FOURTH NERVE / SUPERIOR OBLIQUE PALSY FNP / SOP

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FOURTH NERVE / SUPERIOR OBLIQUE PALSY FNP /
SOP

• LIONEL KOWAL
• RVEEH / CERA
• MELBOURNE

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Types of apparent FNP / SOPAll of
these LOOK THE SAME

• 1. Definite SOP
• Only true HALF the time that it is diagnosed!
• 2. Possible SOP or Resolved SOP
• 3. Idiopathic oblique dysfunction other
• synonyms for CycloVertical Dysfunction of
  uncertain cause CVD
• Mostly due to minor anatomical errors
• 4. Pulley heterotopy radiological diagnosis
• 5. Something quite different Graves, old
  fracture, other vertical rectus disease, post
  ret-det surgery,

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Definite SOP / Possible SOP / CVD / pulley
heterotopy .. can all ?

• Vertical misalignment
• Disrupt horizontal fusion ? horizontal
  misalignment
• Head tilts
• Vertical greater to one side
• Apparent IO OA, SO UA
• CLINICAL PICTURE CAN BE THE SAME IN ALL THESE
  TYPES OF SOP PSEUDO - SOP

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Is it important to differentiate?
LUMPERS Traditional UK approach All SOPs get
similar treatment

• Lumpers vs splitters

SPLITTERS Post 1950s US approach Individualise
treatment to specific subtype of SOP
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Lumpers

• If it looks / smells / sounds a bit like SOP,
  then call it SOP.
• Congenital SOP label used with NO evidence of
  true palsy
• Rx inf obl weakening IO-
• Some lumpers one size fits all. Some 2-3
  different ops
• Nucci Milan, EJO sectional editor, trained Italy
  Chicago, 62 articles in PubMed,

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Splitters

• Knapp important to split
• 7 different types based on detailed measurements
  and versions
• Later subclassified further by others
• some pts do well with IO-
• others will do better with SO plication or SR
  weakening
• Selection bias strabismus specialist tends to
  see pts with inadequate results after IO-
• LK a splitter

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Lumpers vs Splitters EBM
21st Century issues resolved by randomised
prospective trial - still waiting Eminence based
medicine Loudest most forceful charismatic
medical conference personality defines clinical
practice. MOST strabismus specialists are
splitters
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Splitting

• 1. Careful measurements in cardinal positions
• Allows classification into Knapp types or more
  modern variants and likely surgical solution

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Splitting

• 2. Radiology
• Is it a True SO atrophy
• More likely to have floppy SO
• ?less likely to respond to IO-
• ?more likely to need SO

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MRI X-sectional area of SO segregates SOP from
normal SO

• When strabismus specialists made clinical
  diagnosis of SOP, they were wrong 50 of the
  time!!

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Splitting

• 3. Reserve final surgical plan until
  intra-operative FDT
• If SR is tight, more likely to need SR-
• If SO floppy,.
• If IO is tight,
• If IR is tight,
• Need a MUCH larger surgical repertoire than
  Lumpers

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R SOP HEAD TILT TO LEFT
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ADAPTATION TO WEAK SO
R IO OA
ADAPTATIONS MAY DOMINATE THE CLINICAL PICTURE
CORE DEFECT
R SO UA
ADAPTATION TO CHRONIC HYPERTROPIA
TIGHT RSR RIR UA
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SOP image
LSO OK RSO ?absent
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Case 1

• Atrophic SO
• SO UA
• IO OA SOUA gt IO OA
• IR UA presumed tight SR from having had a
  chronic hypertropia
• LUMPERS Inf obl weakening
• SPLITTERS Final decision after FDT

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Splitters

• Atrophic SO and SO UA
• More likely to find floppy SO
• More likely to need SO plication
• Apparent IR UA
• Probably tight SR
• Needs SR- or will have DG diplopia
• If FDT on SO SR are OK IO-

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Principles of treatment

• Acquired SOP 12 mo can Rx earlier if getting
  worse
• Long standing Acquired suppression makes it
  harder to characterise
• SPLITTERS
• Usually have to treat the muscular consequences
  of the SOP rather than the SOP itself

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Principles of treatment

• Make it better - dont over correct
• Trauma look for bilateral SOP
• Accurate measurements
• SPLITTERS
• Tighten floppy muscles
• Recess tight muscles

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Principles of treatment IO-

• Parks IO Rc for 10-15 ? height in PP
• 20 ? To lateral edge IR
• 25 ? 2mm ant to edge IR

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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

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TREATMENT EXPECTATIONS

• LK audit early 90s n450
• Unilateral SOP all sorts
• 1.3 surgeries
• 90 Very Good to excellent

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SOP

• Difficult area of strabismus
• Lumpers vs Splitters unresolved
• Splitters more likely to see the more complex pts
  believe that a more complicated approach is the
  correct one

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The contralateral inferior rectus

• Lumpers
• 1st op inf obl
• 2nd op c/l inf rectus
• Splitters
• Consider c/l inf rectus if tight or if SO UA
  without SO floppiness

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The contralateral inferior rectus

• MRI of the Functional Anatomy of the Inferior
  Rectus Muscle in Superior Oblique Muscle
  Palsy.Jiang L, Demer JL.UCLA Ophthalmology.
  November 2008.
• PURPOSE Biomechanical modeling consistently
  indicates that SO muscle weakness alone is
  insufficient to explain the large hypertropia
  often observed in SOP. MRI to investigate if
  any size or contractility changes in IR may
  contribute.
• 17 pats with unilateral SOP and 18 orthotropic
  controls.
• Diagnosis of SOP based on clinical presentations,
  subnormal contractility small SO muscle size

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The contralateral inferior rectus

• OUTCOME MEASURES X-sectional areas of IR SO.
• RESULTS Patients had 16/-7? of central gaze
  hypertropia and exhibited ipsilesional SO muscle
  atrophy and subnormal contractility.
• CONCLUSIONS ..the contralesional IR is larger
  and more contractile than the ipsilesional IR,
  reflecting likely neurally mediated changes that
  augment the relatively small hypertropia
  resulting from SOP.
• Recession of the hyperfunctioning contralesional
  IR in SOP is a physiologic therapy.