A systematic review of interventions for acalculia following a stroke or brain injury.

Acalculia, an acquired deficit in numerical skills, affects between 30%-60% of brain-injury survivors and impacts independence and wellbeing. Four previous reviews covered interventions for acalculia, but all missed some studies. The current review updates previous work, identifies gaps, and informs future interventions. Web of Science and ProQuest Dissertation databases were systematically searched to identify studies describing interventions for acalculia published before June 2025. To be included, studies had to be written in English, involve an intervention for post-stroke/brain-injury acalculia, directly address numerical skills, and report intervention outcomes. Studies' quality was assessed using the Quality Assessment with Diverse Studies (QuADS) tool. Only 16 publications involving N = 31 participants were identified, alongside one unpublished app-based intervention (N = 18). Most interventions (10) targeted relearning of multiplication tables, followed by interventions for transcoding (4). All interventions were delivered individually (no group interventions) and mostly tailored to individual patients. The most common delivery method was intense repetition ("drill"), and most interventions were conducted in French or German, with only one delivered in non-European language (Japanese), despite evidence for linguistic and cultural effects on numerical skills. Findings highlight the scarcity of evidence for acalculia interventions, and the discussion explores suggestions for future interventions. Urgent work is required to improve provisions for patients.