Table 1

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

Pre-hospital toolPotential indicationExamplesAdvantagesDisadvantages
Clinical prediction scalesIdentify patients who are likely to have large vessel occlusion based on clinical symptomsLos 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 scanDistinguish ischemic stroke from hemorrhagic stroke by ambulance-based neuroimagingMostly 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 detectionLucid 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 ipsilaterallyAlphaStroke, 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 accelerometryIdentifying LVO94 BrainPulse
  • Has been studied in vasospasm (81% sensitivity) and traumatic brain injury95

  • High background noise may interfere with detection of LVO signal

MicrowavesRule out hemorrhageEMTensor, 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 spectroscopyIdentifying severe stroke by visualizing brain tissue oxygenationInfrascanner 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 pulsesPotential to identify hemorrhageSense 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 propertiesCerebrotech 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.