Download The pros and cons of canal wall up versus canal wall down

Review Articles 
The pros and cons of
canal wall up versus
canal wall down
mastoidectomy for
cholesteatoma
Abstract
Rebecca L Heywood
*
DOHNS, FRCS (ORL-HNS)
There has been fierce debate regarding the optimal surgical technique for the management of
cholesteatoma for over 50 years. Choice of technique depends on factors relating to the surgeon, the
patient and the disease process. Much literature has been devoted to the benefits and pitfalls of canal
wall up and canal wall down techniques and their respective effects on measures such as number of
operations required for disease eradication, adequate surgical access, complications, residual/recurrent
cholesteatoma, hearing outcomes and long-term follow up. This article aims to review the pros and cons
of canal wall up versus canal wall down surgery for cholesteatoma.
Keywords
Mastoidectomy, canal wall up, canal wall down, cholesteatoma, hearing.
Introduction
Antony A Narula*
MA, FRCS, FRCS(Ed)
Visiting Professor,
Middlesex University
*
epartment of
D
Otolaryngology
St Mary’s Hospital
Imperial College
Healthcare NHS Trust
London
Correspondence:
Miss Rebecca L Heywood
Department of
Otolaryngology
St Mary’s Hospital
Imperial College Healthcare
NHS Trust
Praed Street
London W2 1NY
Email: rebecca_heywood@
yahoo.com
140
It is widely accepted that cholesteatoma almost
invariably requires surgical management.
There has been ongoing debate regarding
the optimal technique since intact canal wall
or canal wall up (CWU) mastoidectomy
was developed in the decade following the
widespread introduction of the operating
microscope in 1953. At the time of the
national comparative audit of mastoid surgery
overseen by the Royal College of Surgeons
of England in 1991, 80% of procedures
performed by participating surgeons in
England and Wales for cholesteatoma were
canal wall down (CWD) and 9% were CWU.1
Choice of technique depends on factors
relating to the surgeon, the patient and the
disease process. A plethora of literature cites
the benefits and pitfalls of CWU, CWD and
CWD with mastoid obliteration/canal wall
reconstruction techniques. This article aims
to review the arguments for and against
CWU versus CWD surgery for cholesteatoma
by addressing a number of factors which are
affected by the technique performed.
Repeat operations
CWU surgery can provide very limited
exposure (see below), particularly in cases
with poorly developed zygomatic root cells
and a low tegmen.2 A second look procedure
is generally advocated 9 to 12 months after
the primary surgery to remove any residual or
recurrent cholesteatoma, which may not be
seen behind the anatomically normal canal wall,
or to confirm its absence. Reconstruction of
the hearing mechanism may also be performed
at the second look procedure. Conversely
the aim of the CWD technique is to perform
one-stage surgery. Recurrent disease can
be seen more easily in an outpatient setting
owing to the communication of the mastoid
cavity with the external auditory canal. Hence
revision surgery can be reserved for cases of
established recurrence and the total number
of procedures required is lower. CWD surgery
should therefore be considered in frail patients
or those with significant comorbidity who are
not thought to be fit enough for more than one
operative procedure. Similarly it is beneficial in
patients who are unlikely to attend for follow up
or in areas where healthcare provision is poor.
Copyright © 2013 Rila Publications Ltd. The Otorhinolaryngologist 2013; 6(3): 140–143
The pros and cons of canal wall up versus canal wall down
mastoidectomy for cholesteatoma
Nevertheless revision surgery is not uncommon after
CWD procedures. Osborn et al published a retrospective
review of 420 children who underwent 700 procedures for
cholesteatoma.3 Revision surgery was required in 51% of
CWU and 21% of CWD procedures. Despite the higher rate
of revision surgery in CWU cases they believe that CWU
surgery is preferable due to better audiometric outcomes
and easier post-op care. Other proponents of CWU surgery
in children argue that serial general anaesthetics are often
required to remove dressings and perform aural toilet during
the early postoperative period following CWD surgery such
that the total number of procedures performed is no less
for the CWD technique. CWD revision rates should also
be interpreted in light of when they were published – in
the past in the UK many patients had chronic discharge
post CWD surgery without revision. This has changed
over the past 20 years and as a result revision rates for the
CWD technique may be higher than earlier literature would
lead one to believe. A new approach in the assessment of
postoperative cholesteatoma is the use of non-echo planar
diffusion weighted magnetic resonance imaging to detect
recurrent disease. This is useful as an adjunct to second look
surgery but as yet is not reliable enough to replace it, though
it may play an increasing role in reducing second look rates
in the future.4
Access
Cholesteatoma may be removed piecemeal and left behind in
areas of the temporal bone which are poorly visualised during
surgery. Hulka and McElveen demonstrated in a prospective
randomised blinded temporal bone study that the CWD
approach is significantly superior to CWU in visualising
middle ear subsites, specifically the sinus tympani, posterior
crus of stapes and lateral epitympanum (the Eustachian tube
opening could be observed equally well in both approaches).5
Exposure of such subsites is particularly difficult in CWU
procedures in the presence of a low-lying tegmen, contracted
sclerotic mastoid and anterior sigmoid sinus.6 These anatomic
factors may be assessed preoperatively on a CT scan to aid
choice of approach. Alternatively a CWU procedure can
be performed and the canal wall removed intraoperatively
if the exposure is not good enough to adequately remove
the cholesteatoma.7 Surgical techniques have been developed
whereby the canal wall is temporarily removed to provide
the exposure achieved with CWD surgery followed by canal
wall reconstruction and/or partial mastoid obliteration
with a variety of materials to attain the benefits of CWU
surgery.2,7 This enables single stage surgery in up to 90%
of cases.2 The small cavity mastoidectomy, which comprises
a ‘front to back’ approach (attico-antrostomy) in order
to limit the size of the cavity to the extent of the disease,
combines the open cavity technique with a relatively trouble
free mastoid cavity although it is technically demanding.8
More recently the use of middle ear endoscopy has improved
visualisation in CWU techniques leading to a reduction in,
but not eradication of, residual cholesteatoma.9 The KTP
(potassium titanyl phosphate) laser has also been shown to
be a useful adjunct in cholesteatoma eradication. The ability
to deliver energy through a flexible fibre means that it can
be used around corners in areas which are otherwise difficult
to clear of disease. Hamilton showed that the rate of residual
cholesteatoma can be significantly reduced in CWU surgery
by using the KTP laser to remove disease adherent to and
adjacent to ossicles and to heat the surface of bone and soft
tissue (apart from the facial nerve) from which cholesteatoma
has been elevated, thus denaturing any residual microscopic
but viable epithelium.10
Complications of surgery
The rate of major complications reported in the national
comparative audit of mastoid surgery was 7% for CWD, 4% for
CWU and 6% for CWD with obliteration procedures.1 Dead
ear and facial nerve palsy only occurred in CWD surgery. This
may relate to the disease extent, experience of the surgeon and
other factors and cannot simply be attributed to the technique
itself.
Residual/recurrent disease
Residual cholesteatoma is that left behind at the first
procedure, either intentionally, for example over a lateral
semicircular canal fistula, or (usually) inadvertently. It occurs
following CWU or CWD down procedures, most commonly
in the areas which are difficult to visualise as detailed above
(epitympanum and posterior mesotympanum) and therefore
tends to be more prevalent in CWU surgery as a result of
poorer intraoperative exposure.5 Recurrent cholesteatoma is
primarily a problem of the CWU procedure and arises from
posterosuperior retraction pockets.7 The figures cited in the
literature for residual and recurrent disease are extremely
variable, which may be for several reasons. First, it is difficult
to distinguish between the two unless the same surgeon
has performed both the primary and second look/revision
procedure and for this reason residual and recurrent disease
will be discussed further as a single entity. Second, the
residual/recurrent rates published for CWU versus CWD
surgery in many series may not really be comparable as
there may be a tendency to perform CWU surgery for small
cholesteatomas and CWD surgery for much more extensive
disease. Third, the technique used most often by a particular
surgeon is usually that at which he/she is most accomplished.
The single most important factor responsible for failure of
CWD surgery is poor execution of the procedure resulting
in a residual infected mastoid cells, high facial ridge, stenotic
canal/meatus, bony overhangs preventing the cavity from
self-cleaning and therefore promoting the disease process
and failure to isolate the mastoid cavity from the Eustachian
tube orifice and middle ear.11
CWD procedures tend to have lower residual/recurrent
rates of cholesteatoma. As an example of results from a large
otology practice, Karmarkar et al published a retrospective
analysis of 433 primary cholesteatoma cases over a 7 year
period.12 Recurrent/residual disease was present in 12.4% of
CWD cases and 42% of CWU cases. The figures are somewhat
different for cases of extensive cholesteatoma only; a series of
87 ears demonstrated recurrence in 70% of cases 10 to 13 years
after a primary CWU procedure compared to 15% of cases
following CWD surgery.13 The procedure must therefore be
tailored to the disease severity for optimum results.
Hearing
As for residual and recurrent disease rates, there is wide
variation in published hearing outcomes with CWU and
CWD surgery. Hearing thresholds were improved following
Copyright © 2013 Rila Publications Ltd. The Otorhinolaryngologist 2013; 6(3):140–143
141
The pros and cons of canal wall up versus canal wall down
mastoidectomy for cholesteatoma
30% of CWU procedures and 12% of CWD procedures in the
national comparative audit of mastoid surgery – a statistically
significant difference.1 Thresholds were worse after 13% of
CWD and 8% of CWU procedures (not significant). Once
again however, hearing outcomes were unknown in 40% of
cases, so these results do not necessarily give us a clear picture.
Hearing is generally thought to be worse following CWD
than CWU surgery due to: 1. Changes in the resonance of
the middle and external ear due to the mastoid cavity and
2. A shallower middle ear cleft and therefore reduced middle
ear volume. Whittemore et al performed a cadaveric temporal
bone study on the acoustic effects of changes in the volume
of the middle ear air space resulting from CWU and CWD
procedures and found that as long as the middle ear space is
aerated and has a volume of more than 0.7ml there should be
less than 10dB difference between CWU and CWD hearing
outcomes.14
Many other factors apart from the surgical approach affect
hearing results including granulations, infection, status of the
tympanic membrane, method of hearing reconstruction and
Eustachian tube function, which are evident in some of the
following publications.
Tos and Lau achieved significantly better postoperative
hearing results with CWU than CWD surgery but
the preoperative thresholds were also significantly better in the
CWU group, demonstrating that disease severity and other
confounding factors also affect hearing outcomes independent
of the surgical procedure.15
Kim et al found no significant difference in post-operative
air-bone gap (ABG) between CWU and CWD (10.9 vs
13.5dB) or in the proportion of patients with an ABG
<20dB (58.6% vs 68.4%) 3 months after ossiculoplasty.16
This study is notable for the fact that the authors have tried
to exclude confounding factors by comparing CWU and
CWD outcomes in patients with an intact tympanic cavity
and stapes who had a staged ossiculoplasty at least 6 months
after mastoidectomy. Nevertheless their follow up period is
short.
Toner and Smyth published their comparison of patients
who had CWU, CWD with reconstruction and CWD surgery
with follow up of between 8 and 12 years.17 They found that
the hearing benefit at one year (pure tone average (PTA) air
conduction (AC) threshold) was greater in the CWU group,
but that this benefit was lost over a longer period of follow up
of between 7 and 11 years such that the average long-term AC
gain was the same in all 3 groups.
Studies in children show great variability. Murphy &
Wallis had similar hearing outcomes following CWU and
CWD surgery in children.18 Osborn et al found hearing to be
significantly better following CWU surgery (mean PTA 30dB)
than CWD surgery (mean PTA 45dB) in their retrospective
review of 420 children, independent of preoperative hearing
levels and of the condition of the stapes.3
It is also worth considering the Glasgow benefit plot and
Belfast rule of thumb when comparing hearing outcomes. To
achieve patient satisfaction in operations to improve hearing
the ABG must be closed to less than 30dB and/or to within
15dB of the other ear; thus although a specific technique
may improve hearing, if it does not meet these criteria then
it may be clinically irrelevant to compare small differences in
threshold achieved for each surgical technique.
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Wet ears
A ‘wet’ ear can have significant impact on the quality of
life of patients following surgery for cholesteatoma. It may
result in changes in lifestyle, such as adherence to strict water
precautions and dependence on microsuction. Moreover, a
wet mastoid cavity used to be considered ‘safe’ but this has
been shown not to be the case; continued activity in the
absence of cholesteatoma in a modified radical mastoid cavity
can result in an intracranial abscess.19 The national comparative
audit of mastoid surgery collected data on the status of
ears between 3 and 15 months postoperatively, though it is
noteworthy that it was unreported in 22% of cases. There was
no significant difference between the number of dry ears with
open and closed cavities but a statistically significant difference
of 17% wet ears following CWD surgery and 10% following
CWU procedures.1 In contrast Toner found no significant
difference in the number of moist ears and the degree of
wax accumulation following CWU, CWD and CWD with
obliteration procedures.17 At the last consultation, 1 to 24
years after surgery, 95% of cavities were found to be dry and
self cleaning after CWD surgery in a series by Kos et al.20
The status of the cavity is not only affected by the procedure
performed, but also by the skill of the surgeon, cavity size,
shape and extent of epithelialisation.
Hearing aids
Fitting a hearing aid is generally associated with fewer
complications after CWU surgery than CWD surgery due
to an anatomically normal external auditory meatus.2 CWD
surgery requires a meatoplasty for adequate aeration of the
cavity. A widened distorted meatus makes initial fitting of a
mould more difficult and the cavity can subsequently become
wet when the meatus is obstructed by a hearing aid mould.
Deformity
The meatoplasty performed can in some cases be sufficiently
large as to visibly distort the meatus and area of the conchal
bowl. The cosmetic aspects of the surgery should be
considered when performing a meatoplasty.
Follow up
Immediate and long-term postoperative follow up is generally
considered to be more intensive following CWD procedures
since serial debridement is usually required, whereas the ear
maintains its natural anatomy and heals more quickly after
CWU surgery. Toner et al challenge this in their data on
patients who had surgery for cholesteatoma with follow up of
between 8 and 12 years.17 They found no significant difference
in frequency of required follow up between CWU, CWD with
obliteration and CWD procedures.
Khalil et al studied follow up in a group of patients after
CWD surgery.21 They attended for follow up for removal
of the clinical features of chronic cavity inflammation, to
maintain the lining of the cavity in a healthy state and to assess
for the remote chance of complications developing. A median
of 11 and mean of 13.3 visits to outpatients was made over
the study period of 158 months (a mean of 1 visit per year).
The greatest number of visits occurred in the 24 months
immediately after surgery. Only a quarter to a third of patients
were ever discharged. There were no figures for CWU surgery
Copyright © 2013 Rila Publications Ltd. The Otorhinolaryngologist 2013; 6(3): 140–143
The pros and cons of canal wall up versus canal wall down
mastoidectomy for cholesteatoma
for comparison. Nevertheless this study demonstrates the
significant burden on resources required after CWD surgery.
Conclusion
The debate surrounding the pros and cons of CWU versus
CWD surgery for cholesteatoma continues after more than
half a century. A one stage CWD non-obliterative procedure
is still advocated by some who claim that this provides
maximum long term patient benefit with no difference in
hearing outcomes, wet ears, extent of wax accumulation or
frequency of follow up.13, 17, 20 Some believe that CWU surgery
is preferable due to better audiometric outcomes and easier
post-op care.3, 7
They are probably all correct in the right patient, for the
right disease and by the right surgeon. No single method is
suitable for every patient and cholesteatoma surgery should be
individualised according to the patient’s needs and the extent of
the disease.15 Successful surgery also depends to a certain extent
on the availability of modern equipment including operative
endoscopes and low energy laser. Finally, the surgeon’s
expertise is of the utmost importance; as shown above, a CWD
procedure with tympanoplasty may yield a dry ear with hearing
results comparable to those following a CWU procedure in the
right hands.12, 22 As Sheehy said, ‘The key to success in otologic
surgery is not whose technique one uses, but how one uses it
and one’s own ability and judgement’.
Conflict of Interest
All authors have no conflict of interest to declare. No
extraneous funding was obtained.
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