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Clinical Analysis

Most Likely Diagnosis: Superior Semicircular Canal Dehiscence Syndrome (SCDS)

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How the Findings Fit

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Pathophysiology

• Pressure transmitted from sneezing/coughing/straining to directly deflect the cupula → vertigo (Tullio phenomenon variant or Hennebert sign)
• Abnormal bone conduction enhancement and mid-frequency audiometric changes

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Key Differentials to Exclude

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Recommended Investigations

1. High-resolution CT temporal bone (0.5 mm cuts in Pöschl and Stenvers planes) — gold standard imaging for demonstrating canal dehiscence
2. Cervical VEMP (cVEMP) — characteristically shows reduced thresholds (<80 dB) in SCDS due to the third window effect (enhanced saccular sensitivity). This is a key non-invasive diagnostic marker.
3. Ocular VEMP (oVEMP) — typically shows enhanced amplitude in SCDS
4. High-resolution MRI — to exclude other posterior fossa pathology

As noted in Cervical and Ocular Vestibular Evoked Myogenic Potential Testing (p. 2): "Patients with SCDS commonly report pressure-induced (coughing, sneezing, straining) and sound-induced vertigo... Clinical examination may reveal eye movements induced by Valsalva maneuvers, by pressure in the external auditory canal, or by sounds."

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Management

• Avoid pressure-triggering activities (Valsalva, straining)
• Vestibular rehabilitation
• Patient reassurance and activity modification

• Middle fossa craniotomy with canal plugging or resurfacing — resurfacing is preferred as it preserves some function
• Transmastoid approach — lower risk, though slightly less reliable

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Summary

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Detailed Differential Diagnosis: Positional Vertigo with Head Turning

Overview of the Clinical Problem

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Full Differential Diagnosis

1. Superior Semicircular Canal Dehiscence Syndrome (SCDS) ← Top Candidate

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2. BPPV (Benign Paroxysmal Positional Vertigo)

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3. Vertebrobasilar Insufficiency (VBI)

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4. TIA (Transient Ischemic Attack) — Posterior Circulation

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5. Perilymph Fistula (PLF)

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6. Cervicogenic Vertigo

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7. Ménière's Disease

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Diagnostic Differentiation Algorithm

Vertigo + Head Turning
        │
        ├─ Hearing loss present?
        │       │
        │       ├── YES → Trough pattern + Normal ECoG + Pressure trigger
        │       │               → SCDS (CT Temporal Bone + VEMP)
        │       │
        │       ├── YES → Low frequency + Abnormal ECoG
        │       │               → Ménière's Disease
        │       │
        │       └── NO → Purely positional, fatigable, torsional nystagmus
        │                       → BPPV (Dix-Hallpike)
        │
        ├─ Neurological deficits (diplopia, dysarthria, ataxia)?
        │       └── YES → Central cause: VBI / TIA
        │                       → HINTS exam → MRI Brain/MRA
        │
        └─ Post-traumatic + pressure-induced?
                        → Perilymph Fistula

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Confirmatory Tests — By Diagnosis

For SCDS (Primary Candidate)

For VBI / TIA

HINTS exam is more sensitive than MRI in first 24–48 hours for posterior fossa stroke. A normal head impulse test in a vertiginous patient is a red flag for central pathology.

For BPPV

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Treatment — Comprehensive

SCDS Treatment

• Avoid triggers: Valsalva, sneezing hard, heavy lifting, straining
• Vestibular rehabilitation therapy (VRT)
• Patient education on pressure avoidance
• Treat any contributing Eustachian tube dysfunction

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VBI / TIA Treatment

• Avoid extreme neck rotation/hyperextension
• Cervical collar (short-term, controversial)
• Physical therapy for cervical posture
• Risk factor modification: smoking cessation, glycemic control, weight loss

• Vertebral artery stenting or endarterectomy — in significant stenosis with recurrent symptoms
• Cervical osteophyte decompression — if mechanical compression confirmed

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BPPV Treatment

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Why VBI is Unlikely Here (Summary)

1. Age 38 — VBI/TIA in young adults requires cardiac or hypercoagulable workup; atherosclerotic VBI is rare
2. No "5 Ds" — No diplopia, dysarthria, dysphagia, drop attacks mentioned
3. Hearing loss present — VBI does not typically cause cochlear symptoms (cochlea has redundant supply)
4. Pressure/sneezing trigger — Vascular ischemia is not triggered by sneezing; this is mechanically/pressure-mediated
5. Chronic 2–3 year course — TIA is episodic and tends toward progression, not a stable chronic pattern
6. Evidence base — Positional VBI is the most overdiagnosed entity in vestibular medicine; systematic reviews show no vertebral artery flow changes with head turning in most patients

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Clinical Bottom Line

1. Dix-Hallpike bedside (rule out co-existing BPPV)
2. HINTS exam (rule out central pathology)
3. High-resolution CT temporal bone (confirm SCDS)
4. cVEMP + oVEMP (physiological confirmation of SCDS)
5. MRI Brain + MRA posterior circulation (exclude vascular cause, especially given head-turn symptom)