Alexithymie - ein aktuelles Update aus klinischer, neurophysiologischer und entwicklungspsychologischer Sicht

Neurofunctional differences and similarities between persistent postural-perceptual dizziness and anxiety disorder

INTRODUCTION

Persistent postural-perceptual dizziness (PPPD) (ICD-11) and anxiety disorders (ANX) share behavioural symptoms like anxiety, avoidance, social withdrawal, hyperarousal, or palpitation as well as neurological symptoms like vertigo, stance and gait disorders. Furthermore, previous studies have shown a bidirectional link between vestibulo-spatial and anxiety neural networks. So far, there have been no neuroimaging-studies comparing these groups.

OBJECTIVES

The aim of this explorative study was to investigate differences and similarities of neural correlates between these two patient groups and to compare their findings with a healthy control group.

METHODS

63 participants, divided in two patient groups (ANX = 20 and PPPD = 14) and two sex and age matched healthy control groups (HC-A = 16, HC-P = 13) were included. Anxiety and dizziness related pictures were shown during fMRI-measurements in a block-design in order to induce emotional responses. All subjects filled in questionnaires regarding vertigo (VSS, VHQ), anxiety (STAI), depression (BDI-II), alexithymia (TAS), and illness-perception (IPQ). After modelling the BOLD response with a standard canonical HRF, voxel-wise t-tests between conditions (emotional-negative vs neutral stimuli) were used to generate statistical contrast maps and identify relevant brain areas (pFDR < 0.05, cluster size >30 voxels). ROI-analyses were performed for amygdala, cingulate gyrus, hippocampus, inferior frontal gyrus, insula, supramarginal gyrus and thalamus (p ≤ 0.05).

RESULTS

Patient groups differed from both HC groups regarding anxiety, dizziness, depression and alexithymia scores; ratings of the PPPD group and the ANX group did differ significantly only in the VSS subscale 'vertigo and related symptoms' (VSS-VER). The PPPD group showed increased neural responses in the vestibulo-spatial network, especially in the supramarginal gyrus (SMG), and superior temporal gyrus (STG), compared to ANX and HC-P group. The PPPD group showed increased neural responses compared to the HC-P group in the anxiety network including amygdala, insula, lentiform gyrus, hippocampus, inferior frontal gyrus (IFG) and brainstem. Neuronal responses were enhanced in visual structures, e.g. fusiform gyrus, middle occipital gyrus, and in the medial orbitofrontal cortex (mOFC) in healthy controls compared to patients with ANX and PPPD, and in the ANX group compared to the PPPD group.

CONCLUSIONS

These findings indicate that neuronal responses to emotional information in the PPPD and the ANX group are comparable in anxiety networks but not in vestibulo-spatial networks. Patients with PPPD revealed a stronger neuronal response especially in SMG and STG compared to the ANX and the HC group. These results might suggest higher sensitivity and poorer adaptation processes in the PPPD group to anxiety and dizziness related pictures. Stronger activation in visual processing areas in HC subjects might be due to less emotional and more visual processing strategies.

Factorial structure of the 20-item Toronto Alexithymia Scale in a large sample of somatoform patients

Although a strong association between alexithymia and somatization has been postulated in numerous studies, no systematic study has investigated the psychometric properties of the 20-item Toronto Alexithymia Scale (TAS-20) in a sample of patients with somatoform disorder yet. The purpose of this study was to ensure a valid assessment by the German version of the TAS-20 in somatoform samples. We investigated whether the original three-factor model proposed by Bagby et al. (1994a), which is widely used in clinical research and practice, is replicable in a large sample of somatoform patients (n=806). Using confirmatory factor analysis (CFA) the goodness-of-fit of the originally proposed factor structure was compared to three factor models generated with exploratory factor analysis (EFA) and other factorial solutions derived from the literature. Our results demonstrate that the original three-factor model is not replicable in somatoform patients. Instead, the four-factor model by Franz et al. (2001b) described the data best. However, none of the models met all criteria of confirmatory factor analysis. Our results indicate that the three-factor model is not robust in the German version of the TAS-20. At this state of research we recommend to use the TAS-20 sum-score as a measure of alexithymia in somatoform patients in clinical practice.