Bilateral familial vertical Duane Syndrome with synergistic convergence, aberrant trigeminal innervation, and facial hypoplasia.

A 5-year-old girl presented with bilateral familial vertical Duane retraction syndrome with alternating esotropia, elevation deficit, Marcus gunn phenomenon, and facial hypoplasia. Abnormal adducting downshoots on attempting abduction suggestive of a synergistic convergence were noted. Hypothesis suggests aberrant innervations or peripheral anatomic connections between inferior and medial recti.

Introduction

Vertical Duane syndrome, a rare entity, has been described as limitation of the affected eye on elevation or depression associated with globe retraction and narrowing of the palpebral fissure.[1] Synergistic convergence, described as simultaneous bilateral adduction on attempted gaze into the field of action of the lateral rectus muscles, and facial hypoplasia have yet not been described in association with vertical Duane.[2]

Case Report

A 5-year-old girl presented with bilateral drooping of upper eyelids and inward deviation of either eye, with occasional crossing, since birth. There was no history of delayed milestones or any prior systemic illnesses. No prior history existed of spectacle prescription, occlusion therapy or surgical correction. Her father, three paternal uncles, and grandmother also had similar drooping. Her siblings were unaffected.

Ocular examination revealed a moderate compensatory head posture (chin elevation, right face turn, and mild head tilt to the right was noted). Mild facial hypoplasia of the right side with flattening of the right cheek and a broad nasal bridge was also present [Figure 1]. Visual acuity was 6/9 in both eyes (oculus uterque, OU). Cycloplegic refraction showed +0.5 Diopter sphere OU with an acceptance of 6/6. Gross stereopsis was absent, confirmed on titmus fly test. In primary gaze, on prism bar cover test, a large angle alternating esotropia of >90 PD, with V pattern, was noted at 33 and 6 m. Nystagmus was absent.

Figure 1

Bilateral severe congenital ptosis in a 5-year-old girl with facial hypoplasia Convergence is normal

She had bilateral, severe upper lid ptosis of 5 mm with poor levator action (4 mm) and absent Bells phenomenon. MRD 1 and 2 was 2 mm and 5 mm, respectively OU. There was limitation of elevation of both eyes [Figure 2]. The left eye showed mild down-shoot in abduction. The right eye assumed a downward and adducted position on attempted dextro-depression suggestive of synergistic convergence. Convergence was normal in the both eyes [Figure 1]. Narrowing of the palpebral fissure on both sides on adduction was noted [Figure 3]. The child also demonstrated Marcus Gunn jaw winking phenomenon on left side while chewing. Anterior segment, pupillary, and posterior segment examination were unremarkable. A diagnosis of bilateral familial vertical Duane with synergistic convergence, aberrant trigeminal innervation with bilateral severe complicated congenital ptosis with superior rectus weakness, and facial hypoplasia was made. Magnetic resonance imaging (MRI) brain and orbit was reported to be normal.

Figure 2

Nine gaze depiction of ocular motility shows limited elevation in both eyes. The right eye assumes a downward and adducted position on attempted dextrodepression suggestive of synergistic convergence whereas the left eye showed mild down-shoot in abduction

Figure 3

Classic narrowing of palpebral aperture on adduction of either eye is seen, typical of bilateral Duane retraction syndrome

Discussion

Vertical retraction syndrome or the vertical variant of Duane has long been described. DeRespinis et al. in 1993, in their review of patients with classic Duane retraction syndrome, reviewed this rare variation.[1] They described these patients to exhibit some degree of limitation of the affected eye on elevation or depression associated with globe retraction and narrowing of the palpebral fissure. Although not specifically mentioned by the authors, this is presumed to be on horizontal eye movements since palpebral aperture changes occur normally with vertical eye movements.

Since then many cases of spontaneous or familial vertical retraction, mostly unilateral, have been described.[34] Combined horizontal and vertical retraction syndrome has also been reported where the classical horizontal restrictions and retraction are concurrently seen with the vertical variant.[45] Familial and bilateral vertical retraction syndrome was first described by Khodadoust and von Noorden.[6] The syndrome is usually unilateral and sporadic. However, numerous cases of familial transmission have been reported with most being bilateral secondary to an autosomal-dominant inheritance pattern.[1]

Our patient presented with features of bilateral, familial vertical retraction with narrowing of palpebral apertures on adduction suggesting a diagnosis of Duane Syndrome. Although one may be tempted to consider congenital fibrosis of the extraocular muscles (CFEOM) to be the more likely diagnosis, features of globe retraction and palpebral aperture narrowing, point more in favor of Duane retraction. Association with blepharoptosis is seen here and has been frequently associated with Duane.[1] Also association of Duane retraction syndrome is seen with facial hypoplasia which has only once been described.[7]

Vertical retraction is also seen to be associated with atypical strabismus and various congenital abnormalities. Synergistic divergence is a well-established clinical condition in which abduction arises on attempted adduction, leading to simultaneous abduction of both eyes on lateral gaze. Synergistic Convergence, a very rare entity, is the opposite of Synergistic Divergence. It was first described by Kim et al. in a patient with congenital fibrosis of extra ocular muscles[2], as bilateral deficit of abduction associated with simultaneous bilateral adduction on attempted gaze into the field of action of the lateral rectus muscles. Later Christina Pieh et al. reported such an occurrence as an isolated finding.[8] Their patient had no globe retraction, ptosis, no extraocular muscle hypoplasia, and no family history to suggest the diagnosis of CFEOM or Duane as in our case. Aberrant innervation during embryogenesis was suggested as the underlying pathomechanism. It could be due to a pattern of aberrant innervation similar to that in Duane syndrome, which leads to synergistic divergence (type IV). However, instead of aberrant oculomotor nerve fibers, a mis-wiring of abducens motor neurons to the medial rectus muscle was suspected. If most of the abducens nerve fibers were misdirected to the medial rectus muscle, intended abduction would lead to adduction of the eye, and the co-contraction of the lateral and medial rectus muscles would result in globe retraction and eyelid fissure narrowing. An unusual congenital sixth-nerve palsy similar to congenital third-nerve palsies was considered as a cause of mis-wiring since congenital third-nerve palsies often occur with anomalous re-innervation and no other neurologic or systemic abnormalities. However, they also suggested that a misdirection of regenerated nerve fibers to a muscle originally innervated by a different cranial nerve is less probable than a primary aberrant abducens nerve innervation. Again in 2011, Jain et al. reported the existence of synergistic convergence as an ocular motor anomaly where on attempted abduction or on attempted horizontal gaze, both the eyes converge.[9] It was reported in association with kyphoscoliosis and brain stem dysplasia in two sisters.

Our case has features of globe retraction evidenced on narrowing of palpebral aperture on adduction and elevation deficit suggestive of vertical variant of Duane syndrome. Rarity lies in bilateral and familial nature of the case. It is unique in being associated with synergistic convergence, which, to the best of authors’ knowledge, has not been reported to be associated with the Duane retraction syndrome, let alone being associated with the vertical variant. Also authors differ slightly in defining synergisitic convergence as adduction downshoots on attempted abduction resulting from aberrant connections (anatomic or innervational) between inferior rectus (IR) and medial rectus (MR) muscles. IR over action secondary to superior rectus weakness, results in heightened innervations on attempted abduction where depressing function of IR is most prominent. This is also translated to the MR muscle which hypothetically bears aberrant (anatomic or innervational) connections to inferior rectus. This results in synergistic convergence.

Recent reports including imaging findings revealed that an accessory extraocular muscle or a fibrous band appeared to cause restriction on elevation and globe retraction in their cases.[10] We hypothesize that in our case, the deficiency of elevation was either due to bands in association with both inferior recti or aberrant innervations of medial rectus from branch of third nerve supplying inferior rectus. This can then result in adducting down shoots (field of action of medial rectus superimposed with inferior pull by inferior rectus) on attempted abduction (where vertical action of inferior rectus is highest). The reported case is atypical and the balance scale may bend toward a diagnosis of CFEOM with atypical findings of globe retraction on adduction. But the abnormal downshoots on attempted abduction and globe retraction are more commonly seen in Duane syndrome.

Synergistic convergence in itself is a very rare feature and a full understanding of its etiopathogenesis is beyond the scope of current literature reports. We recognize CFEOM and vertical Duane syndrome as being a continuum of extraocular muscle abnormalities and the diagnosis is an amalgamation of all relevant associations.