title: Distracting attention in phobic postural vertigo normalizes leg muscle activity and balance.
abstract: OBJECTIVE
  To examine the triggering causes of inadequate neuromuscular regulation of posture and subjective imbalance in patients with phobic postural vertigo (PPV), a subtype of functional dizziness.
  
  
  METHODS
  Postural performance was assessed by center-of-pressure displacements and surface EMG of lower-limb muscles (the tibialis anterior and soleus) in 10 patients with PPV and 10 healthy controls under 4 stance conditions: standing with eyes open or closed and with or without an additional cognitive dual task. The level of muscle cocontraction and the characteristics of open- and closed-loop postural control were analyzed.
  
  
  RESULTS
  At baseline (i.e., standing with eyes open without dual task), patients exhibited increased muscle cocontractions (p = 0.003), which were further associated with increased open-loop diffusion activity (p = 0.022) and a lowering of the primary feedback threshold for closed-loop control (p = 0.003). However, postural performance of patients improved considerably and normalized to that of healthy controls when performing an additional dual task.
  
  
  CONCLUSIONS
  PPV is characterized by a dissociation of subjective postural instability and objectively maintained balance capabilities. The dual-task effects on balance in patients with PPV indicate that this dissociation might result from an increased attention to postural adjustments at baseline, which is normally required only during demanding balance situations. This internal focus on balance control promotes an inappropriate neuromuscular regulation of posture, with increased muscle cocontractions, higher short-term body sway, and an oversensitivity to external stimuli. However, if patients are distracted, muscle cocontractions and balance control normalize. Such distraction may therefore be an effective coping strategy for preventing PPV attacks in susceptible patients.
authors.affiliation: From the German Center for Vertigo and Balance Disorders (M.W., T.B., R.S.), Institute for Clinical Neurosciences (T.B.), and Department of Neurology (R.S.), University of Munich, Germany. Max.Wuehr@med.uni-muenchen.de.
authors.forename: Max
authors.initials: M
authors.lastname: Wuehr
authors.affiliation: From the German Center for Vertigo and Balance Disorders (M.W., T.B., R.S.), Institute for Clinical Neurosciences (T.B.), and Department of Neurology (R.S.), University of Munich, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Brandt
authors.affiliation: From the German Center for Vertigo and Balance Disorders (M.W., T.B., R.S.), Institute for Clinical Neurosciences (T.B.), and Department of Neurology (R.S.), University of Munich, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Schniepp
mesh_terms: D000328:Adult; D001289:Attention Deficit Disorder with Hyperactivity / Q000209:etiology*; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D006801:Humans; D007866:Leg / Q000294:innervation*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010698:Phobic Disorders / Q000150:complications*; D004856:Postural Balance / Q000502:physiology*; D014717:Vertigo / Q000150:complications*