Superior oblique palsy

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Kono and Demer1Kono R Demer J.L Magnetic resonance imaging of the functional anatomy of the inferior oblique muscle in superior oblique palsy.Ophthalmology. 2003; 110: 1219-1229Abstract Full Text Full Text PDF PubMed Scopus (78) Google Scholar 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 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 described2Mims III, J.L Report of the Annual Meeting of the Texas Society for Pediatric Ophthalmology. Houston, Texas, September 18, 1999.Binocul Vis Strabismus Q. 1999; 14: 318-321PubMed Google Scholar 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),3Plager D.A Superior oblique palsy and superior oblique myokymia.in: Rosenbaum A.L Santiago A.P Clinical Strabismus Management Principles and Surgical Techniques. WB Saunders, Philadelphia1999: 219-229Google Scholar, 4Mims III, J.L 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: 15-24PubMed Google Scholar 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.5Spencer R.F McNeer K.W Structural alterations in overacting inferior oblique muscles.Arch Ophthalmol. 1980; 98: 128-133Crossref PubMed Scopus (21) Google Scholar 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.6Clark R.A Miller J.M Demer J.L Displacement of the medial rectus pulley in superior oblique palsy.Invest Ophthalmol Vis Sci. 1998; 39: 207-212PubMed Google Scholar