CANINE deafness is one of those
subjects that you just know you
should pay more attention to. After
all it is hardly a marginal condition.
More than 80 pedigree breeds
suffer from inherited hearing problems,
creating deafness in one ear or both.
Dalmatians are the worst affected with
nearly 20% unilaterally and around 10%
bilaterally deaf.
Despite that the Kennel Club has
no mandatory programme to record
deafness. Acquired deafness through
old age, infections and a small amount
of adverse drug reactions pushes the
numbers up.
Gert Ter Haar, senior lecturer in
soft tissue surgery at the RVC,
specialises in ear, nose and throat
surgery and takes a keen interest in the
condition, spoke at the London Vet
Show on Dogs going deaf – does it matter
and what can you do to help?
“It might not be as apparent as
some diseases, but I strongly believe
that dogs are really handicapped when they start losing their hearing,” he said.
“It is one of their main senses, I believe
more important to them than eyesight
and as important as their sense of
smell.
“A lot of old dogs actually become
depressive and less responsive because
they have a form of deafness and we
don’t realise it. Clinicians should be
aware that there are several forms of
deafness and, unfortunately, some are
not that easy to cure, but some are.”
Changes in hearing matter
behaviourally, said Mr Ter Haar, as
animals become a danger to themselves
and others if not handled properly.
Deaf pets and traffic, for example,
simply do not mix. Even in the home a
family pet that is startled by unexpected
touch may become aggressive and a
potential hazard to children and adults.
Diagnosis is all important.
Susceptible breeds such as the
Dalmatian, border collie or English
setter (breeds with white colouring
suffer disproportionately) are regularly unilaterally affected.
“Dogs can be
unilaterally deaf and
still be able to hear,”
said veterinary
neurologist Rita
Gonçalves. “That does
not mean you should
breed from them
because litters can
inherit the problem.”
As a family pet, a
unilaterally deaf dog might find it
difficult to localise where sound is
coming from but should still hear
things and respond quite normally.
However, a dog that is deaf in one ear
has a much higher likelihood that its
puppies will be deaf. Breeding from
that dog becomes a lottery and any
responsible pet owner or breeder would
not take the chance.
Diagnosing impaired hearing
“If a dog is profoundly deaf, then
most owners and breeders will figure
that out before it is six weeks old,”
said Judith Skerritt, director at
Chestergates Referral Hospital. “If you
switch the vacuum cleaner on and it
does not wake up, then you know. The
real difficulty is diagnosing impaired
hearing because you can’t necessarily
do that in general practice.”
For that you need the brain stem auditory evoked
response (BAER) test,
or the newly available
otoacoustic emissions
test (OAE) used to
diagnose deafness in
babies. Objective tests
like the BAER measure
electric potential
between the acoustic
nerve and the brain to
see if there is a clear signal.
BAER tests are easily done, said Mr Ter Haar: the trick is
interpretation. No single test can give
all the answers and more sophisticated
diagnostics such as MRI or CT
imaging may be necessary to
determine the type and extent of
deafness, including potential
treatments, bringing in a cost element
for owners.
MRI and CT scans also rule out
more serious conditions such as brain
tumours causing deafness. “We start
with cheap and cheerful tests as a
screen, which we charge around £25
for,” Mrs Skerritt said about
Chestergates’ policy. “Then if there is
anything wrong we would, if the
owner agrees, proceed to more
sophisticated tests like MRI or CT.”
As it is, the BAER test is not
routine at present and prices can vary, though practices can potentially train
nursing staff as certificated BAER
technicians, offering a valuable service
to both breeders and pet owners.
Dog owners may prefer cheaper
methods such as shaking keys in a tin
or calling the dog’s name when it is
not looking but behavioural tests are
poorly diagnostic. “It is a crude
method,” says Mr Ter Haar. For a
more complete work-up MRI and CT
provide information on the middle ear
and acoustic nerve, offering a more
precise range of treatment options.
Treatment for deafness itself runs
the gamut from simple ear cleaning
to the latest hearing implants, though
implants are a bone of contention
among practitioners. He believes the era of cheaper, more functional implants is just around the corner.
“Most vets are not aware that this
area is progressing quite rapidly,” he
says. “Middle ear implants cost
around €8,000. As technology
advances I hope to see cheaper
implants that can be easily managed.”
For others, dogs and hearing aids
are an unnecessary complication.
Deafness is an obstacle that managed
correctly can be overcome by
teaching owners how to use hand
signals and a vibrating collar. “A dog
is just as happy with hand
commands,” said Mrs Skerritt. “You
should have the dog neutered and do
not let it breed; think ahead and in
theory you have a successful pet.”
