Transcript FOURTH NERVE PALSY & SIMILAR / SIMULATING CONDITIONS

FOURTH NERVE / SUPERIOR
OBLIQUE PALSY FNP / SOP
LIONEL KOWAL
RVEEH / CERA
MELBOURNE
Types of apparent FNP / SOP
All 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, …
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

Is it important to differentiate?
LUMPERS
Traditional
UK approach
 Lumpers
vs
All SOPs get similar
treatment
splitters
SPLITTERS
Post 1950’s US approach
Individualise treatment
to specific subtype of
SOP
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,…
Splitters

Knapp: important to split
7 different types based on detailed measurements and
versions
Later subclassified further by others




some pts do well with IOothers will do better with SO plication or SR
weakening……
Selection bias: strabismus specialist tends to
see pts with inadequate results after IOLK: a splitter
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
Splitting……
 1.
Careful measurements in
cardinal positions
Allows classification into Knapp
types [or more modern variants] and
likely surgical solution
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+
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!!
Splitting……
3. Reserve final surgical plan until intra-operative
FDT
If SR is tight, more likely to need SRIf SO floppy,….
If IO is tight,…
If IR is tight,…
Need a MUCH larger surgical repertoire than
Lumpers
R SOP
HEAD TILT
TO LEFT
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’
SOP image
LSO OK
RSO ?absent
Case #1
Atrophic SO
 SO UA
 IO OA
SOUA > IO OA
 IR UA [presumed tight SR from having had a ‘chronic

hypertropia’]
LUMPERS : Inf obl weakening
 SPLITTERS : Final decision after FDT

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
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
Principles of treatment
Make it better - don’t over correct
2. Trauma: look for bilateral SOP
3. Accurate measurements
SPLITTERS
1. Tighten floppy muscles
2. Recess tight muscles
1.
Principles of treatment : IOParks’ IO Rc for 10-15 ∆ height in PP
≈ 20 ∆ To lateral edge IR
≈ 25 ∆ 2mm ant to edge IR
Principles of treatment
Tight 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
TREATMENT EXPECTATIONS
 LK
audit early 90’s n=450
 Unilateral SOP [all sorts]:
 1.3

surgeries
90+% Very Good to excellent
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
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
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
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.