title: High NIHSS values predict impairment of cardiovascular autonomic control.
abstract: OBJECTIVE
  Stroke is frequently associated with autonomic dysfunction, which causes secondary cardiovascular complications. Early diagnosis of autonomic imbalance prevents complications, but it is only available at specialized centers. Widely available surrogate markers are needed. This study tested whether stroke severity, as assessed by National Institutes of Health Stroke Scale (NIHSS) scores, correlates with autonomic dysfunction and thus predicts risk of autonomic complications.
  
  
  METHODS
  In 50 ischemic stroke patients, we assessed NIHSS scores and parameters of autonomic cardiovascular modulation within 24 hours after stroke onset and compared data with that of 32 healthy controls. We correlated NIHSS scores with parameters of total autonomic modulation (total powers of R-R interval [RRI] modulation; RRI standard deviation [RRI-SD], RRI coefficient of variation), parasympathetic modulation (square root of the mean squared differences of successive RRIs, RRI-high-frequency-powers), sympathetic modulation (normalized RRI-low-frequency-powers, blood pressure-low-frequency-powers), the index of sympatho-vagal balance (RRI-LF/HF-ratios), and baroreflex sensitivity.
  
  
  RESULTS
  Patients had significantly higher blood pressure and respiration, but lower RRIs, RRI-SDs, RRI coefficient of variation, square root of the mean squared differences of successive RRIs, RRI-low-frequency-powers, RRI-high-frequency-powers, RRI-total powers, and baroreflex sensitivity than did controls. NIHSS scores correlated significantly with normalized RRI-low-frequency-powers and RRI-LF/HF-ratios, and indirectly with RRIs, RRI-SDs, square root of the mean squared differences of successive RRIs, RRI-high-frequency-powers, normalized RRI-high-frequency-powers, RRI-total-powers, and baroreflex sensitivity. Spearman-Rho values ranged from 0.29 to 0.47.
  
  
  CONCLUSIONS
  Increasing stroke severity was associated with progressive loss of overall autonomic modulation, decline in parasympathetic tone, and baroreflex sensitivity, as well as progressive shift toward sympathetic dominance. All autonomic changes put patients with more severe stroke at increasing risk of cardiovascular complications and poor outcome. NIHSS scores are suited to predict risk of autonomic dysregulation and can be used as premonitory signs of autonomic failure.
authors.affiliation: University of Erlangen-Nuremberg, Department of Neurology, Schwabachanlage 6, D-91054 Erlangen, Germany. max.hilz@uk-erlangen.de
authors.forename: Max Josef
authors.initials: MJ
authors.lastname: Hilz
authors.forename: Sebastian
authors.initials: S
authors.lastname: Moeller
authors.forename: Aynur
authors.initials: A
authors.lastname: Akhundova
authors.forename: Harald
authors.initials: H
authors.lastname: Marthol
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Pauli
authors.forename: Philipp
authors.initials: P
authors.lastname: De Fina
authors.forename: Stefan
authors.initials: S
authors.lastname: Schwab
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001342:Autonomic Nervous System Diseases / Q000209:etiology* / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009316:National Institutes of Health (U.S.); D009460:Neurologic Examination; D012720:Severity of Illness Index; D020521:Stroke / Q000150:complications* / Q000503:physiopathology*; D014481:United States