What is the purpose and procedure of the Dix-Hallpike test in diagnosing benign paroxysmal positional vertigo (BPPV)?

The Dix-Hallpike Test: Diagnosis of Benign Paroxysmal Positional Vertigo

The Dix-Hallpike test is the gold standard diagnostic maneuver for posterior canal benign paroxysmal positional vertigo (BPPV), with a strong recommendation based on diagnostic studies showing its effectiveness in eliciting characteristic positional nystagmus. 1

Purpose of the Test

The Dix-Hallpike test serves to:

• Diagnose posterior semicircular canal BPPV by provoking characteristic nystagmus and vertigo
• Determine which ear is affected (or if both ears are involved)
• Differentiate posterior canal BPPV from other causes of vertigo

Diagnostic Criteria for Posterior Canal BPPV

The diagnosis is confirmed when the following criteria are met:

• History: Patient reports repeated episodes of vertigo with changes in head position relative to gravity
• Physical examination: All of the following must be present:
  • Vertigo associated with torsional, upbeating nystagmus provoked by the Dix-Hallpike test
  • Latency period between test completion and onset of vertigo/nystagmus (typically 5-20 seconds)
  • Provoked vertigo and nystagmus increase and then resolve within 60 seconds from onset 1

Procedure of the Dix-Hallpike Test

1. Patient positioning: Begin with the patient seated upright on the examination table
2. Patient preparation: Warn the patient that the maneuver may provoke intense vertigo and possibly nausea, which will subside within 60 seconds
3. Examiner position: Stand at the patient's side to support their head throughout the maneuver
4. Test execution:
   • Turn the patient's head 45 degrees to one side (e.g., right)
   • Quickly move the patient from seated to supine position with the head hanging 20 degrees below the horizontal plane off the edge of the table
   • Observe the patient's eyes for nystagmus and ask about vertigo symptoms
   • After symptoms resolve, slowly return the patient to the seated position
   • If the first side is negative, repeat the test with the head turned 45 degrees to the opposite side 1

Interpretation of Results

A positive test for posterior canal BPPV shows:

• Nystagmus characteristics: Torsional, upbeating nystagmus with the affected ear down
• Latency: Brief delay (5-20 seconds) between position change and symptom onset
• Duration: Vertigo and nystagmus lasting less than 60 seconds
• Pattern: Crescendo-decrescendo pattern of nystagmus intensity
• Fatigability: Reduced response with repeated testing (though repeated testing is not recommended) 1

Clinical Pearls and Pitfalls

• Bilateral testing: Always test both sides if the first side is negative 1
• Sensitivity limitations: The test has a sensitivity of approximately 79% and specificity of 75%, so a negative test does not rule out BPPV 2
• Contraindications: Use caution or avoid in patients with:
  • Cervical stenosis or limited neck range of motion
  • Severe kyphoscoliosis
  • Vertebrobasilar insufficiency
  • Cervical radiculopathies
  • Morbid obesity (may require additional assistance)
  • Recent neck trauma 1
• Avoid unnecessary imaging: Patients meeting diagnostic criteria for BPPV with typical nystagmus on Dix-Hallpike testing do not require radiographic imaging 1
• Central mimics: Be aware that central causes may mimic BPPV (referred to as CPPV) and should be suspected with atypical nystagmus patterns or negative/atypical Dix-Hallpike testing 1

Test Modifications

For patients unable to undergo the standard Dix-Hallpike test, alternative positioning tests such as the side-lying test can be used, though these modifications are rarely necessary 2.

The "loaded Dix-Hallpike" is a modification that may produce longer duration of nystagmus, stronger symptoms, and improved sensitivity compared to the standard test 3.

Remember that the Dix-Hallpike test is not only diagnostic but also identifies which ear is affected, guiding subsequent treatment with appropriate canalith repositioning procedures such as the Epley maneuver 4.