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

Presumptive motor neuron degeneration in an adult cat

An 8-year-old neutered male Bengal cat was referred because of a 1-year history of progressive and relapsing generalized muscle weakness and muscle atrophy. Before referral, the cat was treated with immunosuppressive doses of oral prednisolone, intermittently for 6 mo, and had responded well when the immunosuppressive dose was maintained. Generalized paresis, diffuse muscle atrophy, and diminished spinal reflexes were present in all limbs, consistent with a generalized lower motor neuron disease. Histopathologic evaluation of muscle biopsies confirmed a pattern of muscle fiber atrophy consistent with chronic and severe denervation. No specific abnormalities were identified in the nerve biopsy or within intramuscular nerve branches. A presumptive antemortem diagnosis of an adult-onset motor neuron degeneration resembling amyotrophic lateral sclerosis (ALS) or spinal muscle atrophy was suspected. However, given the response to immunosuppressive doses of corticosteroids, an autoimmune process or other degenerative process could not be definitively excluded. Key clinical message: In this case, an adult cat had a chronic, progressive history of lower motor neuron weakness and absent spinal reflexes; biopsies revealed a neurogenic pattern of muscle fiber atrophy and histologically normal peripheral nerve and intramuscular nerve branches. Although reports of motor neuron disease are rare in the veterinary literature, this case report highlights the importance of muscle and nerve biopsies that lead to a presumptive diagnosis of motor neuron degeneration.

Immune-mediated polyneuropathy in cats: Clinical description, electrodiagnostic assessment, and treatment

BACKGROUND

Suspected immune-mediated polyneuropathy has been increasingly reported in cats, especially in the last decade, but the condition remains poorly understood.

OBJECTIVES

Refine the clinical description and review the classification of this condition based on electrodiagnostic investigation and evaluate the benefit of corticosteroid treatment and L-carnitine supplementation.

ANIMALS

Fifty-five cats presented with signs of muscular weakness and electrodiagnostic findings consistent with polyneuropathy of unknown origin.

METHODS

Retrospective, multicenter study. Data from the medical records were reviewed. The owners were contacted by phone for follow-up at the time of the study.

RESULTS

The male-to-female ratio was 2.2. The median age of onset was 10 months, with 91% of affected cats being <3 years of age. Fourteen breeds were represented in the study. The electrodiagnostic findings supported purely motor axonal polyneuropathy. Histological findings from nerve biopsies were consistent with immune-mediated neuropathy in 87% of the tested cats. The overall prognosis for recovery was good to excellent, as all but 1 cat achieved clinical recovery, with 12% having mild sequelae and 28% having multiple episodes during their lifetime. The outcome was similar in cats with no treatment when compared with cats receiving corticosteroids or L-carnitine supplementation.

CONCLUSIONS AND CLINICAL IMPORTANCE

Immune-mediated motor axonal polyneuropathy should be considered in young cats with muscle weakness. This condition may be similar to acute motor axonal neuropathy in Guillain-Barré syndrome patients. Based on our results, diagnostic criteria have been proposed.

Serum anti-GM2 and anti-GalNAc-GD1a ganglioside IgG antibodies are biomarkers for immune-mediated polyneuropathies in cats

Recent work identified anti-GM2 and anti-GalNAc-GD1a IgG ganglioside antibodies as biomarkers in dogs clinically diagnosed with acute canine polyradiculoneuritis, in turn considered a canine equivalent of Guillain-Barré syndrome. This study aims to investigate the serum prevalence of similar antibodies in cats clinically diagnosed with immune-mediated polyneuropathies. The sera from 41 cats clinically diagnosed with immune-mediated polyneuropathies (IPN), 9 cats with other neurological or neuromuscular disorders (ONM) and 46 neurologically normal cats (CTRL) were examined for the presence of IgG antibodies against glycolipids GM1, GM2, GD1a, GD1b, GalNAc-GD1a, GA1, SGPG, LM1, galactocerebroside and sulphatide. A total of 29/41 IPN-cats had either anti-GM2 or anti-GalNAc-GD1a IgG antibodies, with 24/29 cats having both. Direct comparison of anti-GM2 (sensitivity: 70.7%; specificity: 78.2%) and anti-GalNAc-GD1a (sensitivity: 70.7%; specificity: 70.9%) antibodies narrowly showed anti-GM2 IgG antibodies to be the better marker for identifying IPN-cats when compared to the combined ONM and CTRL groups (P = .049). Anti-GA1 and/or anti-sulphatide IgG antibodies were ubiquitously present across all sample groups, whereas antibodies against GM1, GD1a, GD1b, SGPG, LM1 and galactocerebroside were overall only rarely observed. Anti-GM2 and anti-GalNAc-GD1a IgG antibodies may serve as serum biomarkers for immune-mediated polyneuropathies in cats, as previously observed in dogs and humans.

Biopsy Characteristics, Subtypes, and Prognostic Features in 107 Cases of Feline Presumed Immune-Mediated Polyneuropathy

Inflammatory polyradiculoneuropathy (IMPN) is one of the causes of sudden onset of neuromuscular signs such as para-/tetraparesis in young cats. Even though most cases have a favorable outcome, persistent deficits, relapses, and progressive courses are occasionally seen. As clinical presentation does not always appear to predict outcome and risk of recurrence, this study was initiated to screen for prognostic biopsy findings in a large cohort of histologically confirmed IMPN cases with clinical follow-up. In total, nerve and muscle specimens of 107 cats with biopsy diagnosis of presumed autoreactive inflammatory polyneuropathy and 22 control cases were reviewed by two blinded raters for a set of 36 histological parameters. To identify patterns and subtypes of IMPN, hierarchical k-means clustering of 33 histologic variables was performed. Then, the impact of histological parameters on IMPN outcome was evaluated via an univariate analysis to identify variables for the final multivariate model. The data on immediate outcome and follow-up were collected from submitting neurologists using a purpose-designed questionnaire. Hierarchical k-means clustering sorted the tissues into 4 main categories: cluster 1 (44/129) represents a purely inflammatory IMPN picture, whereas cluster 2 (47/129) was accompanied by demyelinating features and cluster 3 (16/129) by Wallerian degeneration. Cluster 4 (22/129) reflects normal tissues from non-neuropathic control cats. Returned questionnaires provided detailed information on outcome in 63 animals. They were categorized into recovered and non-recovered. Thereby, fiber-invasive infiltrates by mononuclear cells and mild fiber loss in intramuscular nerve branches correlated with higher probabilities of recovery. Remyelination in semithin sections, on the other hand, is correlated with a less favorable outcome. Animals grouping in cluster 1 had a tendency to a higher probability of recovery compared to other clusters. In conclusion, diagnosis of feline IMPN from nerve and muscle biopsies allowed for the identification of histologic features that were positively or negatively correlated with outcome.