Brain responses to visceral and somatic stimuli in patients with irritable bowel syndrome with and without fibromyalgia

OBJECTIVE

Symptoms of irritable bowel syndrome (IBS) and fibromyalgia (FM) commonly coexist. We hypothesized that one of the mechanisms underlying this comorbidity is increased activation of brain regions concerned with the processing and modulation of visceral and somatic afferent information, in particular subregions of the anterior cingulate cortex (ACC).

METHODS

Regional cerebral blood flow (rCBF) was assessed in age-matched female IBS (n = 10) and IBS + FM (n = 10) subjects using H(2)(15)O positron emission tomography during noxious visceral (rectal) and somatic pressure stimuli.

RESULTS

GI symptom severity was significantly higher in the IBS patients compared with the IBS + FM patients (p < 0.05). In addition, IBS + FM patients rated somatic pain as more intense than their abdominal pain (p < 0.05). Whereas the somatic stimulus was less unpleasant than the visceral stimulus for IBS patients without FM, the somatic and visceral stimuli were equally unpleasant in the IBS + FM group. Group differences in regional brain activation were entirely within the middle subregion of the ACC. There was a greater rCBF increase in response to noxious visceral stimuli in IBS patients and to somatic stimuli in IBS + FM patients.

CONCLUSION

Chronic stimulus-specific enhancement of ACC responses to sensory stimuli in both syndromes may be associated with cognitive enhancement of either visceral (IBS) or somatic (IBS + FM) sensory input and may play a key pathophysiologic role in these chronic pain syndromes.

Sex-related differences in IBS patients: central processing of visceral stimuli

BACKGROUND & AIMS

Women have a higher prevalence of irritable bowel syndrome (IBS) and possible differences in response to treatment, suggesting sex-related differences in underlying pathophysiology. The aim of this study was to determine possible sex-related differences in brain responses to a visceral and a psychological stressor in IBS.

METHODS

Regional cerebral blood flow measurements using H(2)(15)O positron emission tomography were compared across 23 female and 19 male nonconstipated patients with IBS during a visceral stimulus (moderate rectal inflation) and a psychological stimulus (anticipation of a visceral stimulus).

RESULTS

In response to the visceral stimulus, women showed greater activation in the ventromedial prefrontal cortex, right anterior cingulate cortex, and left amygdala, whereas men showed greater activation of the right dorsolateral prefrontal cortex, insula, and dorsal pons/periaqueductal gray. Similar differences were observed during the anticipation condition. Men also reported higher arousal and lower fatigue.

CONCLUSIONS

Male and female patients with IBS differ in activation of brain networks concerned with cognitive, autonomic, and antinociceptive responses to delivered and anticipated aversive visceral stimuli.

Long-term sensitization of primary afferents in adult rats exposed to neonatal colon pain

We have previously shown that colon irritation (CI) in neonates results in chronic visceral hypersensitivity in adult rats, associated with central neuronal sensitization in the absence of identifiable peripheral pathology. The purpose of this study is to assess the relative contribution of peripheral mechanisms to chronic visceral hypersensitivity by examining the changes in responses of primary afferents at thoracolumbar (TL) and lumbosacral (LS) spinal segments to graded colorectal distension (CRD). Afferent discharges were recorded at the cut distal ends of spinal dorsal roots (DRs) in adult control and CI rats. We found that: (1). the average threshold of activation of LS afferents decreased significantly in CI rats; (2). the responses of TL and LS afferents to CRD in CI rats were significantly greater than those in control; (3). the spontaneous activity of LS afferents in CI rats was significantly stronger than that in control; (4). in CI rats, the average responses to graded CRD of LS DRs were significantly higher than those of TL DRs; and (5). the number of both LS DRs and TL DRs activated by CRD in CI rats was significantly larger than control. In summary, the results show that chronic visceral hypersensitivity is associated with peripheral sensitization, as well as central sensitization. TL visceral afferents projecting seem to be more involved in the processing of sensitized nociceptive input from the colon than acute nociceptive input. However, LS afferents seem to be equally important in both sensitized and acute pain states.

Central representation of visceral and cutaneous hypersensitivity in the irritable bowel syndrome

We have previously shown that irritable bowel syndrome (IBS) patients have both visceral and cutaneous hyperalgesia. The neural mechanisms of these forms of hyperalgesia were further characterized by comparing cortical processing of both rectal distension (35, 55mmHg) and cutaneous heat nociceptive stimuli (foot immersion in 45 and 47 degrees C water bath) in IBS patients and in a group of healthy age/sex-matched controls. Our approach relied on functional magnetic resonance imaging neuroimaging analyses in which brain activation in age/sex-matched control subjects was subtracted from that found in IBS patients. These analyses revealed that both rectal distension and cutaneous heat stimuli evoked greater neural activity in several brain regions of IBS patients in comparison to age/sex-matched control subjects. These include those related to early stages of somatosensory processing (e.g. thalamus, somatosensory cortex) as well as those more related to cognitive and affective processing (insular, anterior cingulate, posterior cingulate, prefrontal cortex). Thus, our results support the hypothesis that hyperalgesia of IBS is manifested by increased somatosensory processing at all cortical levels. This was found to be the case not only for visceral hyperalgesia but also for cutaneous heat hyperalgesia, a likely form of secondary hyperalgesia. Furthermore, visceral and heat hyperalgesia were accompanied by increased neural activity within the same brain structures. These results support the hypothesis that visceral and cutaneous hyperalgesia in IBS patients is related to increased afferent processing in pathways ascending to the brain rather than to selectively increased activity at higher cortical levels (e.g. limbic and frontal cortical areas).

Postinfectious irritable bowel syndrome

A small but significant subgroup of patients with irritable bowel syndrome (IBS) report a sudden onset of their IBS symptoms after a bout of gastroenteritis. Population-based surveys show that although a history of neurotic and psychologic disorders, pain-related diseases, and gastroenteritis are all risk factors for developing IBS, gastroenteritis is the most potent. More toxigenic organisms increase the risk 11-fold, as does an initial illness lasting more than 3 weeks. Hypochondriasis and adverse life events double the risk for postinfective (PI)-IBS and may account for the increased proportion of women who develop this syndrome. PI-IBS is associated with modest increases in mucosal T lymphocytes and serotonin-containing enteroendocrine cells. Animal models and some preliminary human data suggest this leads to excessive serotonin release from the mucosa. Both the histologic changes and symptoms in humans may last for many years with only 40% recovering over a 6-year follow-up. Celiac disease, microscopic colitis, lactose intolerance, early stage Crohn's disease, and bile salt malabsorption should be excluded, as should colon cancer in those over the age of 45 years or in those with a positive family history. Treatment with Loperamide, low-fiber diets, and bile salt- binding therapy may help some patients. Serotonin antagonists are logical treatments but have yet to be evaluated.

An Asia-Pacific, double blind, placebo controlled, randomised study to evaluate the efficacy, safety, and tolerability of tegaserod in patients with irritable bowel syndrome

BACKGROUND

Tegaserod has been shown to be an effective therapy for the multiple symptoms of irritable bowel syndrome (IBS) in Western populations. However, little information is available regarding the use of tegaserod in the Asia-Pacific population.

AIMS

To evaluate the efficacy, safety, and tolerability of tegaserod versus placebo in patients with IBS from the Asia-Pacific region.

PATIENTS

A total of 520 patients from the Asia-Pacific region with IBS, excluding those with diarrhoea predominant IBS.

METHODS

Patients were randomised to receive either tegaserod 6 mg twice daily (n=259) or placebo (n=261) for a 12 week treatment period. The primary efficacy variable (over weeks 1-4) was the response to the question: "Over the past week do you consider that you have had satisfactory relief from your IBS symptoms?" Secondary efficacy variables assessed overall satisfactory relief over 12 weeks and individual symptoms of IBS.

RESULTS

The mean proportion of patients with overall satisfactory relief was greater in the tegaserod group than in the placebo group over weeks 1-4 (56% v 35%, respectively; p<0.0001) and weeks 1-12 (62% v 44%, respectively; p<0.0001). A clinically relevant effect was observed as early as week 1 and was maintained throughout the treatment period. Reductions in the number of days with at least moderate abdominal pain/discomfort, bloating, no bowel movements, and hard/lumpy stools were greater in the tegaserod group compared with the placebo group. Headache was the most commonly reported adverse event (12.0% tegaserod v 11.1% placebo). Diarrhoea led to discontinuation in 2.3% of tegaserod patients. Serious adverse events were infrequent (1.5% tegaserod v 3.4% placebo).

CONCLUSIONS

Tegaserod 6 mg twice daily is an effective, safe, and well tolerated treatment for patients in the Asia-Pacific region suffering from IBS and whose main bowel symptom is not diarrhoea.

Brain-gut interaction in irritable bowel syndrome

Abdominal pain occurs commonly in irritable bowel syndrome. The mechanism of pain is likely to be either peripheral or central sensitization of gut nerves or aberrant brain processing. Functional brain techniques are now allowing the study of brain-gut interactions.

[Sensory sensitization, part II: Pathophysiology in dysfunctional disorders. Understanding the inner life of the nerve pathways may explain hitherto unexplainable symptoms]

This article is based on a vast clinical experience from patients presenting with widespread pain syndromes as well as dysfunctional symptoms from inner organs. A literature survey has been performed. Allodynia and hyperalgesia that partly explain the fibromyalgia and local myalgia syndromes seem to arise from a pathophysiological process of nociceptive sensitisation. It is proposed that the concept of "sensory sensitisation dysfunctional disorders" be applied to conditions like bronchial hyperreactivity, Da Costas syndrome, Dercum's disease (Adipositas dolorosa), dry eyes and mouth syndrome, fibromyalgia, gastralgia, globus hystericus, interstitial cystitis, chronic prostatitis, irritable bowel syndrome, photo- and phonosensitivity, rhinitis, tension headache, tinnitus, vestibulitis syndrome. These dysfunctional disorders cannot be satisfactorily explained by presently known pathophysiological models like ongoing inflammatory process, tissue degeneration, fibrosis, blood vessel diseases, tumours, immune reactions, toxic or deficiency conditions, metabolic disturbances. Neurogenic mechanisms also seem to play an important role in the pathophysiology of arthritic conditions, and might be worthwhile to include in forthcoming discussions concerning the aetiology of chronic inflammatory disease.

Novel therapies in the treatment of irritable bowel syndrome

Irritable bowel syndrome (IBS) is characterised by abnormalities in motility, sensation and perception. It is one of the most common conditions encountered in clinical practice, especially by gastroenterologists. Pharmacological treatment of IBS is aimed at the predominant symptom and recent advances in pathophysiology has opened the door to the development of new compounds that target specific receptors. During this review, the most promising investigational and recently approved drugs will be discussed.

A randomized controlled trial of a probiotic, VSL#3, on gut transit and symptoms in diarrhoea-predominant irritable bowel syndrome

AIM

To investigate the effects of a probiotic formulation, VSL#3, on gastrointestinal transit and symptoms of patients with Rome II irritable bowel syndrome with predominant diarrhoea.

METHODS

Twenty-five patients with diarrhoea-predominant irritable bowel syndrome were randomly assigned to receive VSL#3 powder (450 billion lyophilized bacteria/day) or matching placebo twice daily for 8 weeks after a 2-week run-in period. Pre- and post-treatment gastrointestinal transit measurements were performed in all patients. Patients recorded their bowel function and symptoms daily in a diary during the 10-week study, which was powered to detect a 50% change in the primary colonic transit end-point.

RESULTS

There were no significant differences in mean gastrointestinal transit measurements, bowel function scores or satisfactory global symptom relief between the two treatment groups, pre- or post-therapy. Differences in abdominal bloating scores between treatments were borderline significant (P = 0.09, analysis of covariance). Further analysis revealed that abdominal bloating was reduced (P = 0.046) with VSL#3 [mean post- minus pre-treatment score, - 13.7; 95% confidence interval (CI), - 2.5 to - 24.9], but not with placebo (P = 0.54) (mean post- minus pre-treatment score, - 1.7; 95% CI, 7.1 to - 10.4). With the exception of changes in abdominal bloating, VSL#3 had no effect on other individual symptoms: abdominal pain, gas and urgency. All patients tolerated VSL#3 well.

CONCLUSION

VSL#3 appears to be promising in the relief of abdominal bloating in patients with diarrhoea-predominant irritable bowel syndrome. This is unrelated to an alteration in gastrointestinal or colonic transit.

Alterations of brain activity associated with resolution of emotional distress and pain in a case of severe irritable bowel syndrome

BACKGROUND & AIMS

The association of psychosocial disturbances with more severe irritable bowel syndrome (IBS) is well recognized. However, there is no evidence as to how these associations might be mediated. Functional magnetic resonance imaging (fMRI) offers an opportunity to study whether activation of the cingulate cortex, an area involved with the affective and pain intensity coding might be linked to poorer clinical status with IBS. In this case report, we found an association between the severity of a patient's clinical symptoms and psychosocial state, with activation of the cingulate cortex. We also found that clinical and psychosocial improvement was associated with reduced cingulate activation.

METHODS

Observational case report of a young woman observed for 16 years with a history of sexual abuse, psychosocial distress, and functional GI complaints. Psychosocial, clinical, and fMRI assessment was performed when the patient experienced severe symptoms and again 8 months later when clinically improved.

RESULTS

During severe illness, the patient had major psychosocial impairment, high life stress, a low visceral pain threshold, and activation of the midcingulate cortex (MCC), prefrontal area 6/44, and the somatosensory cortex, areas associated with pain intensity encoding. When clinically improved, there was resolution in activation of these 3 areas, and this was associated with psychosocial improvement and an increased threshold to rectal distention.

CONCLUSIONS

Activation of the MCC and related areas involved with visceral pain encoding are associated with poor clinical status in patients with severe IBS and psychosocial distress and appear to be responsive to clinical improvement.

Influence of gender, parity, and caloric load on gastrorectal response in healthy subjects: a barostat study

The gastrocolonic response consists of a prompt increase in colonic tone after a meal. With a barostat and a high compliant air-filled bag, it is possible to measure rectal tone by recording changes in volume at a constant intrabag pressure. The aim of this study was to evaluate the gastrorectal response in males and females as well as the effect of different caloric loads on the gastrorectal response. In 33 volunteers a barostat procedure during basal conditions and after a 600-kcal meal was performed. In 26 volunteers the procedure was repeated with a 1000-kcal meal. A meal response was defined as a decrease in volume of more than 10%. Phasic volume events (PVE) were defined as a 10% decrease in volume of 15-60 sec duration. After a 600-kcal meal, the decrease in volume after 1 hr was 28 +/- 7% (mean +/- SEM, P < 0.001). A meal response was found in 64% of the subjects. Parous females had a diminished meal response compared with nulliparous females (2 +/- 5% and 48 +/- 11%, P < 0.001). After the 600-kcal meal, PVEs increased from 3 to 10/hr (P = 0.001). In the 26 subjects, volume decrease was 40 +/- 9% after the 1000-kcal meal and 20 +/- 7% after the 600-kcal meal (P = 0.28). In the high-calorie meal, 18 subjects (69%) had a response versus 14 (54%) in the low-calorie meal (NS). Enhancing the caloric load of the meal did not increase the amounts of PVEs. In conclusion, a gastrorectal response occurs in 64% of the healthy subjects after a 600-kcal meal. The gastrorectal response can be measured to a similar extent in men and nulliparous women; however, the response is significantly impaired in parous women. This is possibly due to neurogenic damage during childbirth. Increasing the caloric load did not increase the gastrorectal response. Therefore, to study gastrorectal meal response with the barostat, a meal of 600-kcal is sufficient and a correction for parity should be made when results are compared.

Review article: visceral hypersensitivity

Visceral hypersensitivity is highly prevalent in all functional bowel disorders. Most also demonstrate wider patterns of somatic referral of intestinal pain or discomfort. This hypersensitivity may explain the symptoms as the sensitive gut can be more easily provoked by normal or abnormal motor events in the gut. Visceral hypersensitivity may increase during psychosocial stress and during periods of symptom exacerbation, although this requires confirmation. Pharmacological therapy to reduce visceral hypersensitivity is now possible using antagonists to neurotransmitters, opening up an exciting new era for the treatment of functional gastrointestinal disorders.

The cost-effectiveness of psychotherapy and paroxetine for severe irritable bowel syndrome

BACKGROUND & AIMS

Psychotherapy and antidepressants are effective in patients with severe irritable bowel syndrome (IBS), but the cost-effectiveness of either treatment in routine practice has not been established.

METHODS

Patients with severe IBS were randomly allocated to receive 8 sessions of individual psychotherapy, 20 mg daily of the specific serotonin reuptake inhibitor (SSRI) antidepressant, paroxetine, or routine care by a gastroenterologist and general practitioner. Primary outcome measures of abdominal pain, health-related quality of life, and health care costs were determined after 3 months of treatment and 1 year later.

RESULTS

A total of 257 subjects (81% response rate) from 7 hospitals were recruited; 59 of 85 patients (69%) randomized to psychotherapy and 43 of 86 (50%) of the paroxetine group completed the full course of treatment. Both psychotherapy and paroxetine were superior to treatment as usual in improving the physical aspects of health-related quality of life (SF-36 physical component score improvement, 5.2 [SEM, 1.26], 5.8 [SEM, 1.0], and -0.3 [SEM, 1.17]; P < 0.001), but there was no difference in the psychological component. During the follow-up year, psychotherapy but not paroxetine was associated with a significant reduction in health care costs compared with treatment as usual (psychotherapy, $976 [SD, $984]; paroxetine, $1252 [SD, $1616]; and treatment as usual, $1663 [SD, $3177]).

CONCLUSIONS

For patients with severe IBS, both psychotherapy and paroxetine improve health-related quality of life at no additional cost.

Irritable bowel syndrome subtypes according to bowel habit: revisiting the alternating subtype

BACKGROUND

Disturbed bowel habit, diarrhoea or constipation is a key manifestation of irritable bowel syndrome (IBS). In some patients, diarrhoea and constipation alternate, giving rise to the so-called alternating subtype.

AIMS

To assess IBS subtype breakdown (constipation (C-IBS), diarrhoea (D-IBS) or alternating (A-IBS)) according to the Rome II criteria and patients' self-assessment, the predominance in the alternating subtype (i.e. constipation, diarrhoea or neither), and the medical and personal impact, including health-related quality of life (HRQoL), of the different IBS subtypes.

SUBJECTS AND METHODS

Two thousand individuals selected randomly to represent the general population were classified as potential IBS subjects (n = 281) or as non-potential IBS subjects (n = 1719) according to a validated questionnaire. Bowel habit classification was determined using the Rome II IBS supportive symptoms.

RESULTS

Among 201 subjects meeting the Rome I criteria, 15% presented with D-IBS, 44% presented with C-IBS, 19% presented with A-IBS, and 22% presented with normal bowel habit. Among the 63 subjects meeting the Rome II criteria, 23% presented with A-IBS. According to the subjects' self-assessment, of those meeting the Rome I criteria, 16% considered themselves to have D-IBS, 66% to have C-IBS and 18% to have A-IBS. In subjects meeting the Rome II criteria, 24% considered themselves to have A-IBS. Among those classified with A-IBS by the Rome II criteria, most considered themselves to be constipated. Regardless of the subtype self-classification, most subjects reported a normal frequency of bowel movements. Clinical manifestations in A-IBS were very similar to those of C-IBS but with the added presence of defecatory urgency. Abdominal discomfort/pain and frequency of visits to physicians were greater in the A-IBS subtype than in the other two IBS subtypes. HRQoL was affected similarly in all IBS subtypes.

CONCLUSIONS

Approximately one-quarter of subjects with IBS belong to the A-IBS subtype by the Rome II criteria, although the majority consider themselves to be constipated; indeed, clinical manifestations are more akin to the C-IBS subtype than to the D-IBS subtype. Abdominal discomfort/pain and frequency of visits to physicians are greater in the A-IBS subtype than in the other two IBS subtypes, while HRQoL is impaired similarly.

Symptoms across the menstrual cycle in women with irritable bowel syndrome

OBJECTIVE

The purpose of this study was to describe the patterns of GI, somatic, and psychological symptoms across the menstrual cycle in women with irritable bowel syndrome, and to determine whether symptoms differed by oral contraceptive use or predominant bowel pattern.

METHODS

A daily diary was used to assess symptoms across one menstrual cycle. Repeated-measures analysis of covariance, controlling for age and body mass index, was used to compare patterns of symptoms across the menstrual cycle by oral contraceptive use and predominant bowel pattern (diarrhea, constipation, alternating). Data from control women are presented for comparison.

RESULTS

For somatic and psychological as well as GI symptoms, women with irritable bowel syndrome had higher symptom severity than did controls. Women with irritable bowel syndrome using oral contraceptives had lower cognitive, anxiety, and depression symptoms (p < 0.05, but not significant after multiple comparison adjustment), but no differences were seen for most symptoms of irritable bowel syndrome. All symptoms except diarrhea were highest in the alternating group and lowest in the diarrhea group, with the constipation group either intermediate or close to the alternating group. This pattern was significant after multiple comparisons adjustment for GI symptoms, and trending toward significance (p < 0.05, but not significant after multiple comparison adjustment) for menstrual, sleep, and cognitive symptoms. The strongest menstrual cycle effect was seen in somatic and menstrual symptoms. The pattern of symptoms over the menstrual cycle did not differ by predominant bowel pattern or by oral contraceptive use.

CONCLUSIONS

Many of the symptoms examined differed by predominant bowel pattern and menstrual cycle phase, not just the GI symptoms. The menstrual cycle variation was similar regardless of oral contraceptive use or predominant bowel pattern.

The rectum: a window to irritable bowel syndrome?

This report summarizes current concepts and information gathered to date about the rectum in the irritable bowel syndrome (IBS) that were presented at the 10th meeting of IBiS Club held in Leuven, Belgium. A working group of experts in the field of IBS discussed whether the rectum or the whole colon is the better site to test in IBS patients and provided suggestions for a number of areas where further advances are required.