Several pain mechanisms and pathways explain the interconnection between neck pain and headaches. Many anatomical structures in the head and neck are sensitive to pain. The pathways of pain vary depending on the structures involved.
Role of the Trigeminocervical Nucleus
Sensory nerve fibers from the trigeminal nerve and upper spinal nerves converge in the trigeminocervical nucleus located in the upper cervical spine. Pain signals from the face including the top of the head, forehead, eye, and temple area are transferred via the trigeminal nerves. Pain from sources in the neck such as vertebrae, discs, joints, muscles, and/or nerves are transferred via the upper spinal nerves. When a pain input from the neck reaches the trigeminocervical nucleus, it is interpreted as stemming from the trigeminal nerves, and perceived as pain in different regions of the head. Similar mechanism is believed to cause pain from the head to radiate to the neck.
Role of the Dura Mater of the Brain
The dura mater (outer-most covering) of the brain is shown to have direct connections to the rectus capitis posterior minor muscle and ligamentum nuchae at the junction of the head and neck. These suboccipital muscles and ligaments are present at the back of the head, and mechanical traction (pulling/tension) of these tissues may cause movement of the dura.1 This theory suggests the role of the dura in causing neck pain and headaches.
Role of the Immune System
In cases of cervical trauma, the immune system is believed to signal the activation of pain-producing agents, such as substance P and calcitonin-gene-related peptide. This activation leads to increased levels of inflammatory substances, such as cytokines, interleukin-I, and tumor necrosis factor in the bloodstream. This phenomenon is believed to cause pain in the head and neck following trauma.
Role of the Blood Vessels and Brain Tissues
Some blood vessels and brain tissues in the head that are especially sensitive to pain may include:
- Venous sinuses and their tributaries
- Parts of the dura mater of the brain located at the base of the dural arteries
- Cerebral arteries at the base of the brain
Distension, distortion, or inflammation of these delicate structures results in pain perception in the head and upper neck.
A combination of one or more pain pathways or mechanisms is most likely responsible for causing headache and neck pain to occur together.