Is This Small Neck Muscle Driving You Mad?
Headaches, Trauma and the Rectus Capitis Posterior Minor The RCPMi has been considered a muscle of importance in chiropractic literature for a long time. It's only been a recent phenomenon where more mainstream medical science has started to look at its role in headaches and trauma. Two such studies examined the RCPMi in 2016. The first study was published in the American Journal of Neuroradiology. They saw that patients with atrophy in the RCPMi had more severe concussion symptoms and a worse prognosis. You can check out the abstract here: Effect of the suboccipital musculature on symptom severity and recovery after mild traumatic brain injury The second study was published in the presigious headache journal, Cephalgia. The authors found that patients with chronic headache tended to have more hypertrophy in the RCPMi than controls. You can check out that abstract here: Correlation between chronic headaches and the rectus capitis posterior minor muscle In case you weren't paying attention, you should probably find those 2 outcomes to be a little strange. On one hand, having smaller RCPMi had worse outcomes with concussion symptoms. On the other hand, having larger RCPMi was more likely to be associated with chronic headaches. Granted we are dealing with 2 different conditions, but one of the biggest problems with chronic concussive symptoms is chronic headache. It would seem like there should be some overlap. What gives?
How Can That Small Muscle Cause So Many Problems? There's a few unique things about these muscles.
The RCPMi does not connect into bone like most muscles do. It connects into a piece of tissue called the myodural bridge. That means it has a direct link into the outer covering of the brain which is known to be very sensitive to pain.
The RCPMi is too small to provide much in the way of meaningful movement of the head and neck. Inside the belly of this small muscle are abnormally large amounts of prorioceptors called muscle spindles. Proprioceptors help provide feedback to the brain about joint position and movement.
Changes in the RCPMi can deform the myodural bridge which changes movement in cerebral spinal fluid. Abnormal movement of this fluid is associated with headache. So as you can see, even though the RCPMi is small it carries a large baggage of neurology with it.