title: Quantitative motor assessment of muscular weakness in myasthenia gravis: a pilot study.
abstract: BACKGROUND
  Muscular weakness in myasthenia gravis (MG) is commonly assessed using Quantitative Myasthenia Gravis Score (QMG). More objective and quantitative measures may complement the use of clinical scales and might detect subclinical affection of muscles. We hypothesized that muscular weakness in patients with MG can be quantified with the non-invasive Quantitative Motor (Q-Motor) test for Grip Force Assessment (QGFA) and Involuntary Movement Assessment (QIMA) and that pathological findings correlate with disease severity as measured by QMG.
  
  
  METHODS
  This was a cross-sectional pilot study investigating patients with confirmed diagnosis of MG. Data was compared to healthy controls (HC). Subjects were asked to lift a device (250 and 500 g) equipped with electromagnetic sensors that measured grip force (GF) and three-dimensional changes in position and orientation. These were used to calculate the position index (PI) and orientation index (OI) as measures for involuntary movements due to muscular weakness.
  
  
  RESULTS
  Overall, 40 MG patients and 23 HC were included. PI and OI were significantly higher in MG patients for both weights in the dominant and non-dominant hand. Subgroup analysis revealed that patients with clinically ocular myasthenia gravis (OMG) also showed significantly higher values for PI and OI in both hands and for both weights. Disease severity correlates with QIMA performance in the non-dominant hand.
  
  
  CONCLUSIONS
  Q-Motor tests and particularly QIMA may be useful objective tools for measuring motor impairment in MG and seem to detect subclinical generalized motor signs in patients with OMG. Q-Motor parameters might serve as sensitive endpoints for clinical trials in MG.
authors.affiliation: NeuroCure Clinical Research Center, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany. sarah.hoffmann@charite.de.|Department of Neurology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany. sarah.hoffmann@charite.de.
authors.forename: Sarah
authors.initials: S
authors.lastname: Hoffmann
authors.affiliation: NeuroCure Clinical Research Center, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany. jana.siedler@charite.de.
authors.forename: Jana
authors.initials: J
authors.lastname: Siedler
authors.affiliation: NeuroCure Clinical Research Center, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany. alexander.brandt@charite.de.
authors.forename: Alexander U
authors.initials: AU
authors.lastname: Brandt
authors.affiliation: NeuroCure Clinical Research Center, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany. sophie.piper@charite.de.|Centrum für Schlaganfallforschung Berlin (CSB), Klinik für Neurologie, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany. sophie.piper@charite.de.
authors.forename: Sophie K
authors.initials: SK
authors.lastname: Piper
authors.affiliation: NeuroCure Clinical Research Center, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany. siegfried.kohler@charite.de.|Department of Neurology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany. siegfried.kohler@charite.de.
authors.forename: Siegfried
authors.initials: S
authors.lastname: Kohler
authors.affiliation: George-Huntington-Institute, Technology-Park, Johann-Krane Weg 27, 48149, Muenster, Germany. c.sass@asklepios.com.|Department of Neurology, Asklepios Klinikum Harburg, Eißendorfer Pferdeweg 52, 21075, Hamburg, Germany. c.sass@asklepios.com.
authors.forename: Christian
authors.initials: C
authors.lastname: Sass
authors.affiliation: NeuroCure Clinical Research Center, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany. friedemann.paul@charite.de.|Department of Neurology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany. friedemann.paul@charite.de.
authors.forename: Friedemann
authors.initials: F
authors.lastname: Paul
authors.affiliation: George-Huntington-Institute, Technology-Park, Johann-Krane Weg 27, 48149, Muenster, Germany. ralf.reilmann@ghi-muenster.de.|Department of Radiology, Universitätsklinikum Münster, Albert-Schweitzer Campus 1, 48149, Muenster, Germany. ralf.reilmann@ghi-muenster.de.|Department of Neurodegenerative Diseases and Hertie-Institute for Clinical Brain Research, University of Tuebingen, Hoppe-Seyler Str. 3, 72076, Tuebingen, Germany. ralf.reilmann@ghi-muenster.de.
authors.forename: Ralf
authors.initials: R
authors.lastname: Reilmann
authors.affiliation: NeuroCure Clinical Research Center, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany. andreas.meisel@charite.de.|Department of Neurology, Charité - Universitätsmedizin Berlin, Charitéplatz 1, 10117, Berlin, Germany. andreas.meisel@charite.de.
authors.forename: Andreas
authors.initials: A
authors.lastname: Meisel
mesh_terms: D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D005260:Female; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D053581:Muscle Strength Dynamometer; D018908:Muscle Weakness / Q000175:diagnosis* / Q000503:physiopathology*; D009157:Myasthenia Gravis / Q000503:physiopathology*; D010865:Pilot Projects