Is your Back Pain shrinking your Brain?

Chronic Back Pain is Associated with Decreased Prefrontal and Thalamic Grey Matter Density

Apkarian V.A., et al.  Journal of Neuroscience, Nov 2004, 24(46):10410-10415

This research was out of Northwestern University in Chicago Illinois in 2004.  It was the first study to correlate chronic back pain (CBP) with decreased grey matter in the brain.  As we work with patients every day, people who have chronic unremitting back pain for 1 year or more have an accelerated neurodegenerative process underway in their brain.  If we are able to help them we are playing an active role in slowing that process!

The researchers studied 26 people with chronic back pain (unrelenting pain localized around lumbosacral area for greater than 1 year) and 26 control patients.  They performed 2 different types of analysis for estimating global grey matter in the brain and adjusted statistics for age, gender, and type of pain (musculoskeletal and neurogenic/radicular). 

Clinical Pearls:

Normal whole brain grey matter atrophy is 0.5% per year.

Atrophy caused by CBP was measured at 5-11% per year, the equivalent of 10-20 years of aging.

The reduction in grey matter was localized to the dorsolateral prefrontal cortex (DLPFC) and the thalamus.  The DLPFC is responsible for inhibition of the orbitofrontal activity of the brain.  The orbitofrontal area is responsible for perception of pain.  The researchers then extrapolated that with loss of inhibition of the orbitofrontal areas of the brain, chronic pain suffers perceive increased pain.

Patients with neuropathic pain showed a greater loss of cortical grey matter.

Understanding Pain

Mechanisms of Musculoskeletal Pain

Bogduk N. The Journal of Orthopaedic Medicine 28(3) 2006

With three published texts and over 200 indexed articles , Nikolai Bogduk is one of the world’s foremost authorities on biomechanics of the spine and musculoskeletal pain, so when I came across this article I knew it would have some pertinent information that help us understand our patient’s pain.

Sample of Scalene Muscle trigger points and referred pain pattern

Key Points:

Pain transduction is ascribed to free or unencapsulated nerve endings with the following hierarchy of sensitivity; Periosteum, ligament, joint capsule, tendon, fascia, and muscle.

Reminder: that pain from a muscle is more commonly felt over the joint that that muscle moves.

How pain is created in the body: Mechanical or chemical stimuli affect free nerve endings in a peripheral nerve.  Central transmission is then the term used for propagation of action potentials from the first order neurons (free nerve endings) to the second order neurons which form tracks in the spinal cord to higher centers in the brain and thalamus.  Modulation then occurs in these tracks which involved intersegmental and descending pathways from the brainstem that inhibit and control the first synapse in this pain pathway.  Physiologically it then follows that modulation is one of the mechanisms that upper cervical chiropractic helps control pain occurring almost anywhere in the body!

Sensory (afferent) nerves and Sympathetic nerves contribute to mechanisms of inflammation in the body.  Chiropractic adjustments decrease sympathetic tone in the body, help to reduce inflammation and therefore pain.

Clinical Pearl: The next time you have an IME telling you that a patient has a ‘non-anatomical’ distribution of pain and therefore their pain is not genuine,  you can also use this article to cite that ‘Ongoing pain sensitizes the central nervous system to produce larger areas of pain’ that may not follow classic anatomical distributions.