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