypoplasia of cranial nerves VI and VII.

The most common MRI findings are agenesis of cranial nerves, malformations of the posterior fossa [horseshoe shape of the 4th ventricle], and pons hypoplasia [4].

This syndrome should always be suspected when the mother has consumed misoprostol; in addition, it is important to recognize the disease early in order to initiate facial mimicry therapies and, on some occasions, lead to plastic surgery to attempt to recover facial muscles function [5].

Written informed patient consent for publication has been obtained.