Chronic Back Pain May Shrink the Brain!
Scientists Link Long-Lasting Pain With Reduced Levels of Gray Matter
A recent study published in The Journal of Neuroscience has revealed
that people who suffer from chronic back pain (CBP) for one year may
experience a reduction in the brain’s gray matter equivalent to the
amount lost by the average person in 10 to 20 years of normal aging.1
The study is believed to be the first of its kind to show brain
morphometric abnormalities in chronic pain.
Also found in the spinal cord, “gray matter” refers to the darker-
colored tissue of the brain, which is composed of the bodies of
neurons. In the brain, the gray matter includes structures such as
the cerebral cortex, the thalamus, the basal ganglia, and the outer
layers of the cerebellum. Gray matter is considered by many to be
the “thinking” center of the brain, and is responsible for functions
such as memory and information processing.
In the study, investigators compared 26 CBP patients with 26 matched
normal volunteers. The CBP patients experienced unrelenting pain for
one year, “primarily localized to the lumbosacral region including
buttocks and thighs, with or without pain radiating to the leg.” Of
those with CBP, 55 percent had musculoskeletal diagnoses, 20 percent
had pure radiculopathy, and 26 percent had a combination of
musculoskeletal and radiculopathic pain. CBP patients were divided
into neuropathic and non-neuropathic subtypes, with neuropathic
patients experiencing significant radiculopathy, with or without the
presence of musculoskeletal pain.
The normal decrease in neocortical gray matter volume was found to be
2.8 cm3 (0.5%) per year in both groups. After adjusting for age and
gender factors, the investigators found that the resultant gray
matter volume loss was 663 ± 27 cm3 in the control subjects and 590 ±
28 cm3 in the CBP patients, reflecting an 11 percent decrease in gray
matter volume for those with CBP. CBP patients with sciatica had the
largest decrease in gray matter. In addition, the more years someone
had chronic back pain, the more loss of gray matter they suffered.
Interestingly enough, the authors found that the “mean gray matter
volume was not different between neuropathic (nuCBP) and non-
neuropathic (non-nuCBP) subtypes.”
From their findings, the authors arrived at several conclusions:
“The role of the brain in chronic pain conditions remains
speculative. Our results imply that chronic back pain (CBP) is
accompanied by brain atrophy and suggest that the pathophysiology of
chronic pain includes thalamocortical processes.
“Our studies show that CBP (sustained for six months) is accompanied
by abnormal brain chemistry, mainly a reduction in the N-acetyl-
aspartate-creatine ratio in the prefrontal cortex, implying neuronal
loss or dysfunction in this region and reduced cognitive abilities on
a task that implies abnormal prefrontal processing.
“Our results demonstrate regionally specific reduced gray matter in
patients with CBP. At the whole-brain level, this reduction is
related to pain duration, regionally depends on multiple pain related
characteristics, and is more severe in the neuropathic sub-type.
“Given that normal whole-brain gray matter atrophy is 0.5% per year
of aging and that atrophy caused by CBP is 5-11%, the magnitude of
brain gray matter atrophy caused by CBP is equivalent to 10-20 years
of aging. However, this analogy only holds for the overall magnitude,
because the regional specificity of atrophy in CBP is distinct from
that seen with aging.”
While this is the first study to show brain morphometric
abnormalities in chronic pain, it is not the only study of
morphometry in pain conditions. Another study conducted in 2003
looked at migraine patients and found no significant differences. 2
Perhaps even more interesting was the revelation that “only 18% of
whole-brain matter variance could be explained by pain duration.” The
authors note that most of the whole-brain atrophy in CBP
patients “cannot be accounted for by the measured pain
characteristics. ” The authors suggest that this may imply “genetic
and experiential predispositions contributing to the observed
atrophy.”
While this study opens the door for significant speculation, it tends
to generate more questions than it answers. From a chiropractic
standpoint, it is easy to see why chronic back pain can cause
additional symptoms beyond those that would be considered mechanical
in nature. These findings most certainly serve as a serious warning
to patients with back pain to seek care as soon as possible in order
to prevent the condition from becoming chronic.
While there will likely be a number of studies that follow up on
these findings, chiropractic researchers should explore the
possibility of communicating with these authors in an effort to
better understand the details of their methodology and findings. This
is an area of research in which chiropractic could test the impact of
musculoskeletal pain, spinal joint function and the subluxation.
References
1. Apkarian AV, Sosa Y, Sonty S, et al. Chronic back pain is
associated with decreased prefrontal and thalamic gray matter
density. The Journal of Neuroscience, Nov. 17, 2004 24(46):10410-
10475.
2. Matharu MS, Good CD, May A, et al. No change in the structure
of the brain in migraine: a voxel-based morphometric study. Eur J
Neurol 2003;10:53-57.
Contributed by: Dr. Aaron on August 29, 2007 · Filed under: portland oregon chiropractic ·
