Lateral canal BPPV: Which is the affected side?

Abstract Lateral canal BPPV is due to detached otoconia that enter the lateral canal instead of the posterior canal. It is characterized by paroxysmal positional nystagmus which is horizontal instead of vertical-torsional. A geotropic form and a less common apogeotropic form are recognised. The pathological side, which must be identified for successful physical treatment, is usually indicated by nystagmus intensity: the more intense positional nystagmus beats towards the affected ear. In a few cases, there is no evident difference in nystagmus intensity, making it necessary to determine the affected ear on the basis of other indicators.