Trigeminocervical Convergence, Confirmation Bias and Risk Factors

Alastair simplifies the nerve supply of the head and neck into the upper three cervical nerves and the trigeminal nerve, then describes the trigeminal nuclei in the brainstem. The spinal nucleus takes nociceptive input from the trigeminal nerve and the upper cervical nerves, forming the trigeminocervical nucleus. He explains convergence to patients with an analogy of suburbs feeding onto one freeway into the city. Convergence works in both directions. Upper cervical nociception can be felt in the head, but head problems referring into the neck are more common, and at least half of primary and non-cervicogenic secondary headaches include neck pain. Neck pain plus headache does not mean cervicogenic headache. He warns that confirmation bias leads clinicians to stop gathering information that would challenge what they already believe. Risk factors include female sex, medication and caffeine overuse, low socioeconomic status, poor sleep, stressful life events, anxiety, depression, low pain self-efficacy, hypothyroidism, hypertension, smoking, family history, obesity and other musculoskeletal or gastrointestinal pain.