Twitter: @ndubosh.Study objective: Serious neurologic conditions can be missed on initial emergency department (ED) visit and discharge diagnosis oftentimes remains a nonspecific symptom. We aim to examine the incidence of potential harm from serious neurologic conditions in ED patients discharged with a nonspecific diagnosis of headache or back pain, identify specific missed conditions, and determine risk factors for potential misdiagnosis-related harm.Methods: This was a retrospective analysis using the population-based data of 6 US states from the State Emergency Department Databases and State Inpatient Databases from 2006 through 2012. We identified adults (18 years) discharged from the ED with a diagnosis of atraumatic headache or back pain. The primary outcome was a composite of return ED visit and hospitalization for primary diagnosis of a serious neurologic condition or inhospital death within 30 days of ED discharge.Results: There were 2,101,081 ED discharges with a nonspecific diagnosis of headache and 1,381,614 discharges with a nonspecific diagnosis of back pain. Overall, 0.5% of the headache patients and 0.2% of back pain patients had a primary outcome. The most common missed condition for headache was ischemic stroke (18.1%). The most common missed condition for back pain was intraspinal abscess (41%). In both populations, advanced age, male sex, non-Hispanic white, and comorbidities (eg, neurologic disorders, HIV/AIDS, malignancy) were associated with higher odds of outcome.Conclusion: A small proportion of ED patients discharged with nonspecific diagnoses of headache or back pain returned with a serious neurologic condition or inhospital death within 30 days.