The goal of this study is to develop a prognostic score for ischemic posterior circulation strokes, based on our previous work on with the ASTRAL scores (Acute STroke Registry and Analysis of Lausanne) on overall stroke prognosis, intracranial occlusion, recanalization and stroke recurrences. The main question it aims to answer is the modified Rankin score in 3 months after the event.

Participants will be patients with acute ischemic stroke of the posterior circulation with mRS priot to event <3. All the data will be collected retrospectively from patients included in the ASTRAL registry between January 2003 and December 2021. The ASTRAL registry will be used as the derivation cohort of the score. Demographics, acute glucose, NIHSS score and acute imaging of each participant will be used from the derivation cohort in order to create an integer-based prognostic score. After internal validation, we plan to validate the score in external stroke registries to show its validity.

Inclusion Criteria:

• Isolated posterior circulation strokes based on clinical or/and imaging evidence.
• Arriving within 24h at hospital since last proof of good health.

Exclusion Criteria:

• no available data for 3 months modified Rankin Score
• modified Rankin Score≥3 prior the event

The participants included in this study are exclusively patients with acute ischemic stroke of the posterior circulation arriving at the hospital within 24h since last proof of good health. These patients must have a modified Rankin Score <3 prior the event and available data concerning: age, NIHSS, glucose levels at admission, mRS prior to event and 3 months after the event and acute phase imaging characteristics (CT and/or MRI) including large vessel occlusion, leukoaraiosis and ASPECTS score from the acute CT scan.