ICM+: a versatile software for assessment of CSF dynamics

ICM+ software was introduced into the Cerebrospinal Fluid (CSF) Dynamics Laboratory, Addenbrooke's Hospital, Cambridge, UK, in 2003. Since then 1,447 constant rate infusion tests and 123 overnight ICP monitoring sessions (using intraparenchymal bolt) were performed. Various configurations were used: ICP only (identification of CSF dynamics model and overnight ICP monitoring with analysis of compensatory reserve and B waves); ICP and arterial pressure (ABP; analysis of the pressure reactivity index); ICP, ABP and transcranial Doppler blood flow velocity (for assessment of cerebral autoregulation); ICP, ABP and near-infrared spectroscopy (for analysis of the fluctuation of cerebral blood volume); ICP, sagittal sinus pressure and jugular vein pressure (in patients with idiopathic intracranial hypertension to assess the hydrodynamic consequences of cerebral venous sinus stenosis). To assess vascular factors of hydrocephalus a combination of CSF infusion study with PET-CBF studies was performed. The software contains a database of the shunts tested in the Cambridge Shunt Evaluation Laboratory, aiding shunt assessment in vivo in the case of possible underdrainage or overdrainage. The software also enables the digital recording of data, ready for post-hoc manual or batch analysis, the creation of virtual signals (such as critical closing pressure, cerebral compliance etc.) and analysis of their dependency on primary modalities. A collected database of cases and signals forms a powerful reference tool in the investigation and understanding of the complex pathophysiology of hydrocephalus.