Functional imaging in chronic pain
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Transcript of Functional imaging in chronic pain
Functional imaging in chronic pain
Marwan N Baliki Ph.D.
Northwestern University
Department of Physiology
Apkarian pain and emotion Lab
Brain functional/structural changes associated with the transition of pain form acute to chronic state
Outline
Brain imaging in acute and chronic pain
1. Cortical mechanisms of acute and chronic pain 2. Impact of chronic pain on brain structure
Using functional imaging, we can identify suitable brain marker that can predict the onset of chronic pain after injury
Pain is one of the most important functions of the nervous system and provides information about the presence or threat of injury.
“an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.”
Pain: general definition
Pain is a complex perception:
1. Sensory properties – quality, location, intensity2. Affective properties - desire to avoid harm 3. Cognitive properties – appraisal of experience
Multiple distinct states :
1. Acute – transient (seconds to minutes)2. Chronic – maladaptive (can last a lifetime)
Spinal cord pathways of pain
Brain activity for acute pain
Spontaneous pain rating in chronic back pain (CBP)
CBP (spontaneous pain)
CBP (acute thermal pain)
Healthy(acute thermal pain)
Brain activity for CBP
Different clinical pain conditions show distinct brain activity
Brain activity for chronic pain ≠ acute pain
Chronic pain tends to activate limbic regions (amygdala, striatum and hippocampus)
Brain activity for clinical pain is specific for the clinical pain type
Conclusions from functional studies
Chronic pain & brain structure
1.5 cc/year of pain2.5 cc/year of aging
CSF White Gray
Global gray matter changes in chronic pain
Tension headache(Schmidt-Wilcke et al 2005)
CRPS(Geha et al 2008)
Fibromyalgia (Kuchinad et al 2007)
Regional analyses show decreased gray matter in specific regions
Chronic pain is associated with global and local changes in gray matter density
Morphological changes are specific for chronic pain type and reflect clinical properties of the condition
Evidence for reversal after cessation of pain
Conclusions from structural studies
Chronic pain as emotional learning and memory
Apkarian et al 2010
Pain chronification is not simply a consequence of the pain being experienced repeatedly over a sustained time period.
Cortico-striatal and cortrico-limbic brain circuitry may be directly involved in the development and maintenance of chronic pain.
From acute to chronic pain (the clinical dilemma)
Acute pain
Chronic pain
Only a fraction (~ 5%) of subjects who experience an acute painful injury continue to develop chronic pain
No consistent behavioral, psychological or neurobiological factors can predict transition to chronic pain
To localize brain regions showing anatomical and functional changes
Sub-acute pain
A single intense episode of back pain lasting 4-16 weeks and no prior back pain for at least one year
CBP is one of the 3 most common reasons for healthcare visits
Not more than 10-15% of such patients show associated physical changes
There are no scientifically validated treatments
It is associated with spontaneous pain (main reason for seeking medical care)
Why examine back pain ?
Study design
SBP Persisting (SBPp)(no change in pain)
Recovering (SBPr)(>30% decrease in pain)
Predictors
Consequences
Clinical pain parameters
Longitudinal changes in gray matter density
All subjects SBPp only
SBPp and SBPr did not exhibit gray matter density differences at visit 1
Differences in functional connectivity at visit 1
Right insula (visit 1) Right NAc (visit 1)
mPFC – NAc connectivity predicts transition to chronic pain
Prediction convert the visit 1 mPFC-NAc functional connectivity into quartiles (each category defined by z(r) change of 0.17)
Conclusions from longitudinal study
Persistent pain is associated with early mPFC-NAc coupling that is sustained over one year
mPFC – NAc functional connectivity may be a suitable marker for the development of chronic pain
Anatomical and functional changes were observed as early as 16 weeks after injury
Interventions should not only target the classical pain pathways, but also brain regions involved in motivation and emotion processing
Acknowledgments
A Vania ApkarianJaveria HashmiLejian Huang
Alex BariaBogdan PetreSara Berger
Souraya TorbayMarivi Centeno
Ali MansourKristina Hermmann
Amelia MutsoElle Parks