Page 975 - Problem-Based Feline Medicine

44 – THE CAT WITH GENERALIZED WEAKNESS 967

Prognosis PRIMARY HYPEROXALURIA

In cats with a suspected idiopathic peripheral neuro-
pathy, seven cats recovered spontaneously and com- Classical signs
pletely without specific treatment within 4–6 weeks.
● Domestic short-hair cats, 5–9 months old.
● Generalized weakness, absent cutaneous
trunci reflex.
MYOTONIA ● Signs of renal disease may or may not be
present.
Classical signs
● Stiffness and muscle spasm.
● Short, stilted gait. Pathogenesis
● Increased muscle size.
It is suspected that the systemic oxalosis damages the
peripheral nerves.
Pathogenesis
Cats with myotonia have sustained muscle contrac- Clinical signs
tion, which is initiated voluntarily or with stimulation,
Primary hyperoxaluria was reported in a colony of
and sustained involuntarily.
domestic short-haired cats.
Myotonia most often occurs as a congenital problem.
Cats developed clinical signs between 5–9 months of
Excessive muscle contraction is thought to be due to an age.
abnormal muscle cell membrane, which supports
In some instances, clinical signs of weakness occurred
persistent depolarization.
prior to the onset of renal failure.
Postural reactions were depressed.
Clinical signs
Spinal reflexes were inconsistently affected.
Affected cats often have a stiff, stilted gait and have
large, bulky muscles on palpation. The cutaneous trunci reflex was absent in most cats.
Muscle dimpling may occur with direct muscle Other signs of renal failure such as inappetence, weight
percussion. loss, polyuria, polydipsia were sometimes present.

Diagnosis Diagnosis

Electromyography demonstrates the characteristic Positive sharp waves, milder fibrillation potentials, and
myotonic potentials, and muscle biopsies may be sup- occasional bizarre high-frequency discharges were
portive of the diagnosis. found with electromyographic examination.
Pathologically, the neurons in the ventral gray matter of
Differential diagnosis the spinal cord and their proximal axons were most
Rule out other myopathies such as X-linked muscular affected.
dystrophy (increased serum creatine kinase, typical ● Swollen axons were present in the ventral nerve
muscle biopsy findings). Myotonia has characteristic roots and dorsal root ganglion cells.
EMG findings.
Differential diagnosis
Treatment
Rule out other congenital causes of weakness such
No treatment has been described in cats. as hypokalemic myopathy (Burmese, low plasma