How the brain region tells the colon what to do

Many IBS patients with diarrhea-predominant bowel habits show enhanced colonic motor activity in the form of so-called high amplitude giant contractions. These are clusters of contractions that start in the right side of the colon and move rapidly towards the rectosigmoid, thereby propelling colonic contents into the rectum. An enhanced number of these contractions, resulting in overfilling of the rectum may be responsible for the severe, and sometimes uncontrollable urgency that patients experience. One of the major signals that tells the colon to generate these contractions are bursts of activity in the vagus nerve.

In a recent study, using functional brain imaging to identify specific brain regions activated in anticipation of rectal discomfort, UCLA Neuroenteric Disease Program researchers identified a brain region that is activated in IBS patients, but not in healthy control subjects. This brain region normally regulates the balance between stimulatory (vagal) and inhibitory (sympathetic nerves) signals to the colon. In IBS patients that suffer from diarrhea, only the expectation of discomfort arising from the colon resulted in shift of this balance towards the stimulatory side. These findings demonstrate for the first time a specific abnormality within the nervous system of patients with diarrhea- predominant IBS which may be responsible for the enhanced colonic motor activity.

How the brain pays attention to the body

The majority of patients with fibromyalgia also suffer from IBS symptoms, while a smaller number of IBS patients have symptoms of fibromyalgia (FM). The cause for the enhanced sensitivity of patients to either visceral (IBS) or somatic (FM) stimuli remains poorly understood.

UCLA Neuroenteric Disease Program investigators have studied patients with IBS and those with symptoms of both IBS and FM using functional brain imaging techniques. Patients received both visceral stimuli (rectal distension) and somatic stimuli (localized pressure applied to the body surface) while brain activity was monitored. Activation of dorsolateral prefrontal cortex was found in IBS patients during visceral stimuli, a brain region which is primarily concerned with the interpretation and modulation of sensory stimuli. This brain region determines which event the person will pay the greatest attention to. This is partly accomplished by assessing the intensity of the stimulus, its relevance for the individual at a given moment, and its previous experience. In contrast to the patients suffering from IBS alone, patients who also had symptoms of FM activated this brain region during somatic stimuli.

These findings suggest that an important mechanism underlying the hypersensitivity to visceral and somatic stimuli in patients with IBS and FM is the activation of brain regions which are able to amplify and focus a person’s attention to a particular part of the body.

How 5 sessions of class instructions can reduce symptoms and increase quality of life in IBS patients

It has long been known that ineffective coping styles, lack of understanding of what causes IBS symptoms and anxiety over the future of one's symptoms contribute significantly to the suffering and symptom severity of IBS patients. Individual psychotherapy is usually not effective in addressing these issues.

For the past two years, more than 60 patients have undergone the “IBS Class” offered by the UCLA Neuroenteric Disease Program (see the last edition for a detailed description of the class). An analysis of the outcome of this class on patients’ symptoms and quality of life showed these interesting results: (1) Patients suffering from functional dyspepsia with or without IBS did best, showing significant improvement in abdominal pain, sleep disturbances, mood, and quality of life, (2) Patients with chronic abdominal pain syndromes on the other side, in particular when associated with high severity of symptoms and poor quality of life did not benefit, (3) The improvement in symptoms oberved in the responders was greater than that observed with the best medical treatments currently available, and was maintained for at least 6 months after the class had ended.

These findings clearly demonstrate the effectiveness of the IBS Class for patients with moderate symptom severity in either the form of IBS or functional dyspepsia.

How a new IBS drug may help with your symptoms

Out of the many different approaches that are currently being taken to develop a more effective treatment for IBS symptoms, the modulation of the serotonergic system by either drugs that mimic or antagonize the effects of the neurotransmitter serotonin is one of the most popular. During the past year, a phase II study with one of these antagonists, Alosetron, was performed in many centers around the world, including here at the UCLA Neuroenteric Disease Program.

Analysis of the outcomes of this initial study showed some surprising findings: Significantly more female patients (60%) reported adequate pain relief on the drug when compared to placebo (33%). In addition, the drug significantly improved stool urgency, frequency and consistency in female patients. However, no beneficial effect was observed in male patients.

These encouraging findings have resulted in the go-ahead for a larger study aimed at further corroborating the effectiveness of the drug, before it is eligible for FDA approval.

Interested in participating in a research study? Please call us at (310) 268-3432.