CRD summary: The authors concluded that cerebrolysin could improve significantly global clinical impression scores in patients with mild to moderate Alzheimer's disease. There were some limitations to this review, in particular with the reporting of review methodology, but, overall, the authors' cautious conclusion appears appropriate.

CRD commentary: The review addressed a clear question that was defined in terms of the participants, intervention, outcomes and study design. Several relevant sources were searched, but it was not explicitly stated whether attempts were made to minimise publication and language bias. Only relatively higher quality studies that met predefined quality criteria were eligible. Methods were used to minimise reviewer errors and bias in the extraction of data, but it was unclear whether similar steps were taken at the study selection stage (and therefore the validity assessment). Significant heterogeneity was found for three of the four outcomes but potential sources of heterogeneity were not investigated. The direction of treatment effect appeared similar for response rates and cognitive function, but not for ADL. It was not reported whether the data used in the analysis were post-treatment or at the end of the follow-up period. There were limitations to this review but, overall, the authors' cautious conclusion appears appropriate.