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Superior oblique palsy
Strabismus
Key Points
- •CN IV palsy is the most common isolated cyclovertical muscle palsy; congenital cases account for 30–40% and may decompensate in adulthood with large vertical fusional amplitudes (>3–5 PD)
- •The Parks 3-step test systematically localises the paretic cyclovertical muscle: (1) hypertropic eye, (2) worse in right or left gaze, (3) Bielschowsky head tilt test - all three steps must be concordant
- •Double Maddox rod >10 degrees total excyclotorsion or alternating hypertropia in lateral gaze suggests bilateral CN IV palsy - always look for this after head trauma
- •Microvascular CN IV palsy in adults >50 resolves spontaneously in 90% within 3–6 months - observe before planning surgery; re-image (MRI) if no improvement by 3 months
- •The surgical approach follows Knapp classification: small deviation (<15 PD) = IO weakening alone; moderate (15–25 PD) = IO weakening + SO tuck or contralateral IR recession; bilateral = bilateral IO anteriorisation ± Harada-Ito
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17 more sections are included with the Clinical plan.
- Definition
- Epidemiology
- Aetiology and causes
- Pathogenesis
- Classification
- Risk factors and associations