Clinical Reasoning – Identifying Types of Pain

I think one of the key aspects of our clinical reasoning process is in the identification of the types of pain.

Our subjective examination can play significant role in identifying pain type(s).

As posted previously Woolf (2004 and 2010) and Costigan et al (2009) divide pain into the following types:

• Nociceptive
• Inflammatory
• Pathological – subdivided into Neuropathic and Dysfunctional/Functional

Subjectively a patient suffering from Inflammatory pain may report symptoms such as:

• Night pain
• Increased symptoms in the morning upon rising
• Pain that worsens with rest
• Pain that eases with movement
• Constant pain
• Stimulus evoked pain but also potential for non-stimulus evoked (i.e. spontaneous) pain.
• And the cardinal signs of reporting heat, redness, swelling.

A number of these symptoms can occur in other pain states, and even in red flag states hence it is important to put the entire clinical picture together and not just assume inflammatory pain is occurring.

Neuropathic pain can be assessed reliably subjectively and objectively using Neuropathic assessment tools. Some of the assessment tools I have trialled recently include:

• PainDETECT – a purely subjective assessment for neuropathic pain i.e. the patient can fill it out prior to, or after, the assessment.
• LANSS – a subjective and objective screening tool.
• DN4 – a subjective and objective screening tool.

These assessment tools are easily found via an online search e.g. Google.

Personally I think it is important to screen patients for presence of neuropathic pain, particularly if there is any suggestion of non-mechanical behaviour of pain.

Dysfunctional/Functional pain is a different story and one that I am not completely clear on. Conditions that evoke dysfunctional pain include fibromyalgia, irritable bowel syndrome, tension type headache, temporomandibular joint disease, interstitial cystitis, and other syndromes in which there exists substantial pain but no noxious stimulus and no, or minimal, peripheral inflammatory pathology (Woolf, 2010).

Out of interest, Yunus (2007) reports on what is referred to as “Central Sensitivity Syndromes (CSS)”. These syndromes comprise an overlapping and similar group of syndromes without structural pathology and are bound by the common mechanism of central sensitisation. Examples being:

• irritable bowel syndrome
• tension-type headache
• temporomandibular disorders
• myofascial pain syndrome
• regional soft-tissue pain syndrome
• periodic limb movements in sleep
• multiple chemical sensitivity
• female urethral syndrome
• interstitial cystitis
• post-traumatic stress disorder.

Yunus also reports that Depression may also be a member of CSS (see reference).

So these CSS’s and Dysfunctional Pain seem to have an overlap of similar conditions. As previously discussed in the “Pain” post, Central Sensitisation is a mechanism common to Dysfunctional pain.

The above information on Dysunctional Pain and CSS’s shows the importance of screening general health. Particularly if the patient is demonstrating any potential non-mechanical signs or possible amplified pain processing. If so we should be screening for the potential health issues, and psychological health, outlined above, given the potential for them to impact on the patients pain presentation, or be the primary cause of their symptoms.

Perhaps Functional pain can also simply be a result of “central changes” such as psychosocial and lifestyle issues, for example depression, sleep dysfunction, fear, anxiety etc. These issues may then alter descending inhibitory pain pathways and the HPA Axis (see the post regarding this). In particular I think we can strongly consider this pain to be present if the patient presents with non-mechanical pain components and does not screen positively for inflammatory signs/disorders and/or neuropathic pain.

A patient with pure Nociceptive pain will present with clear mechanical signs. That is they will report movements and or postures that cause their pain. Avoidance of these aggravating activities and/or rest will cause complete relief pf symptoms. If you recall from the previous post this is referred to as stimulus evoked pain i.e. pure nociceptive pain should be intermittent in nature. I will discuss the subjective exam in more detail regarding Nociceptive pain in the next post.

Based on the above I think that is highly plausible to expect that we can screen, and identify, pain sufficiently in our subjective exam by asking questions relating to the behaviour and the characteristics of the patients pain.

Naturally our subjective should also focus on other things but I don’t deem them particularly relevant to this particular post, as much of these things relate to basic concepts taught in physiotherapy courses.

References:

• Costigan M, Scholz J, Woolf CJ (2009). Neuropathic pain: a maladaptive response of the nervous system to damage. Annu. Rev. Neurosci. 32 (1-32).
• Walker BF, Williamson OD (2009). Mechanical or inflammatory low back pain. What are the potential signs and symptoms? Manual Therapy 14:314-320.
• Woolf CJ (2004) Pain: moving from symptom control toward mechanism-specific pharmacologic management. Ann Intern Med.140 (441-451).
• Woolf CJ (2010) What is this thing called pain?. The Journal of Clinical Investigation. 120:11 (3742-3744)
• Yunus MB (2007) Fibromyalgia and overlapping disorders: the unifying concept of central sensitivity syndromes. Semin. Arthritis Rheum. 36:6 339-56.