Familial aplasia of the inferior rectus muscles

Congenital anomalies of inferior rectus and its surgical outcomes

Congenital inferior rectus hypoplasia and aplasia is a rare abnormality of the extraocular muscles, and it is the second most common after superior oblique muscle aplasia. It has been reported either in isolation or with coexisting ocular or systemic associations. We describe here cases of inferior rectus hypoplasia/aplasia, their clinical features, and surgical approach to achieve satisfactory outcomes. We retrospectively reviewed medical records from January 2009 to December 2020 of patients with vertical strabismus due to inferior rectus hypoplasia/aplasia at a tertiary eye care center. Those who underwent surgical intervention with an adequate follow up postoperatively were included in the study. Three patients who presented with congenital hypertropia and diagnosed of inferior rectus aplasia/hypoplasia and who underwent strabismus surgery were identified. Diagnosis was based on clinical examination and orbital imaging. Coexisting horizontal deviation was present in two patients. None of the patients had any other ocular, cranial, or systemic anomalies. All patients had isolated inferior aplasia/hypoplasia with normal other extraocular muscles on orbital imaging. Intraoperatively, ipsilateral superior rectus was tight in all patients. All underwent ipsilateral superior rectus recession, whereas two patients with large vertical strabismus required additional inferior oblique anteronasal transposition in the same eye. Satisfactory outcomes were achieved in all three patients without the need for resurgery. Moderate to large vertical A pattern strabismus and limitation of infraduction are common clinical findings. Orbital imaging helps not only in diagnosis but also in surgical planning. Weakening of antagonist superior rectus with anteronasal transposition of inferior oblique not only gives good surgical outcomes but also avoids potential complications related to vertical transposition of either horizontal rectus muscle.

Utility of Anterior Segment Optical Coherence Tomography in Muscle Aplasia

Congenital absence of the extraocular muscles is a relatively rare entity that is diagnosed by magnetic resonance imaging and is usually associated with craniofacial syndromes, microcornea, microphthalmos, and coloboma. The authors describe anterior segment optical coherence tomography as a quick and valuable modality in this setting before subjecting the patient to magnetic resonance imaging or computed tomography. [J Pediatr Ophthalmol Strabismus. 2022;59(2):e20-e22.].

Congenital dysplasia involving both medial and inferior recti: clinical features and surgical outcomes

AIM

To investigate the clinical features and surgical outcomes of congenital dysplasia involving both inferior recti (IR) and medial recti (MR) muscles.

METHODS

A retrospective review was conducted including cases of simultaneous congenital dysplasia of IR and MR that were diagnosed and surgically treated at the Zhongshan Ophthalmic Center, Sun Yat-sen University, China, from July 2009 to November 2019. Ocular motility, ocular alignment at distance (6 m) and near (33 cm) by prism alternating cover test and stereoacuity were assessed in all patients before and after surgery.

RESULTS

A total of five patients (four males and one female; three with right eye and two with left eye congenital dysplasia) were included in this review. The patients ranged in age from 10 to 42y (21±13.4y). The main clinical findings were hypertropia and exotropia of the affected eye, along with motility limitations in adduction and depression. Lateral rectus (LR) recession/transposition combined with IR resection was performed in one case. Two scheduled surgeries were performed in four cases, with one involving superior rectus recession and IR resection and the others LR recession and MR resection. Mean±SD pre-surgical exotropia of 51.0±31.11 prism diopter (PD) and hypertropia of 29.20±7.12 PD in the primary position were decreased to 3.6±12.90 and 3.2±10.09 PD, respectively, at two years after surgery, with a success rate of 60% and an under-correction rate of 40%.

CONCLUSION

The main clinical features associated with simultaneous MR/IR congenital dysplasia are hypertropia and exotropia of the affected eye along with motility limitations in adduction and depression. Scheduled two-stage surgeries achieved a success rate of 60%.

Examination of the Annular Tendon (Annulus of Zinn) as a Common Origin of the Extraocular Rectus Muscles: 2. Embryological Basis of Extraocular Muscles Anomalies

Purpose

Many reports have described anomalous connections of the superior rectus (SR) with other extraocular rectus muscles, in which additional heads of the other three rectus muscles likely provided the connections. We examined how these connections are established during fetal development.

Methods

We analyzed paraffin-embedded horizontal sections from 25 late-stage fetuses. Horizontal sections are best suited for understanding the mediolateral relationships of muscle origins.

Results

We confirmed a common tendinous origin of the lateral rectus (LR), inferior rectus (IR) and medial rectus (MR) muscles that was separated from the SR origin. Notably, eight fetuses (32%) had tendinous or muscular connections between the SR and other rectus muscles that had one of four morphologies: (a) a thin tendon from the SR to the common tendon of the three rectus muscles (2 fetuses), (b) a thin tendon to the LR (one fetus), (c) a thin tendon to the inferior rectus muscle origin (two fetuses), and (d) SR muscle fibers arising from an additional head of the LR (three fetuses).

Conclusions

The SR seemed to issue a thin tendon that passed along the inferior or lateral side of the oculomotor nerve. Conversely, the LR and inferior rectus muscle were likely to carry a supernumerary bundle that reached the SR. The accessory head of the medial rectus muscle showed a stable morphology in that it seemed to also provide an anomalous double head. However, the presence of an accessory head in the LR was rare. In contrast with our previously published diagram of the orbital apex, the accessory head of the medial rectus muscle passed along the lateral side of the superior oblique.

Resection and anterior transposition of the inferior oblique muscle for treatment of inferior rectus muscle hypoplasia with esotropia

Purpose

To report a case of inferior rectus muscle hypoplasia with esotropia, which was treated successfully by resection and anterior transposition of the inferior oblique muscle.

Observations

A 1-year-old boy presented with esotropia. He had esotropia of 15–30° and intermittent left hypertropia. At the age of 3 years, the alternate prism cover test showed esotropia of 35Δ and left hypertropia of 25Δ. Magnetic resonance imaging of the orbit revealed left inferior rectus muscle dysgenesis. Strabismus surgery was performed and a hypoplastic left inferior rectus muscle was identified. We performed bilateral medial rectus muscle recession, and resection and anterior transposition of the left inferior oblique muscle. Nine months after the surgery, the patient had esotropia of 8Δ and left hypertropia of 6Δ.

Conclusions and importance

Resection and anterior transposition of the inferior oblique muscle is useful for hypoplasia of the inferior rectus muscle accompanied by horizontal strabismus.

Surgical treatment of familial absence of the inferior rectus muscle

Familial inferior rectus muscle aplasia is rare. Patients with this condition require surgery to correct hypertropia and anomalous head posture. We report successful surgical outcomes in a father with bilateral and his 2 children with unilateral absent inferior rectus muscle, all 3 of whom were diagnosed preoperatively by imaging.

Inferior oblique anterior transposition for the unilateral hypertropia associated with bilateral inferior rectus muscle aplasia

Bilateral inferior rectus muscle aplasia in the absence of craniofacial abnormality is a rare but possibly under-recognized form of strabismus. Unilateral hypertropia in primary position seems to be a recurrent feature of this condition. We report a case of a 20-year-old woman with left hypertropia in primary position who was found on computed tomography to have bilateral inferior rectus muscle aplasia. A unilateral inferior oblique anterior transposition resulted in correction of the vertical deviation in primary position.

Case report and literature review of inferior rectus muscle aplasia in 16 Japanese patients

PURPOSE

To describe clinical features of inferior rectus muscle aplasia in Japanese patients and to gain insight into its pathogenesis.

METHODS

Case presentation and literature review of 16 Japanese patients with inferior rectus muscle aplasia.

RESULTS

The age at presentation of 16 patients (9 females, 4 males, and 3 with unknown gender) varied from 7 months to 73 years (mean, 21.8 years). The inferior rectus muscle was absent on the right side in 10 patients, on the left side in 4 patients, and on both sides in 2 patients. Structural anomalies of the eye globe, such as microphthalmos, microcornea, and coloboma of varying degrees, were present on the ipsilateral side of the inferior rectus muscle aplasia in 4 patients and on the contralateral side in 1 patient. As surgical findings, anomalous inferiorly located insertion of the medial rectus muscle was discovered in 5 patients: 1 patient in association with microcornea and iris coloboma. Frequent surgical procedures were recession or tenotomy of the superior rectus muscle, combined with downward transposition of the entire or partial tendons of the medial rectus and lateral rectus muscle to the medial and lateral end, respectively, of the putative inferior rectus muscle insertion.

CONCLUSIONS

The association of coloboma with inferior rectus muscle aplasia suggests that abnormal optic fissure closure during embryogenesis might underlie the muscle aplasia.

Anomalous bilateral lateral rectus muscles and anterior polar cataract with dysmorphic features

Congenital anomalies, such as absence, hypoplasia, bifurcation, or reduplication of various extraocular muscles, including lateral rectus muscles have been reported previously. We report a 5-year-old girl who had posteriorly malinserted lateral rectus at 15 mm from the limbus in the right eye with multiple associated ocular and systemic congenital malformations.

Hypoplastic inferior rectus muscle in association with accessory extraocular muscle and globe retraction

Ocular motility problems related to congenital abnormalities of extraocular muscles are rare conditions. Such congenital abnormalities may present in a spectrum from accessory additional rectus muscles to absence of extraocular muscles. Absence of one or more extraocular muscles is a rare condition usually seen in association with craniofacial syndromes and only rarely in isolation. None of the cases with the absence of an extraocular muscle were reported to be in association with an accessory extraocular muscle or paradoxical contraction of an extraocular muscle. We present a case with bilateral hypoplasia of the inferior rectus muscle with an accessory extraocular muscle in association with globe retraction and lambda-pattern exodeviation.