A 30-year-old woman has vertical diplopia, worst when walking downstairs. Examination shows a left hypertropia that increases on right gaze and increases further when she tilts her head to the LEFT. Which muscle is paretic?
- A Left superior rectus
- B Left superior oblique ✓
- C Left inferior oblique
- D Right inferior rectus
Correct answer: B. Left superior oblique
Explanation
The three-step test identifies the paretic cyclovertical muscle. A left hypertropia implicates the depressors of the left eye or elevators of the right. Worse on right gaze implicate the vertically acting muscles used in that direction, narrowing to left superior oblique or left superior rectus. Worsening on left head tilt implicates intortors of the left eye, leaving the left superior oblique. A positive Bielschowsky head tilt test toward the side of the hypertropia is the hallmark of superior oblique palsy, the commonest isolated cranial nerve four palsy cause being trauma.
Reference: Kanski's Clinical Ophthalmology, 9th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.