Identifying the primary pain type...

Figure 1: Knowing whether one is dealing with a predominant nociceptive, neuropathic or centrally sensitised pain complaint will significantly influence the choice of treatment plan. 

Knowing the predominant pain type during a clinical encounter is important in guiding an evidence based Biopsychosocial treatment plan. 

There are methods practitioners have used traditionally to gather information about a pain experience that typically include a 'pain rating' scale where we ask someone to rate their pain experience from 1-10. In this scale "1 is virtually no pain" and "10 is the worst pain imaginable". Diener et al (2016)1 claim that while this may be relevant information for third party payers, the astute clinician will sparingly use the actual word "pain" as current pain science research tells us that this might well influence the pain experience. It must be noted that a further limitation of this scale as an assessment of pain is that it is purely subjective rendering it vulnerable to cultural and emotional influences, amongst others. There is much more valuable information to be gained about a patients pain and this is the type of pain.

As clinicians it is fundamental in understanding the underlying pain mechanisms and differentiating the 3 main types:

  1. Nociceptive

  2. Neuropathic

  3. Central Sensitisation 

(Wijma et al.,  2016)

"In line with emerging research in pain science, it is now well established that "pain is not pain". The biopsychosocial model of pain science has made scientists and physical therapists aware that in some patients the pain experience is predominantly driven by nociceptive information and this will have a more nociceptive dominant mechanism.
In other patients, nociception by virtue of tissue healing, becomes less dominant, but biological and physiological processes in the peripheral nervous system becomes a dominant issue in a persons pain experience resulting in a possible peripheral neuropathic pain mechanism. 
In yet another patient, peripheral nociceptive and neuropathic mechanisms are not the key issues associated with the development and maintenance of the pain experience, but more powerfully driven by the central nervous system, resulting in a dominant central pain mechanism.
The importance of being able to identify which of these  mechanisms is dominant is likely more important clinically than simply just asking a pain rating"

(Diener et al., 2016 P.5) 1

STEP ONE

Wijma et al (2016) 2 outline guidelines first described by Nijs et al (2014) 3 to identify predominant pain type. The first step entails identidying if neuropathic pain is dominating. Neuropathic pain has been defined by Treede et al. (2008) 4 as "pain arising as a direct consequence of a lesion or disease affecting the somatosensory system". Where this lesion occurs would dictate if it was assigned the label of neuropathic (lesion in peripheral nervous system - beyond the spinal cord) or central neuropathic (lesion in the brain or spinal cord). Central neuropathic is distinguished from central sensitisation by lack of damage to the nervous system in central sensitisation.

HISTORY of damage to body tissue in the prev. 6-8weeks
PAIN diminishes according to the natural healing phases
RELATED to tissue damage (an ankle sprain) or potential damage (almost burning a hand)
LOCAL pain, most often with diagnostic signs such as deem, hematomas, skin colorations....
DESCRIBED as sharp, aching or throbbing
— Nociceptive pain - Nijs et al., (2014)

STEP TWO

The second step is to differentiate between predominantly nociceptive and central sensitisation pain. Central sensitisation is likely dominating if the perceived pain and disability (as measured by the Oswestry Disability index) are disproportionate to the nature of injury or pathology AND one of the following criteria:

  1. The presence of a diffuse or neuro-anatomically illogical pain distribution (as per pain chart) that is not in accordance with dermatomes or myotomes.
  2. Hypersensitivity of senses (light, sound, smell, taste, skin) unrelated to the musculoskeletal system (as measured by the Central Sensitisation Inventory - CSI)

A cutoff score of 40 on the CSI indicates a potential central sensitisation being present. 

HISTORY of a lesion or disease of the nervous system, or post traumatic / surgical damage to the nervous system.
INDICATIONS from diagnostic examinations to reveal an anomaly of the nervous system
RELATED to a medical or systemic cause such as stroke, herpes, diabetes or some form of neurodegenerative disease
PAIN and sensory dysfunction are neuroanatomically logical.
DESCRIBED as burning, shooting or pricking
— Neuropathic pain - Nijs et al., (2014)

For an in depth discussion on differentiating the predominant pain type and applying to practice the reader is advised to view Nijs et al. (2014)3 and a more recent paper by Nijs et al. (2015)5 specifically regarding low back pain.

NO HISTORY of a lesion, damage or disease of the nervous system
NO INDICATIONS from diagnostic examinations
NO MEDICAL cause for the pain established
PAIN is neuro-anatomically illogical and segmentally unrelated to the primary source of nociception. Several regions of hyperalgesia at sites outside and remote to the symptomatic area (still at segmentally unrelated sites)
DESCRIBED as vague and dull
— Central Sensitisation - Nijs et al., (2014)

CLOSING notes

There is a whole lot more to a patients pain than simply rating it 1-10 and if the type of pain is not identified then we risk inappropriate management, the implications of which could be adverse outcomes from over / under treatment.  First identify if neuropathic pain is predominating, then differentiate nociceptive and central sensitisation. It is worth noting that two or even all three types may be present to some extent, however it is unusual that one isn't at least dominant and can direct management. 

As a side side note, is sensitisation always a bad thing? Is there a situation where this is actually adaptive and beneficial? Click here to see more detail on this topic.

Next, one can investigate for psychosocial drivers of a maintained pain state utilising the simple ABCDEFW criteria described by Louis Gifford (2014). 

Luke R. Davies :)

 


REFERENCES

1. Diener, I., Kargela, M. and Louw, A. (2016). Listenning is Therapy: Patient Interviewing From a Pain Science Perspective, Physiotherapy Theory and Practice,DOI: 10.1080/09593985.2016.1194648

2. Wijma, A. J., Van Wilgen. C. P., Meeus, M. and Nijs, J. (2016). Clinical Biopsychosocial Physiotherapy Assessment of Patients with Chronic Pain: The First Step in Pain Neuroscience Education, Physiotherapy Theory and Practice, DOI: 10.1080/09593985.2016.1194651

3. Nijs, J., Torres-Cueco, R., Van Wilgen. C. P., Girbes, E. L, Struyf, F., Roussel, N., Van Oosterwijck, j., Daenen, L., Kuppens, K., Van Werweeen, L., Hermans, L., Beckwee, D., Voogt, L., Clark, J., Moloney, N. and Meeus, N. (2014) Applying Modern Pain neuroscience in Clinical Practice: Criteria for the Classification of Central Sensitization Pain, Pain Physician, 17, P.447-457

4. Treede, R. D., Jensen, T. S., Campbell, J. N., Cruccu, G., Dostrovsky, J. O., Griffin, J. W. Hansson, P., Hughes, R., Nurmikko, T. and Serra, J. (2008). Neuropathic Pain: Redefinition and a grading System for Clinical and Research Purposes, Neurology, 70, P.1630-1635.

5. Nijs, J., Apeldoorn, A., Hallegraeff, H., Clark, j., Smeets, R., Malfliet, A., Girbes, E. L., De Kooning, M. and Ickmans, K. (2015). Low Back Pain: Guidelines for the Clinical Classification of Predominant Neuropathic, Nociceptive, or Central Sensitisation Pain, Pain Physician, 18, P.333-346.

6. Gifford, L. (2014). Aches and Pains: TJ International, Padstow, Cornwall, UK.