How well are neurological problems diagnosed? - Veterinary Practice
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How well are neurological problems diagnosed?

reports on the neurology sessions at last month’s London Vet Show

KEYNOTE speaker at the London
Vet Show last month was Professor
Rick LeCouteur who gave four
presentations on neurology and

He covered:

  1. The role of the
    neuro exam in a high-tech world – is it
    really worth the bother?;
  2. Seizure
    management in dogs and cats – what to
    do when phenobarbitone fails;
  3. Use
    and misuse of glucocorticoids in
    neurology/neurosurgery; and
  4. Neurology the fun way: video case

In his first presentation, he began
by asking, “What is the purpose of a
neurological examination? Surely,” he
said, “if it looks like a duck, sounds like
a duck and walks like a duck, it must be
a duck.”

But this was not necessarily so, he
continued. When
resources were limited,
results of a neurological
examination would
direct clinicians to the
appropriate selection
of diagnostic tests
rather than to a blind
ordering of a battery
of tests and the hope
that an answer would be

He added that the results of a
neurological examination enabled the
determination of the significance of
any abnormal findings detected by
means of ancillary diagnostic testing.

The first step to providing the best
medical care was an accurate diagnosis,
he said, pointing out that in human
medicine in America a correct diagnosis
was missed in 14% of acute hospital
admission cases, and autopsy studies
confirmed diagnostic error rates of
between 10% and 20%; in addition,
previously undiagnosed problems were
found at autopsy in 25% of cases.

Even when the diagnosis was correct, up to 45% of human patients
with acute or chronic medical
conditions did not receive
recommended evidence-based care,
while up to 30% of diagnostic tests
ordered or drugs administered were
probably unnecessary.

He believed that most errors in
clinical reasoning were not due to
incompetence or inadequate knowledge
but to the frailty of human thinking
under conditions of complexity,
uncertainty and pressure of time. The
professor also thought the same would
be true in veterinary neurology – and
veterinary medicine in general –
although studies on this were lacking.

The neurological examination was
an extension of the general physical
examination, he said, and should be
completed only after signalment, a complete and detailed
history and the general
physical examination
had been carried out.

The objects of the
examination were to
detect the presence of
a neurological
abnormality and to
determine its location or locations. The most
important point, he continued, is that results of a
neurological examination reflect only
the location or locations of the lesion
or lesions, and not the cause or causes.

Signs seen at a given location will be
the same regardless of the type of
lesion; for example, a tumour or an
abscess might cause the same signs if
they occurred in the same location but
treatment options could vary widely,
depending on the cause.

It was only after the neurological
examination had been completed and
the location of an abnormality
determined that ancillary diagnostic
procedures such as CSF examination,
radiography, CT or MRI, could be done
to establish an accurate diagnosis to
assist in deciding on the most
appropriate treatment.

His conclusion was that the basic
neurological examination was certainly
worth the bother – before turning to
what the high-tech world offered.

Seizure management

Discussing seizure management in dogs
and cats, Professor LeCouteur said that
treatment with anticonvulsants was
indicated in animals with idiopathic
epilepsy seizures; but seizures resulting
from a structural brain disorder
required additional therapy depending on the cause of the disease.
Anticonvulsants were usually contraindicated in animals with
extracranial causes of seizures where
therapy should be directed towards the
primary cause of the seizures, for
example hypoglycaemia.

The overall goal of anticonvulsant
therapy was to eradicate all seizure
activity, he continued, but this goal was
rarely achieved. Most dogs and cats
would benefit from anticonvulsant
medication by reduction in the
frequency, severity and duration of their
seizures and a realistic goal was to
reduce seizure frequency to a point that
was acceptable to an owner without
intolerable or life-threatening adverse
effects to the animal.

He said that, in general, owners
should be encouraged to begin
anticonvulsant medication in epileptic
dogs and cats that were known to have
had one or more seizures within an
eight-week period. Treatment was not
routinely advised in animals with
seizures that occurred less than once
every eight weeks, as owners of such animals often did not follow
instructions diligently and might treat
their animals intermittently.

He acknowledged, however, that
some owners were so distressed by
seizures occurring in their pets that they
were willing to medicate an animal daily
despite a history of infrequent seizures.

Therapeutic success could be
achieved only when serum
concentrations of a given
anticonvulsant were consistently
maintained within a therapeutic range.
It was essential to use anticonvulsants that were eliminated slowly.
He added that few of the anticonvulsant drugs used for the
treatment of epilepsy in humans were
suitable for use in dogs and cats, largely
because of the differences in
pharmacokinetics of anti-epileptic
drugs in animals and humans.

Prof. LeCouteur listed several
potential disadvantages of using more
than one anticonvulsant drug: increased
cost, the need to monitor and interpret
serum concentrations of multiple
drugs, potential drug interactions and
more complicated dosing schedules.
Indications for “polytherapy” included
failure of what he called “diligent
monotherapy” and the treatment of
cluster seizures.

If the initial drug proved
ineffective, a second should be added; if
the animal responded, the vet should
attempt to withdraw the first drug
gradually and continue with polytherapy
if this was unsuccessful.

Potassium bromide, he said, had no
known hepatic toxicity and all adverse
effects were completely reversible once
the drug was discontinued.

It controlled between 70% and 80%
of the epileptic dogs it was used to
treat and was often effective in dogs
that failed to respond to
phenobarbitone therapy.

“When high dose potassium bromide and low dose phenobarbitone
are used together, approximately 95%
of epileptic dogs can be controlled,” he


Speaking about the general
characteristics of neurological disorders,
in his presentation entitled Neurology the
fun way
, Professor LeCouteur said that
neurological disease could be acute or
chronic, progressive or non-progressive.

“Neurological signs reflect only the
location of the lesion(s), not the cause,”
he said, “and neurological disease can
sometimes cause intermittent signs (as
in the case of epilepsy); some
peripheral nerve or neuromuscular
disease and some myopathies cause
signs that fluctuate in severity from
moment to moment or hour to hour or
that vary in severity with exercise.

“Aside from these exceptions, the
signs of neurological diseases tend to
be continuous and fluctuate very little
in severity.

“The clinical signs of neurological
disease are caused by dysfunction of
the neurons,” he continued. “The
neuronal dysfunction can be caused by
direct effects of the disease on the
neurons or by the effects of disease on
the supporting elements (glia) or blood

“Neurological diseases may result from causes inside the nervous system
or outside the nervous system that
cause diseases in other organ systems:
degenerations, malformations,
inflammation, trauma, metabolic
disturbances, neoplasia and nutritional,
toxic and vascular disorders.”

Earlier in this session, Professor
LeCouteur said that understanding the
organisation and relationship of
structures was essential for a clinician
caring for animals with neurological
diseases because a clinician deals with
the entire animal and with the entire
nervous system.

“This requires a global approach
that is based on an appreciation of
how the functions of the various
parts contribute to the function of
the whole.”

Normal functions must be known
before abnormal functions can be
recognised, he continued, and
abnormal functions must be
recognised because neurological
diseases are manifested clinically
almost entirely by dysfunction.

Stating that it wsas uncommon for
the clinical signs to include readily
detectable anatomical changes, he said
that a clinician must therefore rely on
signs of abnormal function to
identify structures that were


“Think carefully before giving
glucocorticoid medication to
neurological patients: more is
definitely not always better and none
at all may be the best option,”
Professor LeCouteur stated in his presentation on the use and misuse
of glucocorticoids in

The decision to use
glucocorticoid medication in
neurological patients, he said, should
be based on a good understanding of
the underlying pathology, positive
pharmacological effects, adverse
effects of the drug, and the
availability of evidence to suggest
that the benefits of treatment
outweigh the adverse effects.
Glucocorticoids can be beneficial in
many circumstances; however, the
temptation to treat severe
neurological disease with
glucocorticoid medication, even in
the absence of specific indications to
do so, is almost universal.

There are, he added, very few
circumstances in veterinary
neurological medicine where absolute
statements can be made relating to
the use of glucocorticoids; however,
judicious use is encouraged.

Summarising, he said there were
no specific indications for the use of
glucocorticoids in severe head trauma
in humans and probably in small
animals; there were no proven clinical
benefits of any glucocorticoid
medication in acute spinal trauma in
small animals and its benefits in
humans were minimal at best; high
doses of glucocorticoids have been
associated with fatal GI adverse
effects in dogs with spinal cord
trauma; and high doses of
glucocorticoids have been associated
with increased incidence of
secondary infections and pneumonia.

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