A Novel Co-occurrence of Jaw-Winking Ptosis and Duane-Like Synkinesis in Möbius Sequence.

Abstract

To the Editor: A 5-y-old child presented with a history of bilateral foot deformity since birth. There was difficulty in breast feeding due to poor sucking and developmental delay. Examination showed masklike dysmorphic facies (Fig. 1a). Associated anomalies were high arched palate, clinodactyly, micrognathia, fissured tongue and bilateral equinocavo-varus foot deformity (Fig. 1b). Ocular examination showed telecanthus with anti-mongoloid slanting of palpebral fissures. There were synkinetic eyelid movements accompanying jaw movements (Marcus-Gunn phenomenon) in the right eye (Fig. 1a). Ocular motility examination showed limitation of abduction in both the eyes and elevation in the right eye. The left eye showed an upshoot on attempted adduction simulating a Duane-like synkinesis. Corneal sensations were diminished in both the eyes with minimal lagophthalmos and exposure keratopathy in the left eye. A diagnosis of Mobius syndrome with various cranial nerve involvements was made. Mobius sequence is a rare congenital cranial dysinnervation disorder (CCDD) with multiple malformations that commonly affects cranial nerves V, VI, VII, IX and XII. The etiology is unclear but genetic, teratogenic and ischemic factors affecting the development of cranial nerve nuclei are thought to be involved [1]. It is now considered a developmental disorder of the brainstem rather than isolated cranial nerve pathology. The explanation of Duane-like synkinesis in these Mobiustype patients raises the possibility of abnormal innervation of the lateral rectus or misinnervation at the medial longitudinal fasciculus [2]. Although there are many case reports of cooccurrence of congenital fibrosis of extraocular muscles (CFEOM) with Marcus Gunn phenomenon; this association with Mobius sequence has not been reported previously. It has become evident that mutations in genes such as ARIX, SALL4, and KIF21A that are important in motoneuronal development can result in well-delineated abnormalities of ocular motility or complex syndromes in which multiple cranial nerves are dysfunctional from birth [3, 4]. However genetic testing was not done in the patient as the facilities were not available in our institute. The child had synkinetic eyelid movements accompanying the jaw and ocular movements suggesting that the various synkinesia may represent a common etiology of aberrant innervations of the cranial nerves in Mobius syndrome. This case expands the ocular phenotype of Mobius sequence and suggests a commonality in the pathogenesis of these congenital conditions.