Symptoms in IBS occur either because of abnormalities of intestinal motility or because of abnormalities of sensation - or through a combination of the two.
It is easy therefore to imagine how violent contractions or spasm of muscle surrounding the intestines can give rise to pain.
In normal people, distension of the gut will trigger nerve fibres lining the gut to transmit signals to higher centres in the brain that register pain. In IBS sufferers, it has been proved
that pain is perceived at much lower levels of distension. This is known as the 'hypersensitive gut' or in scientific terms visceral hyperalgesia. It follows that abnormal motility or
contractility of the intestines will lead to areas of distension that will react because of the hypersensitive gut and register the sensation of pain in the higher centres of the
brain
A variety of features that affect function of the central nervous system or brain have now been shown to affect, by virtue of the connections of the brain gut axis, the events described
above at the 'end organ' level. I.e. in the intestines.
On the one hand, this could be caused by psychological factors for example:
stress
anxiety
depression
Or, on the other hand, by psychological trauma such as:
verbal abuse
physical abuse
emotional abuse
sexual abuse
By virtue of the Brain Gut Axis interconnections, these factors can or will affect function at the 'end organ' level of the intestines. Importantly, it has been shown that IBS patients have
an increased incidence of psychological disturbance and have been exposed to more psychological trauma than the normal population. Moreover, at end organ level, a given amount of stress has
been shown to have a greater adverse effect on intestinal motility and sensation than in non-sufferers.
The modern strategies or treatments that have been developed for IBS reflect researchers understanding of the important role that the brain gut axis plays in causing symptoms. Consequently,
in considering treatment of the different variants of IBS, a concept of centrally and end organ targeted treatment has been developed.
Such centrally targeted treatments could include a variety of therapies to counter the influence of psychological factors of stress, anxiety and depression and psychological
stress on 'end organ' function:
These might include:
physiological explanation of symptom generation
various forms of counselling
simple relaxation therapy
gut-focused hypnotherapy
cognitive behavioural therapy
use of antidepressants
End organ therapy might also involve exploring dietary triggers, prescribing a properly balanced fibre intake for patients with constipation, prescribing anti diarrheoral drugs for bowel
frequency, prescribing smooth muscle relaxants (anti spasmodics) when pain is thought to be due to muscle spasm and specifically targeted pain killers when pain is thought to be due to the
hypersensitive gut.
It must be appreciated that end organ and central therapies are not naturally exclusive and can be used in sequence and combinations.
We and other IBS researchers have identified a number of variants of IBS and as far as central therapy is
concerned, the same central factors can influence the brain gut axis in all these different variants of IBS. This leads us to recommend that patients with any one of the different variants
should be considered on an individual basis and the indications for central targeted therapy (if any) defined specifically for that individual.
In contrast, end organ therapy can be generalised for the different variants of IBS as these variants have been described based on common end organ events that result in consistent symptom
clusters
IBS ResearchUpdate.org Current Page:The
Brain Gut Axis
