Superior Semicircular Canal Dehiscence Syndrome

1. SuperiorSemicircular Canal Dehiscence Syndrome

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”

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

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

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

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

38. 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

44. 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

45. 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

46. 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

47. 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

50. 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

51. Symptoms and signs

52. Audiology preoperatively

53. Vestibular testing

54. SCD repair recovery Duration of surgery 166 mins 24-48 hrs post op nausea and vertigo No intracranial complications No wound complications Length of stay 3.5 days

55. SCD repair outcomes Symptom improvement Audiological hearing preservation closure of air bone gap Vestibular symptom improvement VEMP as objective measure

56. Symptom improvement6 months post op Noise induced vertigo resolved 4/4 Pressure induced vertigo resolved 3/5 Improved 2/5 Internal noises resolved 2/3 Reduced 1/3 Aural fullness reduced 4/6 Tinnitus unchanged 1/1

57. Post op audiology

58. Audiological improvement

59. Post op VEMP’s

60. VEMP outcomes

61. Who to scan? Sound or pressure induced vertigo or oscillopsia Must ask specifically Air bone gap despite normal middle ear function Think about when think Otosclerosis Present acoustic reflexes VEMPs enhanced or normal Tuning fork heard from malleolus or elbow

62. Who to scan? CT temporal bone 0.5mm DIRECT coronal and axial reconstruction in plane of Superior SCC

63. Summary Bizarre history now suspicious Probing history warranted Office examination fun (not for patient) Audiological testing With acoustic reflexes Vestibular testing Seek VEMP thresholds CT scan for confirmation

64. Acknowledgements Mr Robert J Briggs FRACS Dr Mark Paine FRACP Jessica Vitcovic MClinAud, MAudSA(ccp) Joanne Enticott BSc, Dip Aud, MAudSA(cc)