Download Transmastoid resurfacing of superior semicircular canal dehiscence

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C 2011 The American Laryngological,
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Rhinological and Otological Society, Inc.
Transmastoid Resurfacing of Superior Semicircular Canal Dehiscence
Hosam A. Amoodi, MD; Fawaz M. Makki, MD; Michael McNeil, MD; Manohar Bance, MB, MSc, FRCSC
Objectives/Hypothesis: To describe a new and fast surgical technique in treating superior semicircular canal dehiscence syndrome by resurfacing the canal defect via the transmastoid approach without retraction of the whole temporal lobe
and to demonstrate the clinical and audiologic results of the superior canal dehiscence repair. Superior semicircular canal
dehiscence syndrome is a well-described pathology. Surgical procedures through the middle fossa approach to resurface the
superior canal and transmastoid plugging are considered the main surgical therapeutic options for patients with debilitating
symptoms. Both have drawbacks; plugging is invasive to the inner ear, and resurfacing requires a middle fossa approach.
Study Design: Retrospective review.
Methods: Four patients presented with classic symptomatic semicircular canal dehiscence syndrome with radiographic
confirmation of their dehiscence. The patients underwent the resurfacing procedure with a transmastoid approach.
Results: All four patients reported resolution of their symptoms. Audiograms documented some improvement in three
subjects.
Conclusions: The transmastoid approach for resurfacing superior semicircular canal dehiscence is a safe and less-invasive technique than the standard middle fossa approach, which has many potential complications and requires much longer
hospitalization. In our study, the surgeries were completed within 90 minutes, and patients stayed in the hospital only
overnight.
Key Words: Superior semicircular canal, dehiscence syndrome, resurfacing.
Level of Evidence: 4.
Laryngoscope, 121:1117–1123, 2011
INTRODUCTION
Superior semicircular canal dehiscence (SCCD) syndrome (SCCDS) is a relatively new clinical condition,
described by Minor et al. in 1998.1 Patients with this
condition may experience episodic vertigo and disequilibrium in response to intense sound (Tullio phenomenon),
to changes in pressure in the external ear canal (Hennebert’s sign), or to changes in intracranial or middle ear
pressure, along with conductive hearing loss and
autophony.2,3
The abnormal communication between the superior
semicircular canal and the middle fossa exposes the vestibular system to variations in intracranial pressure and
to bone-transmitted sound. This phenomenon results in
a so-called ‘‘third window effect,’’ in which acoustic
energy is lost and the vestibular system is abnormally
stimulated.2,4,5 The incidence of symptomatic SCCD is
unknown. Confirming the diagnosis of suspected superior SCCDS requires a combination of audiometric
From the Division of Otolaryngology–Head and Neck Surgery,
Dalhousie University, Halifax, Nova Scotia, Canada.
Editor’s Note: This Manuscript was accepted for publication
September 1, 2010.
Presented at the 64th Annual Meeting of the Canadian Society of
Otolaryngology–Head and Neck Surgery, Niagara Falls, Ontario,
Canada, May 23–25, 2010.
This work was carried out by all of the authors at Dalhousie
University, Halifax, Nova Scotia, Canada. The authors have no funding,
financial relationships, or conflicts of interest to disclose.
Send correspondence to Hosam A. Amoodi, MD, 10 Northtown
Way, Apt 2401, Toronto, M2N 7L4, ON, Canada. E-mail: hosamamodi@
hotmail.com
DOI: 10.1002/lary.21398
Laryngoscope 121: May 2011
evaluation, vestibular evoked myogenic potentials
(VEMPs), and high-resolution (<1-mm slice thickness)
computed tomography (CT) scanning to visualize the
dehiscence. Audiometric evaluation in patients with
SCCDS usually shows a low-frequency conductive hearing loss with a 5- to 10-db hearing level (HL) air-bone
gap that affects two or more frequencies, and in some
patients the bone conduction thresholds are lower than
0 db HL. Demonstrating the superior semicircular canal
defect by means of high-resolution CT scanning (<1-mm
cuts) is the key to diagnosis of this syndrome. Patients
with SCCDS have larger VEMP amplitudes and reduced
thresholds as compared with non-SCCDS controls,6,7
with both a sensitivity and a specificity of 80%.8
The management of superior SCCDS includes both
conservative and surgical approaches. Ideal patients for
the conservative approach would be asymptomatic
patients or patients with a mild form of the disease who
are not affected greatly by their symptoms. Bilateral
dysfunction is a challenging clinical problem. In these
cases, preservation of vestibular function is as important
as hearing. Resurfacing, plugging, or capping of the
dehisced canal is effective in alleviating the symptoms
and signs associated with SCCDS.1,9 Two main surgical
approaches are currently used to address the superior
canal bony defect: 1) from above via a middle fossa craniotomy and 2) via the transmastoid approach with
direct access to the superior canal. The canal defect is either 1) plugged or occluded or 2) resurfaced. The
transmastoid approaches described usually plug the
canal, and the middle fossa approaches resurface, but
Amoodi et al.: Superior Canal Transmastoid Resurfacing
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plugging can also be performed via the middle fossa
approach. Canal plugging theoretically carries a higher
risk of damage to the vestibular and cochlear structures,
because it is more invasive to the labyrinth. On the
other hand, resurfacing requires a more invasive and
risky approach, via craniotomy and temporal lobe retraction, with the attendant risk of seizure. The
transmastoid approach is more familiar to most otologists and has less of the potential major complications
including cerebrospinal fluid leak, facial nerve injury,
and major intracranial complications.
Plugging of the involved canal entails packing the
canal lumen with fascia and bone dust to eliminate the
flow of endolymph in that canal. Plugging has been performed either through middle fossa3,9–11 or through
transmastoid approaches.12 On the other hand, the
resurfacing technique involves covering the defect with
native tissue (fascia and/or a bone graft) to seal the communication between the labyrinth and brain.
Resurfacing through the middle fossa approach has
reportedly shown variable success.2,4 Very recently,
transmastoid resurfacing similar to our approach has
been described in two patients with good results but
with short follow-up.13 We believe, however, that this
recent report lacks one of the elements that we have
found very useful, namely, direct visualization of the
dehiscence with a mirror technique. Both plugging and
resurfacing techniques have been reported to alleviate
symptoms of superior canal dehiscence, in particular the
sound- and pressure-induced vertigo. Some authors have
suggested that the plugging technique achieves superior
results and symptomatic control as compared with the
resurfacing technique, but it does carry a higher risk of
permanent loss of hearing.14 Canal plugging, through either a middle fossa approach or transmastoid approach,
poses a small risk of global vestibular hypofunction in
addition to a risk of sensorineural hearing loss.15 Brantberg et al. described transmastoid superior canal
occlusion in two patients. Of the two patients, one developed sensorineural hearing loss after the procedure.6
Mikulec et al. described 10 patients who underwent an occlusion procedure of their dehiscence using
bone wax; three had mild high-frequency sensorineural
loss, and one had a temporary hearing loss that recovered with steroids.3 Minor reported a recurrence of
symptoms in four of 11 patients who underwent resurfacing and in one of nine patients treated with canal
plugging2 and hence recommended plugging. Friedland
and Michel reported on two patients with superior
SCCD who experienced a recurrence of their symptoms
several months after resurfacing of their dehiscence
with a calvarial bone graft and fascia.4 Other reports
suggest that middle fossa repair of superior canal
dehiscence, in patients who have undergone revision
surgery and in those who have undergone previous stapes surgery, carries a higher risk of sensorineural
hearing loss, regardless the technique used (resurfacing
or plugging).14
Minor reported five cases of superior SCCD managed with either plugging or resurfacing through the
middle fossa approach. Three patients who underwent
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TABLE I.
Patient Demographics.
Patient No.
Age, yr
Sex
Operated Ear
1
39
Male
Right/left
2
3
38
54
Male
Female
Right
Right
4
51
Female
Left
plugging of the canal had relief of their symptoms. One
patient developed a moderate sensorineural hearing
loss, and another patient developed signs of generalized
vestibular hypofunction with preserved hearing in the
operated ear. Two patients underwent resurfacing of the
canal with fascia and cortical bone, and one developed
vestibular hypofunction after the procedure.9
We describe an approach that combines the advantages of both approaches, that is, fast direct exposure
through the familiar transmastoid approach, but with
accurate localization and direct visualization of the dehiscence, along with the less-invasive resurfacing rather
than canal plugging. We report on four patients (five
ears) with superior SCCDS treated with resurfacing of
the dehiscence through a transmastoid approach; all
patients recovered well, with resolution of their symptoms. All surgeries were completed within 90 minutes,
and patients stayed in hospital just one night, mainly
because of travel distances. If they had lived closer to the
hospital, then they all could have been discharged the
same day.
MATERIALS AND METHODS
This study is a retrospective review of patients who underwent superior SCCD resurfacing surgery with a technique
developed at our institution between November 2005 and May
2008 by the senior author (M.B.). All patients underwent a comprehensive neurotologic evaluation, which included audiograms,
VEMP testing, and high-resolution CT scanning. We describe
four patients who had classic symptoms and findings of SCCDS
(Table I shows patient demographics). VEMP testing showed
hypersensitive responses in all involved ears (except in patient
3, described later). A high-resolution CT scan clearly confirmed
the superior SCCD in all affected ears (bilateral dehiscences in
patients 1 and 2). Patient 3 had concurrent middle ear disease.
Her audiogram revealed bilateral mixed hearing loss with a 40dB air-bone gap, probably mostly due to her chronic suppurative otitis media. She was the only patient with absent
responses on VEMP testing. Patient 4 had undergone previous
surgical repair of the dehiscence through the middle fossa
approach at a different institution. After 6 months of being
symptom free, all her symptoms from before the repair manifested again. All patients underwent surgery to resurface the
canal dehiscence via a transmastoid approach. Patient 1 underwent bilateral superior canal resurfacing in a staged procedure
4 months after the first procedure.
Surgical Technique
Cortical mastoidectomy through a postauricular approach
was commenced; general anesthesia was used. In this procedure, after the horizontal semicircular canal has been
identified, the otic capsule is outlined, and the origin of the
superior semicircular canal from its anterior ampulla usually
Amoodi et al.: Superior Canal Transmastoid Resurfacing
Fig. 1. Buckingham mirror for lifting and visualizing the dehiscence. [Color figure can be viewed in the online issue, which is
available at wileyonlinelibrary.com.]
can be readily seen in these healthy mastoids. The tegmen
dehiscence is usually apparent almost immediately on entering
the mastoid antrum. The superior canal is gently outlined by
drilling away the perilabyrinthine air cells. As attention is
turned toward the tegmen, the dehiscence in the tegmen is usually readily and easily seen without the need for drilling on the
tegmen, although this area may be clarified by drilling away
any overhangs that prevent visualization. We usually try to
avoid bone-dust accumulation in the middle ear by using copious irrigation.
Once the tegmen dehiscence is identified (it might have to
be slightly enlarged to allow access later), a Silastic (Dow Corning, Midland, MI) is placed on the dura, and the dura is lifted
by pressure on the Silastic sheet. This action will lift the dura
off the superior canal easily, and the sheet is then gently moved
over the superior canal to keep the dura raised over this. The
sheet allows for upward retraction of the dura with a sucker or
elevator for the resurfacing and allows for visualization of the
dehiscence.
The next step is a key to effective resurfacing and diagnosis. A Buckingham mirror is pressed against the Silastic
sheeting and used to raise the dura up, and it allows the defect
in the superior canal to be seen easily as a slit. It also allows
the extent of the dehiscence to be seen (Fig. 1).
Fig. 2. (A) The mirror technique for lifting and visualizing the dehiscence. (B) A piece of fascia placed on top of the dehiscence. (C) A piece
of tragal cartilage inserted between the dura and the fascia. (D) Tisseel applied over the repair. [Color figure can be viewed in the online
issue, which is available at wileyonlinelibrary.com.]
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Fig. 3. Patient 1. (A) Preoperative audiograms of the right ear. (B) Postoperative audiograms of the right ear. (C) Preoperative audiograms of
the left ear. (D) Postoperative audiograms of the left ear.
In case 2, we used bone pate harvested previously and
mixed with Tisseel (Baxter Biosciences, Vienna, Austria) to
pack the lumen of the superior canal from above, without further drilling on the canal, with additional cortical bone chips
placed above this. In cases 1 and 3, we used fascia to resurface
the canal and then used tragal cartilage cut to a 0.4-mm thickness to cover this and keep the dura away from the canal
dehiscence (Fig. 2). We have experimented with cortical calvarial bone, but the rigidity of the bone did not allow it to easily
conform to the curved dura in the superior canal region.
Once the defect is visualized, resurfacing can commence
with either fascia, bone chips, or cartilage. We have moved toward a first layer of fascia, covered by tragal cartilage. The
dura traps the fascia and tragal cartilage into place very
securely once it is allowed to come back down.
The dura is allowed to come back down slowly after
removing the Silastic sheet. Finally, another layer of Tisseel is
applied over the repair to hold the fascia and the cartilage in
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1120
place. Layered skin closure is followed by placement of a pressure mastoid dressing. The procedure usually takes between 80
and 90 minutes, including the anesthesia time.
RESULTS
Follow-up times were 20 and 30 months for
patients 1 and 2, respectively, and 4 years for patients
3 and 4. All four patients had almost complete resolution of their superior SCCD symptoms, with all
describing greater than 90% improvement in their
symptoms on the operated side. Postoperatively, they
all had disequilibrium that resolved within a few days
(except patient 2). None of them had evidence of
sound- or pressure-induced nystagmus or autophony
postoperatively.
Amoodi et al.: Superior Canal Transmastoid Resurfacing
Fig. 4. Patient 3. (A) Preoperative audiograms. (B) Postoperative audiograms.
Patient 1 underwent repair of the second side 4
months after the first procedure. Postoperative audiogram showed minimal bilateral air-bone gap in both
ears (Fig. 3). He remained asymptomatic at last followup, 20 months after the second procedure.
Patient 3 underwent ipsilateral ossiculoplasty in
addition to the superior resurfacing procedure. Her postoperative audiogram showed mild worsening of her airbone gap (Fig. 4), most likely from her concomitant middle ear surgery, but she remained asymptomatic for 4
years in regard to the SCCD symptoms. Interestingly,
she presented 4 years later with drainage and otalgia,
and her mastoid was explored. She was found to have
cholesteatoma, which was removed. This is a sequela to
her lifelong chronic suppurative otitis media. At this surgery, we were able to examine the superior canal repair,
which looked intact and had healed well, in keeping
with her lack of SCCD symptoms.
Patient 2 had a more complicated postoperative
course. He had very large dehiscences bilaterally. In this
patient we used bone pate first, before fascia resurfacing; the size of his dehiscence allowed us to pack quite a
lot of bone pate into the canal lumen, which was closer
to the ampulla than the other dehiscences. Postoperatively, he was off balance and ataxic and developed
tinnitus in the operated ear. An urgent audiogram was
obtained that showed mild high-frequency sensorineural
hearing loss (Fig. 5). This hearing loss recovered with
oral steroids except at very high frequency (Fig 5C), but
his tinnitus, although much diminished, persisted. He
also was found to have complete loss of caloric function
on vestibular testing in his right ear. He seemed to
recover from his imbalance initially, but over the next
year he developed persistent imbalance, which seemed
to be related mostly to symptoms from his contralateral
ear, with a large dehiscence there; he said it felt like the
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world was moving with his heartbeat, on mild straining,
and on sudden movements. Components of this imbalance are likely related to his unrepaired dehiscence in
his left ear, because he is quite clear that he has no further autophony, pulsatile tinnitus, body conducted sound
hypersensitivity, or Tullio in his repaired ear. However,
he is understandably not keen to undergo surgery that
may result in bilateral vestibular loss. It should be noted
that this was the only patient who had bone pate used
to resurface his canal, and very likely because of his
large dehiscence, there would have been closer to a plugging of his canal as the pate entered the inner ear.
Patient 4 had transmastoid resurfacing of the dehiscence
after the middle fossa approach failed; we were able to
salvage the repair. Pre- and postoperative audiograms
were within normal limits (Fig. 6). The patient moved
out of town, but she remains in regular email contact
with the surgeon. She has remained asymptomatic for 4
years after surgery. She is illustrative in that we were
clearly able to identify and repair the dehiscence even
after a middle fossa approach had failed.
DISCUSSION
In this study, four patients (five ears) underwent
resurfacing of their superior semicircular dehiscence
through a transmastoid approach. All procedures were
performed by the same surgeon (senior author, M.B.) and
were completed within 90 minutes. It should be noted
that for most otologists, this would be considered a relatively straightforward procedure, as compared with
middle fossa resurfacing or with outlining, blue-lining,
and opening the superior canal to plug it. The patients
had mild unsteadiness after the procedure but were discharged from the hospital within 24 hours. In fact, most
could have been discharged the same day but for the
fact that many had significant travel times to reach
Amoodi et al.: Superior Canal Transmastoid Resurfacing
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Fig. 5. Patient 2. (A) Preoperative audiograms. (B) Postoperative audiograms. (C) Postoperative audiograms after a 1-week course of systemic steroids.
their homes from our institution. All of our patients
experienced almost complete resolution of their preoperative symptoms, and none has experienced a recurrence
of their SCCD symptoms, despite follow-up of up to 4
years in two patients.
No patient experienced a serious deterioration in
bone-conduction thresholds as a result of the surgery, and
all demonstrated improvement in air-conduction thresholds and at least partial closure of the air-bone gap.
Patient 2 is instructive. Although there are many
reasons why he might have developed vestibular loss
and tinnitus, one factor that differentiated him from the
other patients was that substantial amounts of bone
pate were packed into the lumen, and the lumen in this
case was close to the ampulla. Bone pate was used in
this patient because of the (perhaps mistaken) belief
that his large dehiscence and the severity of his symptoms required a hard and definitive repair, and bone
pate was thought to be more likely to be effective than
fascia. We do not currently use bone pate directly in the
dehiscence.
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Otherwise, we feel our approach offers the benefits
of resurfacing (no further drilling and opening of the otic
capsule, no packing into the inner ear) along with the
advantages of the transmastoid approach (no middle
fossa craniotomy, no temporal lobe elevation, no risk of
seizure, rapid surgical time with short hospital stay, positive identification of the defect). In particular, our use
of the Buckingham mirror allows us to positively see the
defect in the canal and to accurately resurface it. We
feel this is a major and key piece of the surgical technique. In middle fossa surgery, there is the risk of
movement of grafts when the temporal lobe is allowed to
retract, and it may be difficult to positively identify the
site of the defect.
The use of the transmastoid dural elevation technique described will also allow plugging of the canal
through the natural dehiscence, without drilling into the
canal for plugging, as described by others. In the one
patient in whom this technique was used, vestibular function was lost; for those who believe in plugging, however,
this approach saves time blue-lining the canal, saves otic
Amoodi et al.: Superior Canal Transmastoid Resurfacing
Fig. 6. Patient 4. (A) Preoperative audiograms. (B) Postoperative audiograms.
acoustic trauma from drilling on the canal, and allows
actual visual confirmation of the bony dehiscence.
The one caveat is that small dehiscences on the
medial side of the superior canal may be difficult to visualize with the mirror. In place of the mirror, an
endoscope may also be used. We have experimented with
this method, but at our institution, the smallest endoscope diameter we had available was too large to fit into
the crevice between the dura and the superior canal.
CONCLUSION
This small initial case series highlights an important clinical entity for which optimal treatment has not
been established. We report an initial result with a new
technique for resurfacing the superior SCCDS through a
transmastoid approach, which is well known by all otologists dealing with mastoid diseases. The transmastoid
approach is relatively safe and is a less-invasive technique than the standard middle fossa approach, which
has many potential complications and requires longer
hospitalization. The procedure offers the possibility of
preserving the physiologic function of the canal, which is
not the case with the occlusion technique. Long-term follow-up will be required to determine whether the
improvement obtained remains effective in the long
term. Further experience with the transmastoid
approach will be needed to determine the pros and cons
of this approach and to compare the result obtained with
this approach with the results of the other surgical technique currently used.
Laryngoscope 121: May 2011
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