Name: assessment of sensory thresholds in dogs using mechanical and hot thermal quantitative sensory testing
Uploaded: 2021-10-26T13:00:00
Description: Watch this Scientific Journal Video about Assessment of Sensory Thresholds in Dogs Using Mechanical and Hot Thermal Quantitative Sensory Testing at JoVE.com

The authors would like to thank Andrea Thomson, Jon Hash, Hope Woods, and Autumn Anthony for handling dogs for QST, Masataka Enomoto for his help screening dogs, and Sam Chiu for his contributions to establishing the protocol for hot thermal QST.

All procedures were approved by the Institutional Animal Care and Use Committee of North Carolina State University.
1. Room set-up and study subject acclimatization
<ol>
	<li>Perform QST in a dedicated space where there is ample room for a QST operator, handler, and dog of any size to move about comfortably. Minimize potential auditory and visual distractions and use a white noise machine to block out ambient sound.</li>
	<li>Place a large yoga mat or similar padding on the floor to ensure t...

<ol>
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It is crucial to the acquisition of accurate data - that reflects the dog&#39;s sensory thresholds - that the dog is as calm, relaxed, and positioned adequately as possible for each measurement. A previous study noted that agitation from restraint or distraction from factors within or outside the testing environment affected dogs&#39; responses to the QST stimuli16. If the dog becomes agitated from recumbency or restraint or is distracted, the dog should be given time to settle before a measuremen...

Quantitative sensory testing (QST) assesses the responses elicited by externally applied stimuli; it is used to evaluate the function of the somatosensory system in humans and animals1. Mechanical stimuli in the form of punctate pressure or deep pressure are applied as a ramped stimulus. The sensory threshold is determined as the force that evokes a psychophysical response1. Hot or cold thermal stimuli can be used as a ramped stimulus or as a fixed intensity stimulus. The sensory threshold is determined as the temperature at which there is a response or the latency to respond to the stimulus. Punctate pressure sensory thresholds are measured using electronic von Frey anesthesiometers or von Frey hair filaments, deep pressure is measured using handheld pressure algometers, and thermal sensory thresholds are determined using a variety of contact thermode systems.
QST provides information about the functioning of both peripheral and central sensory pathways and can be used to evaluate alterations in these sensory pathways (algoplasticity) in various disease processes, particularly those that cause chronic pain1. Meissner&#39;s corpuscles detect punctate pressure, and the sensation is transmitted by A&#946; afferent fibers at non-noxious levels and A&#948; afferent fibers when the stimulus is of a noxious intensity1,2. Deep pressure is detected by Pacinian corpuscles and transmitted by C afferent fibers, noxious heat is detected by Ruffini corpuscles and transmitted by A&#948; and C afferent fibers, and noxious cold is detected by Krause corpuscles and transmitted by C afferent fibers1,2. QST can be used to detect both inhibition (decreased sensitivity, hypoesthesia) and facilitation (increased sensitivity, hyperesthesia) of these receptors and pathways. In dogs, QST has been used to evaluate alterations in sensory thresholds secondary to acute spinal cord injury3,4,5, Chiari-like malformation and syringomyelia6, cranial cruciate ligament rupture5,7, and osteoarthritis (OA)8,9,10. Additionally, some studies have used QST to assess pain alleviation provided by certain analgesics6,11,12,13 and surgical procedures14. These studies have provided important insights into the mechanisms of pain sensation in dogs, such as evidence for peripheral and central sensitization after surgery and diseases causing chronic pain states such as cranial cruciate ligament rupture and OA. This information can help improve the detection and treatment of pain in dogs.
Validation studies of mechanical and hot thermal QST in dogs have shown good feasibility, repeatability, and reliability of QST results over time in normal dogs and dogs with chronic pain from OA8,9,15,16. However, several studies have found poor repeatability and reliability of cold thermal and occasionally von Frey QST1,15,17. These studies used different equipment and methodology but provided evidence that mechanical and hot thermal QST is an accurate, semi-quantitative method of measuring sensory thresholds in dogs. However, attention to precise details, including the setting of the measurements, is critical to optimizing QST in dogs, necessitating a standardized protocol for QST. Sanchis-Mora et al. detailed a sensory threshold examination protocol (STEP) for mechanical and hot and cold thermal QST but encountered difficulty with dogs not responding to the cold thermal QST or the highest gram force von Frey filament used in the study17. The following protocol provides a standard method for mechanical and hot thermal QST in dogs; this protocol can assess sensory thresholds in normal dogs or dogs with various disease processes affecting the somatosensory system. The development of standardized protocols may allow for comparing results across studies and meta-analyses of data to improve the utility of QST in veterinary medicine.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Electronic von Frey anesthesiometer</td>
			<td>IITC Life Science Inc.</td>
			<td>Item # 23931</td>
			<td>Custom made with a 1000g max force load cell</td>
		</tr>
		<tr>
			<td>Medoc Main Station software</td>
			<td>Medoc</td>
			<td>(supplied with TSA-II)</td>
			<td></td>
		</tr>
		<tr>
			<td>SMALGO: SMall Animal ALGOmeter</td>
			<td>Bioseb</td>
			<td>Model VETALGO</td>
			<td></td>
		</tr>
		<tr>
			<td>TSA-II NeuroSensory Analyzer</td>
			<td>Medoc</td>
			<td>DC 00072 TSA-II</td>
			<td>No longer manufactured - new model is TSA-2 with same probes and same function</td>
		</tr>
	</tbody>
</table>

assessment of sensory thresholds in dogs using mechanical and hot thermal quantitative sensory testing

Quantitative sensory testing (QST) is used to evaluate the function of the somatosensory system in dogs by assessing the response to applied mechanical and thermal stimuli. QST is used to determine normal dogs&#39; sensory thresholds and evaluate alterations in peripheral and central sensory pathways caused by various disease states, including osteoarthritis, spinal cord injury, and cranial cruciate ligament rupture. Mechanical sensory thresholds are measured by electronic von Frey anesthesiometers and pressure algometers. They are determined as the force at which the dog exhibits a response indicating conscious stimulus perception. Hot thermal sensory thresholds are the latency to respond to a fixed or ramped temperature stimulus applied by a contact thermode.
Following a consistent protocol for performing QST and paying attention to details of the testing environment, procedure, and individual study subjects are critical for obtaining accurate QST results for dogs. Protocols for the standardized collection of QST data in dogs have not been described in detail. QST should be performed in a quiet, distraction-free environment that is comfortable for the dog, the QST operator, and the handler. Ensuring that the dog is calm, relaxed, and properly positioned for each measurement helps produce reliable, consistent responses to the stimuli and makes the testing process more manageable. The QST operator and handler should be familiar and comfortable with handling dogs and interpreting dogs&#39; behavioral responses to potentially painful stimuli to determine the endpoint of testing, reduce stress, and maintain safety during the testing process.

Mechanical and thermal QST has been performed to detect sensory thresholds in both research and client-owned dogs under various clinical conditions, including normal, healthy dogs, dogs with chronically painful conditions such as OA, dogs with acute spinal cord injury, and to assess post-operative pain and effectiveness of analgesics. Though there is a growing body of work on QST in dogs, no normal range of values has been established for any testing modalities. However, several studies have assessed the feasibility and ...

Watch this Scientific Journal Video about Assessment of Sensory Thresholds in Dogs Using Mechanical and Hot Thermal Quantitative Sensory Testing at JoVE.com

Assessment of Sensory Thresholds in Dogs Using Mechanical and Hot Thermal Quantitative Sensory Testing

This work describes a standard protocol for mechanical and hot thermal quantitative sensory testing to evaluate the somatosensory system in dogs. Sensory thresholds are measured using an electronic von Frey anesthesiometer, pressure algometer, and hot contact thermode.

Quantitative sensory testing (QST) is used to evaluate the function of the somatosensory system in dogs by assessing the response to applied mechanical ...

This protocol for assessing sensory thresholds in dogs using quantitative sensory testing or QST will help standardize studies allowing for valuable comparisons across different studies. This technique provides a noninvasive method to measure sensory thresholds in dogs. Our protocol helps guide researchers on best practices to obtain accurate and consistent data.This protocol can provide insight into mechanisms of pain sensation in dogs, including following surgeries and for diseases associated with chronic pain states. The most important aspect of this technique is being cognizant of canine behavior. To ensure safe, accurate testing, all involved must be mindful of the dog's behavior and anxiety levels.Start with arranging the instrument setup by gently applying a rigid 0.9 millimeter Von Frey tip to the load cell, ensuring that the load cell is securely screwed into the handpiece. Then connect the cord from the handpiece to the recording device through the M0 channel. Next, turn on the recording device and press the max button to record and display the maximum force achieved when the dog responds to the applied stimulus.Zero the instrument by pressing the CLR button. To collect the data and measure thresholds, instruct the dog to lay down and then help the dog to the lateral recumbency position. Apply minimal to moderate restraint to maintain the dog in the position and relatively still.Provide gentle manual support to the limb of the dog being tested to keep the limb off the floor and provide a stable backing to apply force against while not preventing the dog from withdrawing the limb. Once the dog is calm and relaxed, with the limb being tested at 70%extension, apply the stimulus once. Place the Von Frey tip perpendicular to the skin of the area being tested.If the dog exhibits reflex movements from the sensation of the Von Frey tip on the skin, allow the dog to relax the limb again before reapplying the Von Frey tip. When the skin does not cause reflex movements, take a measurement by applying the Von Frey tip. Apply steadily increasing force with the Von Frey tip at 20 grams per second until the dog withdraws the limb, vocalizes.turns to look at the stimulus, or exhibits other movements or behavioral responses indicating the conscious perception of the stimulus. Remove the stimulus when the dog withdraws the limb or the maximum force is reached and record the maximum force applied that is displayed on the recording device. Repeat the measurements for five trials, allowing one minute between each measurement with the dog in lateral recumbency if they remain relatively calm and relaxed with no or minimal restraint.Zero the instrument between each step by pressing the CLR button. Next, record a feasibility score of zero to five to indicate the ease of data collection. Give the dog a break of five minutes before starting measurements with the blunt probed pressure algometer.While setting up the instrument, ensure the small blunt probe is securely screwed into the device. Then turn on the recording device and press the max button to continue when prompted on the screen. Press the unit button until the unit is displayed as grams at the top of the screen and push the zero button to zero the instrument.Next, place and prepare the dog in lateral recumbency to measure the thresholds as mentioned before. Apply the blunt probe perpendicular to the skin of the area being tested to apply a steadily increasing force with the probe at 20 grams per second until the dog exhibits behavioral responses that indicate the conscious perception of the stimulus. Remove the stimulus when the dog withdraws the limb or the maximum force is reached.After recording the maximum applied force from the recording device, repeat the measurements for a total of five trials. Allow the dog to remain in lateral recumbency to sit, stand, or move about the QST room to maintain comfort during the inter-trial interval. Then replace the dog in lateral recumbency before the subsequent measurement.Record a feasibility score of zero to five to indicate the ease with which the data was collected. Give the dog a break of five minutes before starting measurements with the hot thermal probe. Before starting the experiment, prepare the dog as explained before.Then apply the thermode to the skin of the area being tested and click on the start button in the lower left-hand corner of the test tab to start the test. When the dog exhibits movements or behavioral responses that indicate the conscious perception of the stimulus or when the maximum latency is reached, remove the thermode while simultaneously stopping the stopwatch. Record the latency to withdraw.Repeat the measurements for a total of five trials by first clicking the stop button and then clicking the pre-test button in between each measurement to stop heating the thermode. This will allow the software to recalibrate the thermode to prepare for the next application. Record a feasibility score of zero to five to indicate the ease with which the data was collected.The representative analysis summarizes the mechanical and hot thermal QST data from a group of healthy pain-free dogs. The data from the electronic Von Frey aesthesiometer sensory threshold measurements displayed no significant effect of body weights on the sensory thresholds. A similar impact of the body weights was noticed in the data from blunt probed pressure algometer sensory thresholds.On the other hand, the data collected for the hot thermal probe sensory latency showed a significant effect of the body weight on the sensory latency. The overall average, standard deviation, and range of sensory thresholds for the mechanical and hot thermal QST were summarized in the same group of healthy pain-free dogs. This provides reference values for future researchers using these techniques It is most important to reliably identify the dog's behavioral response that indicates the conscious perception of the stimulus which may look different for different dogs.In addition to quantitative sensory testing, collecting behavioral information through validated owner questionnaires and emotional reactivity tests can help provide a comprehensive assessment of the dog's affective state.

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