Delhi Journal of Ophthalmology

Clinical Challenge

Karthika Bhaskaran1, Pramod Pandey2, Ramesh Kekunnaya3, Pradeep Sharma1
1Dr. R.P. Centre for Ophthalmic Sciences, AIIMS New Delhi, India
2GNEC MAMC, New Delhi, India
3LVPEI, Hyderabad, India

Corresponding Author:

Karthika Bhaskaran MD, DNB
Dept of OphthalmologyB
Dr. R.P. Centre for Ophthalmic Sciences,B
AIIMS New Delhi, IndiaB
Email id: karthikab89@gmail.com

Received: 16-JUL-2019

Accepted: 29-AUG-2019

Published Online: 27-DEC-2019

DOI:http://dx.doi.org/10.7869/djo.492

Abstract

Keywords :

This case is presented by Dr. Pradeep Sharma/Dr Karthika Bhaskaran and commented upon by Dr Pramod Pandey and Dr Ramesh Kekunnaya.




Case Report

15-year-old boy presented with history of constant upward deviation of left eye with drooping of left upper lid since birth. He had no complaints of diminished vision or diplopia. There was no history of trauma or diurnal variation of symptoms. Patient had no systemic illnesses and family history was negative.
On examination, unaided visual acuity was 6/6 in both eyes. Mild ptosis was noted in the left eye. Pupillary reactions and posterior segment examination were within normal limits in either eye. No abnormal head posture was noted. Limitation of adduction and depression in the left eye was evident, with the depression deficit being more pronounced in abduction than adduction. In primary gaze, an exotropia of 25 PD and left hypertropia of 35 PD was noted (Figure 1). The vertical deviation increased to 50 PD on levo-version. Sensory examination revealed left eye suppression. Forced duction test for left eye depression was found to be free. Computed Tomography of orbits showed hypoplastic inferior rectus muscle in the left eye (Figure 2).



Intraoperatively, no muscle fibres could be identified. However, anterior ciliary vessels were visible at the muscle insertion site (Figure 3).

Dr. Pramod Pandey:
The clinical presentation broadly conforms to congenital monocular depression deficiency (MDD) with exotropia, ptosis and associated synophrys. Synophrys may be an incidental finding or have syndromic associations like Cornelia de Lange, Patau, Crouzon syndrome etc. The hypertrichosis and highly arched eyebrows here may be suggestive of Cornelia de Lange’s syndrome, however no other features have been noted to suggest any syndromic involvement. Other features include associated adduction deficit in left eye with XT sans AHP. Primary and secondary deviations if present are not known nor is fundus torsion, pattern strabismus or head tilt test results. The differential diagnosis would include pupil sparing partial congenital 3rd nerve palsy sans aberrant innervation, multiple / single EOM hypoplasia/ aplasia, congenital superior rectus fibrosis, Vertical Duane’s syndrome and unilateral CFEOM3 in that order. It was a perfect setting for amblyopia in left eye, patient likely escaped due to alternate fixation, absence of superior rectus contracture also points in that direction, the fixation preference is however not dwelt upon to clarify this point.
High resolution MRI brain and orbits may reveal hypoplastic 3rd nerve in congenital cranial dysinnervation disorders as well as hypoplasia/ aplasia of the extra ocular muscles. Computerized tomography as was evident here invariably betrays hypoplasia, abnormal insertions, associated craniofacial issues in such cases. The adduction limitation present here could be due to associated hypoplasia of the medial rectus muscle which was not explored.
The embryogenesis of extraocular muscles (EOMs) has many gray areas. According to Sevel’s hypothesis the inferior halves of horizontal recti, inferior rectus and inferior oblique develop from inferior mesodermal complex, the rest from superior complex, thus associated medial rectus aplasia of the inferior half could be an accompanying feature. The vertebrate EOMs likely derive from 2 distinct populations of mesenchymal cells, the paraxial that gives rise to Lateral and superior oblique muscles innervated by 6th and 4th cranial nerves respectively and prechordal mesoderm that gives rise to superior, inferior, medial recti and inferior oblique muscles innervated by 3rd cranial nerve. EOMs likely start developing at the origins at the orbital apex and then move forward towards insertions. Present case seems to support that contention as inferior rectus hypoplasia seems to be acutely accentuated as the inferior rectus passes anteriorly in the mid -orbit. Development of EOMs may also require signals from the migrating neural crest cells and developing eye including closure of embryonic fissure. Elucidation of genetic underpinnings may offer further insights.
On surgical exploration, the muscle sheath along with anterior ciliary vessels are invariably present with some attenuated muscle fibers. If attempt was made to hook the muscle, we would have had better insight into these aspects. Due to rarity of the condition and wide variability in clinical presentation there is no unanimity on surgical management of such cases other than recession of a tight superior rectus if present. Horizontal rectus muscle transposition to insertion of inferior rectus, superior rectus/oblique weakening procedures, anterior transposition of the inferior oblique (IO) with/without resection, anterior and nasal transposition of IO have all been described with satisfactory results. Syndromic and craniofacial aspects in non-isolated cases also need to be factored in.
The present case underscores the quintessential point that isolated, non-isolated aplasia/hypoplasia of EOMs should be kept in mind while evaluating atypical congenital motility disorders. It may be worthwhile sharing the surgical approach and the outcomes.

Dr. Ramesh Kekunnaya:
The patient has large hypertropia along with exotropia with significant under action of Inferior Rectus. Presence of ptosis is a bit unusual. Additionally, he has synophrys, not sure of any other dysmorphism. I am assuming that there are no signs of aberrant innervation. The following are the possibilities.
  1. Congenital third nerve palsy - probably excluded because the ptosis is very mild along with adduction limitation, he has limitation of depression in abduction. The combination of MR and IR and mild ptosis is possible in third nerve palsy.
  2. Since these are since birth, it should be congenital abnormality, most probably suggestive of hypoplasia or aplasia of Left Inferior rectus (with or without LPS hypoplasia?)
I would like to look at other muscles as well. MRI is preferable as it has advantage of looking at the morphology of other extraocular muscles and also one can trace the oculomotor nerve along its path.
Probably IR aplasia is a string possibility. I would like to explore the other extraocular muscles as well. If the IR is absent, anterior segment circulation could be compromised. Hence one should be careful regarding the choice of surgery. Following can be an option
  1. Left eye: Nasal Inferior oblique anterior transposition + SR recession +_LR recession +_ Right eye LR recession under GA
  2. 2. Possible ptosis surgery later
Dr. Pradeep Sharma/Dr Karthika Bhaskaran:
Congenital abnormality of extraocular muscles are usually associated with syndromes and rarely in isolation, with unilateral absence being more common than bilateral.1 Association with structural abnormalities of the globe such as microcornea, microphthalmia, iris and uveal coloboma have also been reported.2 Our patient did not have any associated anomalies. The ocular deviation was present since birth, with limited depression in left eye and an A pattern (Figure 1). Since he had freely alternating fixation, he did not develop amblyopia,as also noted by Dr. Pandey. Based on clinical examination, our initial diagnosis was congenital partial third nerve palsy (pupil sparing with no aberrant regeneration). However, CT images clearly showed hypoplastic inferior rectus muscle in the left eye. All the other extra ocular muscles appeared normal. CT also ruled out craniofacial anomalies, which are common associations in such patients.3 Thus, a diagnosis of congenital inferior rectus hypoplasia was made. We agree with the experts that High resolution MRI is the preferred imaging modality in such cases, for the assessment of the oculomotor nerve and extraocular muscles. However, the patient was unable to afford the cost of MRI, whereas CT was available in-house.
Intra-operatively, attempt to hook the inferior rectus revealed no muscle fibres. Since the inferior rectus and the inferior halves of medial and lateral recti arise from a common mesodermal complex4, associated abnormalities in the medial rectus and lateral rectus muscles was looked for. However, neither muscles showed any evidence of hypoplasia or anomalous insertion. The adduction limitation could possibly be due to the lack of adductor function of the inferior rectus muscle. It could also be due to posterior bifurcation of the medial rectus muscle, which may be visualized on MRI as grooving/notching of the muscle.2 Management options include superior rectus recession alone or combined with inverse Knapp’s procedure (±augmentation sutures), Modified Nishida and inferior oblique muscle anterior/anterior nasal transposition (±resection). Surgical planning should take into account the added risk of anterior segment ischemia in such cases because the contribution of the vertical anterior ciliary arteries has been documented to be more than the horizontal arteries.5
In our patient, the forced duction test for superior rectus was free. We performed a Modified Nishida’s procedure in the left eye. Non-absorbable sutures were passed through the inferior one-third of medial and lateral rectus 8 mm from their insertion and then sutured to the sclera 8 mm behind the point where inferior rectus would normally insert, on either side. Compared to inverse Knapp’s, this procedure has the advantage of sparing the anterior segment circulation.
Post-operatively, left hypertropia decreased to 6 PD with considerable improvement in infraduction of left eye (Figure 4). There is now a residual exotropia of 18 PD and left hypertropia of 6 PD, so right eye lateral rectus recession with superior oblique weakening by partial tenectomy of SO has been planned in a second stage to correct the exotropia and A pattern.
To conclude, a high index of suspicion and pre-operative orbital imaging are essential for the diagnosis of extraocular muscle aplasia/hypoplasia. Planning of surgical intervention should consider risks for anterior segment ischemia, especially in older patients.



References
  1. Astle WF, Hill VE, Ells AL, Chi NT, Martinovic E. Congenital absence of the inferior rectus muscle–diagnosis and management. J AAPOS, 2003; 7:339–344.
  2. Matsuo T, Watanabe T, Furuse T, Hasebe S., Ohtsuki H. Case report and literature review of inferior rectus muscle aplasia in 16 Japanese patients. Strabismus, 2009; 17:66–74.
  3. Taylor R.H., Kraft S.P. Aplasia of the inferior rectus muscle. A case report and review of the literature. Ophthalmology, 1997; 104:415–418.
  4. Sevel D. A reappraisal of the origin of human extraocular muscles. Ophthalmology, 1981; 88:1330–8.
  5. Virdi PS, Hayreh SS. Anterior segment ischemia after recession of various recti: an experimental study. Ophthalmology, 1987; 94:1258-71.

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Bhaskaran K, Pandey P, Kekunnaya R, Sharma PClinical Challenge.DJO 2019;30:83-86

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Bhaskaran K, Pandey P, Kekunnaya R, Sharma PClinical Challenge.DJO [serial online] 2019[cited 2020 Jan 25];30:83-86. Available from: http://www.djo.org.in/articles/30/1/Clinical-Challenge-2019-v30-i1_24.html