Page 900 - Problem-Based Feline Medicine

892 PART 10 CAT WITH SIGNS OF NEUROLOGICAL DISEASE

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IDIOPATHIC
● Adult-onset motor neuron disease (p 903)
Chronic progressive generalized weakness with muscle tremors and fasciculations.
TOXIC
● Subacute organophosphate toxicity (p 901)
Generalized weakness, stiff stilted gait, muscle fasciculations or tremors. Muscarinic signs
(miosis and salivation) may be absent.

acetylcholine receptor antibodies, determination of
INTRODUCTION
serum cholinesterase levels, serology for toxoplasmo-
sis, FIV and FeLV, muscle and/or nerve biopsies, or
MECHANISM? a combination of these tests may be required to confirm
a definitive diagnosis.
Neck ventroflexion is typically seen as part of more
generalized muscle weakness. Since cats lack a nuchal
WHAT?
ligament, muscle weakness in this species is often seen
first as ventroflexion of the neck. The most common cause of neck ventroflexion is
hypokalemic myopathy resulting from chronic renal
Affected cats often have a stilted gait and limb weak-
failure.
ness, which may worsen on exercise.
● Other causes of hypokalemic myopathy are seen
They may also show muscle pain, dyspnea, dysphagia, less frequently. They include a hereditary defect in
or megaesophagus. Burmese kittens, administration of inappropriate
IV fluids or excessive furosemide, feeding inap-
Cats with hypokalemic myopathy, polymyositis or
propriate diets and, occasionally, hyperthy-
adult-onset motor neuron disease may show evidence
roidism or hyperaldosteronism.
of muscle pain.
Other causes of neck ventroflexion include primary
myopathies (immune-mediated or toxoplasmosis
WHERE? polymyositis, Devon Rex myopathy), neuromuscular
junction diseases (myasthenia gravis, organophos-
Neck ventroflexion can result from disease affecting
phate toxicity, spider bite), polyneuropathies (adult-
the muscles, the neuromuscular junction or the
onset motor neuron disease) and, very rarely,
nervous system.
hypernatremia.
Physical examination should look for evidence of car-
Although thiamine deficiency can cause neck ven-
diovascular disease or systemic illness. In many neuro-
troflexion, it usually causes an active rather than pas-
muscular diseases generalized muscle weakness may
sive ventroflexion, together with excessive muscle
be the only abnormality.
tone, torticollis and seizure-like episodes of paddling or
A complete blood count may rule out anemia or sys- limb spasticity and opisthotonos.
temic infections. Serum biochemistry may indicate
This chapter deals with disorders that are likely to
hypokalemia, hypernatremia, raised creatinine kinase
present with neck ventroflexion. While this is
level, renal insufficiency or hyperthyroidism.
mostly seen as part of generalized muscle weak-
Electromyographic studies, an intravenous edropho- ness, not all cases of generalized muscle weakness
nium test (Tensilon test), assessment of serum anti- present with neck ventroflexion. Disorders that pri-