Pulled into two syndrome (PITS) in a case of congenital fibrosis of the extraocular muscle.

A four-year-old child with a clinical diagnosis of unilateral congenital fibrosis of extraocular muscles (CFEOM) was planned for inferior and medial rectus muscle recession surgery, adjusted with the status of forced duction test. Due to pathological changes within the muscles subsequent to innervational abnormality, intraoperatively the inferior rectus muscle was pulled into two following the insertion of muscle hook. Moreover, the snapped muscle fibers could not be identified, thus further surgery was abandoned and an observation was commenced. At the end of 6 weeks, there was a significant reduction in the amount of hypotropia but clinically significant perverted convergence with esotropia necessitated further surgical intervention. A second surgical intervention consisting of medial rectus transposition to superior rectus with 3 mm recession was performed to achieve acceptable results in the primary gaze.

Congenital fibrosis of the extraocular muscles (CFEOM) is an uncommon congenital abnormality of cranial nerves and motor neuronincluded under the broad category of congenital cranial dysinnervational disorders (CCDD's).[1] On the other hand, pulled into two syndrome (PITS) is an unusual surgical complication experienced by the surgeon under very rare circumstances in their clinical practice (between 10 and 30 years).[2345] Here in this report, we discuss the clinical difficulty, tailored evaluation, and management of a case of pulled into two of the inferior rectus muscle in a patient with CFEOM.

Case Report

A four-year-old female child was brought with the history of drooping of left upper eyelid along with hypo tropic globe since birth. Clinical examination revealed severe variable ptosis in the left eye with hypotropia of around 15 degrees with an esotropia of around 15 degrees in the primary gaze. [Fig. 1a] Duction movements in the left eye for elevation and abduction were severely restricted, whereas for depression and adduction there was mild to moderate limitation. On attempted up gaze, there was perverted convergence in the left eye. [Fig. 1b] Rest of the anterior and posterior segment examination was essentially within normal limits.

Figure 1

(a) Left eye esotropia with hypotropia in the primary gaze. (b) On attempted upgaze, there is a perverted convergence. (c) Intra-operative tight muscle following the placement of muscle hooks (Narrow distance between the hooks). (d) Intra operative pulled into two (The sudden give away which was felt, has been indicated by the increased distance between the muscle hooks). (e) On a postoperative day one after the second surgery, there was a significant improvement in hypotropia and esotropia

Based on these clinical findings a diagnosis of congenital fibrosis of extraocular muscles was made and the patient was planned for intraoperative forced duction test (FDT) for inferior rectus (IR) followed by the recession of 4.5 mm or more if tight and medial rectus recession of 4.0 mm with intraoperative adjustment. During surgery due to severely tight IR, following insertion of the muscle hooks [Fig. 1c] for suture passage a sudden give away or sudden loss of tension within the muscle was felt. [Fig. 1d] The muscle tendon appeared thinner now with the loss of tension within it, thus it was confirmed as intraoperatively pulled into two of the rectus muscle. Immediately a search for the posteriorly snapped muscle fibers was carried out; however, a definitely expected muscle bulk/fibers could not be retrieved because of the small orbit, thus further surgical intervention was abandoned and the patient was kept under close follow up postoperatively. During subsequent visits at the end of 6 weeks, hypotropia was significantly improved but the perverted convergence was persistent. A second surgical intervention consisting of medial rectus transposition to superior rectus insertion was performed to alleviate this innervational abnormality along with esodeviation. This was taking advantage of the innervation to MR coming during attempted elevation, along with a recession of 3 mm because of its tightness. After the second surgical intervention, a significant improvement in hypotropia and the perverted convergence was achieved with a residual deviation of fewer than 5 degrees along the horizontal and vertical meridian. [Fig. 1e]

Discussion

CFEOM is a type of congenital cranial dysinnervational disorder characterized by the developmental abnormality of the cranial nerve nuclei. It has been broadly classified into three subtypes depending on the specified genes, laterality, and other ocular features.[1] Clinical management of such cases is always a challenge for the surgeon as patients are usually younger and also due to associated complex ocular features. Under such circumstances, a meticulous assessment followed by a tailored surgical approach is necessary for a better postoperative outcome.

Pulled into two syndrome (PITS) is a unique intraoperative complication experienced while handling the tight extraocular muscles of patients with certain pathologically predisposed conditions.[245] such as previous extraocular muscle surgery, cranial nerve palsy, thyroid eye disease, metastatic infiltration of the muscles, and others.[24] These muscles with inherently reduced elastic strength possess an easy tendency for separation of muscle fibres along the belly-tendon junction even after minimal pull manifesting as sudden dehiscence during surgical maneuvering.

In the present case the snapped muscle could not be found even after an extensive search because of the relative hypotropic position of the globe and small orbit for manipulation; thus the surgical procedure was abandoned and postoperative observation was expected. Fortunately, the hypotropia reduced significantly following first surgery because of the reduction in strong downward pull exerted by the tight inferior rectus. But the patient still had the perverted convergence on attempted elevation, so the MR was transposed to the superior rectus insertion. After second surgery the perverted convergence was almost completely disappeared to achieve acceptable results in the primary gaze. This we would like to suggest is an example of targeted strabismus surgery as we have suggested lateral rectus transposition to MR in synergistic divergence cases and inferior rectus transposition to MR in cases of synergistic innervational downshoot, a condition in which there is down shoot on attempted adduction.[6]

Conclusion

To conclude, complex strabismus cases like CFEOM maybe intra-operatively complicated by PITS. Under such conditions, the further surgical plan of action needs to tailored from simple observation to additional “targeted strabismus surgery” depending on the residual deviation and abnormal innervation.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.