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Marcus Gunn, syndrome
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(Gunn syndrome, Jaw-Winking syndrome, maxillopalpebral-ptosis synkinesis)
Unilateral ptosis associated with a mandibulopalpebral synkinesis (that can give a picture of blepharophimosis during feeding). It is the cause of 5% of unilateral ptosis of the newborn. Autosomal dominant transmission with variable penetrance. The diagnosis is made clinically: the ptotic eyelid elevates when the mouth opens or on lateral movement of the lower jaw. This mechanical anomaly could be due to a disorder of innervation from the trigeminal nerve: fibers intended to innervate the external pterygoid muscle, in fact innervate the levator muscle of the eyelid which is normally innervated by the facial nerve.
Many eye anomalies can be associated: amblyopia, strabismus, anisometropia. This syndrome is sometimes associated with CHARGE or Duane syndrome.
In case of closure of the eyelid during the opening of the mouth, one speaks of:
- reverse Marcus Gunn phenomenon when there is a paralysis of the levator muscle of the eyelid (25% of cases).
- Marin-Amat syndrome when there is a sequel of facial palsy without impairment of ocular innervation; however, a few congenital cases associated with partial duplication of 12q have been reported.
Anesthetic implications:
a few cases of oculocardiac reflex during handling of the ptotic eyelid have been reported. Susceptibility to malignant hyperthermia has been suggested based on histological examination of the involved muscles but has not been confirmed by any clinical case (nor genetically).
References :
Updated: December 2016