Hemodynamic effect of cerebral vasospasm in humans: A modeling study

A mathematical model of cerebral hemodynamics during vasospasm is presented . The model divides arterial hemodynamics into two cerebral territories: wi th and without spasm. It also includes collateral circulation between the t wo territories, cerebral venous hemodynamics, cerebrospinal fluid circulati on, intracranial pressure (ICP) and the craniospinal storage capacity. More over, the pial artery circulation in both territories is affected by cerebr al blood how (CBF) autoregulation mechanisms. In this work, a numerical val ue to model parameters was given assuming that vasospasm affects only a sin gle middle cerebral artery (MCA). In a first stage, the model is used to si mulate some clinical results reported in the literature, concerning the pat terns of MCA velocity, CBF and pressure losses during vasospasm. The agreem ent with clinical data turns out fairly good. In a second stage, a sensitiv ity analysis on some model parameters is performed (severity of caliber red uction, longitudinal extension of the spasm, autoregulation gain, ICP, resi stance of the collateral circulation, and mean systemic arterial pressure) to clarify their influence on hemodynamics in the spastic territory. The re sults suggest that the clinical impact of vasospasm depends on several conc omitant factors, which should be simultaneously taken into account to reach a proper diagnosis. In particular, while a negative correlation between MC A velocity and cross sectional area can be found until CBF is well preserve d, a positive correlation may occur when CBF starts to decrease significant ly. This might induce false-negative results if vasospasm is assessed merel y through velocity measurements performed by the transcranial Doppler techn ique. (C) 1999 Biomedical Engineering Society. [S0090-6964(99)00792-X].