The Vision, Aphasia, Neglect (VAN) assessment is a specialized screening tool used rapidly in the pre-hospital environment, often by emergency medical services (EMS) personnel. Its purpose is to quickly identify patients experiencing the most severe types of strokes, which require time-sensitive and specialized medical intervention. By focusing on three distinct neurological deficits, the VAN assessment helps emergency teams triage patients efficiently. This screening method is highly sensitive to strokes caused by a blockage in one of the brain’s major arteries.
How the VAN Assessment is Performed
The VAN assessment begins with a simple check for motor weakness, typically asking the patient to hold both arms out straight for a short period, looking for any drift or inability to lift one side. If no weakness is observed, the patient is generally considered VAN negative for a Large Vessel Occlusion, and the assessment is complete. The presence of any arm weakness, even a mild drift, triggers the next phase of the assessment, which examines the three core components: Vision, Aphasia, and Neglect.
The Vision check (V) involves testing for a visual field cut, where the patient cannot see in a specific quadrant of their vision, or for new double vision. EMS providers may test the patient’s peripheral vision to look for a complete loss of sight on one side. The Aphasia check (A) assesses the patient’s ability to use and understand language, which is distinct from slurred speech. This typically involves asking the patient to name two common objects, repeat a simple phrase, and follow basic commands.
The final component, Neglect (N), checks for a lack of awareness of one side of the body or environment. This can manifest as a forced gaze, where the patient’s eyes are deviated toward one side, or an inability to feel simultaneous touch on both sides of the body. If a patient exhibits arm weakness along with a positive finding in any one of the V, A, or N categories, they are considered “VAN positive.”
Interpreting a Positive Result
A positive result on the VAN assessment carries immediate diagnostic implications. A positive VAN finding—arm weakness plus any one of the Vision, Aphasia, or Neglect deficits—is strongly indicative of a Large Vessel Occlusion (LVO) stroke. These three specific cortical signs are neurologically linked to the large areas of the brain supplied by major arteries, such as the middle cerebral artery. The presence of these combined deficits suggests a large territory of the brain is being deprived of blood flow.
The VAN assessment functions as an efficient screening tool to prioritize patient transport and hospital resource mobilization, rather than providing a final diagnosis. Studies have demonstrated a high degree of accuracy for the VAN tool in detecting LVO. This accuracy means the assessment is highly effective at ruling in the presence of a severe stroke requiring specialized intervention. A positive result immediately signals to the receiving hospital that the patient likely has a blockage in a major vessel and may be a candidate for clot retrieval procedures.
The Urgency of Large Vessel Occlusion
A Large Vessel Occlusion (LVO) refers to a blockage in one of the major, proximal arteries supplying blood to the brain, such as the internal carotid artery or the M1 segment of the middle cerebral artery. These large vessels are responsible for nourishing extensive regions of brain tissue. Their sudden occlusion causes a severe form of ischemic stroke, accounting for a significant portion of all acute ischemic strokes.
The severity of LVO strokes stems directly from the volume of brain tissue that rapidly becomes starved of oxygen and nutrients. Without intervention, these blockages lead to severe disability and high mortality rates. This condition embodies the concept that “time is brain,” as every minute without blood flow causes significant neuronal death. The clinical signs of Vision, Aphasia, or Neglect that result in a positive VAN assessment are direct evidence of this widespread cortical dysfunction caused by the major blockage. The urgent response triggered by a positive VAN aims to minimize permanent neurological damage by restoring blood flow quickly.
Immediate Medical Response and Next Steps
Once EMS providers identify a patient as VAN positive, the immediate response is rapid transport to a facility equipped for advanced stroke care. This often means bypassing smaller hospitals for direct transport to a Comprehensive Stroke Center (CSC) or a hospital with equivalent neuro-interventional capabilities. Pre-arrival notification allows the CSC stroke team to mobilize resources before the ambulance arrives. This crucial step reduces the time between arrival and definitive treatment, which is paramount for LVO patients.
Upon arrival at the Comprehensive Stroke Center, the patient is rushed for immediate brain imaging, bypassing the traditional emergency room process. This sequence prioritizes a Computed Tomography (CT) scan without contrast to rule out bleeding, followed quickly by a CT Angiography (CTA) to visualize the blood vessels and confirm the LVO location.
The definitive treatment pathway for confirmed LVO is mechanical thrombectomy. This procedure involves an interventional neuroradiologist physically removing the clot using specialized tools threaded through a catheter. Although clot-busting medication (intravenous thrombolysis) may be administered immediately, mechanical thrombectomy offers the best chance for a good functional outcome.