Dizziness and the Cervical Spine: Beyond Cervicogenic Dizziness

Read Time: [6 minutes]

Outline:

The cervical spine has been a known source of dizziness since the 1950’s with a classification as cervical vertigo. While the true spinning sensation of vertigo is not common with cervical spine issues, a feeling of imbalance, disorientation, light headedness, swaying, and unsteadiness have all been linked to problems in the cervical spine, especially the craniocervical junction.

Cervicogenic vertigo has a contentious history as a legitimate clinical entity. This stems from the fact that cervicogenic vertigo has no distinct biomarker and remains a diagnosis of exclusion; a leftover diagnosis when a more obvious inner ear cause doesn’t exist.

Cervicogenic vertigo may or may not exist as it’s own unique clinical entity, but there’s little doubt that the cervical spine plays a key role in balance and equilibrium. In this article, we’ll talk about how a dysfunctional cervical spine can be causing dizziness, and how cervical spine interventions can be a useful therapeutic option for people with dizziness disorders of many types.

The Anatomy of Cervicogenic Dizziness

While the diagnosis of cervicogenic vertigo has been contentious, the anatomical connections linking the cervical spine to symptoms of dizziness are not.

Neck Muscles, Ligaments, and Joint Receptors

The neck is loaded with receptors that help the brain know where the head is in relation to the body. These receptors come from the small suboccipital muscles, the cervical discs, the cervical joints, and the cervical ligaments. The receptors from the suboccipital muscles in particular have an unusual amount of density when compared to the rest of the spine [Source]. When you move your neck, these receptors help to control how fast and how far you move your neck. They are also receptors that are very active even if your head isn’t moving because we spend most of our time with our head up fighting gravity. All of these signals are transmitted to the brain which has to make constant decisions about where to put the head next.

Image result for upper cervical spine ligaments and muscles

When you have an injury like a whiplash or head trauma, the muscles and ligaments of the neck are susceptible to injury, and that injury takes away one of the methods that your brain uses to keep track of the head. If your brain can’t tell where your head is in space, then dizziness and a sense of imbalance is the result.

Cerebellum and Vestibular Nuclei

The cerebellum and vestibular nuclei are 2 really important parts of the brain that play a role in dizziness and balance problems originating from the neck.

The vestibular nuclei is the routing center for the signals traveling from your inner ear through the vestibular nerve. The primary job of the vestibular nuclei is to take the information coming from your ears and to calculate where the head is in space and to move the eyes appropriately in response to these signals. While the bulk of the input into the vestibular nuclei is coming from the ears, the vestibular nucleus also receives afferents from the cerebral cortex, visual centers, spinal cord, and cerebellum. It takes in all of this information and calculates where the head is in space based on what you see (visual), head direction (inner ear), and proprioception (muscle and joint activity).

Image result for cerebellum and vestibular nuclei

The cerebellum is generally thought of as a subdivision of the brain that aids in coordination of muscle movements. However, the cerebellum has an large chunks of real estate devoted to eye movements and modulation of the vestibulo-ocular response. The cerebellum also plays a role in how the vestibular system impacts the spinal muscles via the vestibulospinal tract.

These regions of the brain are important because the same muscles, ligaments, and joint receptors we discussed earlier have direct and indirect connections to the vesibular nuclei and the cerebellum.

The Vertebral Artery

The vertebral artery passes through the transverse foramina in the cervical spine. At the level of C1 and C2, the vertebral artery takes on a more tortuous path into the skull to supply the brain stem and cerebellum with oxygen. Most clinicians think of the vertebral artery as a potential source for arterial dissection that can cause stroke. However, there are documented cases of transient vertebrobasilar insufficiency caused by rotation of the neck. This syndrome has been named Bow-Hunter Syndrome or rotational vertebral artery vertigo (RVAO). [Source]

Studies have shown that decreases in blood flow from the vertebral artery can cause transient ischemia through the vertebral artery when the neck is turned in rotation. It’s not known whether the ischemia is affecting the brain stem/cerebellum, or if the ischemia is hitting the labyrinthe itself because of the way the artery branches out toward the peripheral vestibular apparatus.

Beyond Cervicogenic Dizziness

Therapies for the cervical spine can make an impact on cervicogenic dizziness. These therapies can commonly include cervical exercises, osteopathic manipulation, upper cervical chiropractic approaches, and other manual therapy techniques. The use of these modalities has largely been associated in patients who have reported dizziness following a trauma to the neck such as whiplash disorder [Source].

Is there a role to play for cervical spine-based therapies for other causes of dizziness and imbalance?

While there’s limited evidence to pull from, there are numerous anecdotes and case reports of patients with motion sickness, Meniere’s-like illness, and vestibular migraine showing improved outcomes while receiving care focused on addressing cervical spine dysfunction.

Let me be clear, I have no supporting research to support what I’m going to say next. These are just observations from 8 years of working with dizzy patients.

Many patients with feelings of dizziness but do not have full peripheral vestibular loss likely have problems of central processing of sensory information. Plastic changes in the central nervous system that can promote a sense of dizziness can include:

  • Inapporpriate Sensory re-weighting for balance 
  • Inappropriate afferentation into the vestibular nuclei and cerebellum
  • Anxiety related to pathologies or activities that promote dizziness
  • Decreased cellular activity in key sensory areas of the brain due to disrupted hemo/hydrodynamics

Simplified flowchart showing the way sensory information contributes to balance

By understanding some of the interconnected nature of the senses that produce a feeling of balance, we can leverage treatments to create neuroplastic changes in the central nervous system that may help a person adapt when vestibular function is compromised.

When it comes to dizziness, there are so many anatomical players and varying degrees of compromise, we can’t rely on one thing to fix all types of dizziness. By using the cervical spine to help stimulate the proprioceptive system, we might be able to help some patients compensate with a deficit where they weren’t able to before. We may also be removing one extra stressor to the balance system that was preventing the body from compensating appropriately.

The Craniocervical Junction and Headache Disorders

 

Headaches disorders are amongst the most common conditions that people seek treatment from a doctor. While most people will experience a headache of some form,  there are those who develop chronic and repetitive bouts with headaches of different types.

Unlike people who may struggle with an occasional stress headache or feel the effects from an alcohol induced hangover, people with these chronic headaches have a neurological disorder. These headache disorders can stem from:

  • Migraines
  • Cluster headache
  • Post-traumatic/Post-concussive headache
  • Chronic pain/Temporomandibular joint disorders
  • Tension headache
  • Chronic daily headache
  • And more

Each headache has unique characteristics that help to make an effective diagnosis for effective treatment. However, when we look at the reality of a daily patient interaction, we see that people with these headache disorders can have traits that overlap. (Remember this point because this is something I’ll come back to later)

That makes these headaches  extremely burdensome on the patient, but it can also be challenging for a doctor or therapist to find effective solutions. This is particularly challenging considering the rise of medication overuse headaches as a clinical entity in 2004.

Medication overuse headaches were once classified as rebound headaches because of the way headaches could come back with a vengeance after the pain-relieving effects of a medication wore off. It became re-classified in part due to the alarming number of patients showing a regression in their headache symptoms after prolonged and frequent use of medication. While the physiology of this disorder is widely unknown, it does show characteristics of physical dependency as seen with drug withdrawals.

As drug therapies become less effective for this subset of headache patients, there has become a growing need to identify non-pharmacologic strategies to help patients with headache disorders. For many of these patients, a possible solution might lie in the neck.

Headaches and the Cervical Spine

The concept of neck problems contributing to headache disorders isn’t new. Cervicogenic headache is a term coined in 1983 to describe patients suffering from simultaneous head and neck pain [1]. The term has grown to have diagnostic criteria that include:

  • Single sided head pain radiating from the top of the neck
  • Aggravation by specific neck positions
  • Reduced upper cervical motion or painful range of motion
  • Presence of muscular trigger points
  • Normal imaging
  • Unresponsiveness to pharmacologics

Cervicogenic headache does have a contentious history as a distinct clinical entity. Critics have argued that the soft nature of the diagnostic criteria. In the past, cervicogenic headaches seemed to be diagnosed by the effectiveness of cervical spine therapies in relieving the headache. You can see how this complicates the study of these headaches as a distinct clinical entity. In recent years, nerve blocks or ablations in targeted areas of the cervical spine have been used to determine if the cervical spine is the cause of the headache, but these also require more invasive procedures to make an assessment [2].

Headaches originating from the neck seems to have the biggest role in chronic headaches that begin after a concussion or whiplash. Headaches that emerge after these injuries are commonly classified as cervicogenic headache.The neurophysiologic effects of a concussion tend to disappear 7-14 days after the trauma but the ligament and muscle injuries from a head injury can persist leading to a default diagnosis of cervicogenic headace. The study of cervicogenic headache has revealed quite a bit about the physiology of how the neck can play a role in head pain, even those associated with migraine headache [3].

One problem with this idea is that fact that a traumatic injury can sometimes lead to patients who have never suffered a migraine before, can display migrainous symptoms after an injury [4]. This is also complicated by the fact that conservative cervical spine interventions like spinal manipulation and manual therapy appear to be effective in cervicogenic headache [5], but not in migraine [6] in clinical trials.

What do these headaches have in common? How are they different? Can we use their similarities to develop effective treatment strategies for headaches that are resistent to medications?

The Physiology of Headache Pain

There’s a common source for pain related to the head and neck. That source is a bundle of neurons located in the brain stem called the trigeminocervical nucleus (TCN). This nucleus is a hub for nociceptors in the brain. Nociceptors are receptors that transmit information about noxious stimuli to the brain, usually in the form of tissue injury.

While the feeling of pain is far more complex than the sheer amount of nociception your brain receives, for the sake of simplicity in this article, we will say that nociceptors are fibers that carry pain signals. Your TCN is a major player in head AND neck pain.

Head and neck pain pathway

This area in the brain stem is like the Grand Central Station for all of the pain sensing fibers in the head and neck. From the trigeminal nerve you have pain sensing fibers from the face, jaw, teeth, arteries, and meninges, while the neck has fibers from the joints, ligaments, muscles, and skin coming from C1, C2, and C3 nerve roots. All of these fibers converge onto TVN which has to decide if it’s worth going up to the big kahuna at the top of the brain called the cerebral cortex.

For neurovascular headaches like migraine and cluster headaches, it’s suspected that the pain carrying fibers from the arteries in the brain or the outer covering of the brain called the meninges getting irritated by pulsing arteries. These fibers are carried to the  TVN by the trigeminal nerve. For cervicogenic headaches, it’s suspected that the pain generators are coming from the muscles, nerves, or joints from the upper neck.

These overlapping structures allow for some of the referred pain patterns seen in migraine patients expressing neck pain, and also for cervicogenic dysfunction to lead to headaches. It also means that if 2 pieces of anatomy share a neurological pathway, then sometimes treating one area can lead to relief in another.

Interventions in the Cervical Spine and Headache Outcomes

So we know that the convergence of these neural fibers allows for some overlap of pain sensation regardless of the type of headache. What does the research say about treating headaches with cervical spine interventions?

The answer seems to match what you think it would be.

For cervicogenic headaches, recent studies seem to support the idea that addressing the neck with spinal manipulation can be helpful and even provide some relatively long term impact. A 2016 paper showed that upper cervical and thoracic manipulation helped cervicogenic headache patients at 3 months compared to exercise and mobilization [7]. A review paper of several studies on cervicogenic headache and manipulation seems well in favor of treating the neck compared to controls [8].

For migraines, the evidence isn’t so favorable for manual intervetions. There aren’t that many clinical trials to look at, and the ones that are available appear to show no effect [9]. From a pathophysiological standpoint it makes sense because they seem to be clinically distinct entities. However, the clinical experience of people like myself who practice in an upper cervical model of chiropractic have had a much different experience.

There is some evidence that suggests that cervical spine problems may be present as a sub-type of migraine patients [10]. There is also evidence that greater occipital nerve blocks [11] and non-invasive vagal nerve stimulation in the neck [12] can decrease the frequency of headache days and may effectively abort a migraine attack.

A 2016 study by Woodfield studied 11 patients with chronic migraines showing improvements in migraine frequency while receiving a vectored correction to the atlas vertebra [13]. The study also showed some significant effects in intracranial compliance in patients with cerebrovenous drainage abnormalities.

Case Study on NUCCA atlas procedure on venous drainage routes in a migraine patient.

While the concept of cerebrospinal venous abnormalities have been a controversial topic in multiple sclerosis, it may provide insight into some patients with chronic migraine. Multiple studies have documented venous drainage abnormalities in migraine patients and even mTBI, but the significance behind these observations are unknown [13] [14] [15].

Where To Go From Here?

There’s still a lot to learn about the anatomy and physiology of headache disorders. When you consider that migraine headaches are the most common neurological disease in the world.

Predicted research dollars compared to diseae burden

Lots of work needs to be done to understand what treatments will work for which patients, but there’s still some hope that treating the neck may be a key strategy to help people with chronic headache disorders.

 

 

 

Rectus Capitis Posterior Minor in Headache Disorders

Neck muscles have been a source of suffering for patients for a long time. In recent years, one neck muscle in particular is getting a lot of attention in the world of head injury.

Meet the rectus capitis posterior minor (RCPMi)

Image Credit: Duke Univeristy Learning labhttps://web.duke.edu/anatomy/Lab01/Lab2_new2014.html

Yep. It’s that tiny little muscle deep in the middle of your neck. It connects from the top bone in your neck called the atlas, and it connects into the head via connective tissue called the myodural bridge. But more on that later.

All in all, the the RCPMi is not much bigger than the end of your pinky finger, but it’s capable of wreaking havoc on people with neck problems including concussion.

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.

  1. 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.
  2. 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.
  3. 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.

What’s Happening in Headaches and Concussions?

This is where things get a little interesting, because we don’t really know how this muscle is causing problems. More evidence is showing that there is a correlation between this muscle and headaches, but we don’t really know anything about causation yet.

With that being said, this is mostly just speculation on my part, so here it goes.

In my office we are always striving to create symmetry in the structural positioning of the head and neck.

When the head and neck shift, it creates asymmetrical force production in the suboccipital muscles. Image Credit: Daniel O. Clark uppercervicalillustrations.com

When there is an injury like a trauma or whiplash, you create injury in some of these small muscles of the neck. When these muscles are injured, the brain loses some critical feedback mechanisms that helped to maintain proper positioning of the head and neck.

The injury also creates asymmetrical tension on the myodural bridge. This abnormal tension on the dura stimulates the sensitive pain receptors in this tissue leading to head and neck pain. There have even been cases where cutting this muscle can relieve a patient of chronic headache.

That same tension on the dura may also be creating abnormal flow of cerebral spinal fluid which may lead to chronic effects of brain physiology.