Superior oblique palsy

Ophthalmology Volume 111, Number 2, February 2004 The authors’ levator advancement surgery involved an anterior approach via the lid crease, through orbicularis and septum, to the levator aponeurosis. “The levator aponeurosis was separated from the tarsal plates and Mu¨ ller’s muscle with Westcott scissors. The medial and lateral horns of the levator muscle were cut, and the band of levator muscle was sutured to the anterior tarsal plate.” Oculopharyngeal muscular dystrophy, one of the myogenic types of ptosis reported by Wong et al, is a very common type of ptosis in this author’s area because of the large number of French Canadians. Several years ago I reported my experience with levator aponeurotic advancement surgery in 28 patients (47 eyelids) with this disease over a 2-year period.2 The levator muscle is characteristically infiltrated with fat in this syndrome. The fatty infiltration is quite visible to the naked eye, whereas the aponeurosis appears relatively normal (glistening white). Initially, I dissected the aponeurosis away from Mu¨ ller’s (horns intact) and tried to advance the aponeurosis onto the tarsal plate, much like the authors have described. As the levator aponeurosis was dissected away from underlying Mu¨ ller’s, the dissection plane would often become very indistinct about 10 mm above the tarsal plate. Mu¨ ller’s muscle was routinely noted to be infiltrated with fat and also appeared very thickened in the overwhelming majority of patients. When I simply advanced aponeurosis over Mu¨ ller’s and onto the tarsus, the lid would come up, but rarely as much as expected or desired. However, if Mu¨ ller’s was also dissected away from conjunctiva and advanced with aponeurosis (horns left intact), the lid would come up higher and more easily. In addition, as Mu¨ ller’s was dissected away from conjunctiva, it was clearly found to be thicker than normal. Histopathological examination of this thickened, fat-infiltrated Mu¨ ller’s confirmed its involvement in the dystrophic process, a finding that was unrecognized in previous literature.3 I have also found Mu¨ ller’s muscle to be very infiltrated with fat and thicker than normal Mu¨ ller’s in myotonic dystrophy and chronic progressive external ophthalmoplegia. I routinely dissect and advance Mu¨ ller’s with levator aponeurosis (horns left intact) in these individuals as well, when ptosis surgery is required. I apply my technique to those myogenic ptosis patients with at least 5 mm of levator function and do not convert to frontalis slings until levator function is less than 5 mm. All surgeries are done under local standby anesthesia so that lid height can be assessed while the patient sits upright. My surgical goal is similar to that of the authors—that is, to set the eyelid height with the patient awake, so that the eyelids just clear the visual axis and allow adequate lid closure. I encourage the authors to examine Mu¨ ller’s muscle more closely as they dissect aponeurosis away from it in their myogenic ptosis patients. I think they will find not only that it is infiltrated with fat, but also that it often appears much thicker than normal. I suggest dissection of Mu¨ ller’s away from conjunctiva in conjunction with levator aponeurosis, as it is very straightforward. Advancing the levator aponeurosis with Mu¨ ller’s will allow the lid to be elevated more easily and to a higher level than when just the levator aponeurosis (without Mu¨ ller’s) is advanced. Exposure kera-

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topathy secondary to lagophthalmos has not been a problem in long-term follow-up (15 years) with this technique. As these dystrophies are progressive, a recurrence of ptosis can occur at some point. I estimate about a 10% recurrence rate with my technique, which is in keeping with Rodrigue and Molgat’s 13% recurrence of ptosis.4 As long as they have greater than 5 mm of levator function, the technique I describe can be redone. DAVID R. JORDAN, MD, FACS Ottawa, Canada References 1. Wong VA, Beckingsale PS, Oley CA, Sullivan TJ. Management of myogenic ptosis. Ophthalmology 2002;109:1023–31. 2. Jordan DR, Addison DJ. Surgical results and pathological findings in the oculopharyngeal dystrophy syndrome. Can J Ophthalmol 1993;28:15– 8. 3. Johnson CC, Kuwabara T. Oculopharyngeal muscular dystrophy. Am J Ophthalmol 1974;77:872–7. 4. Rodrigue D, Molgat YM. Surgical correction of blepharoptosis in oculopharyngeal muscular dystrophy. Neuromuscul Disord 1997;7(suppl):82– 4.

Author reply Dear Editor: Jordan has made valid comments regarding the appearance of the levator and Mu¨ ller’s muscle in most forms of myogenic ptosis at surgery. Both may appear to have fatty infiltration. The plane between these 2 muscles may be poorly defined, making standard aponeurosis surgery difficult. The description of our surgical technique for levator advancement was too generic and did not include all of the nuances required for this difficult group of patients. Jordan has correctly drawn attention to some of these nuances. Our preference for early frontalis suspension stems from the progressive nature of these conditions and has worked well in our hands with long-term follow-up. VINCENT A. WONG TIMOTHY SULLIVAN PETER S. BECKINGSALE CHRISTINE OLEY Brisbane, Australia

Superior Oblique Palsy Dear Editor: Kono and Demer1 demonstrated in 13 patients with superior oblique (SO) palsy that clinical “overaction of the inferior oblique” is not due to an ipsilateral inferior oblique (IO) that is “too large [hypertrophied] or contracts too much.” In 25 years of a practice focused on pediatric strabismus, I have observed that the distal portion of the IO between the insertion and the lateral edge of the inferior rectus at surgery in more than 50 children with SO palsy with head tilt and in over 200 children with primary IO overaction associated with infantile esotropia and with no head tilt. I routinely dissect out this distal portion of the IO before reattaching it to the globe in a variety of different places, which vary with the purpose of the surgery. My clinical impression is that obvious hypertrophy of the IO is common in the children

Letters to the Editor with overelevation in adduction and infantile esotropia, but that the children with SO palsies and head tilts have smaller, nonhypertrophied IO. I began playing attention to this detail shortly after my scrub nurse (Susan Seekatz), who has worked with me for 22 years, exclaimed during one surgery, “Wow, that’s the inferior oblique that could eat New York!” Clinical impressions can be incorrect, of course, with cases that verify the clinical impression strongly remembered and those that do not simply forgotten. I have previously described2 a 2-year-old child who presented with a left head tilt and overelevation in adduction of the left eye. His mother had taken photographs of her child almost every day with a camera that recorded the date on the photograph. This left head tilt was clearly orthopedic, and the orthopedic surgeon correctly predicted that it would resolve spontaneously. Once the head tilt had disappeared, I recessed the left IO with a preoperative diagnosis of primary overaction of the IO. At surgery, however, the IO was not hypertrophied, and I told the family immediately after surgery that the true diagnosis might be SO palsy. Sure enough, in the next few months a right head tilt developed (as expected for a congenital left SO palsy with a lax tendon),3,4 and a Harada–Ito procedure on the SO tendon was subsequently required to eliminate the head tilt. Spencer and McNeer found structural alterations in primarily overacting inferior oblique muscles associated with childhood esotropia to be similar to the changes in muscle fibers after experimentally induced hypertrophy.5 Have Demer and coworkers found IO hypertrophy in patients with overelevation in adduction associated with infantile esotropia? If so, then perhaps a diagnosis of primary overaction of the IO should be judged suspect, and the alternative diagnosis of SO palsy or pulley heterotopy should be entertained if the IO is not hypertrophied at surgery. Also, I would appreciate their comment on whether the finding of Clark et al that the medial rectus pulley is displaced superiorly in SO palsy could provide adequate explanation for the overelevation in adduction.6 JAMES L. MIMS III, MD San Antonio, Texas References 1. Kono R, Demer JL. Magnetic resonance imaging of the functional anatomy of the inferior oblique muscle in superior oblique palsy. Ophthalmology 2003;110:1219 –29. 2. Mims JL III. Report of the Annual Meeting of the Texas Society for Pediatric Ophthalmology. Houston, Texas, September 18, 1999. Binocul Vis Strabismus Q 1999;14:318 –21. 3. Plager DA. Superior oblique palsy and superior oblique myokymia. In: Rosenbaum AL, Santiago AP, eds. Clinical Strabismus Management: Principles and Surgical Techniques. Philadelphia: WB Saunders; 1999:219 –29. 4. Mims JL III. The triple forced duction test(s) for the diagnosis and treatment of superior oblique palsy—with an updated flow chart for unilateral superior oblique palsy. Binocular Vis Strabismus Q 2003;18:15–24. 5. Spencer RF, McNeer KW. Structural alterations in overacting inferior oblique muscles. Arch Ophthalmol 1980;98:128 –33. 6. Clark RA, Miller JM, Demer JL. Displacement of the medial rectus pulley in superior oblique palsy. Invest Ophthalmol Vis Sci 1998;39:207–12.

Author reply Dear Editor: We appreciate the clinical impression of Dr Mims regarding inferior oblique (IO) muscle hypertrophy in children with overelevation in adduction associated with infantile esotropia (ET), but not in association with superior oblique (SO) palsy. This impression in infantile ET could be tested rigorously using quantitative magnetic resonance imaging, as we did for SO palsy. Such quantitative testing is important, because surgical impressions of muscle belly size are, in our experience, subject to variability from muscle edema that develops rapidly during surgical manipulation. Small children operated for infantile ET could be more prone to rapid development of IO edema than older patients operated for SO palsy because of the necessity of more traumatic dissection of the insertion of the IO’s orbital layer from its connective tissue sheath and pulley, which are more substantial in young people.1 Dr Mims’ case of the 2-year-old child with SO palsy is interesting, but subject to criticisms, including this one. In years of systematic study of extraocular muscle histology by the rigorous technique of serial sectioning of intact, whole orbits,1–3 we have been impressed in comparison by the severe artifacts introduced in specimens removed at surgical biopsy. Examination of comparable normal control muscles is essential to reach meaningful conclusions, yet will be unavailable from biopsies because truly normal muscles are virtually never removed. The changes reported by Spencer and McNeer in “primary overacting” IO muscles associated with childhood ET4 may not be specific for hypertrophy, but could instead reflect growing muscles in early childhood. Using quantitative histological techniques, we have found age-related differences in human extraocular muscle fibers3 and connective tissues.2 A solution to this dilemma may be forthcoming upon completion of our prospective, histological, magnetic resonance imaging study of extraocular muscle anatomy in serially sectioned whole orbits of normal versus naturally and artificially strabismic monkeys supplied by the laboratory of Dr Lawrence Tychsen. Our prospective magnetic resonance imaging study of extraocular muscles in strabismus has not yet achieved an adequate sample of patients with overelevation in adduction associated with unoperated infantile ET. Superior displacement of the medial rectus pulley in SO palsy might explain some cases of overelevation in adduction, though average pulley displacement is small.5 JOSEPH L. DEMER, MD, PHD Los Angeles, California References 1. Demer JL, Oh SY, Clark RA, Poukens V. Evidence for a pulley of the inferior oblique muscle. Invest Ophthalmol Vis Sci 2003;44:3856 – 65. 2. Kono R, Poukens V, Demer JL. Quantitative analysis of the structure of the human extraocular muscle pulley system. Invest Ophthalmol Vis Sci 2002;43:2923–32. 3. Oh SY, Poukens V, Demer JL. Quantitative analysis of rectus extraocular muscle layers in monkey and humans. Invest Ophthalmol Vis Sci 2001;42:10 – 6.

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