title: Visual pursuit response in the severe disorder of consciousness: modulation by the central autonomic system and a predictive model.
abstract: BACKGROUND
  A visual pursuit response is reportedly observed in ~20-30% of subjects in vegetative state (VS/UWS) and predicts better outcome; it is a key marker of evolution into the minimally conscious state (MCS). The probability of observing a positive response, however, has proven variable during the day, with comparable timing of the minima and maxima in VS/UWS and MCS. We verified if measures of sympathetic/parasympathetic balance are possible independent variables on which the occurrence of a pursuit response could depend and be predicted.
  
  
  METHODS
  Fourteen subjects in VS/UWS and sixteen in MCS for more than one year were studied. A mirror was used to test the pursuit response for a total 231 useful trials. Non-invasive measures of the sympathetic/parasympathetic functional state (Heart rate variability descriptors nuLF and peakLF) used in the study of responsiveness in VS/UWS and MCS subjects were recorded and processed by descriptive statistics and advanced Support Vector Machine (SVM).
  
  
  RESULTS
  A pursuit response was observed in 33% and 78.2% of subjects in VS or MCS, respectively. Incidence was higher at HRV nuLF values in the 20-60 range and peakLF values at 0.06-0.12 Hz (76.6%) and at nuLF values in the 10-60 range and peakLF values at 0.05-0.10 Hz (80.7%) in the VS and MCS, respectively. The SVM generated model confirmed the results in the training leave one out and 10 fold cross validation tests (81% and 81.4%).
  
  
  CONCLUSIONS
  The pursuit response incidence depends to a relevant extent on the sympathetic/parasympathetic balance and autonomic functional state. Extensive monitoring appears advisable.
authors.forename: Francesco
authors.initials: F
authors.lastname: Riganello
authors.forename: Maria D
authors.initials: MD
authors.lastname: Cortese
authors.forename: Giuliano
authors.initials: G
authors.lastname: Dolce
authors.affiliation: Department of Neuroscience, Ophthalmology and Genetics, University of Genova, 3, Largo P, Daneo, 16132 Genova, Italy. wgs@dism.unige.it.
authors.forename: Walter G
authors.initials: WG
authors.lastname: Sannita
mesh_terms: D000328:Adult; D000368:Aged; D001341:Autonomic Nervous System / Q000502:physiology; D005133:Eye Movements / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009039:Motion Perception / Q000502:physiology*; D018458:Persistent Vegetative State / Q000175:diagnosis* / Q000503:physiopathology*; D010775:Photic Stimulation / Q000379:methods*; D011237:Predictive Value of Tests; D012720:Severity of Illness Index