Considering the ICHD 3 criteria could be beneficial to distinguish between the primary and non-primary headaches as depicted in 'Plos One'.

Around 0.5 – 4.5% non-traumatic headaches arise at the emergency department (ED); the main cause being the primary headaches. It is improtant for the clinicians to carefully evaluate the impending aetiology of primary headaches for the right diagnosis and management. In the absence of biological or imaging findings to diagnose primary headaches, Joe Munoz-Ceron et al. hypothesized ICHD 3 criteria as a useful tool at the moment to recognise and establish a difference between those patients who are experiencing primary headaches and who may require advanced diagnostic techniques. That is why the present study aimed to evaluate the application of ICHD 3 criteria to distinguish primary from non-primary headaches at the ED.

Interview, examination and categorisation (Primary and Non-primary) of the patients complaining of headache at the ED was carried out using ICHD 3 criteria. Primary headache patients were treated as per the standard set of protocols. Then, telephonic communication after 48 hours was done to ensure a satisfactory outcome. Added diagnostic and curative treatment was given to patients with non-primary headaches (secondary headaches and neuralgias). In both the groups, the investigators examined the prevalence of fulfilled criteria and proportion of common red flags (sleep headache onset, age, associated symptoms, sudden onset, and nonresponse to analgesics, abnormal neurological exam along with the previous consultation after this evaluation.

Out of the total 10450 ED patients, headache contributed to 244 (2.3%) and 77.8% were females. The prevalence of unclassified, non-primary (secondary plus neuralgias) and primary headaches were 8.6%, 32% and 59.4%. The most common etiologies for primary and non-primary causes were migraine and cervical myofascial pain. The factors linked to non-primary etiologies were immunosuppression and age older than 50. Sudden and sleep headache onset and abnormal neurological exam were not statistically significant. History of migraine and similar episodes and fulfilling ICHD 3 criteria were found to be the main determinants linked to primary headaches. Age >50 and immunosuppression were the factors linked to non-primary headaches, observed by the study investigators.