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Duane Syndrome

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Title: Duane Syndrome
Author: Kerri McInnis-Smith, 4th year medical student, Mayo Clinic
Photographer: Dr. Marielle Young
Date: 7/14/2022

Keywords/Main Subjects: Strabismus, Duane Syndrome, Esotropia

Diagnosis: Duane Syndrome

Images or video:

Description of Case: Duane Syndrome, also known as Duane Retraction Syndrome (DRS), is a form of childhood strabismus characterized by globe retraction and palpebral fissure narrowing on attempted adduction.

Epidemiology: The prevalence of DRS in the general population is relatively low, affecting around 1/1000 individuals and accounting for <5% of all strabismus cases.¹ Only one eye is involved in most cases, although up to 20% of affected patients may have bilateral involvement.² For reasons that remain unclear, female patients are more commonly affected (60%) by DRS than male patients (40%) and the left eye is involved more often than the right eye.^1,2 There is osme thought that the unilateral, left-sided, and female predominance could be due to the asymmetry in the thoracic anatomy and thrombosis risk factors.³

Pathophysiology: DRS is caused by abnormal (and sometimes absent) development of the abducens nerve (CN VI) between weeks 4-8 of embryological development. Occasionally, the lateral rectus muscle may receive aberrant innervation from the oculomotor nerve (CN III), contributing to concurrent horizontal recti action and subsequent globe retraction.⁴ Most cases (70%) of DRS are isolated to the below ocular findings, while around 30% are associated with additional ophthalmologic or systemic abnormalities. Some associated conditions include:^2,5,6

• Okihiro’s syndrome: DRS + radial ray defects
• Wildervanck syndrome: DRS + Klippel-Feil anomaly + deafness
• Moebius syndrome: DRS + congenital facial palsy
• Hold-Oram syndrome: DRS + abnormalities of upper limbs and heart
• Morning Glory syndrome: abnormalities of optic disc
• Goldenhar syndrome: abnormalities eye, ear and spine

Risk factors: Although DRS occurs spontaneously in approximately 90% of isolated cases, around 10% of isolated cases are inherited.⁷ The only known risk factor for development of the condition is an affected biological parent. Various genes have been implicated in the inheritance of DRS, including mutations at locus 8q13 and in CHN1 on chromosome 2. Both autosomal dominant and autosomal recessive inheritance patterns have been demonstrated.^2,5

Signs and symptoms:

• Complete or partial absence of abduction and/or adduction
• Retraction of globe on attempted adduction
• Narrowing of palpebral fissure on attempted adduction (induced ptosis)
• Abnormal head position (to compensate for duction deficit and maintain binocular single vision)
• Upshoots or downshoots (43% of cases²): affected eye deviates up/down with attempted adduction
  • May occur secondary to mechanical effect (tight fibrotic muscles) or innervational anomalies²

Diagnosis: Diagnosis of DRS is typically made on clinical grounds alone, with additional imaging usually not necessary. Genetic testing may be pursued if familial inheritance is suspected.

Subtypes: Multiple criteria have been proposed to classify DRS according to clinical signs and symptoms. The most popular classification system, proposed by Huber et al, consists of 3 distinct subtypes:¹

• Type I DRS (75-80%): mainly defective abduction, with normal or minimally defective adduction
  • Esotropia in primary gaze  compensatory head turn toward involved side
• Type II DRS (5-10%): mainly defective adduction, with normal or minimally defective abduction
  • Exotropia in primary gaze  compensatory head turn toward uninvolved side
• Type III DRS (10-20%): defective in both abduction and adduction

Individuals can also be sub-grouped according to their deviation in primary position, including esotropic DRS (eso-DRS), exotropic DRS (exo-DRS), and orthotropic DRS (exo-DRS).¹ These two systems of classifying DRS can be helpful in the decision of whether to manage conservatively or surgically.

Differential diagnosis:^5,7

• Abducens nerve palsy
• Congenital esotropia
• Brown Syndrome
• Marcus Gunn Jaw Winking Syndrome
• One of the associated systemic conditions mentioned above (Okihiro’s syndrome, Goldenhar syndrome, Wildervanck syndrome, Moebius syndrome, Holt-Oram syndrome, Morning Glory syndrome)

Management:

• Non-surgical: Not all individuals with DRS require surgical intervention. Conservative measures, such as observation, refractive correction, or prism glasses to improve abnormal head position are often sufficient to manage symptoms. Young patients should undergo repeat ophthalmology exams to assess for amblyopia. However, once a patient is not at a significant risk of developing amblyopia (around age 10), exams can occur less frequently.²
• Surgical: A subset of patients with DRS (estimated around 41%¹) will progress to requiring surgical intervention. There are four generally accepted indications for which extraocular muscle surgery should be considered:¹
  1. Significant abnormal head posture
  2. Significant deviation in primary position
  3. Severely abnormal eyelid position (retraction and narrowing of palpebral fissure)
  4. Significant upshoot or downshoot during adduction

The exact surgical approach is dependent on the patient’s symptoms, deviation in primary position, and specific duction deficits, but often consists of medial or lateral rectus recession and/or transposition of one or two vertical rectus muscles. Globe retraction can be improved via recessions of the co-contracting horizontal recti muscles.¹

Potential complications: Although isolated DRS is not associated with severe complications, up to 10% of patients may develop amblyopia, especially without regular ophthalmologic exams.¹

References:

1. Gaballah KA. Treatment modalities in Duane’s Retraction Syndrome. Int J Ophthalmol. 2020 Feb 18;13(2):278–83.
2. Kekunnaya R, Negalur M. Duane retraction syndrome: causes, effects and management strategies. Clin Ophthalmol. 2017 Oct;Volume 11:1917–30.
3. Parsa CF, Robert MP. Thromboembolism and Congenital Malformations: From Duane Syndrome to Thalidomide Embryopathy. JAMA Ophthalmol. 2013 Apr 1;131(4):439.
4. Hoyt W, Nachtigäller H. Anomalies of ocular motor nerves: Neuroanatomic correlates of paradoxical innervation in Duane’s syndrome and related congenital ocular motor disorders. Am J Ophthalmol. 1965 Sep;60(3):443–8.
5. Graeber CP, Hunter DG, Engle EC. The Genetic Basis of Incomitant Strabismus: Consolidation of the Current Knowledge of the Genetic Foundations of Disease. Semin Ophthalmol. 2013 Sep;28(5–6):427–37.
6. Kirkham TH. Duane’s syndrome and familial perceptive deafness. Br J Ophthalmol. 1969 May 1;53(5):335–9.
7. Gaur N, Sharma P. Management of Duane retraction syndrome: A simplified approach. Indian J Ophthalmol. 2019;67(1):16.

Faculty Approval by: Marielle Young, MD

Identifier: Moran_CORE_127212

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