title: Cerebrovascular time constant in patients suffering from hydrocephalus.
abstract: OBJECTIVE
  We studied possible link between cerebrospinal fluid (CSF) compensation and indices describing pulsatile inflow of cerebral arterial blood.
  
  
  METHODS
  A total of 50 infusion tests performed in patients with symptoms of normal pressure hydrocephalus (NPH) were examined retrospectively. Waveforms of CSF pressure, noninvasive arterial blood pressure (ABP), and transcranial Doppler (TCD) cerebral blood flow velocity (CBFV) were used to estimate relative changes in cerebral arterial compliance (Ca) and cerebrovascular resistance (CVR). Product of Ca and CVR, called cerebral arterial time constant (τ, unit: seconds), was calculated at the baseline and plateau phase of the test and compared with CSF compensatory parameters such as resistance to CSF outflow, elasticity, slope of amplitude-pressure line, and pulse amplitude of CSF pressure.
  
  
  RESULTS
  Neither of CSF compensatory parameters correlated with hemodynamic indices. However, the change in cerebral perfusion pressure (CPP) provoked change in τ (R  =  0.33; P  =  0.017) secondary to a change in CVR (R  =  0.81; P < 0.0001). Changes in CVR and Ca had a reciprocal character (R  =  -0.64; P < 0.0001) with magnitude of variation in CVR (68%) prevailing over magnitude of changes in Ca (49%).
  
  
  CONCLUSIONS
  Hemodynamics of pulsatile inflow of cerebral arterial blood assessed by cerebral arterial time constant is not directly linked to dynamics of CSF circulation and pressure-volume compensation but is sensitive to changes in CPP during infusion test.
authors: Cyrille
authors: C
authors: Capel
authors: Magdalena
authors: M
authors: Kasprowicz
authors: Marek
authors: M
authors: Czosnyka
authors: Olivier
authors: O
authors: Baledent
authors: Piotr
authors: P
authors: Smielewski
authors: John D
authors: JD
authors: Pickard
authors: Zofia
authors: Z
authors: Czosnyka
mesh_terms: D000328:Adult; D000368:Aged; D001921:Brain / Q000098:blood supply*; D002536:Cerebral Arteries / Q000503:physiopathology*; D006439:Hemodynamics; D006801:Humans; D006849:Hydrocephalus / Q000134:cerebrospinal fluid* / Q000503:physiopathology*; D008875:Middle Aged; D055815:Young Adult
keywords: Cerebral blood flow velocity,; Cerebrospinal fluid,; Hydrocephalus,; Infusion test