In cupulolithiasis affecting the posterior semicircular canal, what distinguishes the positional nystagmus from the more common canalolithiasis form?
- A The latency is shorter than 1 second and there are no symptoms
- B The nystagmus is purely horizontal and never torsional
- C The nystagmus lasts longer than 60 seconds because otoconia are stuck to the cupula itself ✓
- D It cannot be provoked by any positioning manoeuvre
Correct answer: C. The nystagmus lasts longer than 60 seconds because otoconia are stuck to the cupula itself
Explanation
In cupulolithiasis the otoconial debris adheres directly onto the cupula, making it density abnormal and gravity sensitive. Because the particles never settle out of the canal, the provoked nystagmus persists beyond the usual 60 second limit seen in canalolithiasis, often lasting several minutes. It still has a short latency and fatigability may be reduced. It remains provokable by the Dix-Hallpike test and the nystagmus retains the torsional upbeating character of posterior canal stimulation.
Reference: Dhingra, Diseases of Ear, Nose and Throat, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.