Brown's syndrome (superior oblique tendon sheath syndrome) shows a specific pattern on the three-step test for vertical diplopia. Which finding differentiates it from superior oblique palsy?

• A Hypertropia that increases on ipsilateral head tilt (positive Bielschowsky head tilt test)
• B Inability to elevate in adduction with normal or even greater elevation in abduction ✓
• C Greater vertical deviation at near than at distance
• D Hypotropia that increases on contralateral gaze and ipsilateral head tilt

Explanation

Brown's syndrome is characterized by restricted elevation specifically in adduction (the superior oblique tendon sheath is too tight or short to allow the superior oblique to lengthen during elevation in adduction). Elevation in abduction is normal or may be excessive. On the Parks-Bielschowsky three-step test, superior oblique palsy shows ipsilateral hypertropia increasing on contralateral gaze and ipsilateral head tilt. Brown's syndrome typically does NOT show a positive head tilt test and has restricted elevation in adduction as the key diagnostic feature, often with a 'click' on attempted adduction-elevation.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.