Clinical Course and Diagnostic Findings of Biopsy Controlled Presumed Immune-Mediated Polyneuropathy in 70 European Cats

Abstract

There is a paucity of information on the clinical course and outcome of young cats with polyneuropathy. The aim of the study was to describe the clinical features, diagnostic investigations, and outcome of a large cohort of cats with inflammatory polyneuropathy from several European countries. Seventy cats with inflammatory infiltrates in intramuscular nerves and/or peripheral nerve biopsies were retrospectively included. Information from medical records and follow up were acquired via questionnaires filled by veterinary neurologists who had submitted muscle and nerve biopsies (2011-2019). Median age at onset was 10 months (range: 4-120 months). The most common breed was British short hair (25.7%), followed by Domestic short hair (24.3%), Bengal cat (11.4%), Maine Coon (8.6%) and Persian cat (5.7%), and 14 other breeds. Male cats were predominantly affected (64.3%). Clinical signs were weakness (98.6%) and tetraparesis (75.7%) in association with decreased withdrawal reflexes (83.6%) and, less commonly, cranial nerve signs (17.1%), spinal pain/hyperesthesia (12.9%), and micturition/defecation problems (14.3%). Onset was sudden (30.1%) or insidious (69.1%), and an initial progressive phase was reported in 74.3%. Characteristic findings on electrodiagnostic examination were presence of generalized spontaneous electric muscle activity (89.6%), decreased motor nerve conduction velocity (52.3%), abnormal F-wave studies (72.4%), pattern of temporal dispersion (26.1%) and unremarkable sensory tests. The clinical course was mainly described as remittent (49.2%) or remittent-relapsing (34.9%), while stagnation, progressive course or waxing and waning were less frequently reported. Relapses were common and occurred in 35.7% of the cats' population. An overall favorable outcome was reported in 79.4% of patients. In conclusion, young age at the time of diagnosis and sudden onset of clinical signs were significantly associated with recovery (p < 0.05). Clinical and electrodiagnostic features and the remittent-relapsing clinical course resembles juvenile chronic inflammatory demyelinating polyneuropathy (CIDP), as seen in human (children/adolescents), in many aspects.

Keywords: CIDP; GBS; electrodiagnostic; feline; neuromuscular; tetraparesis; weakness.

Figure 1

Nerve fiber teasing preparations showing multiple fiber adhesive and invasive round mononuclear cells (lymphocytes and macrophages) indicated by red arrows at the Schmidt Lanterman clefts, paranodium and along demyelinated segments (indicated by D). Biopsy of the peroneal nerve contrasted with Osmium tetraoxide, scale bar 50 μm.

Figure 2

Semithin section of peroneal nerve featuring reduced density of nerve fibers and mild expansion of the endoneurial fibrocollagenous tissue. There are numerous fibers with marked reduction of myelin sheath thickness (demyelination—black arrows) accompanied by multiple fiber adhesive mononuclear cell infiltrates and overall increased endoneurial cellularity (red arrows). Stained with Azurblue Safranin, scale bar 500 μ–m.

Figure 3

Age at onset. Summary of the outcome in the different age groups with total number of patients for each segment.

Figure 4

Graphic representation of neurologic signs presented by the cats of this cohort.

Figure 5

Electrodiagnostic tests of a 14-months-old male Maine Coon cat with presumed immune-mediated polyneuropathy. (A) Motor nerve conduction studies of the left sciatic-tibial nerve. CMAPs show a marked reduction of amplitude/area and mild temporal dispersion. Motor nerve conduction velocity is 76 m/s [reference range 93.7 ± 9.4 m/s; Ref. (12)]. (B) Motor nerve conduction study of the right ulnar nerve. CMAPs show a marked reduction of amplitude/area. Motor nerve conduction velocity is 64 m/s [reference range 82.1 m/s ± 11.1 m/s; Ref. (12)]. (C) F-waves after supramaximal stimulation of the right ulnar nerve at the carpus. F-waves are characterized by a pronounced chronodispersion (variable minimum latency) and a severe increase in latencies. The values of minimum F-waves latencies vary between 24 and 31 ms [reference range 8.4 ± 0.9 ms; Ref. (42)].

Figure 6

Recovery time. Representation of recovery time in the three groups (weeks: 1–4 months, months: 1–4 months and late: >4 months), with total amount of patients indicated on the y axis.

Figure 7

Association between recovery and age at onset. Demonstration of the relationship between recovery and age at onset of clinical signs. The y-axis shows probabilities of recovery predicted by the logistic regression. Younger cats were more likely to recover (p = 0.005).

Figure 8

Association between the type of onset and recovery. Cats with a sudden onset of clinical signs were more likely to recover (p = 0.037). The y-axis shows probabilities of recovery predicted by the logistic regression. Graph displays estimated probabilities with 95% confidence intervals.