Health status in non-dystrophic myotonias: close relation with pain and fatigue

Abstract

To determine self-reported health status in non-dystrophic myotonias (NDM) and its relationship to painful myotonia and fatigue. In a cross-sectional study, 32 NDM patients with chloride and 30 with sodium channelopathies, all off treatment, completed a standardised interview, the fatigue assessment scale (FAS), and the 36-item Short-Form Health Survey (SF-36). Beside formal assessment of pain, assessment of painful or painless myotonia was determined. The domain scores of the SF-36 were compared with Dutch community scores. Apart from the relationship among SF-36 scores and (1) painful myotonia and (2) fatigue, regression analyses in both NDM groups were conducted to determine the strongest determinants of the SF-36 domains general health perception, physical component (PCS) and mental component summary (MCS). All physically oriented SF-36 domains in both NDM groups (P <or= 0.01) and social functioning in the patients with sodium channelopathies (P = 0.048) were substantially lower relative to the Dutch community scores. The patients with painful myotonia (41.9%) scored substantially (P < 0.05) lower on most SF-36 domains than the patients without painful myotonia (58.1%). Fatigued patients (53.2%) scored substantially lower (P <or= 0.01) on all SF-36 domains than their non-fatigued counterparts (46.8%). The regression analysis showed that fatigue was the strongest predictor for the general-health perception and painful myotonia for the physical-component summary. None of the patients showed below-norm scores on the domain mental-component summary. The impact of NDM on the physical domains of patients' health status is substantial, and particularly painful myotonia and fatigue tend to impede their physical functioning.

Fig. 1

a comparison of the mean values of the 36-item Short-Form health survey profiles (SF-36) of the patients with NDM (n = 62) per subtype and the mean values for the Dutch community. b The effect of painful myotonia on the patients’ mean scores on the SF-36 versus the reported means for the Dutch community. c The effect of fatigue on the patients’ mean scores of the SF-36 scores versus the reported mean for the Dutch community. NDM non-dystrophic myotonia. PhF physical functioning; RFPh role functioning physical, RFE role functioning emotional, SF social functioning, BP body pain, MH mental health, Vit vitality, GHP general health perception, PCS physical component summary, MCS mental component summary. *P < 0.05

Fig. 2

Overview of the outcomes of the multivariate regression analyses conducted to establish the variance and strongest predictor of the general health perceptions and the physical component summary in patients with non-dystrophic myotonia