Brain activation in fecal storage, defecation and fecal incontinence: a 1,5T fMRI pilot study in healthy volunteers

Fecal incontinence is an impaired ability to control gas or stool. It can be
devastating for the patient and result in social isolation and reduced quality
of life. Reports of the prevalence and incidence of fecal incontinence vary
greatly. A United States household survey states a prevalence of 7.1% of
various degrees of fecal incontinence. Elderly people are affected more often
than younger people. Studies of nursing home and geriatric ward residents show
rates from 10% to 60%.
Sacral neuromodulation (SNM) is a promising treatment for intractable FI that
involves chronic electrical stimulation of the third sacral nerve roots. This
technique was introduced in 1995 by Matzel et al[8] to treat patients with
faecal incontinence. Since then multiple large prospective series have
demonstrated a success rate of 74-86% in patients treated with SNM for fecal
incontinence.
The mechanism responsible for the beneficial effect of SNM is still poorly
understood, but it has been suggested by several authors afferent effects to
the brain are essential.
To clarify the central working mechanisms of SNM in patients with fecal
incontinence an imaging study is proposed to identify changes in brain activity
patterns, defined as BOLD signal intensity increase, after implantation of SNM
in fecal incontinent patients. We hypothesize to find differences in
brain-activation between healthy subjects and fecal incontinent patients after
rectal stimulation, but also between fecal incontinent patients that have a
positive result on SNM and those that have no effect of SNM.
Follow-up of brain changes after SNM implantation is only possible by using
1,5T fMRI-scans. It has been proven that an fMRI-cerebrum at 1.5 Tesla with a
send-receive head-coil is safe in patients with an implanted sacral
neurostimulator. The company manufacturing the neurostimulators (Medtronic bv)
approved this application.
To evaluate the effect of SNM on brain-activity changes, the rectum will be
stimulated by balloon distention to mimic rectal filling stool. The balloon
distention will be achieved by using a GI Solar manometry. Previous studies
have demonstrated that balloon distention combined with 1,5T fMRI-scans is a
good technique for imaging changes in brain-patterns. The proposed study will
be a pilot-study for METC-protocol 152020.
The aim of this pilot-study is to verify these previously published results in
our center due to two reasons: 1) this procedure has never been conducted at
our institute and 2) because a send-receive headcoil must be used for safety
reasons related to the neurostimulators used in the main study.

The purpose of the present study is to verify and optimize the quality of the
MRI-images using balloon dilatation during a 1,5T fMRI-scan with a send/receive
head-coil in healthy subjects in Maastricht University Medical Center.
The primary aim of this study is to verify whether good quality images can be
acquired during a 1,5T fMRI-scan with a send/receive head-coil combined with
balloon dilatation. The secondary aim is to optimize the fMRI-settings so the
obtained results from the main study have the highest resolution possible.

In this observational pilot study we will evaluate 1,5T fMRI-scans imaging
during balloon distention. To properly assess the quality of the images,
regions of interest (ROIs) are defined, based on the ROIs of the main study
(METC 152020). ROIs are pre- and postcentral gyrus, thalamus, primary
somatosensory (SI), secondary somatosensory cortex (SII), sensory association
cortex, anterior cingulate cortex (ACC) and the insular cortex.
A Solar GI manometry device will be used to induce rectal filling. To evaluate
and optimize the imaging-quality of brain patterns in this study, we will use a
1.5T fMRI-scanner (MUMC+) with a send-receive head-coil. Using a manometry
device to evaluate changes in brain patterns on fMRI has already been
demonstrated in previous studies.
We choose the sensation of rectal filling and the urge to defecate as our
primary parameters. These primary endpoints are also used in the main study as
most fecal incontinent patients complain of no proper sensation of rectal
filling.

One scan period will take 1 hour and exists of multiple scans:
1. baseline anatomic MRI scan with an empty inflatable balloon in situ
2. multiple fMRI scans during multiple rectal fillings with a computer-driven
GI Solar device up to the threshold of sensation of rectal filling and up to
the urge to defecate.

The potential risks of this study in healthy subjects are due to the fact that
we conduct a 1.5T fMRI-study on patients. Potential adverse events include, but
are not limited to: discomfort due the magnetic field, vertigo with gantry in
motion, metallic taste with gantry in motion, loud noise during the scan,
uncomfortable position during the scan. The balloon catheter used for the GI
Solar-device (which is placed in the control-room) is made of plastic and
latex, so it poses no risks of adverse events during the fMRI-scan.
It is possible that people suffer from vertigo or other complaints of a passing
nature after the scan. It is therefore emphasized that participants bring a
partner for assisting on the travel back home.

The risk of a potential adverse event during the 1.5T fMRI-scan is small for
all participants. The adverse events that can be prevented (loud noise and
uncomfortable position) will be prevented as much as possible by providing
ear-plugs and comfortable pads. The occurrence of any of the other potential
adverse events does not outweigh the information gathered by this study. A
physician and/or technician is always present during the scan-sessions to
ensure maximal care if an adverse event would occur.