This document collates into a single document all SPEAC Aseptic meningitis resources (Risk factors, background rates, ICD9/10-CM & MedDRA codes), tools (data abstraction & interpretation form, tabular summary of key case definition criteria and algorithm for level of certainty determination, pictorial level of certainty algorithm) and guidance (real time investigation, data collection, analysis and presentation) specific to the events described in the Thrombocytopenia Case Definition. This guide can be used by stakeholders to assess the occurrence of aseptic meningitis in several settings including as an adverse event following immunization.