To our knowledge, congenital bilateral trigemino-abducens synkinesis has not previously been reported. Herein we report a case in which ipsilateral jaw movement occurred.
A 21-year-old man had ipsilateral jaw movement associated with abduction of either eye. The patient had been aware of this phenomenon since early childhood. He was a term infant with a normal vaginal delivery and had no dysmorphic features or developmental delay. There was neither history of orbital or ocular trauma, strabismus, or amblyopia nor family history of a similar phenomenon. On examination, his visual acuity was 6/6 OU and his pupils were 3 mm equal and reactive to light and accommodation. Extraocular movements were full with no nystagmus or widening or narrowing of the palpebral fissures in any position of gaze. On abduction to the left or right, subtle ipsilateral jaw movement was noted (Figure 1). Findings from neurological examination were normal and electomyographic study demonstrated that abduction of the eyes produced ipsilateral masseter and pterygoid activity.
A, Patient looking to the left. B, Patient looking to the right.
Freedman and Kushner1 documented that congenital ocular aberrant innervations are more common than previously described and exist in many varieties. Ocular "miswirings" typically involve the sixth nerve and the most recognized clinical entities are Duane syndrome and Marcus Gunn jaw-winking ptosis.
We believe we have now presented the first case of congenital bilateral trigemino-abducens synkinesis. Furthermore, ocular abduction producing ipsilateral masseter and pterygoid activity is contrary to previously reported cases in which jaw movement produced abduction of the eye. Kodsi2 described a 4-year-old girl who exhibited a right intermittent exotropia with mouth opening and chewing movement from birth and McGovern et al3 documented a case of acquired right trigemino-abducens synkinesis following a major head trauma from a motor vehicle crash.
Freedman and Kushner1 hypothesized that trigemino-abducens sykinesis may be due to abnormal sykinesis between the abducens nerve controlling the lateral rectus muscle and the mandibular division of the trigeminal nerve controlling muscles of mastication, including the masseter and pterygoid muscles. The etiology of congenital aberrant innervations involving the nucleus of the abducens nerve may be due to abnormal development and degeneration of the abducens nerve fibers during embryologic development that leads to central or peripheral miswiring. The exact reasons for the common involvement of the abducens nerve and nucleus with aberrant innervation are unknown. The abducens nerve fibers and nucleus develop earlier than the fibers and nuclei of the oculomotor and trochlear nerves, and subsequent degeneration of the caudal branches may lead to the development of abnormal abducens nerve connections, either in the brainstem or peripherally. An abnormal wiring pattern of abducens nerve fibers to the adjacent trigeminal nerves and nuclei in the brainstem could account for the clinical findings of trigemino-abducens synkinesis. On the other hand, miswiring may also result from a peripheral cause. Embryonic nerves are attracted to developing mesenchyme and muscle masses during development and inappropriate attraction of a cranial nerve branch to an extraocular muscle may lead to aberrant ocular innervation.1
Our case further supports the findings of Freedman and Kushner1 that congenital ocular aberrant innervation may be more common than previously reported and highlights the importance of diagnosing bilateral trigemino-abducens synkinesis and its many varieties.
The authors have no relevant financial interest in this article.
Corresponding author and reprints: Dinesh Selva, FRANZO, Oculoplastic& Orbital Unit, Department of Ophthalmology, Royal Adelaide Hospital, North Terrace, Adelaide, South Australia 5000 (e-mail: firstname.lastname@example.org).
Lai T, Chen C, Selva D. Bilateral Congenital Trigemino-abducens Synkinesis. Arch Ophthalmol. 2003;121(12):1796-1797. doi:10.1001/archopht.121.12.1796