During positional testing for suspected horizontal canal BPPV, the supine head turn (Pagnini-McClure maneuver) to the RIGHT produces geotropic direction-changing nystagmus (beats toward the ground) that is STRONGER on the right. This finding indicates:

• A Left horizontal canal cupulolithiasis
• B Left horizontal canal canalithiasis
• C Right horizontal canal cupulolithiasis
• D Right horizontal canal canalithiasis ✓

Explanation

In horizontal canal canalithiasis, turning the head toward the affected side produces the stronger geotropic nystagmus because the canaliths move in the direction of gravity, creating maximal ampulopetal endolymph flow and excitation. Stronger nystagmus when turning right indicates RIGHT horizontal canal canalithiasis. Cupulolithiasis produces ageotropic nystagmus that is stronger with the affected ear up.

Reference: Cummings Otolaryngology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.