Distal polyneuropathy in an adult Birman cat with toxoplasmosis

Abstract

Case summary: A 6-year-old female spayed Birman cat presented with a history of weight loss, stiff and short-strided gait in the pelvic limbs and reluctance to jump, progressing to non-ambulatory tetraparesis over 6 weeks. Poor body condition, dehydration and generalised muscle wastage were evident on general examination. Neurological examination revealed mildly depressed mental status, non-ambulatory flaccid tetraparesis and severely decreased proprioception and spinal reflexes in all four limbs. The neuroanatomical localisation was to the peripheral nervous system. Haematology, feline immunodeficiency virus/feline leukaemia virus serology, serum biochemistry, including creatine kinase and thyroxine, thoracic radiographs and abdominal ultrasound did not reveal significant abnormalities. Electromyography revealed fibrillation potentials and positive sharp waves in axial and appendicular muscles. Decreased motor conduction velocities and compound muscle action potential amplitudes were detected in ulnar and sciatic-tibial nerves. Residual latency was increased in the sciatic-tibial nerve. Histologically, several intramuscular nerve branches were depleted of myelinated fibres and a few showed mononuclear infiltrations. Toxoplasma gondii serology titres were compatible with active toxoplasmosis. Four days after treatment initiation with oral clindamycin the cat recovered the ability to walk. T gondii serology titres and neurological examination were normal after 11 and 16 weeks, respectively. Clindamycin was discontinued after 16 weeks. One year after presentation the cat showed mild relapse of clinical signs and seroconversion, which again resolved following treatment with clindamycin.

Relevance and novel information: To our knowledge, this is the first report of distal polyneuropathy associated with toxoplasmosis in a cat. This case suggests the inclusion of toxoplasmosis as a possible differential diagnosis for acquired polyneuropathies in cats.

Figure 1

Electromyography of the left biceps femoris muscle showing fibrillation potentials and positive sharp waves

Figure 2

(a) Ulnar nerve conduction study showing decreased amplitude, temporal dispersion and polyphasia. (b) Sciatic–tibial nerve conduction study showing decreased amplitude and temporal dispersion

Figure 3

(a) Periodic acid–Schiff (PAS) stain of a cryosection from the cranial tibial muscle showing an intramuscular nerve branch with partial depletion of myelinated fibres and mild mononuclear cell infiltrations. With the PAS stain, myelin stains dark purple. (b) Immunofluorescence staining of cryosections from the cranial tibial muscle using an antibody against feline major histocompatibility complex II. A small cluster of mononuclear cells are highlighted in green with this antibody. (a,b) Scale bar = 50 µm