Woodpecker, About the

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What is the Woodpecker?[edit]

The Woodpecker is multi-use, high precision, programmable, robotic arm. It provides exceptional control over the application of mechanical pressure applied to the body. It is normally applied to the skin including skin overlying tender points and trigger points to test for pain.

The device was inspired by the desire to do pain evoked potential research, in the hope that it would help lead to the first clinically practical, affordable, objective quantifiable tests for mechanical pain in fibromyalgia.

Like woodpeckers the device has “beak” made of a stylus with a rubber tip to apply the pressure. The Woodpecker is It is a mechanical algometer because it applies a pressure pain stimulus. It is an allodynia-meter because it can be used in subjective testing to see if a patient is unduly sensitive to pain. It is also an anaesthesia-meter because it can be used for the subjective testing of sensory loss and reduction of light touch thresholds in patients with peripheral neuropathy.

A little history[edit]

The challenge of designing and building mechanical algometers has been deceivingly difficult because of the numerous constraints of standardization of stimulus, safety, range of force required for application to the body, safety, reproducibility, the need for flexible positioning to reach many body parts and the need to record and graph results.

The Woodpecker is the latest step in the rich and noble 70-year tradition of scientists seeking ways to measure pain and sensory loss due to neurological damage. Mechanical algometers have been in use since Victorian times. Cattell had one in 1911. When used to test pain it is classed as a algometer (dolorimeter).

The “holy grail” of algometry is the long-sought dream of an objective informative test for pain. Tactile Health now has a small pilot evoked potential study which indicates that this possible. The Woodpecker is integral to this.

Our wandering odyssey at Tactile Health[edit]

In 2002, Dr. Doidge was working with respected fibromyalgia expert, Dr. Harvey Moldofsky and his close associate Dr. Jamie MacFarlane. They had many discussions on the need for and possible ideas to build a new improved mechanical pain stimulator. Moldofsky mentioned solenoids. When Doidge began to speak to automation and robotics experts, he was informed that a linear motor was ideal for this type of application.

Doidge teamed up with Joseph Mocanu (PhD medical biophysics) to work on the specifications and design.

After the device was built Doidge’s team (including Dr. Adolfo Cotter and Dr. Albert Ler and Mr. Dave Wickland), began to generate evoked potentials and analyze them. Most of this work involved performing source localization first and then analyzing the force localized data. This led to promising results but they were not adequate for front line clinical testing. The project went into a quiet period for several years until Mario Garingo began to apply machine learning techniques and performing pilot studies without source localization.

Our pilot studies with and without signal averaging have yielded a diagnostic accuracy of 95% for the signal average data and 88 percent for the non-signal averaged “single trial” data.

Operator controlled parameters are[edit]

  • level of pressure applied (from 2 to 3300 grams)
  • duration of application of pressure
  • number of repetitions of application of pressure
  • inter-stimulus interval
  • number of repetitions of force
  • speed of approach of the tip of the device towards the surface of the body
  • acceleration, deceleration, speed of recoil of the device from the body
  • option to control the device by distance of movement of stylus towards or away from the body
  • option to perform instantaneous “tap” testing, (ideal for mechanical pain and light touch evoked potentials and current density evoked reactions using source localization)
  • option to perform “press and hold” testing
  • option to perform ramped pressure testing up or down (for low force light touch or higher force painful touch)


There is a strong need for accurate and early diagnosis of neuropathies and chronic mechanical pain disorders.

As a result, there is a strong need for research to develop early objective tests for these conditions and for tools that help researchers understand their underlying brain mechanisms.

This device may be used for objective pain and light touch research in combination with EEG using evoked potentials or other brain measurement technologies. It can also be used for subjective mechanical pain and touch testing. Cerebral Diagnostics has provisionally patented an EEG/Evoked Potential test for fibromyalgia using this device.

Laser stimulators do not apply stimuli found in nature and so they may be less appropriate for diagnosing clinical cases involving abnormal tenderness. The body has however evolved to react to mechanical pressure.

Mechanical allodynia is one of the main signs in pain medicine. Hand-held stimulators cannot apply the precise reproducible mechanical stimuli needed for research and in the clinic. The Woodpecker can.

Research Uses[edit]

The Woodpecker was first designed for testing mechanical pain, particularly the pain in response to pressing on fibromyalgia tender points. One use is to perform accurate mechanical pressure pain threshold testing and then to obtain a subjective pain response from the patient using a visual analog scale. There are a number of important diseases in which are characterized by a reduced pressure pain threshold i.e. diseases in which the patient feels pain when pressed at a lower force than would normally cause pain in a healthy person.

Common pain disorders, often with trigger points or tender points, that are appropriate for research with the Woodpecker include what could be called “mechanical pain disorders”[edit]

  • Temporo-Mandibular Joint Disorder/Dysfunction (which is sometime like having fibromyalgia in the jaw and is very common)
  • Chronic Fatigue Syndrome (which is a ‘sister’ of fibromyalgia)
  • Myofascial Pain Syndrome (which is like having fibromyalgia in one area)
  • Chronic Widespread Pain
  • Gulf War Syndrome (which opens up the large military market for our product)
  • Complex Regional Pain Syndrome (which is very serious)
  • Some cases of Post-Traumatic Stress Disorder
  • Some cases of Low Back Pain (which is very common)
  • Vulvar Vestibulitis
  • Piriformis Muscle Syndrome

The device may also be integrated with brain imaging modalities to perform research into objective pain testing.

This holds great promise for understanding how the brain processes and mis-processes painful stimuli. This understanding could be part of the platform necessary to create the next generation of treatments for many common pain disorders. The device is appropriate for study of central sensitization disorders.

Neuropathy research[edit]

Many medical disorders result in a loss or reduction of light touch. This includes several dozen known sensory neuropathies the most important of which is diabetic neuropathy. The device can be used to test a hand, foot, or other body parts for the light touch pressure threshold. (This is the lowest pressure to a touch on the surface of the body that a person can recognize.) Surgeons interested in early diagnosis of peripheral neuropathies such as carpal tunnel syndrome may find the device to be useful. Handheld devices such as the Semmes-Weinstein monofilaments are too crude to do many types of research into neuropathy. These filaments come in many sizes but they are often inaccurate. The surface area touching the skin by monofilaments varies according to the angle. They are do not lend themselves to evoked potential research.


The US patent and trademark office has issued a patent on the Woodpecker called “Apparatus and method for exerting force on a subject tissue.“(US8712512B2) This patent provides many useful details as to the utility of this device. It can be viewed at: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=2&f=G&l=50&co1=AND&d=PTXT&s1=doidge&s2=mocanu&OS=doidge+AND+mocanu&RS=doidge+AND+mocanu.

A Canadian patent has also been awarded.

Key Benefits of the Woodpecker[edit]

The Woodpecker is more accurate than the competing mechanical pain and touch testing tools. It can perform and graph light touch thresholds as well as pain thresholds in a reproducible, verifiable, quantifiable, safe and affordable manner. It is more precise in delivering painful stimuli than the hand-held Fischer algometer which is used as a standard device for testing fibromyalgia. It is also more accurate than Semmes-Weinstein mono-filaments which are the standard for diabetic neuropathy.

  • Versatile multipurpose device
  • Provides standardized pain and light touch stimuli to the body
  • Automates the process of applying stimuli
  • The linear motor allows for unrivaled precision
  • Software captures force and time measurement data that can be used for analysis
  • Software and drivers are compatible with any PC
  • Quick and easy-to-use touch screen option so that the user need not learn complex commands
  • Utilizes a programmable logic controller software
  • Automatic self-calibration function before every test
  • Rugged motor built to last
  • Useable in a lab or a clinic setting (not yet approved as a clinical medical device and currently only to be used for research)
  • Non-invasive technology which does not break, burn or freeze the skin

Product Operation[edit]

The device consists of a robotic arm which is secured on a tripod. The operator positions the device over the area of interest such as a fibromyalgia tender point. Then, using a computer (or the touch screen) he or she selects control options for level of force, duration of application of force, speed of approach of the stylus towards the subject’s body part. There is an option to select either what we call a “ramp test” which allows the operator to have a controlled increase in force that is gradual. There is also an option to press only once at a steady force, or to press repeatedly. In principle the device can be used to test for “wind-up”, which is the excessive increase in pain that occurs on repeated applications of a set level of force.

Some Images[edit]

Touch screen.png
Image of the touch screen on the front of the main cabinet.
Copyright Cerebral Diagnostic’s Canada Inc. All rights reserved.
It shows the various touch screen control option parameters on the right. At the time of the photograph it was set to deliver 1.4 kg of force for one second, with the stylus approaching the test area of the skin at a speed of 20 mm a second, and to repeat a total of 10 times, with a resting time when no force is applied for 1 second. (This means that the interstimulus interval is 2 seconds.) The user has the option to select either a simple test or a ramp test. The word “simple” is highlighted in blue which means the device was set to do a series of press and hold stimulations and not a ramp test.

Tip of woodpecker.png
Image showing the tip of the Woodpecker poised to descend and press on the right epicondyle tender point to test for allodynia in fibromyalgia and other mechanical pain disorders.
Copyright Cerebral Diagnostic’s Canada Inc. All rights reserved.

Part of woodpecker.png
Part of the Woodpecker, pointing down and attached to a tripod.
Copyright Cerebral Diagnostic’s Canada Inc. All rights reserved.
This image shows part of a tripod at the bottom right. In the middle there is aluminum bar (horizontally oriented). At the left is the linear motor which is the black rectangular device which will slide downward towards the body part. At the end is the rubber tip that will press on a body part. Between the motor and the tip is a sensor which gives feedback to the controller so that the device can deliver the force. It can be used in pain research applying 2kg of force to a fibromyalgia tender point safely. This level will generally be painful to patients with mechanical allodynia. (Not shown are the legs of the tripod.)

Components box.png
View of the components box for the controller, power and other parts.
Copyright Cerebral Diagnostic’s Canada Inc. All rights reserved.
On the front is a touch screen used for handy entry of the commands to move the device such as the target pressure to be applied.

5 test 3kg.png
Five simple tests at 3 kgs.
Copyright Cerebral Diagnostic’s Canada Inc. All rights reserved.
Graph was created by programming the Woodpecker to alternately press and release for four seconds each. This was done five times. This graph demonstrates that the device performed with precision and repeatability. The target force of 3kg was achieved. Note the lack of overshoot and the squared off appearance proving the precision performance of the device.

Precision woodpecker.png
Graph showing the precision of the Woodpecker in performing ascending staircase testing from 500 to 3000 grams.
Copyright Cerebral Diagnostic’s Canada Inc. All rights reserved.
(Severely sensitive pain patients are often tender at as little as 1000 grams.) The vertical axis is force in grams. The horizontal is time. The clean and clear steps seen here prove that the device functioned precisely by shooting up to the next target force, then levelling off before proceeding the next target. It can also graph lower forces that are more appropriate for testing sensory loss. (See next image.)

Force vs time.png
Force vs. time graph demonstrating the precision of the Woodpecker.
Copyright Cerebral Diagnostic’s Canada Inc. All rights reserved.
The graph above shows the results of delivering a series of forces to create an ascending staircase of stimulations from 2 grams to 100 grams in 2-gram increments. This diagram demonstrates that the device could be useful for the early detection of sensory loss.

Painful touch.png
Painful touch Evoked Potential lowpass filtered at 20Hz.
Copyright Cerebral Diagnostic’s Canada Inc. All rights reserved.
Vertical line indicates the peak occurs at frame 388 (134.8 msec after the stimulus). Troughs are prominent in electrodes FC1, FC2, and CZ. Peaks also occur in electrodes FT10, TP9, TP10. Signal averaging has removed all CNS reactions in the signal that are not time-locked to the pain stimulus.

Side view brain.png
Side view of the brain showing areas of activation in the brain of a patient when pressed by the Woodpecker.
Copyright Cerebral Diagnostic’s Canada Inc. All rights reserved.
Colours refer to frequencies. Image made using EEG source localization tools develop by Cerebral Diagnostics.

Accuracy woodpecker.png
YouTube video demonstrating the accuracy of the Woodpecker
Copyright Cerebral Diagnostic’s Canada Inc. All rights reserved.
1:10 Semmes Weinstein vs. Woodpecker Algometer at 10 grams. https://www.youtube.com/watch?v=RvvYr7KMhP U. This video provides a comparison of the accuracy of Semmes-Weinstein filaments against the Woodpecker. A simple 10 gram Semmes Weinstein monofilament is being pressed against a scale. This video demonstrates firstly that a Semmes Weinstein monofilament that was rated to be 10 grams, does not actually perform at 10 grams, but rather lower, generally at 9 grams. A similar gauge pin placed on the tip of the Woodpecker, consistently performed at 10 grams. The biggest difference which is not shown here is that the woodpecker can press at much lower forces and therefore could be used to detect neuropathy earlier in the disease process.

Accuracy woodpecker 2.png
Second YouTube video showing the accuracy of the Woodpecker.
Copyright Cerebral Diagnostic’s Canada Inc. All rights reserved.
0:52 Woodpecker Accuracy Test vs Ohaus Scale, https://www.youtube.com/watch?v=RaUa6wb2Pto. This video shows near identical readings for internal device force measurements (seen at the left) and the forces read by the scale (seen at the lower right). It provides strong validation that the device is performing accurately.

Pricing, Terms of Payment and Delivery[edit]

Contact Dr. Mark Doidge, Cerebral Diagnostics Canada Inc.

Note that this is a specialized research device that is built one at a time to order.