Page 969 - Problem-Based Feline Medicine

44 – THE CAT WITH GENERALIZED WEAKNESS 961

Differential diagnosis ● Bradycardia (90–120 beats/minute).
● Dysuria and/or distended bladder or incontinence
Hypokalemic myopathy is differentiated on the basis of
with an easily expressive bladder.
hypokalemia.
● Generalized weakness.
Myasthenia gravis may occur concurrently with myositis.
Chronic organophosphate toxicity is differentiated Diagnosis
on the basis of a history of exposure and sometimes
reduced cholinesterase activity. Diagnosis is based primarily on clinical signs and evi-
dence of autonomic dysfunction. The indirect-acting
Treatment parasympathomimetic, physostigmine (0.02 mg/kg IV)
produces no ocular response, but direct-acting pilocar-
Corticosteroid treatment (1–2 mg/kg PO q 12 hours) pine (topically) results in immediate miosis, demon-
may improve clinical signs. strating post-glanglionic denervation hypersensitivity.
Normal cats do not demonstrate these responses.
DYSAUTONOMIA*

Classical signs Differential diagnosis
● Younger cats (< 3 years). Differential diagnoses are many, depending on the pre-
● Acute onset of depression and anorexia. dominant signs. Cats may present with a history of con-
● Dilated pupils, xerostomia, stipation or inability to urinate or dilated pupils,
keratoconjunctivitis sicca, prolapsed third suggesting disease of the colon, lower urinary tract or
eyelids. eyes. Typical cases which exhibit most signs are classi-
● Bradycardia. cal for dysautonomia.
● Megacolon, constipation, loss of anal
reflex. Treatment
● Incontinence, dysuria or distended bladder.
● Weakness. No specific treatment is available, but supportive care is
important, such as syringe or tube feeding.
See main reference page 792 for details (The
Parasympathomimetic agents may improve some clini-
Constipated or Straining Cat).
cal signs.
● Pilocarpine ophthalmic drops (1%/1 drop q 6 h)
Clinical signs
may result in pupillary contraction and increase
Disease is confined to Europe or occurs in imported salivation.
cats. The prevalence has decreased markedly and it is ● Bethanechol (1.25–5 mg PO q 8–12 h) may bene-
now uncommon. fit constipation and urinary retention.
● Metoclopromide (0.2–0.5 mg/kg PO SC q 8 h) may
Younger cats (< 3 years) are more often affected.
improve gastric motility.
Clinical signs are often acute in onset over 48 hours
Up to 70% mortality rate has been reported.
with all cats showing depression and anorexia.
Other signs reflect autonomic system dysfunction and
include: POLYMYOPATHIES
● Ocular signs such as fixed, dilated pupils without
blindness, prolapsed third eyelids and dry eyes Classical signs
(keratoconjunctivitis sicca develops). ● Ventral flexion of the neck.
● Gastrointestinal signs include regurgitation,
● Muscle weakness.
megaesophagus, constipation and megacolon, loss ● +/- Apparent muscle pain and a stiff gait.
of the anal reflexes, dry mouth (xerostomia).