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