Page 888 - Problem-Based Feline Medicine

880 PART 10 CAT WITH SIGNS OF NEUROLOGICAL DISEASE

Bruising and functional damage (neuropraxia) as well lopathies, platelet abnormalities and vasculitis should
as anatomical disruption (axonotmesis and neu- be performed.
rotmesis) may result.
Brachial plexus avulsion resulting in miosis is most Treatment
often associated with tearing or avulsion of sympathetic
Standard critical care protocols for treatment of trau-
nerves that arise in the T1–T3 spinal cord segments and
matized animals should be implemented as needed.
exit the vertebral canal.
Primary treatment for nervous injury is not possible.
Central nervous system trauma may disrupt the sym-
pathetic pathways in either the brain or cervical spinal If it could be determined that a nerve is compressed or
cord. lacerated, surgical decompression or reconstruction is
theoretically possible but is rarely performed.
Misplaced hypodermic needles in the jugular furrow
during blood collection can rarely damage the sympa-
thetic nerves to the eye. Prognosis

Milder injuries usually result in a favorable prognosis.
Clinical signs Conversely, severe injuries may result in permanent
dysfunction.
Miosis may occur with trauma due to involvement of
the sympathetic system.
Prevention
Superficial lacerations, bleeding or bruising may indi-
cate a traumatic etiology. Keep animals in controlled environments that limit
access to automobiles and other traumatic potentials.
Trauma to the central nervous system often results in
paresis, abnormal consciousness or cranial nerve Use caution during jugular venepuncture.
abnormalities as well as miosis.
Trauma to the nerves of the brachial plexus may
cause lower motor neuron signs (paresis or paralysis, TOXINS (ORGANOPHOSPHATE)**
decreased to absent spinal reflexes, decreased to absent
muscle tone) in the ipsilateral thoracic limb as well as Classical signs
Horner’s syndrome in the ipsilateral eye.
● Acute onset of miosis, salivation, urination,
defecation and muscle weakness.
Diagnosis ● Rarely, lethargy, anorexia and persistent
weakness without associated autonomic
The diagnosis is supported by either a history of known
signs.
trauma or superficial evidence of lacerations or bruising.
Damage to the nerves of the brachial plexus may result
Pathogenesis
in signs of denervation on electromyographic studies.
Abnormal potentials usually begin around 5 days after Organophosphate intoxication potentiates the effect
the trauma. of acetylcholine at the neuromuscular junction and
other synapses, by binding with and inactivating acetyl-
Advanced imaging studies (CT or MR) provide the
cholinesterase. This leads to increased acetylcholine
best views of the central nervous system.
concentrations at the neuromuscular junction, increased
receptor stimulation and fatigue.
Differential diagnosis
A delayed neurotoxicity in cats is reported associated
If active bleeding or bruising is present, an evaluation with the use of chlorpyrifos spray for household appli-
for underlying clotting disorders such as coagu- cation against fleas. There is individual variation in