I have had a severe headache for 4 years. symptoms began approx 5 hours after cervical manipulation. neg history of cervical issues. image studies clear

Somatic dysfunction: I'm sorry to hear you've had a headache for 4 years! headaches have a variety of causes, but one of the most common is muscle tension, particularly along the cervical spine and shoulders. You may want to have your neck re-evaluated by an osteopathic physician who practices osteopathic manipulative medicine; they may be able to detect alterations in the cervical spine contributing to the headache.