Cerebral Blood Flow, Autoregulation and Vascular Reactivity in Normal Pressure Hydrocephalus: a systematic review

Normal pressure hydrocephalus is one of the few remediable causes of decline in gait and cognitive function in the ageing population. The roles of the cerebral circulation including haemodynamic reserve and cardiovascular co-morbidity in the pathogenesis, management and prognostication of NPH remain ill-defined. In this systematic review, we have updated Owler & Pickard’s review of 2001 ¹ to examine• whether there are changes in global and regional CBF that are specific to NPH and its clinical manifestations?• whether levels of global and regional CBF are appropriately coupled to cerebral metabolism and/or low enough to equate to ongoing cerebral ischaemia?• whether any changes in global or regional CBF are predictive of outcome after CSF drainage, both temporary and permanent (shunting)?• whether global and regional cerebrovascular autoregulation and reactivity are more sensitive predictors of outcome and reversibility of symptoms in response to both temporary and permanent CSF drainage than baseline rCBF?• whether changes in resistance to CSF outflow, whole brain compliance, local tissue stress and loss of brain tissue volume relate to CBF and disordered cerebrovascular autoregulation and reactivity? Whether any changes in global or regional CBF are the cause or effect (‘chicken and the egg’) of iNPH?• whether a trial is warranted that combines assessments of haemodynamic reserve, CSF outflow resistance and response to temporary CSF drainage?