Abstract
Dyspnea is the impairing, cardinal symptom patients with asthma repeatedly experience over the course of the disease. However, its accurate perception is also crucial for timely initiation of treatment. Reduced perception of dyspnea is associated with negative treatment outcome, but the underlying brain mechanisms of perceived dyspnea in patients with asthma remain poorly understood. We examined whether increasing disease duration in fourteen patients with mild-to-moderate asthma is related to structural brain changes in the insular cortex and brainstem periaqueductal grey (PAG). In addition, the association between structural brain changes and perceived dyspnea were studied. By using magnetic resonance imaging in combination with voxel-based morphometry, gray matter volumes of the insular cortex and the PAG were analysed and correlated with asthma duration and perceived affective unpleasantness of resistive load induced dyspnea. Whereas no associations were observed for the insular cortex, longer duration of asthma was associated with increased gray matter volume in the PAG. Moreover, increased PAG gray matter volume was related to reduced ratings of dyspnea unpleasantness. Our results demonstrate that increasing disease duration is associated with increased gray matter volume in the brainstem PAG in patients with mild-to-moderate asthma. This structural brain change might contribute to the reduced perception of dyspnea in some patients with asthma and negatively impact the treatment outcome.
Highlights
Dyspnea, which is a multidimensional respiratory sensation containing affective and sensory aspects [1,2,3,4], is the impairing and threatening cardinal symptom millions of patients with asthma repeatedly experience over the course of the disease [5,6]
By using functional magnetic resonance imaging we previously demonstrated that patients with mild-to-moderate asthma reported reduced affective unpleasantness of resistive load induced dyspnea when compared to healthy controls [26]
Using voxel-based morphometry, the present study shows that longer duration of asthma was associated with increased gray matter volume in the brainstem periaqueductal grey (PAG) in patients with mild-tomoderate asthma
Summary
Dyspnea, which is a multidimensional respiratory sensation containing affective (unpleasantness) and sensory (intensity) aspects [1,2,3,4], is the impairing and threatening cardinal symptom millions of patients with asthma repeatedly experience over the course of the disease [5,6]. The insular cortex is an important multisensory integration area and involved in the processing of various unpleasant bodily signals and of emotions [27,28,29], whereas the PAG plays an important role in the up- and downregulation of pain sensations and in fear and defensive behaviour [30,31,32] We interpreted these previous results as neural habituation to repeated dyspnea experiences over the course of disease that reduces the perceived affective unpleasantness of dyspnea in asthma [26]. We further hypothesized the gray matter volume in these areas to be related to the perception of dyspnea unpleasantness
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