For a patient presenting with recurrent headaches and no prior history of similar symptoms, initial investigations should focus on identifying any red-flag features that may indicate secondary causes requiring urgent assessment or referral. These features include sudden-onset headache reaching maximum intensity within 5 minutes, new-onset neurological deficits, cognitive dysfunction, personality changes, impaired consciousness, recent head trauma, headaches triggered by cough, Valsalva manoeuvre, sneeze, or exercise, orthostatic headaches, symptoms suggestive of giant cell arteritis, acute narrow angle glaucoma, or a substantial change in headache characteristics. If any of these are present, further investigations and/or referral should be considered NICE CG150.
In the absence of red-flag features, consider using a headache diary for at least 8 weeks to record frequency, duration, severity, associated symptoms, medications taken, possible triggers, and relationship to menstruation to aid diagnosis of primary headache disorders NICE CG150.
Neuroimaging or other investigations are not routinely recommended solely for reassurance in patients diagnosed with tension-type headache, migraine, cluster headache, or medication overuse headache without red-flag features NICE CG150.
Additional considerations for further investigations include patients with compromised immunity, history of malignancy, or unexplained vomiting NICE CG150.