Abstract
Background: Up to 48% of patients with medically unexplained symptoms seen in neurological practice suffer from sensory symptoms, which could be of functional nature or secondary to mental disorders. These patients show high medical care utilization causing elevated health care costs. Despite the high prevalence, little is known about clinical characteristics and pathophysiological mechanisms. For functional disorders such as irritable bowel syndrome a reduction of heart rate variability (HRV) has been shown, suggesting a dysfunction of the autonomic nervous system (ANS). The aim of this study was to investigate psychological data and functional changes of the ANS in patients with medically unexplained sensory symptoms (MUSS). Methods: In this exploratory pilot study, 16 patients (11 females, 31·6 ± 11·9 years) with MUSS, who were recruited at a single tertiary neurological centre, underwent a structured clinical interview (SCID) to evaluate psychiatric comorbidities. Patients and age- and sex-matched healthy volunteers filled in questionnaires, and individual sensory thresholds (perception, pain) were detected by quantitative sensory testing (QST). HRV was assessed at baseline and under three different experimental conditions (tonic pain stimulus, placebo application, cold face test). All tests were repeated after 6-8 weeks. Findings: SCID interviews revealed clinical or subclinical diagnoses of psychiatric comorbidities for 12 patients. Questionnaires assessing somatization, depression, anxiety, and perceived stress significantly discriminated between patients and controls. While there was no difference in QST, reduced ANS reactivity was found in patients during experimental conditions, particularly with regard to vagally-mediated HRV. Interpretation: Our pilot study of neurological patients with MUSS reveals a high prevalence of psychiatric comorbidities and provides evidence for altered ANS function. Our data thus give insight in possible underlying mechanisms for these symptoms and may open the door for a better diagnostic and therapeutic approach for these patients in the future. Funding: No external funding was obtained for this study. Declaration of Interest: All authors declare to have no conflicts of interest. Ethical Approval: Approval for the study was obtained by the Ethics Committee of the medical faculty of Tubingen University (Project No. 765/2015BO2).
Highlights
Unexplained symptoms (MUS) have a high prevalence of up to 49% in primary medical care [1]
Medically unexplained symptoms (MUS) can include functional disorders that exclusively concentrate on a single organic system as well as somatoform disorders which are characterized by several persistent and changing symptoms without sufficient organic origin for at least 2 years
Patients with MUS are often positive for psychiatric diagnoses classified by ICD-10 such as depression or anxiety disorders that only become apparent by elaborate psychological diagnostics and structured clinical interviews [12]
Summary
Unexplained symptoms (MUS) have a high prevalence of up to 49% in primary medical care [1]. Patients with MUS often suffer from the insecurity that an organic origin of their symptoms could be missed and complicate the communication with their treating physicians [2]. Unexplained sensory symptoms (MUSS) are among the most common neurological presentations of MUS next to non-epileptic seizures and functional motor symptoms [8, 9]. A precise definition of MUS and MUSS is difficult because standardized terms for this heterogenic group of patients are missing. MUS can include functional disorders that exclusively concentrate on a single organic system (e.g., irritable bowel syndrome) as well as somatoform disorders which are characterized by several persistent and changing symptoms without sufficient organic origin for at least 2 years. The symptomatic overlap of these definitions makes it difficult for treating physicians to differentiate between the terms
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