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trigeminal neuralgia

Unraveling Trigeminal Neuralgia

trigeminal neuralgia

[8 minutes]

Unraveling Trigeminal Neuralgia

​Most of you have probably never heard of trigeminal neuralgia (TN). It’s a pretty rare disorder that affects about 4-5 people per 100,000. If you or someone you love has ever had it, then you know that this illness can be associated with the worst pain that a human being can experience. The constant and persistant pain is so debilitating that TN has been called “suicide disease” because an estimated 25% of sufferers will take their own life.

​Today we are going to breakdown the anatomy of this devastating disorder, and how we can help.

​The Anatomy of Facial Pain

Trigeminal neuralgia can seem very simple on the surface. The name of the disease stems from the nerve that it attacks called the trigeminal nerve. The trigeminal nerve is one of twelve specialized nerves that come from inside the skull called cranial nerves. As the trigeminal nerve exits the brainstem, it sends branches all throughout the head and neck. Here is a short list of the things connected to the trigeminal nerve:

  • ​Sensation on the surface of the head and neck (especially pain sensation)
  • Sensation in the teeth and gums
  • The meninges
  • Major jaw muscles

​You can see how the nerve spreads and some of its major branches here:

The Trigeminal Nerve

The three main branches of the trigeminal nerve are the opthalmic branch (v1), maxillary branch (v2), and the mandibular branch (v3).

​While trigeminal neuralgia is a very specific illness with a set diagnostic criteria, the cells that form the trigeminal nerve have been implicated in pain issues that include migraine headache and jaw pain (TMD). This is because there is a bundle of cells in your spinal cord that act as a relay station for all pain perception in the head and neck called the trigeminal cervical nucleus.

In the most simple terms, if you were to go to a dentist and had your gums poked, it would fire a receptor called a nociceptor. This nociceptor travels through the trigeminal nerve, into the spinal cord, and up into the brain where it perceives that signal as pain.

Using this idea, scientists have tried to identify lesions along the trigeminal nerve in people with trigeminal neuralgia that consistently set off the pain response. It’s been suspected that an artery near the brainstem can pulse and compress the trigeminal nerve roots. These pulsations explain why patients can feel waves of shock like pain, with brief moments of relief in between.

There is also evidence to suggest that inflammation or trauma in the brain or spinal cord can make the brain more sensitive to the pain response. This is known as central sensitization.

It’s important to know this because knowing if the problem is from a peripheral lesion like an artery warrants a much different treatment than a condition where the pain is mediated from a central location.

Treatment Options

Peripheral Lesions

Most cases of true TN are resistant to anti-inflammatory medications.  When anti-inflammatories fail, they are treated with anti-convulsant medications like Tegretol or Neurontin. These medications can be effective for some, many patients find the side effects (dizziness, brain fog, balance problems) of these medications to be intolerable.

For patients with a peripheral lesion like artery or vein compression, there are surgical options. If patients have a confirmed compression of the trigeminal nerve roots by an artery, a surgery called micovascular decompression can be used to move the offending artery off of the nerve. The surgery has a very high success rate for a large number of TN cases, but it is also is a major surgery which requires cutting through the skull, and has risks that come with neurosurgical procedures.

Other procedures like Gamma Knife radiation can be performed to damage the trigeminal nerve so that it does not transmit the pain signal to the brain. This procedure has been less effective than decompression, and also may require additional procedures.

While these procedures can be great options for TN as a result of a displaced artery, it is unlikely to help those whose symptoms are not part of the peripheral nerve. Some forms of TN may be a brain related issue.

Central Disruption – A Brain Processing Problem

Problems in the peripheral nerve structure are easy to understand. You have delicate nerve tissue that hates to be compressed and you have an offending structure that is rubbing or compressing the nerve roots. When you remove the offending structure, then the nerve problem goes away. In a way, a peripheral lesion is similar to the way that a herniated disc causes the pain from a pinched nerve.

But what if you have this face pain but there’s no sign of a rogue artery pressing against the nerve? The problem may be with processing of pain rather than an offending lesion.

While peripheral problems are easy to understand, central problems can seem more abstract. When the brain and spinal cord aren’t working properly, you can’t do a blood test or look at an MRI and definitively say “This is why you have pain in your face”. In order to test this idea, you often have to perform functional tests which test how your body feels different stimuli.

Central disruption is more of a problem of too much or too little.

What I mean by that is that neurons in the brain can fire too often while other important nerves may not fire enough. When the firing of these nerves is out of balance, then the brain perceives things incorrectly.

Pain experienced in the head and neck can be dictated anywhere along these pathways

Pain experienced in the head and neck can be dictated anywhere along these pathways

The pain pathways of the head and neck converge into an area of the spinal cord called the trigeminal cervical nucleus. So if you have a pain in the head, face, or neck, all of the pain sensing fibers are going to enter into this region which is found in the spinal cord around the level of the first 3 neck vertebrae.

Our perception of pain is dictated by the multiple factors that include the current environment, memory of past pain, genetics, expectations, and our attention. The trigeminal cervical nucleus, thalamus, and somatosensory cortex have a system determining if the brain should pay attention to a painful stimulus. This is what allows people to feel pain differently.

That’s why  our favorite athlete can ignore the pain of a broken leg in order to complete a task. It also allows us to perceive danger if we step on a nail in the dark.

When this system malfunctions, then the trigeminal cervical nucleus is allowing too many pain signals to get through to the brain. When it allows every painful stimulus to get to the brain, then the brain is constantly bombarded with pain signals even if that signal is harmless.

Symptoms of facial pain can be a result of too much firing from the trigeminal cervical nucleus.

That’s what allows a cool breeze to the face, brushing your teeth, or scratching an itch on your face can be wrongly perceived as a painful stimulus that sends them cascading toward miserable facial pain.

When it comes down to it; your brain is perceiving the environment incorrectly because it is letting too much pain stimuli through the pain gate.

This is the cornerstone of the Gate Theory of Pain below.

Pain Gate Theory

 

The good news about a central pain response is that your pain threshold can be changed by several factors as listed in the diagram. While we can’t change our genetics, we can change almost every other factor on that list. From a treatment perspective, there are numerous things we can do to change brain and spinal cord input so that pain output decreases.

Fixing the Neck to Fix the Brain

Chiropractors that focus on the upper neck have found a large amount of success in helping patients with trigeminal neuralgia and other facial pain syndromes. A quick search through chiropractic literature shows a dozen case studies detailing the improvements of patients with facial pain syndromes (including my own here if you want to read it link here).

Obviously these are just case studies and can’t tell you much in themselves(I’ll save my rant on the politics of chiropractic research later. How is there not a formal study on trigeminal nerve issues and chiropractic by now?), but there is a logical rationale that helps explain how the neck can affect facial pain and why 75% of our trigeminal neuralgia patients get substantial improvement.

Let’s look at that graphic and highlight some important components:

Pain Gate Theory

 

Brain input and spinal cord input play a big role in the sensation of pain. A big part of brain and spinal cord input comes from the top 3 nerves in the neck.

When the head and neck shift, brain and spinal cord input get altered in ways that can impact the trigeminal cervical nucleus. In our office, we find that this is particularly common when the Atlas vertebra rotates or twists out of position.

Atlas Rotation

When this shifting occurs 3 things happen:

  1. Torsional forces occur in the spinal cord potentially impacting the trigeminal cervical nucleus
  2. Compressive forces may occur along the vessels that can affect movement of spinal fluid and blood in the head.
  3. Aberrent input into the brain from asymmetry of spinal positioning leading to dominance of nociception (pain) into the brain.

When the neck shifts in this manner, it doesn’t always cause trigeminal nerve issues, but it is tied to other problems like headaches, neck pain, cervicogenic vertigo, and more.

It brings us back to a fundamental principle: upper cervical chiropractic is not about treating a specific condition. It’s about improving the function of the brain and nervous system.

When we correct the structure of the neck, we are looking to decrease these damaging forces into the spinal cord and veins and improve the symmetry of firing into the brain.

The atlas on the left is almost 4 degrees twisted. The Atlas on the right is at just 1.5 degrees.

The atlas on the left is almost 4 degrees twisted. The Atlas on the right is at just 1.5 degrees.

Because if we can play a role in making the brain more resilient, then it has the best chance to make itself resistant the the pain you may experience in your day to day life.

Talk to Dr. Chung