Classification of Chronic Pain - ICD-11

(Below is rough transcription of the above video)

World Health Organisation writes up this great long document called International Classification of Diseases, which essentially lists out every known health problems a person can have, ranging from a finger sprain, to malignant cancers. They review this quite often but the last wholesale review was done in early 90’s when they released the 10th edition.

The 11th one is coming out some time this year and that’s an awfully exciting news for those who are interested in chronic pain because they’re doing a massive update on chronic pain conditions. This is so important for many reasons, so let me go through it with some crucial points:

 

1.      Firstly, the individual conditions that are often used as diagnoses in everyday medicine have been categorised into seven groups or “parents”.

 

These seven groups are:

Chronic primary pain, Chronic cancer pain, chronic posttraumatic and postsurgical pain, chronic neuropathic pain, chronic headache and orofacial pain, chronic visceral pain, and chronic musculoskeletal pain.

 

Some of these are pretty self-explanatory but others need a little more clarification. Let me go through these VERY briefly before discussing WHY these are so important.

 

Chronic primary pain is pain that can’t be explained by another condition. Like persisting back or neck pain that can’t be put down to anything. Other examples are Fibromyalgia, and irritable bowel syndrome.

Chronic cancer pain is pain due to cancer or cancer treatment

Chronic postsurgical or posttraumatic pain is pain that persists at least 3 months after surgery or trauma for no other good reason (because by the 3rd month everything that should be healed, should have been healed, and there typically should be no disabling pain).

Chronic neuropathic pain is due to damage to the nerves, like peripheral neuropathy or nerve trauma.

Chronic headache and orofacial pain is essentially that; headache and jaw or facial pain for one reason or another.

Chronic visceral pain is pain due to some level of disturbances in internal organs, like endometriosis. It is crucial to note that the pain experienced here often has ZERO relationship to the extent of actual internal damage if any. Just like most other pain conditions, the disturbance is NOT at structural level but at pain processing or modulation level.

Chronic musculoskeletal pain is pain as part of a disease process directly affecting some tissues. Like pain because of rheumatoid arthritis, or symptomatic osteoarthritis. This differs from primary pain group which cannot be related to a particular pathology (so pain itself is a primary condition).

 

 

So, let’s get back to WHY such grouping is a great step forward in understanding chronic pain:

Grouping acknowledges the consistency of pathophysiology.

For example, fibromyalgia is under chronic primary pain group, endometriosis is under chronic visceral pain group, and migraine under headache group. That all sounds pretty straight forward.

However some seemingly different conditions have been grouped together. For example, fibromyalgia and irritable bowel syndrome are both in chronic primary pain group. And THAT might be difficult to comprehend for uninitiated since the similarity isn’t obvious at first glance. However, without going into details, they share very much the same pathophysiology, just different locations.

Another good example is pain from autoimmune diseases like lupus, that is under the same group as pain from symptomatic degeneration like osteoarthritis, which again seems somewhat weird because they’re so different, but when it comes to pain they again share the same pathophysiology.

2. Now the second point. This is somewhat obvious but needs pointing out: They’ve given us the seven groups but they’re ALL under the same grand-daddy umbrella of “Chronic pain”. It’s telling us that the groups are not all THAT different.

For example: again, let’s take fibromyalgia, pain from endometriosis and migraine. Upto this point they’ve been considered as very separate entities, and that is reflected in the current edition of the ICD (that’s the tenth). But they actually share some very consistent mechanisms on persistence of pain that actually exist across the most pain conditions.

And while they WOULD be under separate groups under this new edition of ICD, the fact that they will all be within this big umbrella called chronic pain is a reflection of the progress that’s been made in research and the increasing level of acceptance among the health professionals.

3. The third and final point: “Multiple-parenting” will be possible. That means a condition will be able to be described under two or more groups at the same time.

For example: you can have a patient with persistent lower back pain, with chronic primary pain AND chronic musculoskeletal pain as possible “parents”. You could have a patient with jaw pain, that belonged to both chronic primary pain and chronic orofacial pain group.

Why is all this important? Because this allows correct and accurate communication between health professionals and between health professionals and patients. Let’s say that there is a patient with a chronic neck pain after a car crash 5 yrs ago, with MRI showing some disc damages but with unclear clinical implications. If one health professional writes to another: neck pain under likely parents of chronic primary pain and chronic musculoskeletal pain (?disc), that would say so much more, than just writing “whiplash”.

Also, for a condition like fibromyalgia which has so much variety of information and misinformation, wide-recognition of the condition under chronic primary pain group would resolve much misunderstanding between health professionals and patients; similarly, inclusion of pain from endometriosis under chronic visceral pain group might encourage those affected to seek less invasive interventions.

So there you go. Who would’ve thought that taxonomy could be so interesting? For chronic pain conditions, which deals with something that’s so not black-and white and still lacks broad level of knowledge and consensus among health professionals, appreciation and understanding of the classification of chronic pain must be the basic requirement for any clinicians. Because informing our patients of consistent and correct data is so crucial in effective management of pain.

References

Treede, R. D., Rief, W., Barke, A., Aziz, Q., Bennett, M. I., Benoliel, R., . . . Wang, S. J. (2015). A classification of chronic pain for ICD-11. Pain, 156(6), 1003-1007. doi:10.1097/j.pain.0000000000000160