Late in 2011 -
University of Missouri, College of Veterinary Medicine
Spinocerebellar Ataxia with Myokymia & Seizures in
the mid 1990s, we have been studying a constellation of
movement disorders in Jack/Parson/Russell Terriers. The
situation is complicated because there appear to be
several different forms of the disease in the breeds.
What is spinocerebellar ataxia?
term cerebellum in Latin means “the little brain”. The
cerebellum is the part of the brain responsible for
coordinating movements. Ataxia comes from a Greek term
meaning “without order”. When the cerebellum cannot
coordinate movement, the dog can move, but the movement
is poorly coordinated. They are not weak, in fact,
often the movements a dog with ataxia makes are too
strong. They have a goose-stepping gait and when
excited or running, their legs may appear to be going
every which-way. Sometimes they have problems with their
balance and will fall frequently. In order for the
cerebellum to control movement, it needs to get feedback
about what the muscles are doing. This feedback comes
to the brain through the spinal cord. When there are
changes in the spinal cord in a dog with cerebellar
ataxia, the disease is often call spino-cerebellar
What is myokymia?
Myokymia is a problem with the muscles (myo- in medical
terms). Dogs with this symptom have uncontrollable
twitching of the muscles. The twitching tends to run
through a muscle in waves, hence the –kymia portion of
the word which comes from the Greek word for waves.
Attacks of myokymia can be precipitated by exercise or
excitement. The severity can vary from mild muscle
twitching to incapacitating attacks. When severe, the
dog can become rigid and develop a high body
temperature. Such severe attacks can be confused with
seizures, but the dog remains aware of his surroundings
during an attack of myokymia. Some dogs with
spinocerebellar ataxia also have true seizures.
What are the different forms of ataxia in
appear to be at least two different forms of cerebellar
ataxia in these lines, a neonatal cerebellar ataxia and
a later onset of ataxia (spinocerebellar ataxia or SCA)
with or without myokymia or seizures. In the neonatal
form the dogs have ataxia from the time they begin to
walk. The age of onset is similar to the disease in
Coton de Tulears, but
they are caused by different genes.
spinocerebellar ataxia, the dogs develop normally for
the first few months of life. Then beginning at 2-6
months of age they begin to develop ataxia. Thus
spinocerebellar ataxia is also called "late onset"
cerebellar ataxia though the onset still occurs in
fairly young dogs. There could still be other forms of
ataxia as well.
What else can look like spinocerebellar ataxia?
addition to the neonatal ataxia, other diseases can
cause signs of ataxia. Any disease that affects the
cerebellum will produce ataxia. Canine distemper
infections will frequently affect the cerebellum as can
other infections. Though strokes are uncommon in dogs,
they can also affect the cerebellum. In older dogs, a
brain tumor in the cerebellum would produce similar
signs. If necessary, your veterinarian can refer you to
a board certified neurologist who can aid in diagnosing
the cause of ataxia. A directory to a neurologist near
you can be found at
www.acvim.org under "Search for a Specialist".
this a hereditary disease?
Further research is needed, but the pedigrees analyzed
thus far suggest that SCA is inherited as a recessive
trait. In a recessive disease, both parents of an
affected pup appear normal. All animals have two copies
of each gene, one that is inherited from the mother and
one inherited from the father. A dog that has one normal
gene and one gene that causes the disease is a carrier
of the trait. They show no symptoms because the one good
gene is enough for their nerves and muscles to develop
normally, but they will pass that bad gene on to about
half of their offspring. If a carrier dog is bred to
another carrier, then some of the pups (25% on average)
will get a bad gene from each parent. Without one good
gene to carry the day, the nerves cannot function
normally and the unlucky pup has SCA.
Is there a DNA test?
2012, researchers at the University of Missouri found
the mutation responsible for spinocerebellar ataxia in
Jack/Parson/Russell Terriers. Researchers at the Animal
Health Trust in England may have also found this same
mutation. A DNA test is now available and can be ordered
through the Orthopedic Foundation for Animals website (www.offa.org).
Owners of dogs previously sampled for this or other
research projects, or with DNA banked at Missouri for
any reason can request a discounted test by using the
request form found at this link – (click
here), or contact Liz Hansen at HansenL@missouri.edu
for a print version. With the DNA test carriers of the
mutant gene can still be used for breeding as long as
they are bred to a dog that is clear of the mutation.
That way no affected dogs will be born, but the
desirable genetic diversity that these dogs provide the
breed will be maintained. When selecting future breeding
stock, the gene status can be considered in deciding
which pups to keep but does not have to be the sole
factor. As discussed above there are other both
hereditary and acquired causes of cerebellar ataxia.
Thus not every dog with ataxia will have the mutation.
September 1, 2009 University of
Missouri, College of Veterinary Medicine
PLL - Primary Lens Luxation of the eye
A mutation responsible for the development
of lens luxation in many breeds of dogs has been identified
by a team of researchers led by Gary Johnson DVM PhD at the
University of Missouri College of Veterinary Medicine. A DNA
test for this mutation is expected to be available by late
September 2009 through a partnership with OFA (Orthopedic
Foundation for Animals).
Lens Luxation is an eye problem well known
in many Terrier breeds, Chinese Cresteds ,
Australian Cattle Dogs, Tibetan Terriers, and other breeds. The
lens is held in place in the eye by fibers known as zonules. If
these zonules break or disintegrate, the lens can fall out of
place, or luxate. When this happens it often requires immediate
veterinary attention to remove the displaced lens. Lens luxation
can cause secondary glaucoma, which also leads to pain, loss of
vision, and sometimes loss of the entire eye.
Research at the University of
Missouri has led to identification of a DNA mutation that
predicts which dogs are at risk for developing lens luxation as
they age. A simple DNA test will reveal if a dog
is NORMAL (has 2 normal copies of the gene), a CARRIER (has one
normal copy and one mutated copy of the gene) who will not
develop lens luxation but could pass the mutation on to
offspring, or AFFECTED/AT RISK (has 2 mutated copies of the
gene). Wise use of this test gives breeders a tool to avoid
producing individuals at risk of developing lens luxation, while
still retaining many other desirable traits in their dogs.
Breeders and individual owners
will be able to test their dogs using the
testing kit that can be ordered online through the
OFA website (www.OFFA.org). DNA
is collected using a cheek swab, and the barcoded sample will be
tested by the Animal Molecular Genetics Lab at the University of
Missouri, with results reported directly to the owner by OFA.
Owners who had submitted samples
for research prior to Sept 1, 2009 may request test results
for their dogs using this
Test Request Form for existing samples
click here for this form.
Owners of dogs that have been
diagnosed as affected with lens luxation by an
ACVO or ECVO boarded ophthalmologist are eligible to receive a
free DNA test if they send a blood sample, pedigree copy, and a
copy of the ophthalmologist's report –
click here for the instructions and form to submit samples
from affected dogs. Samples from affected dogs may be sent now
Testing for all other dogs
is available through OFA.
Our thanks to the
clubs and many individual owners who have supported this
research and participated in the project by supplying samples
and information on their dogs, as well as monetary support. We
also greatly appreciate support from the Jack Russell
Terrier Club of America, and past support from the
Canine Health Foundation for the early stages
of this research. Please watch this space for updates in the
next few weeks. If you have questions, you may contact Project
Coordinator Liz Hansen at