A 52-year-old woman presents to the ENT clinic with a 3-week history of severe vertigo, nausea, and vomiting. She reports that the room spins violently when she turns her head to the right or lies down on her right side. Hearing is normal bilaterally. Romberg test is negative. Dix–Hallpike maneuver performed on the right side reproduces vertigo with rotatory and upbeating nystagmus lasting 15 seconds. Repeat maneuver 2 minutes later produces less intense symptoms. What is the most likely diagnosis?

Explanation

## Diagnosis: BPPV of the Posterior Semicircular Canal ### Clinical Features Supporting BPPV **Key Point:** The Dix–Hallpike maneuver is the gold-standard diagnostic test for posterior canal BPPV. Reproduction of vertigo with characteristic rotatory and upbeating nystagmus is pathognomonic. **High-Yield:** BPPV accounts for 25–50% of all vertigo cases and is the most common peripheral vestibular disorder. The posterior semicircular canal is involved in 80–90% of BPPV cases. ### Mechanism In posterior canal BPPV, otoconia (calcium carbonate crystals) become detached from the utricle and migrate into the posterior semicircular canal. When the head moves into the Dix–Hallpike position (head extended below horizontal, turned 45° to affected side), gravity causes the otoconia to shift within the canal, deflecting the cupula and triggering vertigo. ### Diagnostic Criteria Met | Feature | Posterior Canal BPPV | Vestibular Neuritis | Meniere's Disease | Central Vertigo | | --- | --- | --- | --- | --- | | **Onset** | Sudden, positional | Acute, continuous | Episodic, fluctuating | Variable | | **Nystagmus type** | Rotatory + upbeating | Horizontal, unidirectional | Variable | Bidirectional, vertical | | **Dix–Hallpike response** | Positive (15–60 sec) | Negative | Negative | Negative | | **Fatigue on repeat** | Yes (hallmark) | No | No | No | | **Hearing** | Normal | Normal | Fluctuating loss | Normal | | **Romberg** | Normal | Abnormal | Normal | May be abnormal | **Clinical Pearl:** The **fatigue phenomenon** (symptom diminishes on repeat testing within minutes) is a hallmark of BPPV and reflects adaptation of the cupula to continued otoconia movement. ### Treatment Algorithm ```mermaid flowchart TD A[BPPV diagnosed]:::outcome --> B{Posterior canal?}:::decision B -->|Yes| C[Epley maneuver]:::action B -->|No| D[Semont maneuver or Epley variant]:::action C --> E[Repeat if needed]:::action E --> F[Symptom resolution in 80-90%]:::outcome A --> G[Vestibular rehabilitation if residual symptoms]:::action ``` **Mnemonic:** **BPPV Posterior = Dix–Hallpike Positive** — the Dix–Hallpike maneuver is the diagnostic test of choice for posterior canal involvement. ### Why This Is the Best Answer The clinical presentation is classic: positional vertigo triggered by head movement, rotatory nystagmus on Dix–Hallpike (pathognomonic for posterior canal), and fatigue on repeat testing (diagnostic of BPPV). Normal hearing and negative Romberg exclude Meniere's and central causes. [cite:Bhattacharyya et al. Neurology 2017; American Academy of Neurology guidelines on BPPV]