Published on: June 18, 2012
by Roger Dobson for The Daily Mail:
For those of you deliberating over whether to have a hip replacement, perhaps this latest finding will convince you: the op could boost your memory and even protect you from dementia.
Studies have found that the brains of people living with chronic pain from conditions such as osteoarthritis shrink at a dramatically faster rate than those without pain.
This accelerated rate, say researchers, may lead to faster mental decline.
Researchers at North Western University in the U.S. compared MRI (magnetic resonance imaging) brain scans from 26 people with chronic back pain for more than a year with those of a healthy comparison group.
Results showed that the back pain sufferers had up to 11 per cent less grey matter (brain cells) than the other group.
This is equivalent to the amount of grey matter normally lost in ten to 20 years.
The reduced brain volume was related to pain duration, with a 1.3 cubic centimetre loss of grey matter for every year of chronic pain.
In another U.S. study, neurosurgeons studied brain scans of people with complex region pain syndrome — a long-term condition usually triggered by an injury — and found a similar decline in grey matter, as well as changes in white matter, which carries messages between neurons.
Again, the changes in patients’ brains were related directly to the length and intensity of their pain.
‘Studies suggest that some chronic pain patients will develop clinical syndromes of poor attention span, reduced cognitive abilities, and possibly dementia,’ says U.S. pain specialist Dr Forest Tennant.
‘Chronic pain may produce a loss of brain tissue and all practising doctors must immediately begin understanding the ramifications of this finding.’
With one in five adults having a chronic pain disorder and one in four adults suffering from back pain at some time in their lives, these findings could indeed have huge implications.
But the good news is that treating the pain with joint replacement surgery seems to reverse the damage to the brain.
Orthopaedic surgeons and neuroscientists at Hamburg University investigated 32 patients with chronic pain caused by hip osteoarthritis.
As in the previous studies, they found a reduction in grey matter in a number of areas of the brain.
Tests six weeks and four months after hip replacement surgery found patients were free of pain, but also showed an increase in grey matter in all four areas of the brain where there had previously been a decline.
That, say the researchers, suggests the brain changes are in response to suffering chronic pain, and not the other way around.
‘As grey matter decrease is at least partly reversible when pain is successfully treated, we suggest the grey matter abnormalities found in chronic pain do not reflect brain damage, but rather are a reversible consequence which normalises when the pain is adequately treated,’ they say.
Work at Oxford University has found similar effects.
Two studies have examined structural changes within the brain in response to having painful osteoarthritis of the hip and found changes identified pre-operatively were reversed after successful surgery that led to pain relief.
In one Oxford study, published in Nature Review Neurology, significant differences were seen in grey matter volume between healthy patients and those with painful hip arthritis.
Areas of the thalamus — which plays a role in alertness, for example — in patients with chronic pain showed reduced grey matter volume.
Nine months after surgery, the loss had been reversed to levels seen in healthy controls.
So why does chronic pain have such an effect on our memory?
One suggestion is that long-term pain, such as arthritis, causes the central nervous system to reorganise itself, in a phenomenon known as ‘neural plasticity’.
The parts of the brain that deal with pain get bigger and more active to deal with the onslaught to the body, meaning other parts — such as those involved with memory — get smaller to compensate.
It’s also thought pain could cause changes in the emotional areas of the brain, which might explain why people with chronic pain are more likely to suffer from depression.
‘The more we understand about pain, the more we recognise how much the brain can change as a result of plasticity,’ says Dr Nicholas Silver, consultant neurologist at the Walton Centre for Neurology and Neurosurgery in Merseyside.
‘Parts of the brain may shrink and other parts may expand their function to work most effectively after damage.
‘What these studies do not tell us is whether the nerves shrink in redundant areas or whether they degenerate and die.
‘For a long time we have recognised that people suffering from chronic pain experience problems with their concentration and memory.
‘It has often been assumed such changes purely reflect disturbances in their mood and will reverse once the pain condition has been appropriately treated.
‘These recent studies have preliminary data to show the problem may be more concerning and suggest patients with chronic pain should possibly best be treated early and vigorously to avoid potential long-term problems with cognition and memory.’
Dr Paul Strutton, senior lecturer in neurophysiology at Imperial College London, adds: ‘There is now good evidence to show grey matter declines in people with chronic pain.
‘We think the plasticity that occurs in the brain is as a result of the pain and not a cause of it.
‘The big question is whether this loss of nerve cells in the grey matter can be reduced or even reversed by treating the pain.’
Research into the area continues: a clinical trial is starting this month at North Western University in which 60 men and women with knee osteoarthritis will be given either a drug called duloxetine, widely used to treat pain, or a sugar pill.
The researchers will use scans to assess effects of pain on grey matter over 16 weeks.
But Dr Silver says the effect of pain on memory may not be limited to long-term conditions.
‘It is of interest that some episodic pain conditions are associated with transient loss of cognition.
‘In patients with chronic migraine, we often see problems associated with memory and concentration, for example difficulty finding words.
‘When patients have had frequent migraine for a long time, they often have a number of other problems related to fatigue, dizziness, sleep, and memory.
‘Once treated, most of these non-headache phenomena improve, but memory often appears to remain problematic, despite the fact the headaches have improved.’
He adds: ‘One has to a be a bit cautious interpreting these snapshot data, as studies will be needed over a duration of time to actually prove the brain atrophies in certain areas in those suffering chronic pain.’
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