Background Age-related sarcopenia may cause physical dysfunction. We investigated the involvement of sarcopenia in dropped head syndrome (DHS). Methods Our study subjects were ten elderly women with idiopathic DHS (mean age 75.1?years, range 55–89). Twenty age- and sex-matched volunteers (mean age 73.0, range 58–83) served as controls. We used a bioelectrical impedance analyzer (BIA) to analyze body composition, including appendicular skeletal muscle mass index (SMI; appendicular lean mass (kg)/(height (m))2). SMI Results Sarcopenia was observed at a high rate in DHS subjects: 70% compared to 25% of healthy controls. Height, weight, BMI, lean mass arm, lean mass leg, axial lean mass, appendicular lean mass, total lean mass, and SMI all had significantly lower values in the DHS group. In particular, total lean mass, lean mass arm, and lean mass trunk were considerably lower in the DHS group. There was no correlation noted between cervical spine alignment and SMI. Conclusions Sarcopenia prevalence was high in the DHS group—70 versus 25% in the control group, suggesting the involvement of sarcopenia in DHS. In particular, axial lean mass and lean mass arm were markedly reduced in the DHS group. DHS is due to significant weakness of the neck extensor group, and chin-on-chest deformity occurs. Until the present, evaluation of DHS has been done using only MRI; no studies have systematically examined skeletal muscle mass. In the present study, muscle mass decrease was noted not only in the neck muscles but also throughout the entire body. Involvement of trunk and upper limb muscles in particular suggests a disuse atrophy of the upper body and spinal muscles. BIA can easily and systemically evaluate skeletal muscle mass. We expect it to contribute to further elucidating the pathogenesis of DHS.
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