Is rotary nystagmus in one direction typical of benign paroxysmal positional vertigo (BPPV)?

Rotary Nystagmus in Benign Paroxysmal Positional Vertigo (BPPV)

Yes, torsional (rotary) nystagmus in one direction is a typical and diagnostic feature of posterior canal BPPV, the most common form of BPPV. 1

Diagnostic Characteristics of Nystagmus in BPPV

Posterior Canal BPPV

• Nystagmus pattern: Torsional (rotatory), upbeating nystagmus during the Dix-Hallpike maneuver 1
• Direction: Mixed torsional and vertical movement with the fast component demonstrating a characteristic pattern
• Timing characteristics:
  • Latency period of 5-20 seconds between maneuver completion and nystagmus onset
  • Crescendo-decrescendo pattern (begins gently, increases in intensity, then declines)
  • Resolves within 60 seconds from onset
  • May reverse direction when patient returns to upright position

Lateral (Horizontal) Canal BPPV

• Nystagmus pattern: Horizontal direction-changing nystagmus during the supine roll test 1
• Two variants:
  • Geotropic type (more common): Horizontal nystagmus beating toward the undermost ear
  • Apogeotropic type: Horizontal nystagmus beating toward the uppermost ear
• Affected ear: Usually the side that produces the most intense nystagmus 1

Diagnostic Maneuvers

Dix-Hallpike Maneuver (for Posterior Canal BPPV)

1. Position patient upright
2. Turn head 45° to the side being tested
3. Quickly move patient to supine position with head extended 20° below horizontal
4. Observe for characteristic torsional, upbeating nystagmus
5. If negative on first side, test the opposite side 1

Supine Roll Test (for Lateral Canal BPPV)

1. Position patient supine with head in neutral position
2. Quickly rotate head 90° to one side and observe for nystagmus
3. Return head to neutral position
4. Rotate head 90° to opposite side and observe for nystagmus 1

Clinical Pearls and Pitfalls

Important Diagnostic Considerations

• The presence of torsional, upbeating nystagmus during the Dix-Hallpike test is the gold standard for diagnosing posterior canal BPPV 1
• A history of positional vertigo alone is not sufficient for diagnosis - the characteristic nystagmus must be observed 1
• Multiple canal involvement can occur in up to 20% of BPPV cases, resulting in multiple types of positional nystagmus 2

Common Pitfalls

• Failure to perform the Dix-Hallpike maneuver on both sides may lead to missed diagnosis
• Confusing lateral canal BPPV with posterior canal BPPV due to inadequate observation of nystagmus direction
• Not recognizing that posterior canal BPPV can transition to lateral canal BPPV during treatment maneuvers (canal switch) 1

Differential Diagnosis

• Other causes of vertigo that may be confused with BPPV include:
  • Ménière's disease
  • Vestibular neuritis
  • Vestibular migraine
  • Posterior circulation stroke (can present with isolated vertigo in up to 25% of cases) 3
  • Central nervous system lesions 1

Treatment Implications

• The type of nystagmus observed directly determines the appropriate treatment maneuver:
  • Posterior canal BPPV (torsional, upbeating nystagmus): Epley maneuver
  • Lateral canal BPPV (horizontal direction-changing nystagmus): Lempert maneuver 2
  • Anterior canal BPPV (downbeating nystagmus): Modified Epley maneuver

In conclusion, the presence of rotary (torsional) nystagmus in one direction during positional testing is not only typical but is a defining diagnostic characteristic of posterior canal BPPV, which is the most common form of BPPV.