OTOLOGY SEMINAR
Superior Canal Dehiscence Syndrome( SCDS)
R3 陳泓里
2002/11/20
1.Definition of SCDS:
A syndrome of sound-and/or pressure- induced vertigo due to dehiscence of
bone overlying the superior semicircular canal
2. History review:
Hennebert (1911):
Eye movement evoked by pressure in external auditory canal in patients
of congenital syphilis (Hennebert sign)
Tullio (1929):
Evoke eye and head movement in the plane of fenestrated canal
of pigeon by loud noise
Similar movement in patient of otosyphilis with labyrinthine fistula
“Tullio phenomenom”
Suzuki(1963~1966)):
eye movement by ampullary nerve stimulation ( monkey and cat)
Nadol(1977):
“Hennebert sign” in advanced Meniere’s disease
Adhesion of saccule with footplate without fistula formation
Minor (Archives 1998): Superior Canal Dehiscence Syndrome
Vertical and torsional eye movement induced by pressure or sound
Dehiscence of bone overlying SSC by CT scan by HRCT
Change of middle ear or intracranial pressure→
inhibition/ excitation of SSC ampulla by endolymph movement
3. Clinical presentation:
Vertigo/ dizziness, osillopsia, tilt of visual field triggered by
tone( 500~2000Hz, 100~110 dB, loudness near the affected ear)
pressure change of external ear canal( pressure on tragus,
pneumatic otoscope)
pressure change of middle ear (Valsalva against pinched nose)
pressure change of CSF space (Valsalva against closed glottis,
lifting, violent cough, compression of jugular vein)
Eye movement trigger by sound and pressure change
Ex. Loud sound near the affected right ear
two components in slow phase
vertically upward
torsionally away from stimulated ear( clockwise by patient)
followed by nystagmus in reversed direct with low amplitude
Persistent dysequilibrium, unsteadiness(13/17 Minor 2000) and
associated autonomic symptoms: most disabling and debilitating
Subjective tinnitus evoked by eye movement
3.Epidemiology:
rare incidence, no more than 50 patients since first report
17 patients of most updated series of Lloybd B. Minor (AJO 2000)
M: F= 8: 9 ( 27~50 yrs)
R: L: B= 5: 8: 5
4. Etiology and pathogenesis:
Temporal bone survey of 1000 specimen by Carey( Archives 2000)
Complete dehiscence: 5 ( middle fossa floor and superior petrous sinus)
Thickness < 0.1 mm: 14 , contralateral thickness( 0.07+-0.05 mm)
Infant with uniformly thin bone and gradual thickening until 3 yrs of age
 approximately 2 % of population failed to develop normal thickness of
temoral bone overlying the superior semicircular canal
 disruption of the bone leaded by mild head trauma or barotrauma
Dehiscence of bone overlying the superior semicircular canal over tegmen
as a mobile third window to inner ear
(Head trauma? Chronic otitis media? Otosyphilis?autoimmune? neoplasm?)
 sound or pressure induce outward or inward of dehiscent membranous canal
 pressure gradient across ampulla
 ampullopetal or ampullofugal endolymphatic flow in SSC
 deflection of cupula
 inhibition or excitation vestibular afferent flaring
 eye movement with torsional and vertical component according to Ewald law
Clinical Evaluation:
a)History review with compatible symptom/ sign
b) Eye movement/ symptoms elicit by tone and maneuver
* No spontaneous, gaze-evoked, head-shaking nystagmus
Symmetric vestibulo-ocular reflex
* Signs usually parallel symptoms
Frenzel google to avoid visual suppression
Scleral serch coil of contact lens in darkness (Minor 2000)
T: clockwise as positive
V: downward as positive
H: rightward as positive
Video-oculography by video eye monitor system ( Ostrowski 2001)
Vector analysis
“Three-dimension spatial reference convention” (Hixson 1966)
stimulated canal could be determined by observing which cancal
vector matching composite vector of patient
c) Audiometry:
Mild conductive hearing loss in low and mid tone
(5-10 dB air-bone gap with normal bone conduction)
conductive hyperacusis by third mobile window
Subjective tinnitus evoked by eye movement
d) Vestibular evoked myogenic potential:
third mobile window increases the responses of vestibular receptor
to sound and pressure stimuli
VEMP of the dehiscent ear had decreased threshold than normal control
( 76+-8 dB NHL vs 96+-5 NHL)
(Streubel 2001)
VEMP of the dehiscent ear had larger amplitude for comparable
stimulus intensity( Brantberg)
* consider SCD if acoustc reflex and VEMP present in the conductive HL
prior to stapes surgery
* Standard vestibular test, such as ENG, rotatory chair, calorie test revealed no
abnormality
e) High resolution computerized tomography(HRCT) of temporal bone:
0.3 mm resolution, ( Ultra-HRCT 0.1 mm resolution)
Differential Diagnosis: perilymphatic fistula, otosclerosis
Management( Minor 2000):
Low salt diet, diuretics, minor tranquilizer, vestibular suppressants
Appropriate discussion and recommendation regarding to avoidance of provocative
stimuli (10/17)
Grommet insertion for impaired E tube dysfunction(1/17)
Surgical intervention(5/17): for chronic and debilitating symptoms
middle fossa approach
1) Plugging of superior semicircular canal (2/5)
2)Resurfacing the dehiscent semicircular canal(3/5)
possibly postoperative sequelae
unilateral vestibular hypofunction
sensorineural hearing
Problems to be investigate in the future.
The relationship of image finding and the property of dehiscence that render the
labyrinth responsive to pressure and sound
The possibility of involvement of other vestibular receptor( utricle, saccule)
Otolith receptor of saccule in response to pitch or pressure
vestibulosympathic reflex: autonomic symptoms
utricle, saccule: maintain orthostasis: body version or ocular tilt
Reference:
1.
Minor LB, Solomen D , Zinreich JS, et al. Sound – and/ pressure- induced vertigo due to
dehiscence of superior semicircular canal. Arch Otolarygol Head Neck Surg 1998; 124
249-258.
2.
Minor LB. Superior canal dehiscence syndrome. Am J Otol 2000; 219-19
3.
Carey JP, Minor LB, Nager GT. Dehiscence of thinning of bone overlying the superior
semicircular canal in a temporal survey. Arch Otolaryngol Head Neck Surg 2000; 126 137-147
4.
Hwang JH, Lin KN. Superior Canal Dehiscence Syndrome –Report of two cases. J Taiwan
Otolaryngol Head Neck Surgery 2002; 37 130-134
5.
Ostrowski VB, Byskosh A, Hain TC. Tullio Phenomenon with dehiscence of superior semicircular
canal. Otol Neurotol 2001; 22 61-65
6.
Streubel SO, Cremer PD, Carey JP, et al. Vestibular-evoked myogenic potential in the diagnosis of
superior canal dehiscence syndrome. Acta Otolaryngol 2001; Suppl 545 41-49
7.
Hirvonen TP, Carey JP, Liang CJ, et al. Superior canal dehiscence: mechanism of pressure
sensitivy in the chinchilla Model. Arch Otolaryngol Head Neck Surg 2001; 127 1331-1336
8.
Colebatch JG, Day BL, Bronstein AM et al. Vestibular hypersensitivity to clicks is characteristic of
the Tullio phenomenon. J Neurol Neurosurg Psychiatry 1998; 65 670-678