In a 48‑year‑old woman who develops dizziness, headache, and a sensation of the room spinning immediately after a Valsalva maneuver, with a normal neurologic examination and no spontaneous nystagmus, what is the most likely diagnosis?

Most Likely Diagnosis: Superior Canal Dehiscence (SCD) or Perilymph Fistula

The most likely diagnosis in this patient is superior canal dehiscence (SCD) or perilymph fistula, given the characteristic Valsalva-triggered vertigo with a normal neurologic examination and absence of spontaneous nystagmus. 1

Diagnostic Reasoning

Why This is NOT BPPV

The key distinguishing feature here is the pressure-related trigger (Valsalva maneuver) rather than a positional trigger:

• BPPV is characterized as a "triggered episodic vestibular syndrome" where vertigo is provoked by position changes (head turning, lying down), not pressure changes 1
• The 2017 BPPV Clinical Practice Guideline explicitly states that SCD differs from BPPV in that vertigo is induced by pressure changes and not position changes 1
• BPPV would require a positive Dix-Hallpike maneuver showing torsional upbeating nystagmus, which is not described here 1

Why SCD or Perilymph Fistula Fits

Both conditions share the pathognomonic feature of pressure-induced vertigo:

• SCD presents with vertigo triggered by Valsalva maneuvers, straining, or loud sounds (Tullio phenomenon) 1
• Perilymph fistula similarly produces vertigo and nystagmus triggered by pressure changes 1
• Both can occur with or without hearing symptoms initially
• The normal neurologic exam and absence of spontaneous nystagmus effectively rule out central causes

Differentiating Between SCD and Perilymph Fistula

Perilymph Fistula is more likely if:

• History of recent ear surgery (middle ear or mastoid procedures)
• History of barotrauma or head trauma
• Fluctuating hearing loss accompanies the vertigo 1

SCD is more likely if:

• No surgical history
• May have conductive hearing loss pattern (lower bone-conducted thresholds compared to air-conducted thresholds) 1
• Symptoms triggered by loud sounds or own voice (autophony)

Recommended Diagnostic Workup

1. CT temporal bones - definitive test for SCD, will show bony dehiscence of the superior semicircular canal 1
2. Vestibular evoked myogenic potential (VEMP) testing - alternative diagnostic test if available, shows abnormally low thresholds in SCD 1
3. Audiometry - may reveal conductive hearing loss pattern characteristic of SCD

Critical Pitfall to Avoid

Do not dismiss this as simple BPPV based solely on the complaint of "dizziness" and "room spinning." The Valsalva trigger is the critical historical feature that distinguishes pressure-related vestibular disorders from position-related BPPV. Missing this distinction could delay appropriate imaging and definitive diagnosis of a surgically correctable condition.

The headache component, while present, is less specific but could represent increased intracranial pressure transmission through the dehiscence or be coincidental. The absence of other neurologic findings makes central pathology (stroke, tumor) unlikely 1.