An older definition describes an acute stroke as the first 24 h after symptom onset, a subacute stroke as the phase between day 1 and day 5, and a stroke older than 5 days as chronic [2]. Another definition describes an early hyperacute phase (0–6 h), a late hyperacute phase (6–24 h), an acute phase (1–7 days), as subacute phase (1–3 weeks) and a chronic phase (> 3 weeks) [3].

If you look through the definition, statements [4, 5] and guidelines [6,7,8], you won’t get any wiser. In order to create clear definitions in these papers, mixed terms such as “acute stroke < 6 hours” or “acute stroke < 4.5 hours” are often used. The question is also who should set and name these times in the interdisciplinary competition. In our opinion, it’s actually quite clear: only the imaging.

Due to the individual compensation possibilities for different collaterals and anatomical variants of the patients, one cannot and should not set a fixed time for the stages of the stroke. For example, a recent prospective study found a Diffusion-Weighted Imaging (DWI)-Fluid-Attenuated Inversion Recovery (FLAIR) mismatch in 52.6% of patients between 4.5 and 10 h after symptom onset [9]. This indicates that an active or acute infarction process is ongoing at this time, and under certain circumstances, a thrombectomy might still be considered appropriate.

For this reason, the nomenclature of the phase of a stroke should be strictly based on imaging to accelerate interventions and simplify interdisciplinary communication. We recommend a simple, logical division into three phases: (1) “acute stroke” for the phase when we can detect a mismatch and interventions make sense, (2) “subacute stroke” for the phase in which secondary complications may occur and, if necessary, a decompressive (hemi-) craniectomy can be performed, and (3) the chronic state after stroke in which gliosis zones and scars form.