CONCLUSION: A short clinical course and frequent recurrence are common features of persistent geotropic direction-changing positional nystagmus with neutral position (positional nystagmus of light cupula: PNLC) and cupulolithiasis of the lateral semicircular canal. It is suggested that PNLC is caused by light debris attached to the cupula of the lateral semicircular canal. OBJECTIVES: PNLC is a sub-type of direction-changing positional nystagmus. It is thought to be caused by anti-gravitational deviation of the cupula of the lateral semicircular canal (light cupula); however, the exact mechanism is yet to be elucidated. To this end, the clinical features of PNLC were studied. METHOD: Clinical charts of 27 patients (13 men and 14 women) with PNLC were reviewed. RESULTS: The nystagmus had resolved within a week in 70% and within 30 days in 89% of the patients. The recurrence rate was 33%. The subjects did not have a history of alcohol intake, head trauma, or vestibular neuritis.
CONCLUSION: A short clinical course and frequent recurrence are common features of persistent geotropic direction-changing positional nystagmus with neutral position (positional nystagmus of light cupula: PNLC) and cupulolithiasis of the lateral semicircular canal. It is suggested that PNLC is caused by light debris attached to the cupula of the lateral semicircular canal. OBJECTIVES: PNLC is a sub-type of direction-changing positional nystagmus. It is thought to be caused by anti-gravitational deviation of the cupula of the lateral semicircular canal (light cupula); however, the exact mechanism is yet to be elucidated. To this end, the clinical features of PNLC were studied. METHOD: Clinical charts of 27 patients (13 men and 14 women) with PNLC were reviewed. RESULTS: The nystagmus had resolved within a week in 70% and within 30 days in 89% of the patients. The recurrence rate was 33%. The subjects did not have a history of alcohol intake, head trauma, or vestibular neuritis.