Duane Syndrome
- Congenital malformation of the sixth nerve nucleus with disturbed innervation of the extraocular muscles
- Absence of axons destined for the lateral rectus muscle with preservation of axons destined for the medial longitudinal fasciculus
- Axons from the ipsilateral third nerve nucleus sprout into the sixth nerve to innervate the lateral rectus muscle (“dysinnervation,” “miswiring”)
- Pattern of misalignment varies according to the type of miswiring
- Diplopia is not prominent—it is intermittent or even absent
- Face turn toward the lesioned side is common
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Duane syndrome Type 1 has the following features
- Abduction deficit
- Esotropia
- Narrowing of the palpebral fissure height with adduction of the affected eye
- Upshoot or downshoot of the adducting eye (sometimes)
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Duane syndrome Type 2 has the following features
- Adduction deficit
- Exotropia
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Duane syndrome Type 3 has the following features
- Abduction and adduction deficits
- Esotropia in ipsilateral gaze, exotropia in contralateral gaze
- Acquired sixth nerve palsy
- Orbital restrictive syndrome
- Myasthenia gravis
- Spasm of the near reflex
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Tip: most patients with these four acquired causes of an abduction deficit will report diplopia; patients with Duane syndrome rarely report diplopia, probably because the lesion is congenital and they have suppressed the image from the deviating eye
- Look for narrowing of the palpebral fissure on adduction of the affected eye
- Look for upshoot or downshoot on adduction of the affected eye
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Tip: ask to look at childhood photographs, which may disclose a face turn and/or eye misalignment
- Extraocular muscle surgery is indicated for a face turn
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Trap: patients with Duane syndrome are often misdiagnosed as having an acquired abduction deficit, triggering unnecessary investigations and inappropriate work waivers