John Rossmeisl, Jr.

Background Neurofilament light chain (NfL) is a frequently used biomarker in humans for both diagnostic and therapeutic monitoring purposes in various neurologic diseases. Hypothesis/Objectives It was hypothesized that dogs with diagnosed structural epilepsy (SE) would have a significantly higher serum NfL concentrations compared to dogs with idiopathic epilepsy (IE). The secondary hypothesis was that dogs would have a significantly higher serum NfL concentrations when measured within 7 days after a seizure compared to being seizure‐free for at least 30 days. Animals Fifty client‐owned dogs presented to the neurology service for evaluation of seizures were enrolled. Fourteen dogs had SE and 36 dogs had IE. Methods Prospective cohort study performed on 52 serum samples obtained for NfL concentration measurement using single molecule array technology. Results The median serum concentration of NfL in dogs with SE was significantly higher (109 pg/mL; range, 11.4‐741.3 pg/mL) than in dogs with IE (17.7 pg/mL; range, 5.8‐188 pg/mL; Wilcoxon rank sum test, P = .001). No significant relationship was found between serum NfL concentration and time of sampling in relation to the most recent seizure in dogs with IE. Conclusions and Clinical Importance Serum NfL may serve as an adjunctive biomarker for the differentiation of SE and IE.

Background Fibrocartilaginous embolic myelopathy (FCE) is a well‐documented condition in dogs although rarely reported in chondrodystrophic breeds. Genetic associations have not been defined. Objectives Define the association of the chondrodystrophy‐associated FGF4L2 retrogene with histopathologically confirmed cases of FCE. Animals Ninety‐eight dogs with a histopathologic diagnosis of FCE. Methods Retrospective multicenter study. Dogs were genotyped for the FGF4L2 and FGF4L1 retrogenes using DNA extracted from formalin‐fixed, paraffin‐embedded tissue. Associations between breed, FCE and retrogene status were investigated with reference to a hospital population and known breed and general population allele frequencies. Results FGF4L2 genotype was defined in 89 FCE cases. Fibrocartilaginous embolic myelopathy was present in 22 dogs from FGF4L2 ‐segregating breeds with allele frequencies of ≥5%; however, all dogs were wild type. Two Labrador retrievers with FCE carried FGF4L2 alleles. Frequency of the FGF4L2 allele was significantly ( P < .001) and negatively associated with FCE relative to predicted hospital‐population dogs. FCE was overrepresented in Boxer, Great Dane, Yorkshire Terrier, Bernese Mountain Dog, Miniature Schnauzer, Rottweiler, and Shetland Sheepdog breeds. Conclusions and Clinical Importance Study data based on genotypically and histopathologically defined cases support the historical observation that FCE is uncommon in chondrodystrophic dog breeds. FGF4 plays an important role in angiogenesis and vascular integrity; anatomical studies comparing chondrodystrophic and non‐chondrodystrophic dogs might provide insight into the pathogenesis of FCE.