Mims et al, Anti elevation syndrome after anterior transposition of the ...

Antielevation Syndrome After BilateralAnterior Transposition of the InferiorOblique Muscles: Incidence and PreventionJames L. Mims III, MD, a and Robert C. Wood, MPH bBackground: Unilateral 1 and bilateral 2 anterior transpositions of the inferior oblique muscle (ATIOs) for primary inferioroblique (IO) muscle overaction may produce apparent new or recurrent overaction of the contralateral IO muscle.This effect has been termed “antielevating” and can produce overaction of the contralateral elevators inadduction that mimics recurrent or new overaction of the IO muscle of the other eye. This phenomenon may betermed the antielevation syndrome (AES). Kushner 2 has hypothesized that this complication of the ATIO is producedprimarily by the posterior fibers of the IO muscle. The purpose of this study is to correlate the frequency of this syndromein a large series of patients with the mm of lateral displacement (spreading) of the IO muscle reattachmentsite. Methods: There was a combination of 123 patients who received ATIO from Mims and 77 patients who receivedATIO from Kushner. 2 ATIO was performed according to a previously published technique. 3 Results: All 16 patients(14 from Mims and 2 from Kushner) with AES had received bilateral anterior transposition of the posterior fibers ofthe IO muscle to at least 2 mm anterior to the lateral end of the inferior rectus (IR) muscle with spreading laterally3 to 5 mm. Among children who had the posterior fibers of their IO muscles placed 2 to 4 mm anterior to a line drawnlaterally from the insertion of the IR muscle, the incidence of AES was significantly larger with more spreading outof the new IO muscle insertion. Conclusions: AES may be prevented by attaching the posterior fibers of the IO muscleno more than 2 mm lateral to the IR muscle insertion site. This complication responds to bilateral nasal IO musclemyectomy in many cases. (J AAPOS 1999;3:333-6)Anterior transposition of the inferior oblique muscle(ATIO) was first suggested by Scott, 4 on the basisof computer simulations. ATIO was first reportedby Elliott and Nankin, 5 who found that the anterior transpositionwas an effective way to reduce inferior oblique(IO) muscle overaction. Elliott and Parks 6 performedasymmetric IO muscle surgical procedures in a series ofpatients to compare the effectiveness of ATIO with denervationextirpation. In 67% of their patients there appearedto be a recurrent overaction of the inferior oblique muscle(OAIO) on the side of the IO muscle that had previouslyreceived the denervation extirpation. Stein and Ellis 1pointed out that this difference in the postoperative recurrenceof OAIO could be explained by the difference in theFrom the University of Texas Health Science Center (UTHSC-SA), a,b and the Santa RosaChildren’s Hospital, Baptist Medical Center, a San Antonio, Texas.Presented at the 24th Annual Meeting of the American Association for PediatricOphthalmology and Strabismus, April 4-8, 1998.Submitted March 30, 1998.Revision accepted June 7, 1999.Reprint requests: James L. Mims III, MD, Suite 511, 311 Camden, San Antonio, TX78215.Copyright © 1999 by the American Association for Pediatric Ophthalmology andStrabismus.1091-8531/99 $8.00 + 0 75/1/101390surgery that had been performed in the other eye in eachseries. They proposed that the difference was related tothe limitation of elevation in abduction of the contralateraleye caused by the anterior transposition procedure.After ATIO, the normal, increased innervation of theIO muscle on supraduction produces a powerful force vectordirected inferiorly, an effect Kushner termed “antielevating.”This antielevating force can produce overaction ofthe contralateral elevators in adduction that mimics recurrentor new overaction of the IO muscle of the other eye.This phenomenon may be termed the antielevation syndrome(AES). The purpose of this study is to correlate thefrequency of this syndrome in a large series of patientswith the mm of lateral displacement (spreading) of the IOmuscle reattachment site and to suggest how to preventthe development of AES.SUBJECTS AND METHODSA retrospective chart review was conducted on all of theauthor’s patients on whom an ATIO was performed froml982 to l994. The location of the posterior fibers was tabulatedaccording to the inspection of the typed operativenotes from the hospital records. Although the lateral end ofthe inferior rectus (IR) muscle insertion curves posteriorly,when the muscle is placed on a straight muscle hook, aJournal of AAPOS December 1999 333

Journal of AAPOSVolume 3 Number 6 December 1999Mims and Wood 335TABLE 1. AES cases corresponding to each degree of anterior transposition and lateral displacement of the IO musclemm temporal to lateral end of IR muscle(X, lateral displacement) 1 mm 2 mm 3 mm 4 mm 5 mmmm anterior to lateral end of IR muscle 4 mm 0/1 0/0 0/6 1/4 1/4(Y, anterior transposition) 3 mm 0/0 0/1 0/4 1/5 0/32 mm 0/15* 0/1 5/46 3/30 5†/171 mm 0/31* 0/0 0/1 0/1 0/10 mm 0/29*The numerator of each fraction is the number of cases of AES; the denominator is the total cases with a specific level of anterior transposition (mm anterior to a line drawn laterallyfrom the IR muscle insertion) and lateral spreading (mm lateral to the lateral end of the IR muscle insertion).*All of these cases are from Kushner. 2†Two of these 5 cases are from Kushner. 2TABLE 2. Various group characteristics among Mims’ patients (N = 123)Comparisons of those who did and did not have AESMo of follow-up* Patient age at MROU (mo) Patient age at ATIO (mo) OAIOAll who did not have AES (N = 109)87.2 ± 4.2 22.4 ± 2.0 35.5 ± 2.3 1.9 ± 0.07All who did have AES (N = 14)45.5 ± 4.3 18.2 ± 3.8 29.4 ± 4.4 2.0 ± 0.14Comparisons among those whose IO muscleswere placed 2 mm or more anterior to aline drawn laterally from the insertion of theIR muscle with 3, 4, or 5 mm of lateral displacementMo of follow-up* Patient age at MROU (mo) Patient age at ATIO (mo) OAIO3 mm: posterior IO muscle insertion placed at X,Y of 3,4 or 3,3 or 3,2. (N = 56)81.8 ± 5.4 24.7 ± 3.1 44.8 ± 5.0 1.8 ± 0.14 mm: posterior IO muscle insertion placed at X,Y of 4,4 or 4,3 or 4,2. (N = 39)69.8 ± 6.3 21.7 ± 2.9 31.6 ± 3.7 1.8 ± 0.095 mm: posterior IO muscle insertion placed at X,Y of 5,4 or 5,4 or 5,2. (N = 22)97.9 ± 10.8 15.1 ± 3.4 43.2 ± 5.4 2.2 ± 0.16The ± designates ± 1 SE of the mean.*Months of follow-up is after the ATIO and extends to either the surgical date for AES or to the last visit in the office.MROU, Bilateral medial rectus muscle recession.Kushner 2 extended this idea to explain an abnormalmotility pattern he observed in some patients after bilateralATIO. This pattern resembles marked recurrent OAIOassociated with a Y or V pattern and exotropia in upgaze.Small alternating hypertropias (right hypertropia in leftgaze and left hypertropia in right gaze) may be present infar side gazes, but these hypertropias are much smallerthan those seen in cases of primary OAIO with a similarappearance on version testing. A limitation of elevation ofthe abducting eye is frequently demonstrable. Kushner 2has hypothesized that this complication of ATIO is producedprimarily by the posterior fibers of the IO muscle.In this study, all 16 patients with AES had receivedbilateral anterior transposition of the posterior fibers ofthe IO muscle to at least 2 mm anterior to the lateral endof the IR muscle, with displacement 3 to 5 mm lateral tothe lateral end of the IR muscle insertion. Is the incidenceof AES increased with more lateral displacement of theTABLE 3. AES: dependence on amount of anterior transposition and lateraltransposition (percentages of patients with AES after ATIO)X (lateral displacement)Y (anterior transposition) 0-2 mm 3 mm 4 mm 5 mm0-1 mm 0% 0% 0% 0%2-4 mm 0% 8.9% 12.8% 25%These percentages were derived from the data in Table 1.This progression in incidence of AES with more spreading out of the new IO muscleinsertion laterally was significant (P = .011).posterior fibers of the IO muscle? When we combined ourpatients with those previously reported on by Kushner, 2we found that for those patients with posterior fibers of theIO muscle placed at least 2 mm directly anterior to the lateralend of the IR muscle, the amount of lateral displacementof the new IO muscle insertion significantly

336 Mims and Woodincreased the incidence of AES (P = .011). A similar analysisusing only our patients indicated only a trend in thisdirection, not statistical significance (P = .19). There werenot enough patients who were anteriorly transposed 0 to 1mm with concurrent displacement 3 to 5 mm laterally todetermine whether lateral displacement was also a hazardwith less anterior displacement.For now, it appears that if the new insertion of the IOmuscle is anteriorized more than 1 mm (Y >1 mm), the newinsertion of the IO muscle should not be spread out morethan 2 mm, unless the severity of the DVD warrants risk oflater development of AES. The mm of anteriorization ofthe IO muscle’s posterior fibers beyond the lateral edge ofthe IR muscle insertion required to effectively treat variousdegrees of DVD severity is not yet well characterized. 12-14Also, whether spreading out the muscle less will decreasethe effectiveness of ATIO in the treatment or prevention ofDVD has not yet been studied adequately.Once AES has developed, properly performed bilateralnasal myectomy is preferable to denervation-extirpationbecause denervation-extirpation can unleash significantDVD. Prevention should be possible because the AESappears to be the result of an excessive downward forcevector after ATIO. AES may be prevented by attaching theposterior fibers of the anteriorized IO muscle no morethan 2 mm lateral to the IR muscle insertion.Bunching the IO muscle insertion at the lateral edge ofthe IR muscle insertion as described by Kushner 2 shouldbe associated with a very low incidence of AES; the incidenceand cure of DVD were not reported. 2 This studydid not include enough patients with lateral displacementat the exact level of the IR muscle insertion as described byKratz et al 12 to predict the incidence of AES in this technique.Placing the new IO muscle insertion 4 to 5 mm justlateral to and parallel with the anterior end of the IR muscle,as recently described by Guemes and Wright, 15 shouldJournal of AAPOSVolume 3 Number 6 December 1999reduce the incidence of AES, but may reduce the controlof DVD. The technique of ATIO as described by Mims 3should probably be limited to severe cases of DVD.References1.Stein LA, Ellis FJ.Apparent contralateral inferior oblique muscleoveraction after unilateral inferior oblique weakening procedures. JAAPOS l997;1:2-7.2.Kushner BJ.Restriction of elevation in abduction after inferioroblique anteriorization. J AAPOS 1997;1:55-62.3.Mims JL, Wood RC.Bilateral anterior transposition of the inferiorobliques. Arch Ophthalmol 1989;107:41-4.4.Scott AB.Planning inferior oblique surgery.In: Reinecke RD, editor.Strabismus. New York: Grune and Stratton; 1978. p. 347-54.5.Elliott RL, Nankin SJ.Anterior transposition of the inferior oblique.J Pediatr Ophthalmol Strabismus 1981;18:35-8.6.Elliott RL, Parks MM.A comparison of inferior oblique muscleweakening by anterior transposition or denervation-extirpation.Binocular Vision Eye Muscle Surg Q 1992;7:205-10.7.Weakley DR, Stager DR.Inferior oblique weakening procedures.Ophthalmology Clin N Am 1992;5:57-65.8.Mims JL.Benefits of bilateral anterior transposition of the inferiorobliques. Arch Ophthalmol l986;104:800-1.9.Stager DR, Weakley DR Jr, Stager D.Anterior transposition of theinferior oblique: anatomic assessment of the neurovascular bundle.Arch Ophthalmol 1992;110:360-2.10.Stager DR.The neurovascular bundle of the inferior oblique muscleas its ancillary origin. Trans Am Ophthalmol Soc 1996;94:1073-94.11.Stager DR.The neurovascular bundle of the inferior oblique muscleas the ancillary origin of that muscle. J AAPOS l997;1:216-25.12.Kratz RE, Rogers GL, Bremer DL, Lequire LE.Anterior tendondisplacement of the inferior oblique for DVD. J Pediatr OphthalmolStrabismus l989;26:212-7.13.Bacal DA, Nelson LB.Anterior transposition of the inferior obliquemuscle for both dissociated vertical deviation and/or inferior obliqueoveraction: results of 94 procedures in 55 patients. Binocular VisionEye Muscle Surg Q 1992;17:219-25.14.Ziffer AJ, Isenberg SJ, Elliott RJ, Apt L.The effect of anterior transpositionof the inferior oblique muscle. Am J Ophthalmol 1993;116:224-7.15.Guemes A, Wright KW.Effect of graded anterior transposition ofthe inferior oblique muscle on versions and vertical deviation in theprimary position. J AAPOS 1998;2:201-6.