Transcript FOURTH NERVE PALSY & SIMILAR / SIMULATING CONDITIONS

FOURTH NERVE /
SUPERIOR OBLIQUE
PALSY
& SIMILAR / SIMULATING
CONDITIONS
DR LIONEL KOWAL
RVEEH / CERA
MELBOURNE
Types of FNP / SOP
used 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
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
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]
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
JOE DEMER
• Coming to SQUINT CLUB 2006
• MELBOURNE
• APRIL 21-22
R SOP
HEAD TILT
TO LEFT
R IO OA
R SO UA
TIGHT RSR
RIR ‘UA’
SOP image
LSO OK
RSO ?absent
SOP image
RSO clearly smaller than LSO
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 V Klin Monatsbl Augenheilkd. 2005 May
Demer: X-sectional area of SO
segregates SOP from normal SO
Up gaze to down gaze:
 x-sectional area of SO in normals only
Change in x-sectional area from up to
down gaze segregates SOP from
normals
Real SOP
Head injury
• ARIX gene
• Vascular disease
• Rare: SOP- specific CNS pathology [LK:
1/500]
Fake SOP
Abnormal cyclovertical anatomy
– Craniofacial anomalies
– Posteroplaced trochlea [Bagolini]
• Abnormal physiology
– Brodsky’s wild pitch
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
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
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
Principles of treatment
1.
2.
3.
4.
5.
Make it better - don’t over correct
Trauma: look for bilateral SOP
Accurate measurements
Tighten floppy muscles
Rc tight muscles
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]
Principles of treatment :
IO OA
1.
2.
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
Principles of treatment
Tight SR
2. ‘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
Sequelae of SOP:
IO OA & tight SR
REAL CONG R SOP
& CONG ET FIXING
WITH PARETIC R EYE
 L HYPO
NOT ‘IDIOPATHIC
IR FIBROSIS’
R SO atrophic
R SO atrophic
TREATMENT MORBIDITY
• Sup Obl
– Brown’s
– Ptosis
• Inf Obl
– Upgaze restriction
– Lid change
TREATMENT MORBIDITY
• Sup Rectus
–Ptosis / lid retraction
• Inf Rectus
–Lid retraction
–Progressive over correction
TREATMENT
EXPECTATIONS
• LK audit early 90’s n=450
• Unilateral SOP [all sorts]:
–1.3 surgeries
– 90+% VG to excellent
SOP
• Difficult area of strabismus
• Imaging has been under- utilised
• Natural history of different sub types &
their treatments not well defined