Eur Arch Otorhinolaryngol DOI 10.1007/s00405-013-2711-x

OTOLOGY

Superior canal dehiscence syndrome: clinical manifestations and radiologic correlations Issam Saliba • Anastasios Maniakas • Lina Zahra Benamira • Jade Nehme • Me´lanie Benoit • Ve´ronique Montreuil-Jacques

Received: 10 June 2013 / Accepted: 16 September 2013 Ó Springer-Verlag Berlin Heidelberg 2013

Abstract The objective of this study is to describe the superior canal dehiscence syndrome (SCDS) and its vestibule–cochlear manifestations, while analyzing dehiscence size, audiogram and vestibular-evoked myogenic potential (VEMP) changes following dehiscence obliteration. We conducted a prospective study in a tertiary referral center. All Patients diagnosed and surgically treated for SCDS were operated through a middle fossa craniotomy (MFC). Clinical and radiological data were collected. The main outcome measures were Air-bone gaps, Pure-tone average (PTA), speech discrimination scores (SDS) and VEMP thresholds and were correlated to dehiscence size. 28 patients were included in this study with a mean dehiscence size of 4.68 mm. Phonophobia and imbalance were the most debilitating cochlear and vestibular symptoms, respectively. At 2 months postoperatively, low-frequency air-bone gaps showed a statistically significant improvement (p \ 0.001). SDS and PTA did not show any statistically significant changes 2 months postoperatively (p = 0.282 and p = 0.295, respectively). VEMP threshold differences between operated and contralateral ears were statistically significant preoperatively (p \ 0.001) and nonsignificant 2 months postoperatively (p = 0.173). Dehiscence size only showed a statistically significant correlation with preoperative total cochlear symptoms, while

I. Saliba (&)  A. Maniakas  L. Z. Benamira  J. Nehme Department of Otolaryngology, Head and Neck Surgery, Montreal University Hospital Center (CHUM), Notre Dame Hospital, University of Montreal, 1560 Sherbrooke East, Montreal, QC H2L 4M1, Canada e-mail: [email protected] M. Benoit  V. Montreuil-Jacques Department of Audiology, Montreal University Hospital Center (CHUM), University of Montreal, Montreal, QC, Canada

remaining insignificant with all other variables measured. Air-bone gaps, VEMP and computerized tomography remain essential tools in diagnosing and following SCDS. Dehiscence size is an independent factor in the analysis of SCDS, with cochlear symptomatology being associated to dehiscence sizes. Finally, it is shown that overall symptomatology, audiometric results and VEMP thresholds return to normal values post-obliteration, confirming the continuing success of the MFC approach for SCDS obliteration Keywords Superior canal  Dehiscence syndrome  Hyperacusis  VEMP  Middle cranial fossa  Autophony  Phonophobia

Introduction The superior canal dehiscence syndrome (SCDS) was identified by Minor et al. in 1998 [1] as a syndrome of vertigo and oscillopsia. Patients will usually present only cochlear, only vestibular or vestibulocochlear signs and symptoms. Current clinical practice has attributed this condition to the dehiscence of the bone overlying the superior semicircular canal [2, 3] that can be visualized by high-resolution computed tomography (CT) scans of the temporal bones [4–6], as well as at the time of surgical repair [1, 7–9]. Prevalence rates of superior canal dehiscence reported in the literature range from 0.4 to 0.7 % [2, 10, 11] with a majority of patients being asymptomatic. The diagnosis of SCDS is therefore only made following both clinical and radiological findings [12]. Several etiologies have been linked to SCDS with hereditary, developmental, intracranial hypertension, and post-traumatic causes being the most common hypotheses referred to,

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either as predispositions to SCDS or as exacerbations towards symptomatic SCDS of an already dehiscent bone [2, 3, 13]. Several cochlear symptoms have been reported, with autophony, hyperacusis, symptomatic hearing loss, aural fullness or pressure, and pulsatile tinnitus being the most commonly encountered [4, 14]. Vestibular symptoms, such as imbalance, vertigo, oscillopsia, Tullio phenomenon, and Hennebert sign, are also usually found in a large percentage of patients with SCDS [2, 4, 15]. Surgical treatment of symptomatic SCDS by plugging or resurfacing is traditionally done via a middle fossa craniotomy (MFC) [4, 16]. Some centers will also perform the less invasive transmastoid approach that has shown similar positive postoperative outcomes and can even be performed under local anesthesia [17–21]. Resurfacing of the canal, however, has been shown to have poorer long-term control of symptoms with higher risk of recurrence when compared to plugging [4, 19]. In this study, we present the pre- and postoperative clinical manifestations of patients diagnosed with and treated for symptomatic SCDS at our centers as well as our interpretation of their pre- and postoperative audiometric and vestibular-evoked myogenic potential (VEMPs) values. Finally, as our primary objective, we investigate the correlation between the size of dehiscence and the patients’ symptomatology, audiograms and VEMP thresholds.

Materials and methods We performed a retrospective study of all patients diagnosed with SCDS and operated between 2007 and 2011 at our tertiary care center. The diagnosis was made using high-resolution temporal-bone CT scans. The imaging for SCDS is a high-resolution 0.6 mm collimation of the temporal bones with images that are reformatted with multiplanar reconstruction (Po¨schl view) following the presentation of signs and symptoms associated to SCDS. No orthogonal plane (Stenver view) reconstruction was performed at this time. A dehiscence was noted when there was a complete absence of bone overlying the semicircular canal. Bone thinning above the semicircular canal was not considered as a dehiscence. To ensure a thorough comprehension of the patients’ symptomatology, a complete medical history was obtained collecting as much information as possible on the presence of pre- and postoperative signs and symptoms. Patients were asked to characterize a list of preoperative cochlear and vestibular signs and symptoms as absent, present but tolerable, or debilitating, and the same cochlear and vestibular signs and symptoms postoperatively as resolved, improved, or worsened, as well as any other unusual manifestations. Presence of

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Me´nie`re’s disease, otospongiosis, perilymphatic fistulas, other otologic surgeries prior to their SCDS diagnosis, severe trauma to the head before or after SCDS diagnosis, severe headaches or episodes of blurry vision prior to SCDS diagnosis, or diseases such as osteoporosis, hypertension and diabetes were all investigated in each patient. Duration of recovery to normal life and general outcome satisfaction were also recorded. Two separate observers performed measurements of dehiscence size with the mean value used to study the correlation with the symptomatology and audiogram results of the patients. Pure-tone average (PTA) using air-conduction values at 500, 1,000, 2,000 and 4,000 Hz, air and bone-conduction audiograms from 250 to 4,000 Hz, speech discrimination scores (SDS) and cervical VEMP thresholds were measured pre- and postoperatively in both the operated and contralateral ear. 500 Hz tone bursts were the administered stimuli for the VEMP test. Statistical analysis All data was tabulated using Microsoft Excel. The Pearson Correlation Coefficient was used for the analysis of correlations in our study; the mixed model for repeated measures (MMRM) was used for the difference between preoperative and postoperative debilitating cochlear and vestibular symptoms, audiogram, SDS values, and VEMP threshold differences, while the T test was used to compare operated and contralateral ears for the latter variables. For all statistical analyses, p \ 0.05 was considered significant. All statistical analyses were performed using SPSS 19.0.

Results Between 2007 and 2011, a total of 187 patients with SCDS were identified, evaluated and questioned; of these, 28 (15 males and 13 females) were found to have debilitating symptoms requiring surgical intervention. The interventions were performed by the first author (IS) via a middle fossa craniotomy (MFC). No patient refused the surgery because of this approach. Average postoperative hospitalization was 2.5 days (range 2–3 days). All patients had a minimum follow-up of 2 months. Preoperative patient characteristics Mean age at the time of diagnosis was 44 years (range 27–60 years). Only the right ear was affected and operated on in 10 patients, only the left ear in 11, and in 7 patients with bilateral SCDS one had only the right ear operated, while the others only had the left. All patients presented a

Eur Arch Otorhinolaryngol Table 1 Patient clinical data and findings at diagnosis Patient number

Age (years)

Gender

Symptom duration prior to diagnosis (years)

Type of symptoms

Dehiscence location

Dehiscence size (mm)

Dehiscence operated

1

42

M

3.17

C?V

L

2.65

L

2

30

M

2.17

C?V

L

3.35

L

3

57

M

4

C?V

L

4.8

L

4

43

M

8

C?V

R

4.1

R

5

33

F

1.25

C?V

L

4.15

L

6

57

M

1.5

C?V

R

4.3

R

7 8

41 45

F M

1 2.5

C?V C?V

R L

4.1 4.4

R L

9

27

M

8

C?V

L

4.9

L

10

54

M

10

C?V

R

5.35

R

11

46

F

2

C?V

L

3.35

L

12

36

M

1.83

C?V

R

4.65

R

13

52

F

1.92

C?V

R

2

R

14

37

M

10

C?V

L

8

L

15

49

F

2

C?V

B

R4.8/L5.15

L

16

38

F

5

C?V

L

3.85

L

17

41

M

2

C?V

R

6.8

R

18

53

F

1.75

C?V

R

5.15

R

19

37

M

5

C?V

B

R4.75/L5.15

L

20

34

M

1

C?V

B

R3.6/L5.5

L

21

39

F

3

C?V

B

R4/L2.55

R

22 23

45 41

F F

3 3

C?V C?V

B R

R3/L4.4 4.95

L R

24

44

F

4

C?V

L

3.85

L

25

54

M

30

C?V

B

R5.6/L6.2

L

26

45

M

5

C?V

B

R3.95/L5.45

L

27

60

F

8

C?V

L

5.5

L

28

37

F

4

C?V

R

5

R

M Male, F Female, C Cochlear, V Vestibular, R Right, L Left, B Bilateral

variety of vestibule–cochlear symptoms. Eleven (39 %) patients reported a history of previous trauma to the head. Two separate observers measured the dehiscence size with no significant difference among their reports (p = 0.940). An average of the two measures was used for this study. Mean dehiscence size of operated ears was 4.68 mm (range 2.00–8.00 mm, SD 1.20 mm, mean standard error 0.88 mm). Mean dehiscence size of the operated ear in bilateral SCDS was 5.12 and 4.04 mm for the contralateral ear. SCDS diagnosis was made after 4 years of symptoms in approximately 40 % of patients (mean 4.79 years, range 1–30 years). Patient demographics and dehiscence characteristics are summarized in Table 1. Signs and symptoms present at diagnosis are summarized in Table 2. Phonophobia, autophony and pulsatile tinnitus were found to be the most debilitating cochlear symptoms (75, 61 and 54 %, respectively) (Fig. 1), while the three most

common debilitating vestibular symptoms were imbalance/ dizziness, motion dizziness and oscillopsia with effort (32, 29 and 25 %, respectively) (Fig. 2). The mean number of debilitating cochlear symptoms per patient was four (range 0–8), while patients reported having only two debilitating vestibular symptoms (range 0–7), on average. Of the four signs studied, none were debilitating, while the Tuning fork malleolus, vertigo by insufflations with a Siegle pneumatic speculum and the Valsalva maneuver were all similarly present and tolerable (36, 43 and 46 %, respectively). Postoperative patient characteristics All patients showed a positive postoperative outcome of their cochlear symptoms. Ten (10 of 28) patients reported complete resolution, while 18 noted an improvement. No patient presented with worsening cochlear symptoms postoperatively. Vestibular symptoms improved in 16 (16

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Eur Arch Otorhinolaryngol Table 2 Clinical symptoms and signs at diagnosis No. of patients Absent

Tolerable

Hypoacusis

11

12

Tympanophony

Debilitating

Symptoms Cochlear 5

16

11

1

Autophony

0

11

17

Tinnitus

5

19

4

Pulsatile tinnitus Phonophobia

3 2

10 5

15 21

Aural fullness

2

18

8

Footstep sound

12

12

4

Eating sound

12

9

7

Oculophony

11

9

8

Sense of vibration

13

8

7

Vertigo

19

7

2

Vertigo with effort

19

5

4

3

16

9

Motion dizziness

11

9

8

Tullio phenomenon

12

12

4

At rest With walking

16 18

7 5

5 5

With effort

14

7

7

Tuning fork malleolus

18

10

0

Vertigo by insufflations with Siegle pneumatic speculum

16

12

0

Valsalva maneuver

15

13

0

Hennebert

27

1

0

Other forms of hyperacusis

Vestibular

Imbalance/Dizziness

Fig. 2 Debilitating vestibular symptom prevalence

of 28), fully resolved in 11, while one patient had only one tolerable vestibular symptom preoperatively, which remained as such 2 months postoperatively. Five (5 of 28) presented subpalpebral oedemas and four had subcutaneous temporal oedemas. Only one tolerable cochlear or vestibular symptom was present 2 months postoperatively, on average, per patient (range 0–3 and 0–4, respectively). Of the 20 patients presenting some form of tolerable sign, one patient reported no change, one an improvement and 18 a complete resolution. Normal quality of life was recovered, on average, 5.67 weeks postoperatively (range 2–12 weeks).

Oscillopsia

Signs

Unusually loud hearing of a person’s own voice (Autophony) or own breathing (tympanophony) or own eyes movement as they change the direction of their gaze (Oculophony)

Fig. 1 Debilitating cochlear symptom prevalence

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Audiograms, pure-tone average and speech discrimination scores Audiograms were recorded preoperatively in all 28 patients (Fig. 3a), immediately following surgery in 27 of 28 patients (Fig. 3b), and 2 months postoperatively in 26 of 28 patients (Fig. 3c). Preoperative audiograms showed large air-bone gaps (ABGs), particularly in low frequencies, that remained stable or worsened immediately following plugging of the dehiscence. However, a statistically significant improvement to the mean preoperative ABG values was obtained 2 months postoperatively at frequencies 250 Hz [25.2 dB (SD 9.8 dB) to 9.6 dB (SD 10 dB)], 500 Hz [15.8 dB (SD 9.9 dB) to 2.1 dB (SD 4.6 dB)] and 1,000 Hz [11.5 dB (SD 9.9 dB) to 6.6 dB (SD 7.3 dB)] (p \ 0.001, p \ 0.001 and p = 0.049, respectively). Mean preoperative ABG values were statistically significantly different between operated and contralateral ears at 250 Hz [25.2 dB (SD 9.8 dB) vs. 11.0 dB (SD 8.9 dB), respectively] and 500 Hz [15.8 dB (SD 9.9 dB) vs. 6.3 dB (SD 7.3 dB), respectively] (p \ 0.001), while showing a nearsignificant difference at 1,000 Hz [11.5 dB (SD 9.9 dB) vs. 6.8 dB (SD 6.5 dB), respectively] (p = 0.061). 2 months postoperatively, there was no statistically significant difference between ears when looking at mean ABG values (p = 0.135 to p = 0.937).

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in the low frequencies (250–1,000 Hz). The average dehiscence size for these patients was 4.76 mm (range 3.35–6.8 mm). Mean values at 250, 500 and 1,000 Hz preoperatively were -8.85, -0.77 and -1.54 dB, respectively. 2 months postoperatively, mean values increased to 1.67, 11.54 and 2.69 dB, respectively, with only four (4 of 13) patients maintaining negative values at 250, 500 and/or 1,000 Hz. Preoperative and 2-month postoperative SDS values were available for 26 (26 of 28) patients. No statistically significant difference was shown in SDS between mean preoperative and 2-month postoperative values in operated (90.00 vs. 92.15 %) and contralateral ears (98.22 vs. 97.76 %) (p = 0.282 and p = 705, respectively). Specifically, in the operated ears, 5 (19 %) patients demonstrated an average decrease of 5.6 % in their SDS, 15 (58 %) patients remained with the same score (of which 13 initially had 100 %), while 6 (23 %) showed a mean improvement of 12 % 2 months postoperatively. No statistically significant difference was found when comparing operated and contralateral ear SDS values (p = 0.99). Vestibular-evoked myogenic potentials

Fig. 3 Operated ears: a mean preoperative audiogram, b mean immediate postoperative audiogram, c mean 2-month postoperative audiogram

Mean PTA values were measured in both operated and contralateral ears preoperatively and 2 months postoperatively. No statistically significant difference was seen in contralateral ears between preoperative (12.90 dB) and 2-month postoperative (12.4 dB) values (p = 0.861). Likewise, no statistically significant difference in mean PTA values was found between the two time points for the operated ear (21.74 and 16.25 dB, respectively) (p = 0.295). However, a statistically significant difference was seen between operated and contralateral preoperative mean PTA (p = 0.044), a difference that was non-significant 2 months postoperatively (p = 0.333). Negative preoperative bone-conduction audiogram values were recorded in thirteen (13 of 28) patients, especially

VEMPs were recorded pre- and postoperatively. Four (4 of 28) patients were excluded from these analyses due to missing values. When comparing operated to contralateral ear, an additional seven (7 of 24) patients with bilateral dehiscences were also excluded. Pre- and postoperative VEMP thresholds were compared in the operated and contralateral ears (Table 3), as well as pre- and postoperative differences in VEMP thresholds between the two ears when bilateral values were available. 23 (23 of 24) patients showed abnormal (B75 dB) preoperative VEMP in the operated ear, while one patient had 80 dB. 23 (23 of 24) patients demonstrated a mean increase in VEMP threshold of 19 dB (range 5–40 dB) 2 months postoperatively. The remaining patient showed no change in VEMP value. Mean preoperative VEMP thresholds were 61 dB (range 50–80 dB; SD 8 dB) in the dehiscent ear and 81 dB (range 70–90 dB; SD 7 dB) in the normal ear (p \ 0.001), while postoperative values were 80 Db (range 65–90 dB; SD 8.7 dB) and 81 dB (range 70–90 dB; SD 7.5 dB) (p = 0.521), respectively, an overall increase that is statistically significant in the operated ear (p \ 0.001) and non-significant in the contralateral ear (p = 0.484). The mean preoperative threshold differences between the dehiscent and the contralateral ears, when available, were 19 dB, while the mean 2-month postoperative difference was 4 dB, a statistically significant change (p \ 0.001).

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Eur Arch Otorhinolaryngol Table 3 Pre- and postoperative vestibular-evoked myogenic potential (VEMP) in operated and contralateral ears

N/A not available

Patient ID

Operated ear

Contralateral ear

Preoperative

Postoperative

Preoperative

Postoperative

1

65

65

80

90

2

55

70

75

90

4

65

75

85

80

5

65

70

80

80

6

65

90

85

85

7

65

85

90

90

8

65

75

85

80

9

65

75

75

75

10

55

75

80

80

11

75

85

N/A

N/A

12 13

55 80

65 90

70 75

70 75

14

50

75

75

70

15

75

90

N/A

N/A

16

50

90

90

90

19

60

75

N/A

N/A

20

60

90

N/A

N/A

21

50

90

N/A

N/A

22

55

90

N/A

N/A

23

55

90

90

90

24

60

80

75

75

26

55

75

N/A

N/A

27

60

75

90

90

28

65

75

70

75

Mean

61

80

81

81

Correlation analysis between dehiscence size and tolerable and/or debilitating symptoms

Correlation between dehiscence size and audiogram results

All patients were included in this correlation analysis. No statistically significant correlation was noted between dehiscence size and tolerable or debilitating cochlear symptomatology at diagnosis, (r = 0.269 p = 0.166 and r = 0.38 p = 0.847, respectively) (Fig. 4a, b). However, a statistically significant correlation was found between dehiscence size and overall cochlear symptomatology at diagnosis (r = 0.400; p = 0.035) (Fig. 4c). Vestibular symptomatology, whether tolerable, debilitating or both, had no statistically significant correlation with dehiscence size (r = -0.237 p = 0.225; r = 0.022 p = 0.911 and r = -0.171 p = 0.385, respectively). Likewise, overall vestibule–cochlear symptomatology had no statistically significant correlation with dehiscence size, whether it be tolerable (r = 0.086 p = 0.662), debilitating (r = 0.039 p = 0.854) or both (r = 0.145 p = 0.461).

Dehiscence size was compared to audiogram results in our patients to try and see if larger preoperative ABGs, worse audiogram progressions from a preoperative state to 2 months postoperatively, or worse preoperative PTA results correlated with larger dehiscences. No statistically significant correlation was found in ABGs at any frequency preoperatively (p = 0.296 to p = 0.762) or 2 months postoperatively (p = 0.159 to p = 0.924). Likewise, patients had similar outcomes following dehiscence obliteration, with no statistically significant correlations between dehiscence size and postoperative audiogram outcome (p = 0.287 to p = 952). Finally, preoperative and 2-month postoperative PTA values in the operated ear also did not statistically significantly correlate with dehiscence sizes (r = 0.022; p = 0.910 and r = -0.159; p = 0.458, respectively).

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Fig. 5 Dehiscence size versus preoperative (a), and postoperative (b) vestibular-evoked myogenic potential (VEMP) thresholds. Asterisk represents a statistical significance

as 2 months postoperatively (r = -0.097; p = 0.653) (Fig. 5b).

Discussion

Fig. 4 Association between dehiscence size and number of symptoms. a Dehiscence size versus tolerable cochlear symptoms, b dehiscence size versus debilitating cochlear symptoms, and c dehiscence size versus total cochlear symptoms. Asterisk represents a statistical significance

Correlation analysis between dehiscence size and vestibular-evoked myogenic potential Using the VEMP values recorded from the eligible patients, a correlation analysis was made with dehiscence size. No statistically significant correlation between VEMP threshold and dehiscence size was found in our patients preoperatively (r = -0.250; p = 0.208) (Fig. 5a), as well

In this study, 28 patients underwent obliteration of their superior canal dehiscence via a MFC, with \6 weeks needed, on average, to return to their normal life. Preoperatively, patients included in this study suffered symptoms of SCDS for a mean of 4.79 years prior to diagnosis, suggestive of the unawareness of this pathology a few years ago. In concordance with this theory, our patients reported progressively increasing symptoms, reaching, on average, four debilitating cochlear symptoms and two debilitating vestibular symptoms per patient at the time of diagnosis. Furthermore, patients had, on average, four tolerable cochlear symptoms and two tolerable vestibular symptoms due to this disease. Therefore, overall, SCDS in our patients seemed to incur more cochlear than vestibular symptoms, a finding that differs from its current description in the literature [4, 9, 22]. Furthermore, eating hyperacusis was a novel form of hyperacusis reported by 57 % of our cases. To our knowledge, this symptom has

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never been described in the literature and should be incorporated in patient symptomatology when SCDS is suspected, as it can be quite debilitating, with surgical intervention as its sole treatment. Postoperatively, all patients had positive vestibule– cochlear outcomes, with only three (3 of 28) patients reporting one to two persisting debilitating cochlear or vestibular symptoms, confirming the continuing success of the MFC approach. Moreover, tolerable cochlear and vestibular symptoms decreased to one per patient, on average. One patient (#18) noted no change of overall vestibular symptomatology, with one vestibular tolerable symptom remaining following dehiscence obliteration. Such an outcome has been previously reported in the literature, and it is thought to stem directly from the SCD plugging procedure [16]. Nevertheless, dwelling symptoms seem to resolve with time. Four signs previously described in the literature [9, 14, 23, 24] for SCDS were studied in our patients: Tuning fork malleolus, vertigo by insufflations with a Siegle pneumatic speculum, Valsalva maneuver and Hennebert sign. No patient reported debilitating signs, rendering them less significant when assessing surgical indications, although remaining clinically important for postoperative evaluation. As with symptomatology, patients demonstrated a favorable outcome, with one patient reporting no improvement, one with a significant improvement and the remaining having a complete resolution. Such results demonstrate that dehiscence obliteration is also highly effective in restoring normal sign manifestations. Auditory manifestations Audiogram results showed the characteristic SCDS lowfrequency large ABGs that have been repeatedly described in the literature [4, 14, 25, 26], with statistically significant improvement following surgical intervention. Even though our immediate postoperative audiograms at times demonstrated a worsening of the ABG, an effect attributed to the presence of liquid, blood and postoperative oedema in the recently operated ear, low-frequency ABGs were significantly decreased in size at 2 months following surgery. Furthermore, we demonstrated that although mean preoperative ABG values significantly differed between ears, following obliteration there was no significant difference between them at any measured frequency. Negative preoperative audiogram values were recorded in almost half of our patients; their mean age (42.9 years) and dehiscence size (4.76 mm) were comparable to the overall cohort means (43.5 years and 4.68 mm), excluding any hypothesis that younger patients with smaller dehiscences would have better audiogram values. Therefore, we can assume that although patients present themselves

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with variable sized dehiscences, they can still maintain normal hearing capacities, measured by audiograms. Furthermore, three patients demonstrated an improvement in audiogram values 2 months postoperatively with the negative bone-conduction values that were not present preoperatively, suggesting that dehiscence obliteration cannot only better one’s hearing, but can likely return it to normal levels. When looking at postoperative SDS in operated and contralateral ears, overall, our patients showed an insignificant, yet noteworthy increase compared to preoperative values. SDS values were, therefore, concordant with the current suggestion that speech discrimination does not tend to significantly alter when a dehiscence is surgically obliterated [18, 27]. VEMP responses As it has been described by Welgampola et al. [25], the VEMP test has become an indispensable tool in the current diagnostic and procedural follow-ups for SCDS due to its characteristic low thresholds in the affected ears and the normalized values once operated upon. In our analysis, we did not only look into the overall improvement in the operated ear postoperatively, but also studied the mean difference between dehiscent and contralateral ears preand postoperatively. As can be seen in the literature [9, 14, 25], our VEMP thresholds increased significantly following surgery, reaching near-to-normal values (normal [75 dB), while the mean difference between affected and normal ears decreased from 19 to 4 dB, further strengthening the association between the effectiveness of VEMP measurements and SCDS obliteration outcomes. One of our patients (#13) improved her VEMP from 80 to 90 dB. Even though the preoperative VEMP was normal, she was treated due to the debilitating vestibule–cochlear symptoms affecting her quality of life. It is important to note that this patient presented the smallest dehiscence (2 mm) of our series, further supporting the notion that dehiscence size does not correlate to the number of debilitating symptoms discussed below. Dehiscence size as an independent variable Pfammatter et al. [28] described the possible association between dehiscence size (less or more than 2.5 mm), SCDS symptoms, and lower VEMP thresholds, reporting that there is a statistically significant correlation between large dehiscences ([2.5 mm) and the presence of vestibule– cochlear symptoms, as well as between dehiscence size and lower VEMP thresholds. We did not use this breakdown format seeing as though we only had one patient with a dehiscence of \2.5 mm; we instead ran correlation

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analyses. Overall, when using dehiscence size as an independent variable, a significant correlation was only found in preoperative cochlear symptomatology and when looking at the total number of symptoms (i.e., tolerable ? debilitating). For vestibular and overall vestibule– cochlear symptoms, no significant correlation was found with dehiscence size. Thus, the present results suggest that patients with larger dehiscences can present with more cochlear symptoms. Interestingly, in our patients with bilateral SCDS (seven patients) we operated the more symptomatic side, which in fact was the side with a larger dehiscent size (5.12 vs. 4.04 mm). It is hard, however, to compare this study to Pfammater et al.’s, as our study analyzed 11 different cochlear symptoms compared to the latter’s 2, and the symptom grading system was different, with our study using three qualifications (absent, tolerable and debilitating), versus the latter’s use of present (?) or absent (-). Finally, in a recent study by Chien et al. [29], where an analysis was performed with one of the largest cohorts of SCDS patients (n = 85), it was also demonstrated that dehiscence size was not correlated with vestibular or cochlear symptomatology. Additional studies are thus warranted to establish true consensus on the symptomatology of SCDS. Interestingly, our results on dehiscence size versus VEMP thresholds also showed a similar trend to Chien et al.’s study, while opposing Pfammater et al.’s findings. Our present results demonstrate that there is no correlation between the size of the dehiscence and preoperative VEMP thresholds. Furthermore, following dehiscence obliteration, patients were found to have even more comparable VEMP thresholds amongst them, regardless of their dehiscence size at diagnosis. An additional analysis using dehiscence size as the independent parameter was run to study the possible correlation between dehiscence size and preoperative audiogram ABGs, PTA and audiogram improvement preoperatively to 2 months postoperatively. This analysis was performed following a hypothesis that larger dehiscences might result in worse audiogram results or larger ABGs. Our results, however, suggest that there is no significant difference between dehiscence size when looking at ABGs, PTA or audiogram postoperative progression. Thus, all ears showed similar outcomes, reaching new audiogram values that were not significantly different. This suggests that regardless of the size of the preoperative dehiscence, if properly obliterated, its audiometric outcome should be just as successful.

Conclusions Patients with SCDS can present themselves with vestibular and cochlear, more vestibular than cochlear, or, as seen in

this study, more cochlear than vestibular symptoms. Furthermore, eating hyperacusis should be added to the symptomatology investigated in patients presenting with SCDS, as it can be a debilitating symptom. Careful attention needs to be placed on patients with bilateral SCDS, as their symptoms may recur shortly following unilateral treatment. VEMP thresholds in SCDS ears return to normal or near-normal values post-obliteration, regardless of the preoperative dehiscence size. Lastly, regardless of the preoperative dehiscence size, patients’ audiograms improve in a similar manner postoperatively. Due to the novelty of this pathology and confounding findings currently available in the literature, further studies with large cohorts are warranted. Conflict of interest

None.

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Superior canal dehiscence syndrome: clinical manifestations and radiologic correlations.

The objective of this study is to describe the superior canal dehiscence syndrome (SCDS) and its vestibule-cochlear manifestations, while analyzing de...
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