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Superior Semicircular Canal Dehiscence Syndrome
Built from Haynes-Glasscock-Shambaugh Surgery of the Ear, Seventh Edition
What’s inside
8 sections · 92 slides
Pathophysiology
- Definition of superior canal dehiscence syndrome
- Third mobile window mechanism
- Consequences of pressure shunting
- Bone conduction hyperacusis
- Route of pressure change at the superior canal ampulla
- Excitation and inhibition of the superior canal
Clinical presentation
- Presenting complaints in SCDS
- Frequency of vestibular symptoms
- Character of SCDS vertigo
- Frequency of auditory symptoms
- Autophony in SCDS
Diagnostic evaluation
- Three pillars of the SCDS diagnosis
- Examination of sound-evoked eye movements
- Yield of provocative manoeuvres
- Plane of sound-evoked nystagmus in superior canal excitation
- Significance of the nystagmus plane
- Audiometric findings in SCDS
- Audiogram in left superior canal dehiscence
- SCDS versus otosclerosis
- Cervical VEMP: principles
- Cervical VEMP thresholds in SCDS
- Ocular VEMP: principles and advantages
- Limitations of VEMP testing
- Computed tomography of the temporal bone
- Superior canal dehiscence on Poschl and Stenvers reformats
- False positives on temporal bone CT
- Role of magnetic resonance imaging
- Barany Society criteria: symptoms
- Barany Society criteria: tests and imaging
- Barany Society criteria for the diagnosis of SCDS
Differential diagnosis
- Conditions that mimic SCDS
- Patulous Eustachian tube versus SCDS
- Perilymphatic fistula and canal fenestration
- Vestibular migraine as a confounder
- Managing coexistent migraine before surgery
Operative decision making
- Selecting patients for surgery
- Conductive hearing loss as an indication
- Vestibular course after canal plugging
- Functional consequence of plugging the canal
- Bilateral superior canal dehiscence
- Timing and risk of second-side surgery
- Near dehiscence
Surgical approaches
- Middle fossa versus transmastoid approach
- Concerns with transmastoid plugging
- Perilymph handling during transmastoid repair
- Round window plugging and reinforcement
- Indications favouring a transmastoid approach
Middle fossa technique
- Steps of the middle fossa repair
- Positioning and incision planning
- Planning the middle fossa incision
- Harvest of temporalis fascia
- Temporalis fascia harvest with Raney clips applied
- Craniotomy planning and dimensions
- Technique of the craniotomy
- Middle fossa craniotomy
- Elevation of the middle fossa dura
- Dural elevation to expose the superior canal
- Suction discipline at the dehiscence
- Plugging the superior canal
- Plugging the dehiscent superior canal
- Closure of the middle fossa craniotomy
- Replacement of the bone flap with titanium plates
Postoperative care and outcomes
- Immediate postoperative care
- Recognising an epidural haematoma
- Dizziness outcomes after repair
- Autophony outcomes after repair
- Hearing outcomes after superior canal plugging
- Risk of hearing loss after repair
- Summary of diagnosis
- Summary of management
- References
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- Haynes-Glasscock-Shambaugh Surgery of the Ear, Seventh Edition
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