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OtolaryngologyHead and Neck Surgery (2006) 134, 431-436

019doie form of vestibulopathy once recognized. When patientssent with typical symptoms, workup with CT is reliable andurate. Surgical intervention results in reversal of symptoms inst cases with low morbidity.M rating: C-42006 American Academy of OtolaryngologyHead and Neckrgery Foundation, Inc. All rights reserved.

uperior semicircular canal dehiscence syndrome (SCD)is a recently described form of peripheral vestibulopathy

which absence of bone over part of the superior canal

MATERIALS AND METHODS

We performed a retrospective chart review of all patientsidentified at our institution with SCD from January 1999 toJuly 2004. Patients who presented with symptoms suspi-cious for SCD, such as Tullios phenomenon, pressureevoked vertigo, or chronic disequilibrium, underwent CTfor further evaluation. The CT performed was a 1 mm perRIGINAL RESEARCH

eversible Peripheral Vestreatment of Superior Can

dd A. Hillman, MD, Thomas R. Kerted Clough Shelton, MD, Pittsburgh, Penn

ity, Utah

JECTIVE: Superior canal dehiscence (SCD) is a recentlycribed disorder that results from absence of bone over theerior semicircular canal. We have reviewed 30 cases of SCDnd at our institution and report their presentation, workup, andponse to therapy.UDY DESIGN: Retrospective chart review of all patientsgnosed with SCD from 1999 to 2004 at the University of Utah.SULTS: Thirty patients were identified with SCD. Patientssented with chronic disequilibrium (63%), Tullios phenome-

n (41%), pressure evoked vertigo (44%), hearing loss (30%),pulsatile tinnitus (7%). ENG performed early in our series

ealed abnormal nystagmus with sound presentation, Valsalva,tympanogram; however, history and CT examination alone wasd to identify this condition in most of our patients. Twenty-en of the 30 patients had some symptoms related to SCD; theer 3 were found to have incidental SCD on CT examination. Ofse patients, 14 had severe enough symptoms to warrant opera-e intervention. All, but one had resolution of their symptomsFrom the Pittsburgh Ear Associates (Dr Hillman), Pittsburgh, PA,partment of Otology (Dr Kertesz), Prince of Wales Hospital, Randwick,stralia, and the Division of Otolaryngology (Drs Hadley and Shelton),iversity of Utah College of Medicine, Salt Lake City, UT.

420

4-5998/$32.00 2006 American Academy of OtolaryngologyHead and Neck:10.1016/j.otohns.2005.10.033lopathy: TheDehiscence

B, BS, FRACS, Kevin Hadley, MD,ania; Randwick, Australia; and Salt Lake

ds to significant vestibular symptoms.1,2 Diagnosis isde by history, examination, and confirmation of missingne over the superior semicircular canal by high resolution. Once recognized, this syndrome can be treated with

rgical intervention, which leads to a high rate of symptomolution and patient satisfaction.Common symptoms include sound-induced vertigo (Tul-s phenomenon) and pressure/Valsalva-induced vertigo.ese symptoms have been historically reported with ves-ulopathy caused by Menieres, Lyme disease, congenitalafness, congenital syphilis, and perilymph fistula.3-6 Withreful workup and a high degree of suspicion, SCD can beferentiated from these other vestibular disorders. Sincesenior author (C.S.) began evaluating patients for SCD

1999, we have regularly identified patients who meet thegnostic criteria. To date, 30 patients with SCD have beenntified at our institution.In this article, we describe the patient presentation andReprint requests: Todd A. Hillman, MD, Pittsburgh Ear Associates,E. North Ave., Ste 402, Pittsburgh, PA 15212.

E-mail: todd_hillman@hotmail.com

Surgery Foundation, Inc. All rights reserved.

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432 OtolaryngologyHead and Neck Surgery, Vol 134, No 3, March 2006tion, noncontrasted, coronal with a window width/ levelting of 4000/450, a protocol that gives excellent bonytail. We identified 30 patients who met our initial radio-phic criteria for SCD, which was absence of bone oversuperior semicircular canal on one coronal cut. Three

tients had SCD noted on imaging examinations that wererformed for other conditions and did not have symptomst to be related to SCD. Therefore, these patients were notluded in this study.Historical variables including age, sex, date of presenta-n, and symptoms at the time of presentation, were noted.y reports of dizziness with loud sounds or with strainingre recorded and the source of such symptoms noted.ysical examination findings and initial audiometric re-lts were noted. Results of vestibular function testing (ifrformed) were also recorded.Patients whose symptoms were debilitating were offered

rgical intervention. Surgical repair was performed by ac-ssing the dehiscence through a middle fossa approach,ntifying the area of dehiscence, and covering the defectth hydroxyapatite bone cement as described by Smullenal.7 Early repairs were performed with fascia and CRSne cement. More recent repairs were performed by

Figure 1 Presentation symptomsure 2 Source of noise-induced vertigo in patients with Tul-s phenomenon.

Figcing temporalis fascia over the defect and coverings with fast setting hydroxyapatite bone cement (Nor-

CRS, Synthes Corporation, Paoli, PA). The bonement was allowed to harden after placement and the

poral lobe retraction released to allow the dura tover the repair.Patients were followed for several months after surgery.ose with less than 3 months of follow-up were not includedanalysis of response to surgical intervention. Patients wereessed for persistent symptoms, postoperative auditoryction including 4 frequency average (0.5, 1, 2, and 3z) of air and bone conduction, speech discrimination, and

rioperative complications.

SULTS

irty patients were diagnosed with SCD at our institutioner the time period studied. As stated previously, thegnosis was incidental in 3 patients. These patients weret symptomatic from the dehiscence and therefore not

quency seen in SCD patients.ure 3 Source of pressure-evoked symptoms by percentage.

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433Hillman et al Reversible Peripheral Vestibulopathy: The . . .luded in this study, which left 27 patients to be studied.e average age at the time of diagnosis was 47.5 years.ghteen were female and 9 were male. Presentation symp-

s were diverse and are presented in Fig 1. The mostmmon complaints were constant disequilibrium (63%),llios phenomenon (41%), and vertigo with straining or

ure 4 Audiograms from patients diagnosed with SCD on the-bone gaps predominate.ssure changes (44%). Hearing loss and pulsatile tinnitusre also common complaints. Hearing loss was seen in

shoMi% of patients; 4 (15%) patients had a conductive hearings component attributed to the superior canal dehiscence.e source of the noise and pressure evoked symptoms areown in Figs 2 and 3.When conductive hearing loss was seen, it tended to bedominantly in the low frequencies. These audiograms are

ar as a conductive hearing loss was identified. Low frequency30losThsh

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same ewn in Fig 4. This is a pattern that has been observed bynor et al8 as well in a recent publication. There did not seem

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434 OtolaryngologyHead and Neck Surgery, Vol 134, No 3, March 2006be the nadir at 2 KHz that is often seen with otosclerosis.herwise, there was no distinct pattern recognizable thatuld help to distinguish the conductive hearing loss in SCDm that seen with other ossicular chain abnormalities.The diagnosis in each case was confirmed by CT (Fig 5).e SCD was seen on the left side in 14 (52%) patients, onright side in 4 (15%) patients, and bilateral in 9 (33%)

tients. Of the 27 symptomatic patients diagnosed, 14 weremptomatic enough to warrant surgery. Five of these pa-nts were noted to have bilateral dehiscence on preopera-e CT. The more symptomatic side was corrected first.o of these patients had resolution of symptoms afterair of the first side. Later they became symptomatic onopposite side and subsequently underwent surgery to

air the second side. Another patient with unilateral SCDtially had symptom resolution for 5 months with progres-e return of symptoms after that. A repeat CT showed arsistent fistula on the same side and he underwent revisionrgical repair. Therefore a total of 17 operations wererformed on 14 patients. One patient had less than a monthlow-up after surgery at the time of this article preparationd therefore was not included in analysis of treatmentults, which leaves 16 operations on 13 patients for symp-

control analysis. During the operation, all patients werend to have a fistula on the suspect ear except for one who

d a blue line only. This patient had a CT that showed aehiscence on 1 cut only. This is the reason we now insist2 consecutive cuts of 1 mm thickness that show dehis-

nce as our diagnostic criterion.Of the 13 patients who underwent surgical intervention,had postoperative audiometric data available for review.e average presentation air/bone pure tone averages, air-

ure 5 CT shows absence of bone over the superior semicir-ar canal.ne gap, and postoperative hearing results are shown inble 1. Only 2 patients presented with 10 dB air/bonep, which decreased but was not eliminated after surgery.e patient had a decrease in sensorineural function (4quency average) of 10 dB after surgery. This patient whouired revision for persistent dehiscence had a decrease ofdB after the second surgery.The patients preoperative vestibular symptoms resolveder the surgery in 12 of the 13 patients. As stated above, 1tient was initially cured but had recurrent symptoms 5nths after surgery that prompted a repeat CT. This re-

aled a recurrent dehiscence as a result of a shift of thene cement on the previously operated side, and revisionrgery was offered. This was performed and the patient hasen symptom-free since. Therefore, only 1 patient hadrsistent vestibular symptoms after final definitive repair.erestingly, this was the 1 patient who was noted to havelue-line and not a true dehiscence of the superior semi-cular canal at the time of surgery. She had typical symp-

s including vertigo with loud sounds and straining, bute did not have objective physical examination findingsch as nystagmus.

SCUSSION

perior canal dehiscence is a condition caused by thesence of bone over 1 or both of the superior semicircularnals that leads to dysfunction of the vestibular end organa result of altered fluid flow mechanics. The absence ofne allows for dural contact into the inner ear and alteredid dynamics, the likely explanation for the frequentlynd Valsalva-associated symptoms. In addition, thisird window has been theorized to be a cause of inner

r conductive hearing loss as well as the Tullios phe-menon often seen in patients with this disorder.9,10The characteristic presentation of SCD has been de-ibed as dizziness in the presence of loud noises or pres-

re-evoked dizziness from changes in atmospheric pres-re, heavy lifting, or straining, the same symptoms thatve been historically attributed to perilymphatic fistula.e of these symptoms was present in each patient de-ibed in a series of 17 patients by Minor.1 Most, but not, of our patients (17 of 26, 65%) presented with at least 1these 2 complaints. The most common complaint of

able 1earing presentation and results for all patients andhe intervention subset

Entire group(N27, 2 bilateral)

re-op Air PTA 26.0 dBre-op Bone PTA 20.9 dBre-op ABG 5.1 dBumber with ABG 10dB Pre Op 4 (14.3%)PTA, Pure tone average; ABG, air bone gap; dB, decibel.

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435Hillman et al Reversible Peripheral Vestibulopathy: The . . .tients in our series was a sensation of constant disequi-rium (15 of 26, 58%). Seven (27%) of the patients whosented with chronic disequilibrium did not have either oftypical symptoms of noise or pressure-induced ver-

o, which reinforces that a high degree of suspicion forD should be maintained for patients with chronic imbal-

ce as well. Only 2 patients in our series did not have asentation with 1 of these 3 complaints. One had an acute

rtigo spell lasting 3 days with a sudden hearing loss andlong-term vestibular symptoms. The other had pulsatile

nitus on the same side as the dehiscence as their solemplaint.Pressure-evoked dizziness had a variety of precipitating

uses in our study. Although most of the patients with thisa symptom complained of dizziness when they lifted ofavy objects or strained, 2 noted dizziness with flying.ise-induced dizziness was caused most often by loudpulsive sounds, but in 2 of our patients, the dizziness wasoked with loud singing by the subject. One patient in-ted that only certain notes (in the alto range) caused hisziness.When we suspect SCD as a possible cause of vestibu-athy, we proceed with high resolution coronal CT of theporal bone to confirm or refute the diagnosis. All of our

tients but 1 had the dehiscence confirmed at the time ofrgery. This patient, who appeared to have a dehiscence oncut, at the time of surgery had only a blue line of theperior canal. Because of this false-positive, we now con-m the diagnosis of SCD by the absence of bone over theperior canal on 2 consecutive cuts. In our series, thisiographic criteria would have changed the false-positivee from 6% to zero.It should be emphasized that this low false-positive ratedirectly attributable to the fact that we are scanning

tients with highly suspicious symptoms for SCD. If ager group of subjects with vague symptoms wereeened with CT scans, then false-positives could be foundtentially leading to unwarranted surgical exploration. In aent review, Belden11 described that a CT scan with 1 mm

llimation has a positive predictive value of only 50% ingeneral population to illustrate this potential pitfall. This

why our patients must have significant symptoms as wellevidence of bone over the superior canal on at least 2

nsecutive cuts. If the symptoms are not typical, objectivestibular testing should be performed to look for nystag-s with sound or pressure presentation to verify the CTdings. Alternatively, ultra-high resolution CT scanning5 mm cuts) may also be used to provide better specificityproposed by Minor.2Recently, we have questioned whether SCD could be

curately diagnosed by MRI as well. This question hassen out of the fact that a large percentage of the patientshave treated for SCD present with nonspecific disequi-

rium. Some of these patients have indications to undergoeening MRI, and it would be convenient for this test to be

le to confirm or refute SCD. One recent study suggested pat high resolution, T2 weighted, fast spin echo MRI had asitivity of 96% and a specificity of 98% for the identi-

ation of SCD.10 We continue to use CT as our modalitychoice for SCD evaluation.Early in the series, we used ENG testing as an adjunct forgnosis.12 A total of 7 patients underwent modified ENGting specifically designed to examine SCD. All of thetients eventually diagnosed with SCD by CT had at leastbnormality on ENG, typically abnormal nystagmus withd sounds, tympanogram, or Valsalva. In our experience,

wever, we noted that high resolution CT had enoughsitivity and specificity to stand alone the definitive diag-

stic test for SCD when typical symptoms were alsosent. If we suspect, based on history and examination,t the patients symptoms are multifactorial or atypical,still use ENG testing to help with the evaluation.

Many of the patients (48%) initially diagnosed at ourtitution did not require surgery. These patients had mild

mptoms or additional diagnosis that compounded theirmptoms. For instance, 2 of the nonoperative patients had

diagnosis of benign positional vertigo in addition toD during the workup. Although 1 had chronic disequi-rium and the other Tullios phenomenon in combinationth the positional vertigo, they both felt well enough afternalith repositioning that no further treatment was neces-y.Surgery is performed through the middle fossa approachth fascia and hydroxyapatite cement placed over the bonyfect (Fig 6). We have had good success with this ap-ach, but there can be technical hurdles. The bone cementuse is a fast setting type (Norian CRS, Synthes Corpo-

ion, Paoli, PA) that hardens in 5 minutes and curesdily in a wet environment. This cement is a clear im-vement over the slower setting formulation that was used

rly in our series, which was prone to microfracture andnot set as well in a wet environment. Keeping the

rdened cement in position can be difficult, however, as itn slip off the underlying bone when the dura is released.oviding a large surface area of contact between the ce-nt and the middle fossa floor is helpful to prevent dis-cement. The area covered by the cement is significantlyder than the dehiscence, at least a centimeter in radiusm the superior canal. Also, we have found that allowingpropriate time (at least 5 minutes) for hardening and notnipulating the dura after release of retraction to take acond look, keeps the repair in place.Surgical repair provides a high success rate (93%). The 1

tient that required revision had displacement of the ce-nt. This has not happened again since we began use ofnew cement formulation and the maneuvers described

ove. The 1 failure in our series was an error of diagnosisher than a failure of the repair.Bilateral dehiscence was noted in 9 (33%) of our pa-nts. Of these, 5 went on to surgical repair initially on thee that was felt to be the most symptomatic. Although the

tients were counseled that bilateral repair may be needed,

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had normal ossicular chains at the time of stapedectomy andno other explanation for their hearing loss. In this article,they note that 3 patients did not have round window reflexesdespite normal stapes mobility and states that there could besome inner ear abnormality not visible that cause thisphtivbil

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436 OtolaryngologyHead and Neck Surgery, Vol 134, No 3, March 2006ly 2 (40%) patients had recurrent symptoms that requiredair of the opposite side. Both of these patients reportedprovement of their symptoms after the initial repair andth are symptom-free after their second surgery. We con-ue to target treatment to the subjectively most symptom-c side, however, in the hopes that most of the patientsth bilateral SCD will not go on to need repair of bothes.Superior canal dehiscence is a highly treatable vestibu-athy once recognized. Up to 0.7% of individuals may

ve absence of the bone over the superior semicircularnal on the basis of a recent temporal bone survey byrey et al.10 Although it is unlikely that this many indi-uals have symptomatic disease, it is probable that SCD is

der-diagnosed.Besides imaging patients with classic symptoms of SCD,is our current practice to image young patients withronic disequilibrium and those with symptoms that sug-st perilymph fistula. We have 3 patients who had pulsatilenitus on presentation that resolved after surgical repair inFor patients with pulsatile tinnitus with no source iden-ed on the standard workup, we are now performing a CTn to rule out SCD. The conductive hearing loss seen inD can also masquerade as otosclerosis. SCD should be

nsidered in stapedectomy cases with an unchanged post-erative conductive deficit despite uncomplicated surgery.use et al13 in 1980 described the term inner ear conduc-e hearing loss in reference to 4 patients who seemingly

ure 6 Repair of SCD involves restoration of the bone thatarates the superior canal from the intracranial space. This isformed by placing temporalis fascia over the defect and placing

ne cement over a broad span of the middle fossa bone over andund the fascia. (Reprinted by permission of C Shelton, MD.)enomenon. SCD is 1 possible explanation for a conduc-e hearing loss seen in the face of normal ossicular mo-ity.

NCLUSION

perior canal dehiscence is a reversible vestibulopathy,th a wide range of presentations, but characteristic imag-

findings. The treatment for disabling cases involvessure of the defect with fascia and bone cement. Successtreatment is high, with resolution of symptoms in greatern 90% of patients who require surgical intervention.

FERENCES

Minor LB, Solomon D, Zurich JS, Zee DS. Sound- and/or pressure-induced vertigo due to bone dehiscence of the superior semicircularcanal. Arch Otolaryngol Head Neck Surg 1998;124:24958.Minor LB. Superior canal dehiscence syndrome. Am J Otol 2000;21:919.Kwee HL. The occurrence of the Tullio phenomenon in congenitallydeaf children. J Laryngol Otol 1976;90:5017.Nields JA, Kueton JF. Tullio phenomenon and seronegative Lymeborreliosis. Lancet 1991;338:1289.Davis RE. Diagnosis and management of perilymph fistula: the Uni-versity of North Carolina approach. Am J Otol 1992;13:859.Friedland DR, Wackym PA. A critical appraisal of spontaneous peri-lymphatic fistulas of the inner ear. Am J Otol 1999;20:26176; dis-cussion 769.Smullen JL, Andrist EC, Gianoli GJ. Superior semicircular canaldehiscence: a new cause of vertigo. J La State Med Soc 1999;151:397400.Minor LB, Carey JP, Cremer PD, et al. Dehiscence of bone overlyingthe superior canal as a cause of apparent conductive hearing loss. OtolNeurotol 2003;24:2708.Rosowski JJ, Songer JE, Nakajima HH, et al. Clinical, experimental, and

theoretical investigations of the effect of superior semicircular canal de-hiscence on hearing mechanisms. Otol Neurotol 2004;25:32332.Carey JP, Minor LB, Nager GT. Dehiscence or thinning of boneoverlying the superior semicircular canal in a temporal bone survey.Arch Otolaryngol Head Neck Surg 2000;126:13747.Belden CJ, Weg N, Minor LB, et al. CT evaluation of bone dehiscenceof the superior semicircular canal as a cause of sound- and/or pressure-induced vertigo. Radiology 2003;226:33743.Kertesz TR, Shelton C, Wiggins R, et al. Superior semi-circular canaldehiscence: Resurfacing with calcium phosphate bone cement. Aust JOtolaryngolgoy 2001;4:16773.House JW, Sheehy JL, Antunez JC. Stapedectomy in children. Laryn-goscope 1980;90:18049.

Reversible Peripheral Vestibulopathy: The Treatment of Superior Canal DehiscenceMATERIALS AND METHODSRESULTSDISCUSSIONCONCLUSIONREFERENCES