What is the typical direction of nystagmus in patients with Benign Paroxysmal Positional Vertigo (BPPV)?

Nystagmus Direction in BPPV

The direction of nystagmus in BPPV depends on which semicircular canal is affected: posterior canal BPPV produces torsional (rotatory) upbeating nystagmus, while lateral (horizontal) canal BPPV produces horizontal direction-changing nystagmus that is either geotropic (beating toward the ground) or apogeotropic (beating away from the ground). 1

Posterior Canal BPPV (Most Common)

Classic nystagmus pattern during Dix-Hallpike maneuver:

• Torsional (rotatory) component with upbeating vertical component when the affected ear is positioned downward 2, 3
• The nystagmus appears after a brief latency (typically 3 seconds) and lasts approximately 30-40 seconds 4, 5
• The torsional component rotates toward the affected, undermost ear 6
• Upon returning to sitting position, approximately 79% of patients show downbeating nystagmus, while 21% have no nystagmus but experience brief vertigo 3

Important nuance: The horizontal component direction during Dix-Hallpike testing is variable and unreliable for diagnosis—it may point toward the affected side (57%), away from it (27%), or show no significant horizontal component (16%) 3. Focus on the vertical upbeating component for diagnosis, not the horizontal direction. 3

Lateral (Horizontal) Canal BPPV

Nystagmus pattern during supine roll test:

• Direction-changing horizontal nystagmus that reverses when the head is turned to the opposite side 1, 4
• Geotropic form (more common): Nystagmus beats toward the ground on both sides, with the strongest nystagmus indicating the affected ear 1
• Apogeotropic form: Nystagmus beats away from the ground on both sides, with the side opposite the strongest nystagmus being the affected ear 1
• Mean latency of 3-3.4 seconds with duration of 32-40 seconds 5

Critical Diagnostic Distinctions

Red flags suggesting central pathology rather than BPPV:

• Downbeating nystagmus without a torsional component on Dix-Hallpike strongly suggests bilateral floccular lesion or cervicomedullary junction pathology requiring urgent neuroimaging 2, 7
• Direction-changing nystagmus that does not follow typical BPPV patterns indicates central cause 2
• Baseline nystagmus present in primary position (before any positioning maneuver) suggests central pathology 2

Mixed Canal Involvement

Posterior canal BPPV can convert to horizontal canal BPPV during positioning maneuvers, with the same ear remaining affected 1. In these cases, you may observe typical torsional upbeating nystagmus that transitions to strongly horizontal nystagmus 1. Approximately 16-25% of BPPV cases show simultaneous involvement of both posterior and horizontal canals 8.

Common Pitfalls

• Do not rely on the horizontal component direction in posterior canal BPPV—it is inconsistent and unreliable for determining the affected side 3
• Always perform both Dix-Hallpike and supine roll testing to avoid missing lateral canal involvement if only traditional Dix-Hallpike is performed 1
• Misdiagnosing central positional nystagmus as BPPV can occur when downbeating nystagmus without torsional component is mistaken for BPPV 2, 7
• In horizontal canal BPPV, remember that geotropic and apogeotropic forms have opposite rules for determining the affected ear 1