Simple methods for determining the affected side and performing otolith repositioning in cases of lateral semicircular canal-benign paroxysmal positional vertigo-canalolithiasis: Healthy-ear-down 135° maneuver and affected-ear-down 135° maneuver.

OBJECTIVE: To develop simple and effective methods for determining the affected side and promoting early symptom resolution in lateral semicircular canal-benign paroxysmal positional vertigo (L-BPPV) due to canalolithiasis, including its geotropic (L-BPPV-can-geo) and apogeotropic (L-BPPV-can-apo) variants.

METHODS: A total of 146 cases of paroxysmal geotropic positioning nystagmus (PGPN, L-BPPV-can-geo) and 285 cases of persistent apogeotropic positional nystagmus (PAPN) due to peripheral vestibular disorders were analyzed. Positional and positioning nystagmus were observed and recorded using infrared charge-coupled-device equipped video goggles. The healthy-ear-down 135° maneuver (H-135°M) and affected-ear-down 135° maneuver (A-135°M) were used to determine the affected side and serve as canalith repositioning procedures (CRPs). Differences in slow-phase velocity of horizontal nystagmus were compared between L-BPPV-can-apo and L-BPPV-cupulolithiasis (L-BPPV-cup) cases.

RESULTS: In L-BPPV-can-geo, the affected side was identified in 98% of cases using the supine head roll test (SHRT), lying-down nystagmus, and H-135°M. A single H-135°M resolved PGPN and vertigo by the next day or the day after in 69% of cases, increasing to 80% after a second H-135°M. Non-PGPN nystagmus occurred in 18% of cases following H-135°M, including posterior canal-BPPV variants, and canalith jam. In L-BPPV-can-apo, the affected side was successfully identified in all cases using SHRT, nystagmus direction in the face-up supine or forward-bending position, and A-135°M. The direction and intensity of nystagmus in representative cases of L-BPPV-can-apo and L-BPPV-cup were consistent with findings expected for a heavy cupula. Among PAPN cases unresponsive to SHRT, a single A-135°M induced a transition to L-BPPV-can-geo in 35% of cases, while 65% remained unchanged indicating L-BPPV-cup. Among PAPN cases of peripheral origin, 2% are classified as L-BPPV-can-geo (utricular side), 44% as L-BPPV-can-apo (canal side), and 54% as L-BPPV-cup. A-135°M is useful in differentiating L-BPPV-can-apo from L-BPPV-cup. Additionally, when a slow-phase velocity of nystagmus in the healthy-ear-down head position is more than twice that in the face-up supine position, L-BPPV-can-apo is more likely than L-BPPV-cup. Canalith jam was observed in both PGPN and PAPN cases, and improved with H-135°M or A-135°M.

CONCLUSIONS: H-135°M and A-135°M proved effective for both determination of the affected side and treatment of L-BPPV-can-geo and L-BPPV-can-apo cases. Canalith jam typically presents with unidirectional nystagmus either toward the affected or healthy side; however, this unidirectional nystagmus may be accompanied by PGPN or PAPN. The pathophysiology suggests that the directionality of the jam and its location-whether in the anterior or posterior segment of the lateral canal-may influence clinical presentation.