Page 971 - Problem-Based Feline Medicine

44 – THE CAT WITH GENERALIZED WEAKNESS 963

If clinical signs are present, rapid institution of treat- Pathogenesis
ment is indicated with 0.5–1.5 ml/kg IV of 10%
The cause of many degenerative neuropathies is not
calcium gluconate. Infuse calcium slowly over
known.
10 minutes while monitoring heart rate. Stop infu-
sion if bradycardia occurs.
Short-term maintenance involves either SC calcium Clinical signs
(1–2 ml of 10% calcium gluconate diluted 1:1 in 0.9%
These diseases are often breed-specific with clinical
saline q 8 hours) or IV calcium (10–20 ml of 10% cal-
signs beginning in cats less than 1 year of age.
cium gluconate in 500 ml of 0.9% saline) with rate
adjusted to maintain normocalcemia. Monitor calcium Weakness with decreased to absent spinal reflexes
2–3 times daily initially. are typical signs.
Longer-term maintenance includes oral calcium A degenerative polyneuropathy occurs in young
(25 mg/kg q 8–12 hours) and vitamin D. The active Birman cats.
form of endogenous vitamin D (called calcitriol or
3
1,25 dihydroxycholecalciferol) is used at 2.5–10 ng/kg Clinical signs begin at 8–10 weeks of age.
● The gait is characterized by a “dropped-hock”
q 24 hours or synthetic vitamin D (dihydrotachysterol)
3
at 0.02–0.03 mg/kg q 24 hours for 3 days, then appearance and hypermetria and ataxia.
0.01–0.02 mg/kg q 6–24 hours. Cats with Neimann–Pick type-A storage disease
may have alterations in peripheral nerves. These
Calcium should be monitored carefully, as hyper-
diseases may have weakness as part of the clinical
calemia is nephrotoxic.
syndrome.
● Adjustments to doses should be made every 1–3
days based on calcium concentrations. Other degenerative neuropathies may occur in a variety
of breeds and at various ages.
If hypocalcemia is the result of thyroidectomy, calcium
and vitamin D therapy can be reduced gradually over
2–3 weeks, and stopped if calcium remains in the nor-
Diagnosis
mal range.
A tentative diagnosis is based on finding signs of
Prognosis weakness in a young Birman cat. Electrodiagnostic
evaluations may reveal abnormalities such as fibrilla-
Acute hypocalcemia following bilateral thyroidectomy tion potentials, positive sharp waves, and decreased
can be fatal if not recognized early and appropriate nerve conduction velocities depending upon the patho-
therapy instituted. logic process present.
● In general, neuropathies with demyelination tend
Prevention to be associated more commonly with decreased
nerve conduction velocities, whereas neu-
When performing bilateral thyroidectomy, allow 3–4 ropathies with predominant axonal abnormalities
weeks between removal of each lobe. tend to be associated with fibrillation potentials
and positive sharp waves (denervation potentials).
DEGENERATIVE NEUROPATHIES Mild to moderate fibrillation potentials, consis-
tent with denervation, or decreasing nerve con-
Classical signs duction velocity may be found in some cases with
electromyography and nerve conduction velocity
● Weakness with decreased to absent spinal testing, respectively.
reflexes.
● “Dropped-hock” gait in young Birman cats. Histologic lesions involving the axon or the myelin
sheath may be present on peripheral nerve biopsy.