Strabismus alignment a surgical challenge

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Achieving alignment of strabismus can be difficult in children with syndromic craniosynostosis as the causes are multifactorial.

Dr. EdmondBy Cheryl Guttman Krader; Reviewed by Jane C. Edmond, MD

Houston-Children with syndromic craniosynostosis and strabismus are difficult to align.

Surgeons often need to combine several approaches to address the multiple abnormalities in these patients, said Jane C. Edmond, MD, associate professor of ophthalmology and pediatrics, Baylor College of Medicine, Cullen Eye Institute, Houston.

Patients with syndromic craniosynostosis characteristically have a V-pattern strabismus with a large exotropia on up gaze that diminishes in down gaze, she noted.

They have marked apparent overaction of the inferior oblique muscle(s) with possible underaction of the superior obliques, which causes a hypertropia, occuring ipsilateral to the coronal suture fusion.

“No one surgery is a perfect fit to treat all of these problems reliably, and surgeons should absolutely plan for the undercorrected,” Dr. Edmond said.

Multifactorial causes

Causes for classic strabismus in children with syndromic craniosynostosis are multifactorial. Coronal synostosis causes ipsilateral orbital extorsion and superior lateral orbit elongation, leading to globe extorsion with upward offset of the medial rectus and downward offset of the lateral rectus.

As a result, the medial rectus behaves like an elevator in adduction, and as a corollary, the lateral rectus muscle may be acting as a depressor in abduction. This simulates inferior oblique overaction.

In addition, superior orbital rim retrusion may lead to superior oblique trochlea retrusion resulting in superior oblique underaction and secondary inferior oblique overaction.

Overelevation in adduction may also be secondary to anomalous insertions or agenesis of extraocular muscles, particularly the superior rectus and the superior oblique.

Therefore, Dr. Edmond cautioned surgeons to provide clear instructions to the radiologist when ordering imaging in these children.

“Do not rely on the radiologist alone to identify these problems of the extraocular muscles without a specific request, and learn to read your own scans preoperatively,” she said.

Multiple options

Surgical procedures for addressing inferior oblique overaction strabismus include simple weakening of the muscle by myectomy or recession, which Dr. Edmond noted can provide good results in patients with isolated over-elevation in adduction.

However, it is not appropriate for more complex strabismus that is often found in patients with syndromic craniosynostosis.

Inferior oblique antero-positioning is an option for weakening treating the over-elevation in adduction. This procedure converts the inferior oblique to an antielevator in adduction, improves the V pattern by muscle weakening, and also improves excyclotorsion.

If done unilaterally it may induce anti-elevation syndrome, although that may be desirable, Dr. Edmond said.

Anterior and nasal inferior oblique transposition has also been performed in children with superior oblique agenesis, and it may be especially useful in patients with significant inferior oblique overaction.

This procedure converts the inferior oblique to an anti-elevator in adduction and an intorter. It improves the V pattern and excyclotorsion while also improving superior oblique underaction.

Vertical offsets of the medial and lateral recti is yet another option for surgical correction of the V pattern.

However, Dr. Edmond described it as a “wimpy” procedure and suggested it be used only as an adjunct and never as the primary method of correction of a V pattern in these patients.

“Vertical offset of the horizontal muscles reduces, but never eliminates, inferior oblique overaction or superior oblique underaction,” she explained. “While it improves the V pattern some, it unfortunately increases excyclotorsion.”

Superior oblique strengthening-a superior oblique tuck-offers one more option. Its benefits include reduction or elimination of overelevation and underdepression in adduction along with improvement of the V pattern and excyclotorsion.

However, it is suitable only for children with a normal superior oblique muscle, which may be missing in patients with syndromic craniosynostosis.

Jane C. Edmond, MD

E: jedmond@bcm.edu

Dr. Edmond did not indicate any proprietary interest in the subject matter.

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