Multiple Chemical Sensitivity

Symptoms that patients attribute to the environment when no environmental cause can be identified are known as "idiopathic environmental intolerance" (IEI). IEI is often associated with a major psychological and socio-professional impact. Specific diagnostic tools and evidence-based treatment programs are still lacking. As a result, IEI patients often feel left behind by physicians and public health policies.
A number of environmental agents are singled out by IEI sufferers, including chemicals (cleaning products, tobacco smoke), electromagnetic fields generated by cell phones and base stations, air conditioning and infrasound emitted by wind turbines. Patients hold one or more of these environmental agents responsible for a very wide range of chronic, non-specific physical symptoms such as diffuse pain, fatigue, dizziness, dyspnoea, hot flushes, nausea, tinnitus or palpitations, but also cognitive symptoms such as loss of memory or concentration. However, the medical examination of IEI patients shows no evidence of bodily dysfunction.
Furthermore, numerous exposure studies have shown that environmental agents did not alter the biological parameters of IEI patients, that patients could not reliably distinguish between real and fictitious exposures, and that they only presented symptoms when they thought the exposure was real, whether this was true or not. This suggests that IEI symptoms can be considered "functional", resulting from an alteration in the way the body is felt rather than from injury to the body itself. Recently, several authors including Lemogne and Pitron have proposed a cognitive model of body awareness and more specifically of functional physical symptoms.This model is part of a Bayesian understanding of brain function, which is increasingly seen as a process underlying all perceptual experiences.From this perspective, bodily experiences are the result of probabilistic calculations Two sources of information are integrated, weighted by their reliability (accuracy) with regard to the current context: the body's sensory signals on the one hand (i.e. peripheral nerve inputs) and "priors" about the body on the other (i.e. pre-existing information from previous bodily experiences, beliefs about the body, emotions, etc.). In functional physical symptoms, it has been suggested that priors override the body's sensory signals, thus skewing bodily perception.This would be the consequence of an imbalance between low-precision sensory signals on the one hand, and high-precision priors on the other.
In line with this model, Van den Bergh and Witthöft have proposed an understanding of IEI as arising from a nocebo effect.Here, we propose a research project with patients suffering from IEI to test and validate this Bayesian theoretical model of IEI, the main study C22-19, BELIEFS which is currently recruiting.
This ancillary study, C24-26 BELIEFS-VS, enables us to include a population of healthy volunteers whom we will compare with the IEI patients in the main C22-19 BELIEFS study.

Idiopathic Environmental Intolerance (IEI) denotes a functional disorder represented by heterogeneous symptoms that sufferers attribute to specific environmental agents and for which there may be no solid evidence of an underlying physiological cause.
We are conducting a randomized controlled trial study to compare patients before and after a newly developed cognitive behavioral therapy treatment program for IEI, with respect to behavioral and psychometric variables.
The results of this research project are expected to contribute to advancements in the clinical treatment of IEI, as well as to elaborate on existing theoretical models of IEI.

Background:
Functional somatic disorders (FSD) are frequent in all medical settings and characterized by persistent physical symptoms that cannot be explained by other somatic or psychiatric conditions. In recent decades, a number of different types of functional somatic disorders have been defined, but so far there is no clear explanation for the pathophysiology.
The high prevalence of olfactory problems in some patients with FSD suggests that olfactory symptoms are a potential diagnostic biomarker, especially in patients with multiple chemical sensitivity (MCS).
The olfactory system is a unique sense with direct pathways to the limbic system, which is associated with emotion and mood. The focus on the olfactory system has revealed a significant association of this sense with numerous diseases.
Hypotheses:
Patients with MCS and FSD have normal olfactory tests (normosmic subjects according to TDI score using "sniffing test") but differ in habituation test compared to healthy controls.
MCS and FSD patients have different odour perception processing in the brain as a "fingerprint" of functional somatic disorder compared to healthy controls.
Research plan:
The aim of this parts of the study is to identify specific MRI and paraclinical measures for MCS and BDS. In the first phase, 5 patients with MCS and 5 healthy controls will have a full clinical test of the olfactory system at the Flavour Institute, AU. In addition, they will be scanned (for "fingerprinting") where the investigators expect to find changes in olfactory connectivity similar to those seen in depression. This phase of the study will lead to a conclusion on the exact MR parameters to be used in the main study. In the second phase of the study, 10 patients with MCS, 10 with FSD, and 10 healthy controls will be evaluated using a test battery of questionnaires and paraclinical tests.
Perspectives:
Previous imaging studies have focused on pain stimulation paradigms, rest-state fMRI, and DTI, but the olfactory system may be the "missing link" in identifiying a quantitative candidate in terms of whole-brain computational modeling and could potentially be used as a "fingerprint" in diagnosis and treatment monitoring.