Neurofilament light chain as a biomarker of meningoencephalitis of unknown etiology in dogs
Neurofilaments (Nfs) are neuron specific proteins that are highly expressed in axons. When axonal damage occurs, Nfs are released into the cerebrospinal fluid (CSF) and blood stream. Neurofilament light chain (NfL) concentration in the CSF and blood have recently shown to reflect neuroaxonal damage and could be potential biomarkers for disease progression in humans.
Studies with central nervous system (CNS) biomarkers in veterinary medicine are scarce. It is important that they are easy to measure and have high cost efficiency. NfL can be a potential biomarker for veterinary use since their concentration can be easily measured in CSF and serum.
With this study, the authors hypothesized that NfL serum and CSF concentrations would increase in dogs with meningoencephalitis of unknown etiology (MUE).
Thirty-six healthy and 38 MUE diagnosed dogs were included in the study. Dogs with the disease were treated with a combination of prednisolone and other immunomodulatory drugs, with the corticosteroide being tapered to a maintenance dose. NfL CSF and serum concentrations were measured at the beginning and compared between healthy and MUE dogs to evaluate differences at the onset of clinical signs.
To evaluate the effect of seizures on NfL concentrations, dogs were divided into 2 groups: those with MUE and seizures and those with MUE but without seizures. In both groups, NfL concentrations were also measured at the beginning to compare and evaluate its value as a biomarker for seizures in dogs with the disease.
NfL concentrations were measured after treatment or before death and compared to those obtained at the beginning to evaluate its use in monitoring response to treatment.
Authors were able to discover that serum NfL concentrations in dogs with MUE was significantly higher in those that were healthy. Another important finding was that, in dogs with the disease, NfL concentrations dropped significantly in those that responded to treatment when compared to those that didn’t. In regard to seizures, although the concentrations of NfL were higher, that difference was not statistically significant.
An important consideration to remember is the difficulty in diagnosing MUE. Magnetic resonance imaging has high specificity and sensitivity in the diagnosis of this disease. Despite this, authors discovered that some dogs with increase in NfL concentrations with the disease showed no changes in the MRI and CSF cytology. Therefore, an increase in NfL concentration can support the diagnosis of MUE in cases of MRI and CSF cytology changes.
In conclusion, despite the limitations of this study, the authors consider that NfL cand be a potential biomarker for MUE and have an important role in diagnosing and evaluating response to treatment.
Yun, T, Koo, Y, Chae, Y, et al. Neurofilament light chain as a biomarker of meningoencephalitis of unknown etiology in dogs. J Vet Intern Med. 2021; 35( 4): 1865– 1872.
https://doi.org/10.1111/jvim.16184
