Dyspnea in Patients with Stiff-Person Syndrome

Background: Stiff-person syndrome (SPS) is a rare autoimmune disorder that leads to progressively worsening stiffness and spasm of thoracic and proximal-limb musculature. Dyspnea has been reported but not analyzed in patients with SPS. Materials and Methods: For this prospective study, 17 patients were recruited from a university-based neurology clinic. History and exam were performed, demographic information collected and available imaging reviewed. Dyspnea was assessed using vertical visual analog scales (VAS), the University of California San Diego Shortness of Breath Questionnaire (UCSD-SOBQ) and dyspnea "descriptors". Standardized assessments of SPS severity were performed by an experienced neurologist. Forced vital capacity (FVC) spirometric analysis was performed on all patients. Results: Fifteen of 17 patients complained of dyspnea, including dyspnea at rest, with exertion, and disturbing sleep. A restrictive pattern was the most common abnormality noted on spirometry. FVC (r = -0.67; P < 0.01) and forced expiratory volume in 1-second (FEV1) (r = -0.76; P < 0.01) percent predicted correlated with dyspnea measured by VAS over the preceding 2 weeks. Pulmonary function did not correlate with UCSB-SOBQ or standardized measures of SPS severity. Conclusions: Dyspnea in SPS is common and occurs at rest with exertion and disturbs sleep. The finding of restrictive physiology and correlation between pulmonary function variables and dyspnea support the hypothesis that thoracic cage constriction by rigidity and/or spasm of the muscles of the trunk causes or contributes to the sensation of dyspnea. The possibility of diaphragmatic involvement requires further study.