“Inverted Brown pattern”: A Tight inferior oblique muscle masquerading as a superior oblique mus...
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“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.

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“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


Purpose
Purpose muscle masquerading as a superior oblique muscle underaction – clinical characteristics and surgical management

  • To characterize and evaluate surgical management of patients with unilateral deficiency of depression in adduction

  • i.e. SO underaction, without significant ipsilateral IO overaction


Methods
Methods muscle masquerading as a superior oblique muscle underaction – clinical characteristics and surgical management

  • 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


Results
Results muscle masquerading as a superior oblique muscle underaction – clinical characteristics and surgical management

  • 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


Results continued
Results continued muscle masquerading as a superior oblique muscle underaction – clinical characteristics and surgical management

  • 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


Conclusions
Conclusions muscle masquerading as a superior oblique muscle underaction – clinical characteristics and surgical management

  • “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


Discussion
Discussion muscle masquerading as a superior oblique muscle underaction – clinical characteristics and surgical management

  • “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


Discussion1
Discussion muscle masquerading as a superior oblique muscle underaction – clinical characteristics and surgical management

  • “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


Discussion2
Discussion muscle masquerading as a superior oblique muscle underaction – clinical characteristics and surgical management

  • 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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