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 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 JLDemer JL et al MRI of the functional anatomy of the sup obl muscle. IOVS & 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 KSiepmann K, Herzau V Klin Monatsbl Augenheilkd MayHerzau V

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. 1999Sato M

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 R x 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 ∆ 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

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