Somatosensory Rehabilitation of Pain explained to Medical Doctors
[Citation] : Bouchard, S. (2020). Guesteditorial Somatosensory Rehabilitation of Pain explained to Medical Doctors. e-News Somatosens Rehab, 17(1), 3-12.
Sarah Bouchard, MSc OT, CSTP®[1]
To the readers of e-News Somatosens Rehab and to those who will read this article by reference, I am delighted to count you among this growing network and to notice that we share a common interest, namely the management of neuropathic pain and their symptoms via somatosensory rehabilitation.
Let me introduce myself. I am an occupational therapist working in a private clinic since 2014, also practicing with a physical and mental health clientele living with chronic pain.
Having a keen interest in understanding and managing pain, I completed a 2.5-year graduate certificate on chronic pain management at McGill University. Still not having satisfactory answers concerning the management of neuropathic pain after my graduation in 2018, I followed the training on somatosensory rehabilitation of pain the next year.
It was during this training that I saw great potential in the approach and came to realize that I could have used it with my past problematic cases of neuropathic pain. Unfortunately, their condition had been ignored/not treated effectively by all of the professionals in their file, due to a lack of knowledge.
After collaborating on the 4th edition of the book entitled DOULEURS NEUROPATHIQUES : Évaluation clinique et Rééducation sensitive (which can be translated in by “NEUROPATHIC PAIN: Clinical Assessment and Somatosensory Rehabilitation”), Claude J. Spicher approached me at the end of 2019 to write a Guesteditorial.
Over the past few months, I participated in a conference led by specialists in neuropathic pain who did not know the Somatosensory Rehabilitation of pain Method (SRM). Due to this, I decided to dedicate this article explaining the somatosensory rehabilitation approach to medical doctors, so they can recognize the neuropathic or somaesthetic symptoms, understand the usefulness of this non-invasive approach and prescribe an evaluation with a somatosensory therapist of pain if needed.
Here is my explanation of what somatosensory rehabilitation of pain is and when to prescribe it.
What is neuropathic pain?
Neuropathic pain is a condition caused by a lesion or a disease affecting the somatosensory nervous system (Finnerup et al., 2016). According to the Atlas of cutaneous branch territories, when a patient reports neuropathic pain, he has axonal lesions of at least one cutaneous nerve branch, including Aβ neurofibers (de Andrade Melo Knaut et al., 2019). To this day, there are six known aetiologies of Aβ neurofibers lesions (Woolf & Mannion, 1999; Horowitz, 2007; Spicher et al., 2020):
Traumatic (a cut, torn or crushed nerve after a contusion, fracture, injection, surgery, etc.);
Compression (edema, inflammation, hernia, tight orthopedic cast, CTS, etc.);
Psychosomatic (interpersonal conflict);
Metabolic (diabetes, multiple sclerosis, cerebrovascular lesions, etc.);
Infectious (after bite, post-herpetic, shingles, bacteria, etc.);
Biochemical (radiotherapy, chemotherapy, capsaicin, etc.).
Two mechanisms of peripheral neuropathic pain can be stimulated following a cutaneous branch nerve lesion (Woolf & Mannion, 1999):
Adaptative neuroplasticity that decreases stimulus-independent pain;
Restoration of the tacile sense / pain inhibition that decreases stimulus-evoked pain.
What is stimulus-independent pain?
Stimulus-independent pain, also known as spontaneous pain, can be described as: “burning”, “lancinating”, “electric shock-like”, “jabbing” or “cramping” and is often accompanied by “pins-and-needles” sensations and sometimes by “intractable itching” (Horowitz, 2007).
However, spontaneous neuropathic pain in conjunction with other signs and symptoms can confirm hypoaesthesia[1]. Indeed, according to the somatosensory rehabilitation approach, specific peripheral neurological symptomatology is one of the four examinations used to confirm hypoaesthesia. Nonetheless, even though patients can feel different symptoms when they have stimulus-independent pain, there are only five somatosensory qualifiers used to examine and document axonal lesions. Three out of the five symptoms listed below are enough to make this test positive (Spicher, 2006):
1. “Tingling”
2. “Numb”
3. “Radiating”
4. “Dull”
5. “Tugging”
In French, the five qualifiers are: « décharges électriques », « irradiation », « picotements »,
« fourmillements » and « engourdissement ».
The four examinations used to establish hypoaesthesia are:
1. Aesthesiography, to identify the territory of the hypoaesthesia;
2. Static 2-point discrimination test, to understand the quality of the hypoaesthesia;
3. Tingling signs, to acknowledge the site of axonal lesions and a distal sign of regeneration;
4. Somatosensory qualifiers, to determine the peripheral neurological symptomatology.
An aesthesiography (Fig. 1) is a cartography of the skin surface affected by a partial lesion of the branch of a nerve. It is determined with a set of 20 Semmes-Weinstein aesthestiometers, also known as monofilaments or calibrated von Frey filaments (Fig. 2) and then reproduced on a graph paper. It “circumscribes the hypoaesthetic territory of the skin portion where [the] aesthesiometer is not detected” (de Andrade Melo Knaut et al., 2019). 240 different nerve branches in the body can be affected and evaluated. They are distributed in 10 domains:
Trigeminal domain;
Occipital domain;
Cervical domain:
Brachial domain;
Thoracic domain;
Lumbo-abdominal domain;
Lumbo-femoral domain;
Femoral domain;
Sciatic domain;
Sacral domain.
Figure 1: aesthesiography of a patient with partial hypoaesthesia of the dorsal branch of ulnar nerve.
Figure 2: evaluation of an aesthesiography - the minimum force required to bend the nylon of the filament.
A static 2-point discrimination test is done to determine the presence of a vibrotactile sense and in the meantime, its quality. It is measured with a 3-point or a 2-point aesthesiometer (Fig. 3). There are 5 stages of cutaneous sense (Spicher et al., 2015):
S0 – anaesthesia;
S1 – no protective sense;
S2 – a poor vibrotactile sense;
S3 – a fair to correct[2] sensitivity;
S4 – a good sensitivity.
Figure 3: 2-point aesthesiometer used to make a static 2-point discrimination test.
“A tingling sign is a sensation triggered by a mechanical stimulus in the distal part of an injured nerve or at the site of an injury. This sensation radiates peripherally, from the point where it is triggered to the cutaneous distribution of the nerve. This tingling response can be compared with that produced by a weak electric current, as in Transcutaneous Electrical Nerve Stimulation (TENS). This unpleasant sensation is not « severe pain » and « does not persist ».“ (Spicher, 2006). There are four tingling signs (Table I) (Spicher et al.,1999):
T0 – where the site of the axonal lesions is and where there is no distal sign of regeneration;
The neuroma – where the site of the axonal lesions is and needs to be desensitized;
T00 – where the site of the axonal lesions is and doesn’t need to be desensitized anymore;
T++ – where the sign of regeneration is and shouldn’t be desensitized.
Table I: the four tingling signs T0, neuroma, T++ and T00 (adapted from Spicher et al., 2020).
The somatosensory qualifiers, listed previously, are usually evaluated with the taking of the McGill Pain Questionnaire (Melzack, 1975), which includes those 5 words on 78 possible symptoms, classified in 20 groups and 4 categories. The questionnaire used in French is Questionnaire de la Douleur Saint-Antoine.
At least three out of those four tests need to be positive to attest to the presence of hypoaesthesia. These tests can be done by a somatosensory therapist of pain.
What is stimulus-evoked pain?
Stimulus-evoked-pain, also known as touch-evoked pain, can be described as the sensation of pain produced by a noxious stimulus (mechanical; e.g. pinprick - chemical; e.g. acid - thermal; e.g. low temperature) or by an innocuous stimulus (e.g., light touch). For this article, I will only talk about the touch-evoked pain caused by a static mechanical innocuous stimulus, which is called a static mechanical allodynia[3] (Merskey & Bogduk, 1994).
There are two assessments used to establish the presence of static mechanical allodynia:
Allodynography, to identify the allodynic territory;
Rainbow Pain Scale, to determine the severity of the allodynia.
Figure 4: personalized VAS made with a patient.
Like an aesthesiography, an allodynography is used to map the skin surface of the affected nerve distribution. In this case, it maps the painful territory with a 15.0 gramforce monofilament as a stimulus, but only after a personalized Visual Analog Scale (VAS)
(Fig. 4)has been made previously with the patient, since he needs to perceive at least 3 cm/VAS.
The rainbow pain scale represents a hierarchy of seven severities of static mechanical allodynia (Table II). Each color is associated with the force applied on the skin with a specific monofilament to perceive it, by definition, as painful. The smaller the calibrated monofilament used to create a touch-evoked pain is, the more severe the static mechanical allodynia is and the longer it will take to treat it. This scale is also useful for predicting the likely length of treatment needed for the allodynia to resolve. On average, it takes about one month to switch from one severity/color to the next level; and once the violet level allodynography is negative, we need to add an extra month before the person is able to freely touch what used to be the allodynic territory.
Note: the rainbow pain test (named the fifth point) is done once the allodynography is completed. At that moment, a two second stimulus applied in the centre of the territory, starting from red and working up to violet if necessary is sufficient to define the severity of the allodynia.
Table II: the seven severities of the rainbow pain scale with the proper monofilament used to detect it and the clinical interpretation of the severity (Packham et al., 2020).
Even though the McGill Pain Questionnaire is not needed to determine the presence of static mechanical allodynia, the result of the questionnaire helps somatosensory therapists of pain determine which stage of Aβ axonal lesions the patient is at. A score of 20 points and more is concerning.
What are the stages of Aβ axonal lesions that can lead to somaesthesic and/or neuropathic conditions?
There are 5 stages of somaesthesic and/or neuropathic condition (Rajkumar et al., 2019):
Stage I: Tactile hypoaesthesia;
Stage II: Simple mechanical allodynia;
Stage III: Intermittent neuralgia;
Stage IV: Persistent neuralgia;
Stage V: Complex Regional Pain Syndrome (CRPS).
Note that vibrotactile hypoaesthesia, static mechanical allodynia and underlying vibrotactile hypoaesthesia can all present a stage III, IV or V.
What is the Somatosensory Rehabilitation of pain Method and how does it treat neuropathic symptoms?
SSR is a method developed by Claude J Spicher to test and treat somatosensory disorders of neuropathic pain patients. This method aims to increase the quality of touch of the hypoaesthetic cutaneous territory or to normalize the sensation of touch of the allodynic cutaneous territory (Packham et al., 2020; Rajkumar et al., 2019). Note that when the hypoaesthesia decreases, the neuropathic pain also decreases (Rajkumar et al., 2019; Spicher et al., 2020).
Treating the hyposensitivity
Once the hypoaesthesia has been confirmed with the presence of three positive assessments out of four, the Pressure Perception Threshold (PPT) search can be done.
The PPT is used “to determine the minimum pressure detected, at a specific point’’(de Andrade Melo Knaut et al., 2019) and its result is compared to a specific norm according to the part of the body evaluated (the palmar and plantar face [0.1g], the dorsal face of the foot and the hand [0.3g] or the rest of the body [0.6g]).
The PPT result helps to determine the quality of vibrotactile sense to allow the somatosensory therapist of pain to choose the right treatment for the patient. Note that the permanent assessment, done every appointment, is part of the rehabilitation, that some clinics can also do a stimulation of nerve substitution if they own the proper equipment and that specific exercises executed at home, consisting by touching the hypoaesthetic territory in different manners, complete the rest of the rehabilitation. The three different treatments that can be performed by the patient are:
Line Rehabilitation;
Asperity Rehabilitation;
Hands-on Therapy.
In other words, “The rehabilitation of hyposensitivity is based on the adaptive neuroplasticity of the somatosensory system, and it involves direct stimulation of the hypoaesthetic skin area mapped by aesthesiography.” (Boer, 2019). It takes about 6 weeks to resolve a light hypoaesthesia (Spicher et al., 2020).
Treating the static mechanical allodynia
Once the static mechanical allodynia has been confirmed, and the color of the rainbow pain scale determined, the search of a distant comfortable zone to counter stimulate starts. This step is crucial because 2/3 of the treatment is to avoid, at all costs, touching the allodynic territory and the uncomfortable zone, if it exists (Spicher et al., 2020). That territory can change as the allodynia reduces, but in the meantime, the patient and his therapists must stop touching the determined zone and any distal branch from the territory, because somatosensory stimuli are afferent and pass through the zone that should not be stimulated.
Avoiding touching the designed territory also means that the patient has to stop wearing clothes and jewelry, shaving, sleeping, putting cream, putting ice or hot, etc. on that part of the body. The other 1/3 of the treatment is to start the distant vibrotactile counter-stimulation to reduce the intensity and the territory of the allodynia.
Once the allodynia is gone, an underlying hyposensitivity can be found (Rajkumar et al., 2019). It is important to treat the underlying hyposensitivity so the allodynia doesn’t come back. It takes a few weeks to be able to touch the previously allodynic territory and then to treat it.
Note that distant vibrotactile counter-stimulation is known to be an evidence-based practice method level 2b (Spicher & Degange, 2005; Spicher, Degrange & Mathis, 2005; Chaput et al., 2017; Spicher, 2019a).
Which symptoms or descriptors from a patient might suggest that they can benefit from SSR?
The symptoms of stage 1 (pure somaesthesic condition) that can be evoked by patients are: “Tingling”, “Tugging” and “Numbness”. In French, those words are: « Picotements », « Fourmillements » et « Engourdissement » (Rajkumar et al., 2019; Spicher et al., 2020).
The qualifiers of neuropathic pain (mostly for stage III and IV) that can be evoked by patients are: “Throbbing”, “Flashing”, “Shooting”, “Radiating”, “Spreading”, “Stinging”, “Lacerating”, “Tearing”, “Hot”, “Burning”, “Cool” and “Cold”. In French, these words are : « élancements », « En éclairs », « Décharges électriques », « Rayonnante », « Irradiation », « Piqûre », « Coups de poignard », « Déchirure », « Chaleur », « Brûlure », « Froid », « Glace ».
The descriptions you may hear in your office from a person suffering from hypoaesthesia:
“I don’t feel the same sensation on each arm.”
“The sensation of this side of my body is weird/ blurry.”
“I feel numbness in this part of my body.”
“I can’t feel the pedal underneath my foot when I drive.”
“I feel like pins and needles in this part of my body.”
Etc.
The descriptions you may hear in your office from a person suffering from allodynia:
“I can’t wear my watch on this wrist anymore.”
“I can't wear the same shoes has before; the pressure is unbearable; it increases my pain after I wear them.”
“I can’t sleep on my back anymore; it’s too painful/it makes the pain worse.”
“I have difficulty showering; the pressure of the water on my skin is bothering me.”
“The sensation on my tongue is weird / I feel like a have toothache once my headache starts.”
“My pain increased highly, up to two days after having treatment in physiotherapy/ osteopathy/ massage therapy.”
Etc.
The behavior changes you may see in your office in a patient with allodynia:
A patient who used to have long hair shaved her head to avoid the stimuli of her hair;
A patient is wearing a boot on one foot and sandal on the other foot or wearing shorts in winter;
A patient with a sleeve up on one side while they talk about the pain on that arm;
A patient having a painful and high reaction to light touch;
A patient having more neuropathic pain after an injection;
Etc.
What should you do if you think your patient is suffering from hypoaesthesia, allodynia or complex regional pain syndrome?
If you think your patient may suffer from one of the listed conditions, an evaluation with a somatosensory therapist of pain would be recommended.
Even though there are currently 1318 therapists worldwide who have engaged in courses, there are 117 certified somatosensory therapists of pain that you can find in your region by visiting www.neuropain.ch (Spicher, 2019b).
Which results should you expect from a somatosensory therapist of pain?
Besides seeing an improvement of the condition of your patient every week, if he or she applies and respects the recommendations given to them, the information you may receive, in a letter, from a somatosensory therapist of pain are:
The kind of somaesthetic and/or neuropathic condition the patient presents (Hypoaesthesia, Allodynia, Neuralgia or Complex Regional Pain Syndrome);
The stage of the Aβ lesions (I to V);
The name of the affected nerve branch es (1 to 240 branches);
The affected territory (presented by an aesthesiography or an allodynography);
The results of the static 2-point discrimination test, in millimeters (in presence of Hypoaesthesia);
The results of the Pressure Perception Threshold perceived, in grams (in presence of Hypoaesthesia);
The McGill Pain Questionnaire scores (or Questionnaire de la Douleur St-Antoine in French);
The representation of the territory to avoid touching (in presence of Allodynia)
Besides the norms of the static 2-point discrimination test, that change from one branch to another and can’t be listed here, all the information needed to understand each result is explained previously.
Conclusion
I hope this article helped you better understand neuropathic pain and the associated symptoms of an individual suffering from it. Please refer anyone you know who is suffering from these symptoms so they can be treated with a non-invasive procedure.
Thank you for sharing this article to help raise awareness about what neuropathic pain is and to help educate people in the treatment options that are available.
References
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Boer, K. (2019). Is somatosensory rehabilitation effective without a generator of vibrations? e-News Somatosens Rehab, 16(1), 9-14;
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[1] Mercier, Qc, Canada e-mail : sarah.bouchard.ergo@hotmail.com website : www.sarahbouchardergo.com
[1] Hypoaesthesia: diminished sensitivity to a tactile and/or vibratory and/or thermal stimulation. For this article, I will be using the term hypoaesthesia to describe diminished vibrotactile sensitivity.
[2] S3+ – correct sensitivity only for the hand.
[3] Allodynia: Pain due to a stimulus which does not normally provoke pain.
