Change of nystagmus direction during a head-roll test in lateral semicircular canal cupulolithiasis.

OBJECTIVE: To demonstrate positional nystagmus during a head-roll test in two patients with lateral semicircular canal (LSCC) cupulolithiasis who presented with spontaneous detachment of otoliths from the LSCC cupula, and to confirm that otoliths may adhere to both the utricle and canal sides of the cupula. PATIENTS AND METHODS: Using video nystagmography, positional nystagmus was evaluated in two patients with LSCC cupulolithiasis who showed the change of nystagmus direction during a head-roll test. RESULTS: Both patients presented with persistent left-beating and right-beating nystagmus when the head was bent forward and backward, respectively. This suggests the presence of either cupulolithiasis on the right side or light cupula on the left side of the LSCC. In Case 1, transformation from cupulolithiasis to canalolithiasis occurred, implicating the detachment of otoliths from the canal side of the right LSCC cupula. In Case 2, vigorous right-beating nystagmus was followed by persistent left-beating nystagmus when the head was rolled to the left. Following this, direction-fixed left-beating nystagmus was observed at all positions, which may indicate that otoliths attached on utricle side of the right LSCC cupula were detached and fell into the utricle under the influence of gravity. A conversion of nystagmus direction may be explained by an expression of short-term adaptation of vestibular tone. CONCLUSIONS: Otoliths can be attached to either side of the cupula in LSCC cupulolithiasis. Because it is difficult to determine the attached side at the time of diagnostic maneuver, the therapeutic approach should include maneuvers designed to detach otolith particles from both the utricle and canal side.