Superior Semicircular Canal Dehiscence - Stanford Hospital & Clinics

UC SF 

Superior Semicircular Canal Dehiscence 

Lawrence R. Lustig, MD 

Department of Oto-HNS 

University of California San Francisco

54 y.o. man with sound-evoked vertigo and 

oscillopsia 

• History: 

- Sensation of motion (vertigo) when he heard loud noises in his right 

ear 

- “Fluttering vision” (oscillopsia) when he made whistling, trilling, or 

humming noises 

- No past history of otologic disease 

• Exam: 

- Negative for: spontaneous, gaze-evoked, or positional nystagmus; 

head-shaking induced nystagmus; head thrust sign 

- Normal otoscopic exam 

- Weber (512 Hz) lateralized to right 

- Normal air and bone conduction thresholds 

- Eye movements evoked by sound in right ear

54 year old with sound-induced vertigo

Brödel M: Unpublished drawing of the anatomy of the human ear

Overview 

• Eye movements 

• Mechanism 

• Audiometric Diagnosis 

• Etiology 

• CT imaging 

• Surgical correction 

• Apparent conductive hearing loss

Overview 


• Mechanism 


• Etiology 




Eye movements evoked by stimulation of 

individual semicircular canals

Hennebert’s Sign in a left ear with SSCD

Overview 


• Mechanism 


• Etiology 




Minor et al. Arch Otolaryngol Head Neck Surg 1998; 124:249-258

Third mobile window

Physiology of a 3 rd Mobile Window 

Merchant et al, 2009

Overview 


• Mechanism 


• Etiology 




Cervical VEMP Responses 

• Example of normal 

VEMP from click 

stimulation of right 

ear. 

• The early 2 waves 

(p13-n23 

components) seem 

to be of vestibular 

origin. 

click 

R SCM 

50 μV 

L SCM 

Colebatch & Halmagyi Neurology 42:1635-1636

Lowered cVEMP Threshold in SCD 

41-year-old man with left SCD syndrome 

Streubel et al. Acta Otolaryngol Suppl 2001; 545:41-495

VEMP Responses in SCD Syndrome 

• 25 patients (diagnosis = 3-D eye recordings, CT) 

• VEMP threshold in dehiscent ears = 75 +/- 7 dB* 

• VEMP threshold for normal controls = 98 +/- 4 

dB* 

(*p < 0.001) 

• VEMP from contra ear did not differ from normal 

controls 

Streubel et al, Acta Otolaryngol 2001

ECoG = Alternate Diagnostic Modality 

• Increased SP/AP 

ratio (>0.4) 

• Seen in 14/15 

cases of SSCD 

• Reverses with 

surgical correction 

Arts et al, O & N, 2008

Symptoms in 53 patients with SSCD 

Sound-induced vertigo/oscillopsia 44 (83%) 

Pressure-induced vertigo/oscillopsia 39 (74%) 

Conductive hyperacusis 27 (51%) 

9 patients had undergone previous middle ear 

exploration for possible perilymphatic fistula 

Minor et al, Otol Neurotol 2003

Additional auditory Sx: 

• autophony (40%) 

• hyperacusis to bodily sounds (65%) 

• hearing loss (40%) 

• aural pressure (45% 

• tinnitus (35%) 

Yuen et al, O & N, 2009

Signs in 53 patients with SSCD 

• Sound-induced eye movements 38 (72%) 

• Valsalva-induced eye movements 37 (70%) 

• EAC pressure-induced eye movements 23 (43%) 

• Sound-induced head tilt 8 (15%) 


Overview 


• Mechanism 


• Etiology 




Temporal Bone Study 

Carey JC et al, Arch Otolaryngol, 2001 

• 1000 bones screened for MF dehiscences 

from the JHU temporal bone archives 

• 8 “thinned” (

Range of bone over SC

Middle 

Fossa 

Dehiscence 

sps

Bilateral SC dehiscences

Is there a congenital basis? 

24 wks gest. 2 mths 

4 mths 

10 mths 

Courtesy of John Cary, Johns Hopkins

• Unknown 

Genetics 

• 1 patient also with simultaneous COCH 

mutation (DFNA9) 

Hildebrand et al Am J Med Genet, 2008

A good CT 

1-mm slice thickness 

Coronal reconstruction 

Filtered to remove noise 

…and a better one 

0.5-mm slice thickness 

Canal plane reconstruction 

Minimal filtering

Superior Canal Dehiscence by CT 

1.0-mm 

collimation CT 

Sensitivity 27/27 

(100%) 

Specificity 112/139 

(81%) 

0.5-mm 


27/27 

(100%) 

159/161 

(99%) 

Belden et al. Radiology 226: 337-43, 2003

Superior Canal Dehiscence 

Positive 

Predictive Value 

Negative 

Predictive Value 

1.0-mm 


27/54 

(50%) 

112/112 

(100%) 

Belden et al. Radiology 226: 337-43, 2003 

0.5-mm 


27/29 

(93%) 

159/159 

(100%)

3D CT of SSCD, Crane et al, O & N, 2008

Overview 


• Mechanism 


• Etiology 




Middle Fossa Approach

Surgical correction: 

Resurfacing or plugging with fascia in lumen

Surgical Correction 

18 patients (9 men, 9 women) 

Age: 27 – 59 yrs (median: 40) 

Symptoms and signs completely resolved: 13 

Partial relief of symptoms and signs: 2 

Transient sensorineural hearing loss: 2 


Surgical Correction – Post Op 

• 38% have vestibular hypofunction following 

correction Agarwal et al, O & N, 2009 

Early > late dysfunction 

Larger dehiscence = more hypofunction 

• 94% show improved autophony 

Crane et al, O & N, 2010 

• Significant SNHL 5-16% 

eg. Phillips, J Clin Neurosci, 2010

Meta-analysis of Surgical results 

Vlastarakos et al, Eur Arch Otorhinolaryngol,2009 

• 64 operations 

• Indications: 56 vestibular, 7 auditory 

• Success Rate: 

33 plugging (bone pate/wax) – 97% 

16 resurfacing (bone/fascia) – 50% 

15 capping (hydroxyapetite) – 93%

Transmastoid Correction 

Deschenes et al, Laryngoscope, 2009 

• Mastoidectomy 

• Identify posterior and superior canals 

• Blue-line SSC 

• Fenestrate on either end of dehiscence 

• Plug with bone wax and pate 

• Cartilage graft to MF 

• Alt: just resurface through MF 

(Larry Lundy, personal communication)

Overview 


• Mechanism 


• Etiology 




48 y.o. man with pulsatile oscillopsia 

• CC: “My eyes jump with my heartbeat” 

• Oscillopsia also induced by pressure & Valsalva 

• 25 dB air-bone gap noted for right ear 

ipsi- and contralateral acoustic reflexes intact 

tympanometry: pulsation on right 

• Right stapedectomy 

post-op: no change in thresholds 

• Revision right stapedectomy 

air conduction thresholds slightly worse

48 y.o. man with pulsatile oscillopsia 

• Torsional eye movements in time with pulse 

• Valsalva against pinched nostrils: vertical-torsional 

nystagmus with slow phase components directed 

upward and superior pole of right eye moving 

counterclockwise 

• Intact VEMP response from right ear

Audiogram

CT Scan showing dehiscence

Comparison of pre- and post-op thresholds 

Post-op 

Pre-op

Inner Ear Conductive Hearing Loss 

“Inner ear conductive hearing loss is a term we have 

used to describe a situation in which there is a 

consistent conductive element in the hearing 

impairment but no evidence of tympanic membrane 

or ossicular problem.” 

“We do not have an explanation for this phenomenon 

but suspect that there is some inner ear abnormality 

not visible on the polytome X-ray.” 

House JW et al. Laryngoscope 1980

Summary 

• Etiology: developmental abnormality and 

then erosion or traumatic event resulting in 

disruption of bone 

• Audiological findings: air-bone gap in the 

absence of middle ear pathology, bone 

conduction thresholds better than 0 dB NHL 

• CT imaging: specificity improved with 0.5 mm 

collimation and multiplanar reconstruction, 

should never be used as the exclusive 

method for diagnosis

Summary 

• VEMPs: lowered thresholds 

• Treatment: 

surgical plugging or resurfacing of the 

dehiscence when symptoms and signs are 

debilitating 

Middle Fossa or Transmastoid

Superior Semicircular Canal Dehiscence - Stanford Hospital & Clinics

Create successful ePaper yourself

Delete template?

Save as template?