UoM administered thesis: Doctor of Medicine

  • Authors:
  • Tarig Algladi


Background: Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder (FGID) which can be defined as chronic, relapsing visceral pain with bloating associated with change in bowel habit. It affects up to 10-15% of the adult population in the UK and is more common in females. The cost of IBS in terms of health care utilisation is substantial, exceeding £45.6 million per year in the UK alone, yet its pathophysiology is incompletely understood. Visceral pain is the main and most difficult symptom to manage in IBS and many IBS female sufferers compare it to labour pain in its severity. Modulating visceral pain in healthy volunteers and IBS patients is therefore an important research area. Non-invasive magnetic stimulation may play a crucial role in this respect. Aim:The aim of this study is to ascertain whether non-invasive repetitive magnetic stimulation applied to the motor cortex and/or lumbosacrum can modulate gastrointestinal pain originating from the anorectum. Methods:Participants: 16 healthy volunteers and 10 IBS patients aged 18 and above were included in the study.Questionnaires: Healthy volunteers and IBS patients were asked to complete anxiety and depression questionnaire and IBS patients were requested to fill in an IBS severity questionnaire.Motor measurements in healthy subjects: Single-pulse lumbosacral magnetic stimulation (LSMS) was applied to the lumbosacral area for the anal sphincter where the largest motor evoked potential (MEP) amplitude response was detected. Single-pulse transcranial magnetic stimulation (TMS) was then performed at the pre-determined resting motor thresholds (RMT) for the anal sphincter and the hand.Sensory measurements in healthy subjects and IBS patients: Electrical stimulation was used to assess the changes in sensory and pain thresholds in the anorectal area. The subjects were asked to score the pain intensity using five-point categorical rating scales. In addition they were asked to describe the pain experienced using a shortened form of the McGill Pain Questionnaire. Intervention: Healthy volunteers received 6 paradigms of magnetic stimulation in a randomised order i.e. 3 repetitive LSMSs (1 Hz, 10 Hz and sham) and 3 repetitive TMSs (1 Hz, 10 Hz and sham) to investigate their modulatory effects on visceral sensitivity and to determine which of these interventions is most effective. The most effective active interventions (1 Hz rLSMS and 10 Hz rTMS) together with one sham were then trialled in a randomised fashion on IBS patients.Post intervention: Motor excitabilities were repeated at 30 min after each intervention. The assessment of sensory and pain thresholds at anal sphincter and rectum were done immediately, 30 and 60 min after each intervention. Results:Application of 1 Hz rLSMS led to alterations of anal sphincter motor excitabilities and resulted in a significant increase in the amplitude of lumbosacal-anal motor evoked potentials (MEPs) in healthy volunteers recorded at 30 min post intervention. In healthy volunteers, 1 Hz rLSMS and 10 Hz rTMS caused a significant increase in the rectal pain thresholds experienced immediately, 30 and 60 min after each intervention. 10 Hz rLSMS and 1 Hz rTMS only led to a significant rise in rectal pain thresholds immediately after their application. Furthermore, there was a significant increase in the rectal pain thresholds immediately, 30 and 60 min following 1 Hz rLSMS and 10 Hz rTMS in IBS patients. Conclusion:The application of magnetic stimulation to the cortical and lumbosacral areas to modulate visceral pain is a new concept, which reduced rectal sensitivity to painful stimuli and offers a much needed new approach in the management of abdominal pain in patients with IBS.


Original languageEnglish
Awarding Institution
Award date1 Aug 2012