FOURTH NERVE / SUPERIOR OBLIQUE PALSY & SIMILAR / SIMULATING CONDITIONS
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FOURTH NERVE / SUPERIOR OBLIQUE
PALSY& SIMILAR / SIMULATING
CONDITIONS
DR LIONEL KOWALRVEEH / CERA
MELBOURNE
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
Definite/ Possible/ Fake SOP can all
– Vertical misalignment– Disrupt horizontal fusion & horizontal
misalignmentCVD 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. Make it better - don’t over correct
2. Trauma: look for bilateral SOP
3. Accurate measurements
4. Tighten floppy muscles
5. 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. 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
2. 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 treatmentTight SR
2. ‘Chronic hypertropia’ may tight SR, spread of comitance & [apparent] IR UA wch may come to dominate the clinical picture.
SR Rc requiredRecessing 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