The National Institutes of Health Stroke Scale (NIHSS) is a standardized, objective clinical tool that has become a gold standard in emergency and urgent care services for quantifying the severity of neurological deficits in patients who have suffered a Stroke (AVC), particularly the ischemic type, which is the most common. Although initially developed for research purposes, its application is now fundamental for the rapid and precise assessment of the degree of brain injury. The scale consists of 11 items that evaluate crucial neurological areas such as level of consciousness, visual function, limb motor strength, sensation, and language and speech functions. Each of these items receives a score of 0, indicating normalcy, up to a maximum value that varies according to the severity of the detected alteration. The total NIHSS score is the sum of the values of each item, ranging from 0 to 42. The final score is of paramount importance for clinical decision-making, as the higher the score, the greater the severity of the stroke; for example, scores between 1 and 4 generally indicate a mild stroke, while scores above 21 signal a severe stroke. This score directly guides the patient's eligibility for acute treatments, such as thrombolysis, which requires rapid action. Furthermore, the NIHSS is used to monitor the patient's progress over time, document the therapy's effectiveness, and ensure objective and uniform communication among medical teams, making it an indispensable tool in the modern and agile management of stroke.