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Purpose

“Inverted Brown pattern”: A Tight inferior oblique muscle masquerading as a superior oblique muscle underaction – clinical characteristics and surgical management Guyton et al J AAPOS 2006; 10:565-572. Purpose.

alana-fulton
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Purpose

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  1. “Inverted Brown pattern”: A Tight inferior oblique muscle masquerading as a superior oblique muscle underaction – clinical characteristics and surgical managementGuyton et alJ AAPOS 2006; 10:565-572

  2. Purpose • To characterize and evaluate surgical management of patients with unilateral deficiency of depression in adduction • i.e. SO underaction, without significant ipsilateral IO overaction

  3. Methods • Retrospective study • Patients with diplopia in downgaze who had • Ipsilat IO muscle weakening • Contralat IR muscle recession • Patients showed unilateral deficiency of depression in adduction, suggesting SO muscle underaction, with no or minimal IO muscle overaction • 8PD hypertropia in involved quadrant of downgaze • No more than 6-7PD of overelevation in adduction

  4. Results • 12 pts • 3 had prev surgery for Brown syndr • 4 had prev orbital floor trauma • Exaggerated forced duction testing • Recorded for 9 pts (other 3 not recorded) • Tight IO muscle recorded for 7pts (78%), with no laxity of SO tendon

  5. Results continued • 12 pts • 4 had contralateral IR muscle recession • But in all 4, deficiency of depression in adduction recurred • Ave FU 16mo (7wks to 5yrs) • 8 had IO muscle weakening procedure • IO recession (5) or • IO denervation & extirpation (3) – for excessive tightness on exaggerated FDT • Achieved overall improvement of ocular alignment • 9 subsequent patients with similar pattern of misaligment treated with IO weakening • Good results

  6. Conclusions • “Inverted Brown pattern” • Caused by tight or inelastic IO muscle • Treatment: • IO muscle weakening procedure • Even though no significant IO muscle overaction • Better results than IR muscle recession

  7. Discussion • “Inverted Brown pattern” not the same as “Reverse Brown Pattern” • “Reverse Brown Pattern” - Jampolsky coined the term to describe cases of • Thyroid myopathy with asymmetric upgaze deficiencies due to asymmetric IR muscle tightening

  8. Discussion • “Inverted Brown pattern” inverted wrt Brown syndrome • Difference: • Y pattern sometimes seen in Brown synd • No Y pattern in “inverted Brown pattern” • Due to less side slip of IO muscle – firmly attached to IR muscle sleeve whilst more slip occurs with SO tendon causing Y pattern

  9. Discussion • Customary treatment for apparently underacting SO with no or minimal IO overaction • Ipsilateral SO tuck or • Contralateral IR recession • Consider IO muscle weakening • Good results (small numbers, no longterm follow-up) • Analogous to Brown Syndrome • Low complication rate (rare fat adherence syndrome)

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