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Intracranial pressure dynamics in patients with severe head injury: A mathematical study

The time pattern of intracranial pressure (ICP) was examined in five patients with severe head injury using an original mathematical model of craniospinal dynamics. With this model we simulated the ICP response to the injection or withdrawal of small amount of fluid into the cranial cavity, and the ICP pulse amplitude sincronous with the cardiac beat. Results of our simulations indicate that, in two patients, the time pattern of ICP can be explained through a balance between CSF production rate, CSF reabsorption rate and the storage capacity of the craniospinal system. However, in the other three patients, the ICP time pattern exhibited an anomalous response following fluid injection or fluid withdrawal. The model explains these responses imputing them to active changes in cerebral blood volume induced by regulatory mechanisms. In conclusion, our study supports the idea that the ICP pattern cannot be imputed only to CSF dynamics and craniospinal compliance. In several cases the interaction between ICP and cerebral hemodynamics must be also taken into account to gain sufficient understanding of the biomechanical factors leading to ICP changes in patients with severe head injury.