Ptosis and Rhythmic Eye Movement in a Young Child

Answer: Marcus Gunn syndrome
 

The patient was given an initial diagnosis of Marcus Gunn syndrome and was referred for further evaluation with an ophthalmologist at 6 months of age. The patient’s ankyloglossia was causing poor elevation of tongue, worsening his difficulty with feeding. He was treated with a lingual frenotomy during this visit and referred to an occupational therapist.

Discussion
Marcus Gunn syndrome is a rare form of congenital ptosis. It was first reported in 1883 by Scottish ophthalmologist Robert Marcus Gunn, MA, MBEdin, FRCSEng, who defined the condition as “a unilateral ptosis present at birth with an associated winking reflex in response to jaw movement.”¹ Recent literature states that the etiology of the condition may be caused by abnormal connections between the trigeminal mesencephalic nucleus and the superior division of the oculomotor nucleus.² The motor fibers of the mandibular branch of the trigeminal nerve normally innervate the lateral pterygoid, but the aberrant connections can cause the trigeminal nerve to indirectly innervate the levator palpebrae superioris, resulting in eyelid retraction.^3,4 The synkinetic elevation of the eyelid with a variety of jaw movements is commonly referred to as the “wink phenomenon.”⁵

The defining feature of Marcus Gunn syndrome compared to other congenital blepharoptosis is the synchronous movement of the jaw and eyelid.⁶ Recent studies have found the prevalence of Marcus Gunn syndrome to be 8.5% of all congenital ptosis cases.⁷ The syndrome is typically found sporadically in nature; however, some cases of autosomal dominant inheritance have been reported.^2,8 The left eye is typically more affected in this disorder than the right, with bilateral cases rarely being reported.^3,9

For patients with Marcus Gunn syndrome, early detection and referral is important. The lack of information given to general pediatricians about the disease, coupled with its often subtle physical findings, allow the disease to go undiagnosed for extended periods. A proper clinical examination to rule out other ocular deformities and diagnose Marcus Gunn syndrome includes, but is not limited to, evaluating the patient for unilateral blepharoptosis, upper eyelid movement with opening of the jaw, and hypotropia.⁴ This “wink phenomenon” is unique to Marcus Gunn syndrome and can help pediatricians recognize the diagnosis early.

Without an early diagnosis, patients are at increased risk of developing secondary complications, which is the main cause of morbidity in this condition. Specifically, the ocular abnormalities found in Marcus Gunn syndrome, including ptosis and strabismus, can lead to amblyopia, a disorder where the brain fails to process information from one of the eyes. If left untreated, this can lead to a permanent decrease in vision. Varying incidences of amblyopia for patients with Marcus Gunn syndrome have been reported; studies have found incidences ranging from 34% to 59%.^10,11 These significant numbers, combined with the irreversibility of the condition, show the importance of early screening and detection.

Treatment and management
The primary management of patients with Marcus Gunn syndrome is to first address associated ocular or physical conditions, such as correcting anisometropia or using occlusion therapy for amblyopia. After this is accomplished, most cases are managed conservatively with frequent monitoring, and symptoms usually lessen as the patient ages.¹² Surgery is recommended for patients whose symptoms do not significantly improve over time; however, there is controversy over which procedure should be performed, and recommendations can vary based on the age of the patient and the severity of the condition.^4,13 For patients with severe ptosis, the most common surgical procedure is bilateral levator excision with bilateral frontalis sling.¹³ In this approach, bilateral levator muscles are dissected and autogenous fascia lata is used as a sling to suspend the eyelid to the brow. The sling transfers the elevating function of the frontalis muscle to the ptotic eyelid.¹⁴ This procedure results in a symmetrical lid position in primary gaze and downgaze.¹³

Patient outcome
Our patient underwent ophthalmology evaluation at 5 months of age that confirmed the diagnosis of Marcus Gunn syndrome. During this examination, the patient showed no signs of amblyopia or strabismus but did have mild hyperopic refraction, which is normal for his age. A conservative management approach by active monitoring of the patient’s ocular symptoms was recommended. His follow-up ophthalmology appointment at 8 months of age did not show any significant changes. The patient was eating well and developing appropriately. He showed no signs of amblyopia, and no changes were made to his treatment plan.

Conclusion
Marcus Gunn syndrome is an uncommon pediatric ophthalmic condition where abnormal neurological developments lead to a congenital ptosis associated with a winking motion that occurs simultaneously with jaw movement. This condition remains relatively rare in the field of general pediatrics, but it is important to recognize and treat early because of its potential for severe complications. These complications, including blindness, may be prevented with interdisciplinary care and correct management.