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Superior Semicircular Canal Dehiscence Syndrome

Superior Semicircular Canal Dehiscence Syndrome. Dr Craig Semple ENT Fellow Ottawa Hospital, CHEO. Case-1. 36 F Right Stapedectomy 1 year ago Bucket handle prosthesis Persistent CHL right ear. Case 1. Felt off balance Blowing nose caused oscillopsia Counterclockwise rotatory nystagmus

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Superior Semicircular Canal Dehiscence Syndrome

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  1. SuperiorSemicircular Canal Dehiscence Syndrome Dr Craig Semple ENT Fellow Ottawa Hospital, CHEO

  2. Case-1 • 36 F • Right Stapedectomy 1 year ago • Bucket handle prosthesis • Persistent CHL right ear

  3. Case 1 • Felt off balance • Blowing nose caused oscillopsia • Counterclockwise rotatory nystagmus • Valsalva against nostrils • Positive pressure in EAC • Weber to right • Could hear when placed on ankle

  4. Case 1 • Reoperation • No perilymphatic fistula • Prosthesis seemed to be loose • Replaced with a McGee prosthesis

  5. Case 1 • Post op • No change in Audio • No change in Vestibular symptoms or signs • CT • 2.8mm dehiscence in Right Superior SCC • Symptoms not disabling • Hearing aid • Avoidance

  6. Case 2 • 44 M • Chronic dysequilibrium • Very disabled • Unable to drive, work • Vertigo with valsalva and loud sounds • Troubled by his eyelids blinking, chewing, vertebrae moving

  7. Case 2 • Rotatory nystagmus with Valsalva • VEMPs enhanced bilaterally (L>R) • Bilateral CHL, Left-moderate, Right-mild • CT scan • bilateral L>R Superior SSC dehiscence

  8. Case 2 • Disabling symptoms • Resurfacing procedure bilaterally 6 months apart • Relieved his vestibular symptoms totally • CHL resolved

  9. Case 3 • 47 M • Pulsatile oscillopsia for 10 years • “My eyes jump with my heartbeat” • Increased rate when exercising • Also when blowing nose • Chronic dysequilibrium and unsteadiness • No sound induced symptoms

  10. Case 3 • Rotatory nystagmus in time with his pulse • Audio CHL right side • Acoustic reflexes were intact bilaterally

  11. Case 3 • CT • 4.4mm dehiscence of right SCC • Disabling symptoms • Resurfacing procedure • Relieved his vestibular symptoms totally

  12. Superior Semicircular Canal Dehiscence Syndrome • Lloyd Minor described 1998 • Oscillopsia and or Vertigo • Pressure and or Sound induced • Conductive hearing loss • Tulio’s phenomenon • Hennebert’s Sign • Autophony

  13. Signs Defined • Tullio phenomenon • Vestibular symptoms with or without eye movements in response to a sound stimulus • Hennebert sign vs Fistula sign / test • Otosyphilis • Menieres • Perilymph fistula • Shea “cancer eating at the integrity of otolaryngology” Superior SCC Dehiscence

  14. Pathophysiology • SSC bony dehiscence in middle cranial fossa • 3rd window • Able to move in opposite direction as oval window and allow flow through membranous labyrinth • Membranous labyrinth sensitive to sound and pressure stimuli

  15. Etiology ? • Unknown • Onset usually insidious and diagnosed in 40’s • ? Related to head trauma • ? Developmental defect of skull base • ? Benign intracranial hypertension

  16. Etiology ? • Hirvonen 2003 Acta Otolaryngology • Direct 0.5mm slice temporal bone CT scans • 27 SCD patients • 88 Controls (Other otological problem) • Measured bone thickness over SCC

  17. Etiology ? • Controls 0.67+/- 0.38 mm • And left and right correlated • SCD 0.31+/- 0.23 mm • If dehiscent on one side likely thin on other • ? Bony developmental problem

  18. Temporal bone study - Carey et al 2000 • 1000 Temporal bones, 596 adults • 5 specimens (0.5%) complete dehiscence • 1 middle fossa floor • 4 superior petrosal sinus contact with canal • 14 (1.4%) 0.1 mm thick • 8-sinus, 6-floor • Abnormalities tended bilateral • Uniformly thin until 3 yrs of age • Failure of post-natal bone development

  19. Presentation • Acoustic symptoms • Hyperacusis to bone conducted sounds • Conductive hearing loss (Conductive hearing gain) • Vestibular symptoms • Vertigo • Oscillopsia • Chronic dysequilibrium • Vestibular symptoms evoked by • sound stimuli (Tullio phenomenon) • pressure stimuli (Henneberts sign)

  20. Presentation • Variable presentation • Clinical features vary markedly • Minor et al • 6/17 presented with both auditory and vestibular symptoms • Kertesz et al • 0/7 presented with both auditory and vestibular symptoms

  21. Hyperacusis to bone conducted sounds • Able to hear • eye movement or pulse • Heal strike when walking • Through buttocks when sitting on park bench • Tuning fork when placed on ankle • Good hearing underwater • Own joints move

  22. Hyperacusis to bone conducted sounds • Why? • 2 possibilities • 3rd window acting as an amplifier to bone conducted sound • 3rd window dissipating energy from air conducted sound

  23. Evoked Eye Movements - Rules for PSSC and SSSC • In plane of Canal (Ewald’s 1st Law) • BPPV- Dix Hallpike • Geotropic nystagmus • rotatory toward down most ear • Vertical component- Upbeating

  24. 1- Acoustic stimuli • Evokes eye movements in plane of dehiscent canal

  25. 2- Change in pressure in EAC • Transmitted pressure to tympanic membrane and stapes • +ve pressure • Stapes inward • Ampulofugal flow in SSC- stimulatory

  26. 2- Change in pressure in EAC • Transmitted pressure to tympanic membrane and stapes • -ve pressure • Stapes outward • Ampulopetal flow in SSC- inhibitory

  27. 3- Valsalva maneuvers • Against pinched nostrils • Stimulates SSC • Against closed glottis • Inhibits SSC

  28. 3- Valsalva maneuvers • Against pinched nostrils • Air to middle ear through ET • Force stapes inward • Ampulofugal flow through SSC • Stimulates SSC

  29. 3- Valsalva maneuvers • Against closed glottis • Raised intrathoracic/Jugular then intracranial pressure • Pressure on 3rd window in middle cranial fossa • Ampulopetal flow Inhibits SCC

  30. Nystagmus Towards + pressures Nostril valsalva Nystagmus Away - pressure Glottic valsalva Summary eye movements

  31. Diagnosis • History • Acoustic symptoms • Hyperacusis to bone conducted sounds • Conductive hearing loss (Conductive hearing gain) • Vestibular symptoms • Vertigo • Oscillopsia • Chronic dysequilibrium • Vestibular symptoms evoked by • sound stimuli (Tullio phenomenon) • pressure stimuli (Henneberts sign)

  32. Audiology • Air bone gap • Especially BC less than 0dB • Normal Tympanometry • Present acoustic reflexes • Normal or Enhanced VEMP

  33. Vestibular Evoked Myogenic Potentials (VEMPs) • Short latency relaxation potentials • Surface electrodes on SCM whilst tonically retracted • short latency of 12 msec from stimulus onset • Turn head away from loud sounds? • Stimulus by Loud clicks or Tone burst • Specialized equipment or current ABR equipment

  34. Vestibular Evoked Myogenic Potentials (VEMPs) • Pathway • Saccule • Inferior vestibular nerve • Vestibular nuclei • Medial vestibulospinal tract • Accessory nucleus • Accessory nerve • SCM muscle

  35. Vestibular Evoked Myogenic Potentials (VEMPs) • Useful for • SSCC Dehiscence • ? Menieres • Diagnosis? • Treatment titration- gentamicin • Otosclerosis

  36. VEMPS suggestive of Superior SSCD • SSCD • Thresholds <70 dB HL • Thresholds 70-90 dB HL with Air Bone Gap

  37. Computed Tomography • High resolution scans • 0.5mm DIRECT axial DIRECT coronal • Reconstruction in plane of Superior SCC • Routine scans are not appropriate for screening (axial direct and coronal reconstruction) • Diagnostic • 0.5mm slices in plane of SCC - Reconstruction • Dehiscent on 1 or more slices • 0.5mm slices in direct coronal plane- Direct • present on 2 slices

  38. Management • Avoid stimuli • Most disabling is chronic dysequilibrium • Likely from SSC susceptible to all minor movements of CSF • Surgery • Ventilation Tube • Middle Fossa Resurfacing, Canal Plugging

  39. Middle Fossa Resurfacing • Minor et al 2000 suggested two methods • Plugging SCC with fascia and bone • Resurfacing the canal with temporalis fascia and split calvarial bone • Kertesz 2000 • Added Calcium phosphate bone cement to the resurfacing procedure

  40. Plugging / Resurfacing procedure • Middle cranial fossa approach • 5cm curvilinear incision vertically from tragus • 5x5cm craniotomy • 2x2cm piece of bone taken from this flap • 1x1cm temporalis fascia harvested

  41. Plugging / Resurfacing procedure • Dehiscence in area of arcuate eminence identified • plugged with fascia and bone pate (other) • Better long term results vs resurfacing alone • Split Calvarial bone • Fascia superiorly • Bone Cement-if used placed superiorly rather than fascia • Patient sat up for 10 minutes whilst cement sets to minimise pulsations of CSF

  42. GSPN IAC MMA Arcuate Em

  43. Patient series at RVEEH 6 patients operated from 2001-2007 Age 28 - 49 4 male ; 2 female 1 case bilateral SCD 1 case previous MEVT (for CHL and pressure) 2 previous head trauma

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