Could Superior Semicircular Canal Dehiscence (SSCD) be a cause of intermittent dizziness triggered by lights and sounds in an elderly patient with a complex medical history and a negative brain Magnetic Resonance Imaging (MRI)?

Could SSCD Be a Cause of Intermittent Dizziness Triggered by Lights and Sounds?

SSCD is unlikely to be the primary cause of light-triggered dizziness in this patient, but it remains a plausible explanation for the sound-triggered component and should be evaluated with high-resolution CT temporal bone if clinical suspicion is high.

Understanding SSCD's Characteristic Triggers

SSCD presents with a distinct clinical pattern that differs from what you're describing:

• SSCD is triggered by pressure changes and loud sounds, NOT by visual stimuli 1, 2, 3
• The hallmark symptoms include autophony, inner ear conductive hearing loss, Hennebert sign (vertigo induced by pressure changes), and sound-induced episodic vertigo (Tullio phenomenon) 2, 3
• Vertigo in SSCD is induced by pressure changes rather than positional changes, distinguishing it from benign paroxysmal positional vertigo 1, 2

Why Light-Triggered Dizziness Points Away from SSCD

The light-triggered component of your patient's symptoms is inconsistent with SSCD:

• SSCD responds to acoustic stimuli and pressure changes (Valsalva, straining, loud noises), not visual triggers 3, 4, 5
• Light-triggered dizziness suggests alternative diagnoses such as vestibular migraine, which commonly presents with photophobia and visually-induced vertigo
• If lights are triggering symptoms, consider vestibular migraine as a primary differential 1

When to Pursue SSCD Workup Despite Negative Brain MRI

A negative brain MRI does not exclude SSCD because:

• Brain MRI is insufficient for evaluating SSCD; the diagnosis requires high-resolution CT temporal bone without IV contrast 1
• CT temporal bone with fine-cut (0.5-0.6 mm) collimation reformatted parallel and orthogonal to the superior canal plane is the gold standard imaging 3
• SSCD can be readily diagnosed on CT temporal bone without IV contrast 1

Clinical Algorithm for Evaluating SSCD in This Patient

Proceed with SSCD evaluation if:

1. Sound-induced vertigo is present - Ask specifically about vertigo triggered by loud noises, own voice (autophony), or hearing one's footsteps 2, 3, 6
2. Pressure-induced symptoms occur - Inquire about vertigo with Valsalva, straining, coughing, or ear pressure changes 3, 4, 6
3. Conductive hearing loss pattern exists - Bone conduction hyperacusis is characteristic 3, 5, 6

Physical examination findings that support SSCD:

• Perform Tullio testing: Apply loud tones to the ear and observe for vertical-torsional eye movements in the plane of the superior semicircular canal using Frenzel goggles 6
• Test for Hennebert sign: Apply pressure to the ear canal and look for evoked nystagmus 2, 3

Recommended Diagnostic Pathway

If clinical suspicion for SSCD exists based on sound/pressure triggers:

• Order CT temporal bone without IV contrast with 0.5-0.6 mm slice thickness, reformatted in Pöschl and Stenver planes 1, 3
• Consider vestibular evoked myogenic potentials (VEMPs), which show lowered thresholds in SSCD 3, 6
• Audiometry may reveal an air-bone gap with paradoxically better bone conduction 3, 5

Critical Pitfall to Avoid

Do not dismiss SSCD based solely on the negative brain MRI - standard brain MRI lacks the resolution to detect superior canal dehiscence 1. The temporal bone requires dedicated high-resolution CT imaging with specific reformatting 1, 3.

Alternative Diagnosis for Light-Triggered Symptoms

Given the light-triggered component, vestibular migraine should be strongly considered as it presents with:

• Episodic vertigo lasting minutes to hours
• Photophobia and visually-induced dizziness
• May coexist with sound sensitivity
• Fits the "spontaneous episodic vestibular syndrome" category 1

Treatment Considerations if SSCD is Confirmed

• Surgical repair (plugging, resurfacing, or capping via middle fossa or transmastoid approach) is effective and curative 3, 7, 5
• Medical management with acetazolamide shows promising results for mild-to-moderate symptoms, with 77.78% showing symptom reduction in recent studies 7
• Surgery should only be pursued in patients with clinically significant manifestations 3