Diseases that can cause secondary headaches in patients include an ear infection, influenza, acute sinusitis, glaucoma and meningitis, according to Mayo Clinic. Hangovers, blood clots, carbon monoxide poisoning, dehydration and a concussion may also cause secondary headaches. Secondary headaches occur as a symptom of an underlying medical condition that activates the pain-sensing nerves in the head.
For example, the symptoms of meningitis include fever, headache and confusion, notes MedicineNet. A doctor may administer antibiotics for meningitis first, as opposed to finding out another cause of a secondary headache. These symptoms may also indicate a brain hemorrhage or a brain tumor, but meningitis may become fatal very quickly.
Doctors could examine a patient's medical history and do a complete medical exam as a starting point to find a cause of a secondary headache in a nonemergency situation, says MedicineNet. A blood test, computerized tomography scan, magnetic resonance image and lumbar puncture may help pinpoint a specific cause of secondary headaches. Blood tests could help find an electrolyte imbalance or inflammation that could lead to headaches, whereas CT scans and MRIs indicate problems with the head. A lumbar puncture, otherwise known as a spinal tap, can find bleeding in the brain or meningitis as a cause of secondary headaches.
Doctors may look for warning signs of secondary headaches, according to the American Headache Society. These signs include the worst headache of someone's life, an abrupt onset of a headache with no warning, and a fundamental change in recurring headaches.