|Dr. Sener began by congratulating the surgeons for this difficult case with an excellent outcome. Here are his answers to our questions :
(1) Do you feel recommending orbital imaging studies in suspected muscle injuries is?
Mandatory. I think orbital imaging is mandatory for this kind of an obvious medial rectus injury presenting with immediate exotropia. It will not only provide invaluable information about the site and extent of the injury but also mechanical and innervational consequences by combining the kinetic mode.
(2) What would you do as an initial approach to this case?
This kind of a case needs immediate intervention at the moment of recognizing a transected muscle, if possible right on the table. The first measure should be placing a temporary stay suture in order to keep the torn sides as close as possible and preventing the contracture of the antagonist muscle. I use a nonabsorbable 5.0 spatulated needle in order to pass from the nasal limbus, engaging the episcleral fibers and pulling the eye towards the nose then suturing with a bolster at the nasal skin. If cheese-wiring occurs, one can pass the suture from either or both of the vertical recti. In this case special attention must be exercised in order to protect the cornea from chronic suture contact. Botulinum toxin injection (BTI) might seem handy, however there are two important caveats. First, its required action is delayed –a few days or a week- and second during or following a strabismus repair any adjustment to a desired target can be erroneous because the real magnitude of the deviation would be disguised. BTI would follow my primary strabismus repair if needed. The goal should be trying to bring back together the transected parts. The regenerative capacity of the extraocular muscles can be surprising. I have seen an originally exotropic case whose transected portion of the lateral rectus was sewn back to the stump 8 mm from the insertion, upon when the surgeon noticed that it should in fact needed recession not resection, and the outcome was surprisingly good. The injury in this case may not be limited to a straightforward transection but a segment of muscle may actually be missing or destroyed and at this far posterior location there might be an associated nerve injury. Parenteral corticosteroid injection under antibiotic coverage and gastric protection should be useful in diminishing the inflammation and protecting the orbital content against bacterial contamination from the sinusitis.
(3) Which approach would you choose to treat medial rectus muscle injuries after endoscopic sinus surgery?
The second step in this particular case is to form a team with an orbital surgeon and an ENT specialist with significant experience in endoscopic sinus surgery. The MR indicates that the proximal end of the muscle is way behind the globe near the orbital apex. The orbital surgeon would most likely use a transcaruncular incision, however this will give limited access to the far posterior compared to an endoscopic transethmoidal approach which can provide exposure up towards the optic canal. The major problem facing either of the specialists is in fact the disturbed orbital anatomy especially the intraorbital fat tissue of both the intra and extraconal space and hematoma. We had to go through with such a procedure in order to expose and transect the fibrotic bands of a severe CFEOM infantile case (Strabismus surgery in congenital fibrosis of the extraocular muscles: a paradigm. Sener EC, Taylan Sekeroglu H, Ural O, Oztürk BT, Sanaç AS. Ophthalmic Genet. 2014 Dec;35(4):208-25; Case 15). Although our goal was to create a controlled medial rectus transection through endoscopic sinus surgery, the fat tissue was completely obscuring our sight and the transection had to be carried on with blind maneuvers. In this aspect, the surgeons of this case have to be congratulated in being able to isolate the proximal end and effectively passing the suture in a very tight place. I was wondering whether this kind of a repair would as well be effective by suturing the distal end of the transected medial rectus to the posterior orbital periosteum as long as there is enough innervation at the distal portion. If suturing of the transected ends turns out to be successful, I would leave the globe at about 15 pd of esotropic state. BTI can be added at any time following the surgery, especially if there is no sign of recovering adduction in a few weeks. One may not be lucky enough in isolating the torn muscle, or the muscle may not recover with the appropriate innervation. Then ciliary vessel sparing monovertical transposition with 3-4 mm resection and moderate to large lateral rectus recession would be my surgical option. Unfortunately, BTI alone in this magnitude of exotropia has not been successful in my hands regardless of the dose increments. The contralateral lateral rectus recession may be added in order to match the left gaze deficit. I would leave the second vertical rectus as the last step as a protection against anterior segment ischemia. As far as circulation concerned, I do not have any experience with Nishida transposition technique, however I suspect this technique or a partial tendon thickness transposition should leave more scar tissue than a controlled cilary vessel sparing full tendon transposition, and this will make things even more complicated if and when a revision is needed. When everything else fails in correcting the exotropia, and cosmesis remains as a significant issue, I found the nonabsorbable suture fixation of the medial rectus insertion to the posterior lacrimal crest through caruncular incision being very useful in maintaining alignment at the primary position although this will obviously restrict the lateral gaze.
(4) Assuming the medial rectus was adherent to the orbital defect, would you expect a positive forced duction test?
One must consider the fact that extensive scar throughout the medial orbit is unavoidable in this case and the forced duction test would be positive if enough time has passed for fibrosis of the orbital soft tissue to take over.
(5) What would be the optimal time for surgery? & (6) If the muscle had been transected and a large segment were missing or destroyed, what would be your surgical approach?
I believe I tried to explain these points in 2, and 3.