What is the most likely diagnosis and initial management for sudden-onset vertigo triggered by turning the head to the left?

Sudden-Onset Vertigo with Listing to the Left

The most likely diagnosis is benign paroxysmal positional vertigo (BPPV) of the left posterior semicircular canal, and you should immediately perform the Dix-Hallpike maneuver to confirm the diagnosis, followed by the canalith repositioning procedure (Epley maneuver) if positive. 1, 2

Diagnostic Approach

Perform the Dix-Hallpike maneuver first to evaluate for posterior canal BPPV, which accounts for 85-95% of all BPPV cases. 1, 2 The sudden onset and positional nature strongly suggest BPPV rather than central pathology. 1

Executing the Dix-Hallpike Maneuver

• Turn the patient's head 45° toward the left (affected side) while seated 1
• Rapidly move the patient to supine position with the head extended 20° beyond horizontal 1
• Observe for the characteristic nystagmus pattern and ask about vertigo 1

Positive Test Criteria (All Must Be Present)

• Latency period of 5-20 seconds (rarely up to 60 seconds) between completing the maneuver and symptom onset 1, 2
• Torsional (rotatory) and upbeating nystagmus toward the forehead 1, 2
• Crescendo-decrescendo pattern with nystagmus and vertigo resolving within 60 seconds of onset 1, 2
• The affected ear is the one facing downward during the positive test 2

If Dix-Hallpike Is Negative

Proceed immediately to the supine roll test to evaluate for lateral canal BPPV, which accounts for 10-15% of cases and is frequently missed when only Dix-Hallpike testing is performed. 2, 3

Supine Roll Test Technique

• Position patient supine with head neutral 2
• Rapidly rotate head 90° to one side and observe for purely horizontal nystagmus (not torsional) 2, 3
• Wait for symptoms to resolve, then repeat to opposite side 2
• The side with stronger nystagmus indicates the affected ear in geotropic variant 2

Red Flags Requiring Immediate Neuroimaging

Stop and obtain urgent MRI if you observe any of these findings suggesting central pathology rather than BPPV: 1, 4

• Downbeating nystagmus on Dix-Hallpike without torsional component 1
• Direction-changing nystagmus without head position changes (periodic alternating nystagmus) 1
• Gaze-evoked nystagmus that persists with sustained gaze 3
• Baseline nystagmus present without provocative maneuvers 1
• Associated neurologic findings: dysarthria, dysmetria, dysphagia, sensory/motor deficits, or Horner's syndrome 1
• Profound imbalance out of proportion to vertigo (suggests cerebellar infarction) 4

Immediate Treatment

If Dix-Hallpike confirms posterior canal BPPV, perform the Epley maneuver immediately at the bedside, which has a 70-90% success rate. 2 Do not repeat the Dix-Hallpike to demonstrate fatigability, as this unnecessarily subjects the patient to repeated vertigo and may interfere with treatment. 1

Critical Management Points

• Do NOT prescribe vestibular suppressants like meclizine, as they delay recovery and cause drowsiness without addressing the underlying pathophysiology 2
• Reassess with complete positional testing if treatment fails after 2-4 attempts, as canal conversion occurs in up to 6% of cases 2
• Multiple canal involvement occurs in 4.6-6.8% of cases, most commonly ipsilateral posterior and lateral canals 2

Common Pitfalls to Avoid

• Never rely on history alone to distinguish between posterior and lateral canal BPPV, as presenting symptoms are often indistinguishable 2
• Do not skip the supine roll test if Dix-Hallpike is negative but clinical suspicion remains high, as this misses 11.8-13.6% of lateral canal cases 2
• Be aware that CNS adaptation may cause spontaneous nystagmus direction changes without repositioning, potentially confusing diagnosis 2, 3
• Consider vestibular migraine if vertigo episodes last 5 minutes to 72 hours with associated migraine features (photophobia, phonophobia, headache), as this has a 3.2% lifetime prevalence 1