FOURTH NERVE / SUPERIOR OBLIQUE PALSY & SIMILAR / SIMULATING CONDITIONS

1. FOURTH NERVE / SUPERIOR OBLIQUE PALSY& SIMILAR / SIMULATING CONDITIONS DR LIONEL KOWAL RVEEH / CERA MELBOURNE

2. Types of FNP / SOPused as synonyms • 1. Definite SOP • 2. Possible SOP or Resolved SOP • 3. Fake SOP • Idiopathic oblique dysfunction & other synonyms for … • “Cyclovertical dysfunction of uncertain cause” CVD

3. Definite/ Possible/ Fake SOP can all  • Vertical misalignment • Disrupt horizontal fusion &  horizontal misalignment CVD can also be a consequence of loss of horizontal fusion - seen in any horizontal strab • Head tilts • Vertical greater to one side • Apparent IO OA, SO UA CLINICAL PICTURE CAN BE THE SAME IN ALL TYPES OF SOP

4. How to tell definite from fake: Simonsz • GA: take off SO, inject sux & measure L-T curve • LA: take off SO; ask pt to look up / down & measure L-T curve • When good clinicians made clinical diagnosis of real SOP, they were wrong 50% of the time Klin Monatsbl Augenheilkd. 1992 Length-tension measurement of oblique eye muscles in strabismus operations for differentiating trochlear paralysis and strabismus sursoadductorius [German]

5. How to tell definite from fake : Demer • Joe Demer • Coronal scans : can you see the muscle belly? • Upgaze to downgaze: watch SO belly move back & increase in size When subspecialist clinicians made clinical diagnosis of real SOP, they were wrong 50% of the time!! Demer JL et al MRI of the functional anatomy of the sup obl muscle. IOVS. 1995 & in 1994 AAPOS / ISA joint meeting proceedings

6. JOE DEMER • Coming to SQUINT CLUB 2006 • MELBOURNE • APRIL 21-22

7. R SOP HEAD TILT TO LEFT

8. R IO OA R SO UA TIGHT RSR RIR ‘UA’

9. SOP image LSO OK RSO ?absent

10. SOP image RSO clearly smaller than LSO

11. How to tell definite from fake : Herzau • Is congenital SO strabismus a paretic disorder? A[n] MRI study [German] …full blown clinical picture of a congenital SOP … symmetrical muscle volumes on both sides in all coronal sections • CLINICAL PICTURE OF REAL SOP CAN BE WRONG Siepmann K, Herzau VKlin Monatsbl Augenheilkd. 2005 May

12. Demer: X-sectional area of SO segregates SOP from normal SO

13. Up gaze to down gaze:  x-sectional area of SO in normals only

14. Change in x-sectional area from up to down gaze segregates SOP from normals

15. Real SOP Head injury • ARIX gene • Vascular disease • Rare: SOP- specific CNS pathology [LK: 1/500]

16. Fake SOP Abnormal cyclovertical anatomy • Craniofacial anomalies • Posteroplaced trochlea [Bagolini] • Abnormal physiology • Brodsky’s wild pitch

17. Telling definite from fake does it matter? • “Anomalous SO tendons [clinically] are nearly always associated with [radiologically] attenuated SO muscle … provides … explanation for the phenomenon of laxity of the SO tendon” • Sato M. Magnetic resonance imaging and tendon anomaly associated with congenital superior oblique palsy. Am J Ophthalmol. 1999

18. Telling definite from fake - does it matter? Forewarned / forearmed • Atrophic SO on scan  floppy SO tendon on FDT : may need SO tuck • SO tuck more difficult / higher morbidity c.f. other surgeries • Real SOP: ?less reliable long term prognosis than ‘fake’ SOP

19. Possible / Resolved • Radiological changes may be too subtle for routine scans • SOP may have resolved leaving small permanent change in L-T curve of SO same mechanism as small ET remaining after 6th n. paresis resolves

20. Principles of treatment • Make it better - don’t over correct • Trauma: look for bilateral SOP • Accurate measurements • Tighten floppy muscles • Rc tight muscles

21. Principles of treatment Acquired: wait 12 mo [can Rx earlier if getting worse] Long standing: Acquired suppression makes it harder to characterise Usually have to treat the muscular consequences of the SOP rather than the SOP itself [hence Knapp 1-7]

22. Principles of treatment : IO OA • Weak SO often  IO OA as a consequence, and this may dominate the clinical picture far more than the SO UA of the ‘original’ SOP • Fake SOP often manifests as IO OA Parks’ IO Rc for 10-15 ∆ height in PP ≈ 20 ∆ To lateral edge IR ≈ 25 ∆ 2mm ant to edge IR

23. Principles of treatmentTight SR • ‘Chronic hypertropia’ may  tight SR, spread of comitance & [apparent] IR UA wch may come to dominate the clinical picture. SR Rc required Recessing SR will increase extorsion unless it is temporally transposed

24. Sequelae of SOP: IO OA & tight SR

25. REAL CONG R SOP & CONG ET FIXING WITH PARETIC R EYE  L HYPO NOT ‘IDIOPATHIC IR FIBROSIS’

26. R SO atrophic

27. R SO atrophic

28. TREATMENT MORBIDITY • Sup Obl • Brown’s • Ptosis • Inf Obl • Upgaze restriction • Lid change

29. TREATMENT MORBIDITY • Sup Rectus • Ptosis / lid retraction • Inf Rectus • Lid retraction • Progressive over correction

30. TREATMENT EXPECTATIONS • LK audit early 90’s n=450 • Unilateral SOP [all sorts]: • 1.3 surgeries • 90+% VG to excellent

31. SOP • Difficult area of strabismus • Imaging has been under- utilised • Natural history of different sub types & their treatments not well defined