BIOMARKERS IN VETERINARY NEUROLOGY

摘要

A biomarker may be as broadly denned as any observable feature that can be used to inform on the state of the patient , and in this context may include biochemical or molecular species, monitoring parameters (e.g., blood pressure, spO_2), imaging characteristics, and other parameters. The term is most commonly used to refer to biochemical or molecular species analyzed within a biological sample, but this also includes a broad range of substances (e.g., proteins, electrolytes, amino acids, sugars, lipids) assayed from a variety of sources such as biological fluids (blood, urine, cerebrospinal fluid [CSF]) or tissues. This definition is also quite broad and would comprise parameters assessed as part of routine complete blood counts, serum biochemicalpanels, urinalyses, CSF evaluations or special immunohistochemical markers on tissue biopsies (e.g., vimentin or glial fibrillary acidic protein [GFAP] expression). The focus of this talk will be novel analytes within the blood and CSF of veterinary patients with neurologic disorders that might be used to aid in clinical decision-making.The information gained from such analyses might take several forms but we will focus here on improvements in diagnosis, therapy and prognostication. Conventional diagnostic tests routinely used in veterinary neurology include diagnostic imaging (e.g., magnetic resonance imaging, computed tomography, myelography, radiography), CSF analysis and electrodiagnostic tests. Although effective in reaching a definitive or presumptive diagnosis in many patients, a substantial number of animals with neurologic disease cannot be diagnosed with such a strategy. Specific challenges include the differentiation of some inflammatory and neoplastic conditions, differentiation of stroke from inflammation, and weighing the relative contribution of a disease process to dysfunction when there are several disorders or comorbidities present. Histopathological examination of a tissue biopsy remains the gold standard for diagnosis but the central nervous system (CNS) provides challenges to tissue procurement not faced with other organ systems. Although biopsy of CNS lesions is becoming more widespread, such procedures are invasive, costly, associated with potential morbidity, require specialized interpretation and are frightening for many owners. Thus a biomarker obtained through less invasive means that could provide information relative to diagnosis would be a welcome addition to the clinician's toolbox.In addition to providing information on broad categories of disease (e.g., inflammation vs. neoplasia), potential diagnostic uses for biomarkers include differentiation of different neoplasms or inflammatory conditions that appear similar with other tests (e.g., meningioma vs. histiocytic sarcoma; necrotizing meningoencephalitis [NME] vs. granulomatous meningoencephalitis [GME]) or correlation with the grade of a neoplasm (and therefore impacting therapeutic options and prognosis). In terms of treatment, a biomarker might theoretically predict a response to a specific therapeutic intervention or might be used to monitor the response of the patient to the therapy. Finally, a marker that correlated to ultimate prognosis might be quite useful in some scenarios. One example would be a marker that might better predict the response of dogs to decompressive surgery for intervertebral disk herniation when there is a complete spinal cord injury (i.e., absent nociception).