Award Photo CVM  

Advancing the health and well-being of animals and people


Fellow: Ruth Van Hatten
Mentor: Peter Scrivani
Co-Mentors: Rodrigo Bicalho; Ellis Loew; Manuel Martin Flores; Santiago Peralta

Department of Clinical Sciences
Contact Information:   Email:  rav63@cornell.edu; Phone: 607-253-3241
Sponsor:  American College of Veterinary Radiology - Resident Research Grant
Grant Number: N/A
Title:  Comparison of Electroretinography and Brainstem Auditory Response to Three-dimensional Time-of-Flight Magnetic Resonance Angiography for Detecting Reduced Blood Flow in the Maxillary Arteries of Cats with the Mouth Opened
Annual Direct Cost:  $7,500
Project Period:  07/01/2012-06/30/2013

DESCRIPTION (provided by applicant):  Blindness and deafness are reported complications in cats following general anesthesia for dental procedures. These complications are devastating and infrequent, but the frequency may be underestimated if there is unilateral vision or hearing loss. In a pilot study we showed that blood flow through the maxillary arteries is reduced in some cats when the mouth is opened versus closed. We believe that this observation is due to mechanical obstruction of the maxillary arteries due to compression by the jaw. Since the maxillary arteries supply the eyes and inner ears we proposed that prolonged and excessive opening of the mouth may be a factor in the development of these complications. Additional factors (e.g., concurrent hypotension or hypoxemia, anatomic variation) likely play a role in the development of these complications and minor changes in hypotension or hypoxemia may be amplified in cats with reduced blood flow.  To investigate the role of these other variables in future research projects, and possibly to screen client-owned cats prior to dental procedures, it is desirable to have an efficient test that identifies which cats have reduced blood flow in the maxillary arteries when the mouth is opened.  Imaging methods are excellent for demonstrating functional changes in blood flow. In our pilot study, we used three-dimensional time-of-flight magnetic resonance angiography to document changes in blood flow in the maxillary arteries with different mouth positions.  Whereas this method is non-invasive, quick, sensitive to blood-flow changes, and feasible, it also is costly and has limited availability. Therefore, a comparable test that is less costly and readily available is desirable. During our pilot study, we observed cats with reduced blood flow frequently had abnormal results during electroretinography or brainstem auditory response testing. Based on this observation, we hypothesized that the combination of electroretinography and brainstem auditory response would produce comparable results to three-dimensional time of-flight magnetic resonance angiography regarding blood flow in the maxillary arteries when the mouth is opened versus closed—even though these electrodiagnostic tests do not directly measure blood flow but rather the integrity of the entire system. If the two methods are interchangeable for clinical or research use, then an additional benefit of electrodiagnostic testing is that it indicates whether the eyes, ears, or both structures are at risk of injury when there is reduced blood flow. Currently, it is unknown why the eyes and ears are not equally affected.  To investigate our hypothesis, we will perform a method-comparison study to determine the amount of agreement between electrodiagnostic testing and magnetic resonance imaging using the Kappa statistic. The sample population will consist of 15 cats admitted to our hospital for a dental procedure. Exclusions will be made for cats with coexisting conditions that make extended anesthesia time unsafe (eg, congestive heart failure, unregulated diabetes or hyperthyroidism), existing blindness or deafness, or lack of owner consent. Observers for electrodiagnostic testing and for magnetic resonance imaging will be blinded to each other’s results. If there is insufficient agreement between methods, then we will recommend the continued use of both electrodiagnostic testing and magnetic resonance imaging in future research projects.