title: Nonlinear variability of body sway in patients with phobic postural vertigo.
abstract: BACKGROUND
  Subjective postural imbalance is a key symptom in the somatoform phobic postural vertigo (PPV). It has been assumed that more attentional control of body posture and / or co-contraction of leg muscles during standing is used to minimize the physiological body sway in PPV. Here we analyze nonlinear variability of body sway in patients with PPV in order to disclose changes in postural control strategy associated with PPV.
  
  
  METHODS
  Twenty patients with PPV and 20 age-matched healthy subjects (HS) were recorded on a stabilometer platform with eyes open (EO), eyes closed (EC), and while standing on a foam rubber with eyes closed (ECF). Spatio-temporal changes of the center of pressure (CoP) displacement were analyzed to assess the structure of postural variability by computing the scaling exponent α and the sample entropy (SEn) of the time series.
  
  
  RESULTS
  With EO on firm ground α and SEn of CoP displacement were significantly lower in patients (p < 0.001). For more difficult conditions (EC, ECF) postural variability in PPV assimilated to that of HS.
  
  
  CONCLUSIONS
  Postural control in PPV patients differs from HS under normal stance condition. It is characterized by a reduced scaling behavior and higher regularity. These changes in the structure of postural variability might suggest an inappropriate attentional involvement with stabilizing strategies, which are used by HS only for more demanding balance tasks.
authors: Department of Neurology, University of Munich , Munich , Germany ; German Center for Vertigo and Balance Disorders, University of Munich , Munich , Germany.
authors: Roman
authors: R
authors: Schniepp
authors: Max
authors: M
authors: Wuehr
authors: Cauchy
authors: C
authors: Pradhan
authors: Sergej
authors: S
authors: Novozhilov
authors: Siegbert
authors: S
authors: Krafczyk
authors: Thomas
authors: T
authors: Brandt
authors: Klaus
authors: K
authors: Jahn
keywords: DFA; psychogenic; sample entropy; scaling exponent; stance; vertigo
references: Exp Brain Res. 2006 Sep;174(2):256-69
references: 16685508
references: Circulation. 2000 Jun 13;101(23):E215-20
references: 10851218
references: Neurosci Lett. 2000 May 5;285(1):21-4
references: 10788698
references: Neurology. 1997 May;48(5):1161-6
references: 9153437
references: Acta Neurol Scand. 1997 Jan;95(1):23-8
references: 9048981
references: Arch Phys Med Rehabil. 2005 Oct;86(10):2034-40
references: 16213250
references: Proc Natl Acad Sci U S A. 2002 Feb 19;99 Suppl 1:2466-72
references: 11875196
references: Neurology. 1996 Jun;46(6):1515-9
references: 8649539
references: J Gerontol A Biol Sci Med Sci. 2002 Mar;57(3):B115-25
references: 11867648
references: Gait Posture. 2002 Aug;16(1):1-14
references: 12127181
references: Am J Physiol Regul Integr Comp Physiol. 2002 Sep;283(3):R789-97
references: 12185014
references: Neurobiol Aging. 2002 Jan-Feb;23(1):23-6
references: 11755014
references: J Neurophysiol. 1987 Sep;58(3):525-42
references: 3655881
references: J Neurol. 2009 Aug;256(8):1258-62
references: 19363634
references: Gait Posture. 2007 Jun;26(1):128-34
references: 16982195
references: Exp Brain Res. 2007 Jul;181(1):1-11
references: 17401553
references: Med Eng Phys. 2009 Oct;31(8):1023-31
references: 19608447
references: J Neurol. 1994 Feb;241(4):191-5
references: 8195816
references: Can J Physiol Pharmacol. 1981 Jul;59(7):733-47
references: 7032676
references: Exp Brain Res. 2008 Nov;191(3):265-76
references: 18696056
references: J Electromyogr Kinesiol. 2011 Apr;21(2):291-7
references: 20558082
references: Am J Physiol Heart Circ Physiol. 2000 Jun;278(6):H2039-49
references: 10843903
references: Neurosci Lett. 1999 Jan 15;259(3):149-52
references: 10025580
references: Arch Neurol. 1988 Jul;45(7):737-9
references: 3390028
references: J Neuroeng Rehabil. 2010 Jul 30;7:38
references: 20670457
references: Exerc Sport Sci Rev. 2002 Jan;30(1):26-31
references: 11800496
references: Neurobiol Aging. 2002 Jan-Feb;23(1):1-11
references: 11755010
references: Acta Neurobiol Exp (Wars). 2001;61(2):105-12
references: 11512407
references: Hum Mov Sci. 2011 Apr;30(2):203-12
references: 20542347
references: J Anxiety Disord. 2003;17(4):369-88
references: 12826087
references: Chaos. 1995;5(1):82-7
references: 11538314
references: J Exp Psychol Hum Percept Perform. 1999 Jun;25(3):837-51
references: 10385989
references: Nonlinear Dynamics Psychol Life Sci. 2005 Oct;9(4):435-61
references: 16194301
references: Clin Neurophysiol. 2006 Aug;117(8):1692-8
references: 16797231
references: Gait Posture. 2003 Oct;18(2):101-8
references: 14654213
references: J Neurol Neurosurg Psychiatry. 2006 May;77(5):658-64
references: 16614028
references: Arch Otolaryngol Head Neck Surg. 2007 Feb;133(2):170-6
references: 17309987
references: Phys Rev Lett. 1994 Aug 1;73(5):764-767
references: 10057531
references: J Neurol Neurosurg Psychiatry. 1995 Nov;59(5):472-6
references: 8530928