Surgical Management of Duane Syndrome

Duane retraction syndrome (DRS) is best thought of as a special type of ocular dysmotility caused by improper innervation, or dysinnervation, of one or more extraocular muscles. A classification scheme for DRS is established in the literature; however, variability of dysinnervation results in a spectrum of clinical presentation. Successful management of DRS requires disciplined evaluation of ocular motility, thoughtful surgical decision-making (including whether or not to intervene) and skillful management of patient expectations of surgical outcomes.

Etiology

DRS is congenital and believed to be caused by the maldevelopment of the abducens nerve (CN VI). Hypoplasia of the motor neurons in the CN VI nucleus occurs with sparing of the internuclear neurons, resulting in an ipsilateral abduction deficit. Magnetic resonance imaging of the brainstem and orbits has revealed small or absent CN VI nuclei, with dysinnervation of the lateral rectus muscle (LR) by branches of the oculomotor nerve (CN III) from both the inferior and superior divisions.^1,2 The extent of relative LR paresis versus dysinnervation determines the type of DRS and associated features.

DRS and congenital cranial dysinnervation disorders

DRS should be viewed within the larger context of cranial nerve maldevelopment and dysinnervation. Thus syndromes as varied as DRS, congenital fibrosis of the extraocular muscles, Moebius syndrome, monocular elevation deficiency, congenital ptosis and congenital CN III, CN IV and trochlear nerve pareses are nosologically related, sharing an abnormality in interdependent cranial nerve and muscle development, with varying degrees of dysinnervation.^3,4 With this understanding, the clinician can more easily recognize the spectrum of the dysinnervation syndromes and not be surprised by patients with "atypical Duane syndrome."

Clinical findings

Although clinical presentation can vary, DRS usually presents with characteristic ocular motility disturbances. Horizontal duction deficit is most often a limitation of abduction, depending on the relative degree of LR dysinnervation. Therefore, DRS usually presents with an esotropic deviation and/or an ipsilateral compensatory face turn. However, DRS can present with exotropia, hypertropia or orthotropia. Co-innervation of CN III to the LR and medial rectus muscle (MR) can result in globe retraction, which is easily recognized as a narrowing of the palpebral fissure in attempted adduction. Similarly, the aberrantly innervated LR (and occasionally the vertical rectus muscles) can contract during adduction, causing oblique eye movements commonly referred to as up-shoots and down-shoots. Huber originally proposed a classification scheme of DRS based on electromyography of the extraocular muscles.⁵

DRS Classification

Adapted from Teed RGW, Saunders RA. Diagnosis and Surgical Management of Ocular Motility Syndromes. In: Wilson ME, Trivedi RH, Saunders RA, eds. Pediatric Ophthalmology Current Thought and A Practical Guide. Leipzig, Germany: Springer-Verlag Berlin Heidelberg; 2008:193-212.

DRS Management

The surgeon and DRS patient must recognize that restoring normal ocular motility is an unrealistic goal. The best management is often observation. A small compensatory face turn, allowing for sensory fusion, is an acceptable endpoint. Surgical intervention is indicated in patients with a manifest deviation in primary-gaze position, a large face turn, severe globe retraction or large up- and down-shoots.

Surgical Planning for DRS with deviation and/or compensatory face turn

Adapted from Teed RGW, Saunders RA. Diagnosis and Surgical Management of Ocular Motility Syndromes. In: Wilson ME, Trivedi RH, Saunders RA, eds. Pediatric Ophthalmology: Current Thought and A Practical Guide. Leipzig, Germany: Springer-Verlag Berlin Heidelberg; 2008:193-212.

Management of Associated Features of DRS Patients

Adapted from Teed RGW, Saunders RA. Diagnosis and Surgical Management of Ocular Motility Syndromes. In: Wilson ME, Trivedi RH, Saunders RA, eds. Pediatric Ophthalmology: Current Thought And a Practical Guide. Leipzig, Germany: Springer-Verlag Berlin Heidelberg; 2008:193-212.

Special considerations

In most cases of DRS, a moderate recession of the antagonist rectus muscle yields acceptable results. Certain cases can be challenging, however, and require more complex management. The surgeon must recognize that the relative dysinnervation (and resultant tonic activity) of the affected LR will influence the operative result. For example, a large recession of the ipsilateral MR in Type I DRS can cause an unacceptable adduction deficit. For this reason, ipsilateral MR recessions greater than 6mm should generally be avoided, particularly in patients with co-contraction.

Bilateral MR recession can be effective at increasing the field of single binocular vision.^7,8 In these cases, the contralateral MR can be recessed more than the ipsilateral MR. However, surgery on the contralateral MR will be less useful if the affected LR has little normal function. In cases with a small angle esotropia and a large abduction deficit, the surgeon may want to avoid the contralateral MR.⁹

Classic teaching prohibits rectus muscle resection in DRS. Indeed, tightening the dysinnervated LR will likely worsen globe retraction. However, resection procedures can be helpful in certain cases. In patients with small-angle esotropia and poor abduction but only mild globe retraction, an ipsilateral MR recession and a small LR resection can yield good results.¹⁰

Vertical rectus muscle transposition (VRT) can be quite effective, particularly for treatingType I DRS with poor abduction. However, VRT can worsen globe retraction and can cause postoperative vertical strabismus. VRT should be considered for patients with Type I DRS that  resembles CN IV palsy with minimal associated features.

References

1. Demer JL, Clark RA, Lim KH, Engle EC. Magnetic resonance imaging of innervational and extraocular muscle abnormalities in Duane-radial Ray syndrome. Invest Ophthalmol Vis Sci. 2007;48(12):5505-5511.
2. Yonghong J, Kanxing Z, Zhenchang W, et al. Detailed magnetic resonance imaging findings of the ocular motor nerves in Duane's retraction syndrome. J Pediatr Ophthalmol Strabismus. 2009;46(5):278-285.
3. Traboulsi EI. Congenital abnormalities of cranial nerve development: overview, molecular mechanisms, and further evidence of heterogeneity and complexity of syndromes with congenital limitation of eye movements. Trans Am Ophthalmol Soc. 2004;102:373-389.
4. Traboulsi EI. Congenital cranial dysinnervation disorders and more. J AAPOS. 2007;11(3):215-217.
5. Huber A. Electrophysiology of the retraction syndromes. Br J Ophthalmol. 1974;58(3):293-300.
6. Denis D, Dauletbekov D, Girard N. Duane retraction syndrome: Type II with severe abducens nerve hypoplasia on magnetic resonance imaging. J AAPOS. 2008;12(1):91-93.
7. Saunders RA, Wilson ME, Bluestein EC, Sinatra RB. Surgery on the normal eye in Duane retraction syndrome. J Pediatr Ophthalmol Strabismus. 1994;31(3):162-169.
8. Farvardin M, Rad AH, Ashrafzadeh A. Results of bilateral medial rectus muscle recession in unilateral esotropia Duane syndrome. J AAPOS. 2009;13(4):339-342.
9. Archer SM. Contralateral medial rectus muscle recession in patients with Duane syndrome. J AAPOS. 2004;8(3):296.
10. Morad Y, Kraft S, Mim JL 3rd. Unilateral recession and resection in Duane syndrome. J AAPOS. 2001;5(3):158-163.