Invasive Multimodal Neuromonitoring in Aneurysmal Subarachnoid Hemorrhage: A Systematic Review

Aneurysmal subarachnoid hemorrhage is a devastating disease leaving surviving patients often severely disabled. Delayed cerebral ischemia (DCI) has been identified as one of the main contributors to poor clinical outcome after subarachnoid hemorrhage. The objective of this review is to summarize existing clinical evidence assessing the diagnostic value of invasive neuromonitoring (INM) in detecting DCI and provide an update of evidence since the 2014 consensus statement on multimodality monitoring in neurocritical care.

Three invasive monitoring techniques were targeted in the data collection process: brain tissue oxygen tension (ptiO2), cerebral microdialysis, and electrocorticography. Prospective and retrospective studies as well as case series (≥10 patients) were included as long as monitoring was used to detect DCI or guide DCI treatment.

Forty-seven studies reporting INM in the context of DCI were included (ptiO2: N=21; cerebral microdialysis: N=22; electrocorticography: N=4). Changes in brain oxygen tension are associated with angiographic vasospasm or reduction in regional cerebral blood flow. Metabolic monitoring with trend analysis of the lactate to pyruvate ratio using cerebral microdialysis, identifies patients at risk for DCI. Clusters of cortical spreading depolarizations are associated with clinical neurological worsening and cerebral infarction in selected patients receiving electrocorticography monitoring.

Data supports the use of INM for the detection of DCI in selected patients. Generalizability to all subarachnoid hemorrhage patients is limited by design bias of available studies and lack of randomized trials. Continuous data recording with trend analysis and the combination of INM modalities can provide tailored treatment support in patients at high risk for DCI. Future trials should test interventions triggered by INM in relation to cerebral infarctions.