Table 1

Tools and technologies for the pre-hospital triage of acute ischemic stroke

Pre-hospital tool	Potential indication	Examples	Advantages	Disadvantages
Clinical prediction scales	Identify patients who are likely to have large vessel occlusion based on clinical symptoms	Los Angeles Motor Scale (LAMS), Rapid Arterial oCclusion Evaluation (RACE) scale	Simple, fast, easy to use with brief training Reasonably high specificity for LVO for instruments like LAMS/RACE	Overall limited sensitivity for LVO, risk of missing out many patients who stand to benefit from EVT Stroke represents only a minority of EMS calls; continuous maintenance of training may be required
Mobile stroke units (MSU), on-board CT scan	Distinguish ischemic stroke from hemorrhagic stroke by ambulance-based neuroimaging	Mostly in Germany and the USA	The only system that currently allows safe pre-hospital thrombolysis by definitively ruling out hemorrhage Can detect LVO with on-board angiography90 91	Expensive investment in equipment and personnel (on-board CT tech and physician or similar provider for giving thrombolysis)
Transcranial Doppler ultrasonography (TCD)	Identifying LVO via high vessel velocities and emboli detection	Lucid Robotic System	Sensitivity 91% and specificity 85% for identifying LVO per conference presentation92	Cumbersome Operator-dependent when not robotic Some patients do not have an adequate bone window
Electroencephalography (EEG)	Identify major strokes by confirming substantial loss of neuronal activity ipsilaterally	AlphaStroke, BrainScope One	Amenable to rapid quantitative interpretation at point-of-care Brainscope studied in traumatic brain injury with 92% sensitivity for abnormal CT93	Can have high background noise especially in an ambulance Non-specific findings are common in various pathologies; Brainscope specificity 51% for abnormal CT in TBI93
Brain accelerometry	Identifying LVO94	BrainPulse	Has been studied in vasospasm (81% sensitivity) and traumatic brain injury95	High background noise may interfere with detection of LVO signal
Microwaves	Rule out hemorrhage	EMTensor, EMvision, Strokefinder	Useful in ruling out large hemorrhagic strokes96	Cannot rule out small bleeds Application limited by poor penetration of microwaves into brain
Near-infrared spectroscopy	Identifying severe stroke by visualizing brain tissue oxygenation	Infrascanner 2000	Can detect large ischemia, hemorrhage Sensitivity of 88% and specificity of 91% for detecting hematomas >3.5 mL within 2.5 cm of the brain surface97	Limited field or depth of penetration
Radiofrequency pulses	Potential to identify hemorrhage	Sense Diagnostics	Can detect ICH expansion (pre-clinical studies)98 99	Maturing technology, unclear application
Volumetric impedance phase-shift spectroscopy (VIPS)	Identify severe stroke by detecting small changes and asymmetries in electrical properties	Cerebrotech Visor	Wireless visor on the head Sensitivity 93% and specificity 87% to identify severe stroke100 (broadly defined as LVO or NIHSS >6 or ICH >60 mL or large established stroke	Data have come from a derivation study to create the VIPS selection algorithm—validation is required in pre-hospital settings Technology relies on sending/receiving radio waves which can be modified by implants like plates/screws or metallic hair extensions

EMS, emergency medical services; EVT, endovascular thrombectomy; ICH, intracerebral hemorrhage; LVO, large vessel occlusion ; NIHSS, National Institutes of Health Stroke Scale; TBI, traumatic brain injury.