In Part 1 of this 3-part series, I began with a conversation about the four types of pain problems we frequently see in our TMJ and orofacial pain practice. (Read Part 1 Here)
They are:
1. Nociceptive (Somatic) Pain
2. Neuropathic Pain
3. Nociplastic Pain
4. Neuroimmune Pain
In this installment, I discuss why BOTOX®* could be a valuable therapeutic tool for treating Nociceptive and Neuropathic pain, the most common pain problems in our TMJ and Orofacial Pain practice.
Muscle Pain Problems
What follows is a discussion of the potential progression of muscle pain (a type of nociceptive pain) from simple to more complex, which is common in our practice and typically happens in several stages:
Stage 1: Muscle Guarding
At its onset, muscle pain is usually the result of what we call muscle guarding. This occurs due to muscle overuse, injury, or the threat of injury. As the brain prompts a protective response, the muscle shortens. When a muscle remains shortened, blood flow is reduced, resulting in less oxygen and nutrients delivered.
With time, the contracted muscle is depleted of energy resources, and the biochemistry of the muscle becomes acidic, with lactic acid and other irritating substances accumulating.
Stage 2: Local Muscle Soreness
The next stage is called local muscle soreness and begins the potential transformation from a pure nociceptive muscle pain problem to one with a neuropathic element. This can occur when the altered biochemical environment irritates the peripheral nerve endings in muscle tissue. If that happens, pain intensity can escalate, and the potential for what is called heterotopic or referred pain becomes likely.
Now, the pain problem is not just a response to irritated muscle tissue but also due to nerve excitation within the muscle. The condition causes changes in how the brain interprets incoming noxious information, a component of what is called central excitatory effects.
Why BOTOX® Can Help Relieve Nociceptive & Neuropathic Pain
BOTOX® can be a potential source of relief for the type of muscle pain described above when first-line therapies fail or if a patient arrives already with a persistent problem. Here’s why:
- BOTOX® can inhibit the release of the excitatory neurotransmitter acetylcholine at the neuromuscular junction.As a result, the initiating steps that lead to muscle contraction are blocked. Put more simply, by blocking nerve signals that cause muscles to contract, there is a partial incapacitation of muscle function.If muscle guarding (Stage 1) is the stage encountered, it can be limited or reversed. If the origin of the muscle disorder is identified, reduced, or eliminated, the subsequent stage of local muscle soreness can be prevented.
- BOTOX® can bind to sensory neurons in the impacted muscles and immediately reduce the release of pain-producing neurotransmitters.As a result, even if a local muscle soreness (Stage 2) problem is present with the consequent irritation of peripheral nerve endings and central excitatory effects, the transformation to a neuropathic pain problem can be stopped or at least minimized.Due to these therapeutic potentials, one to three BOTOX® treatment sessions at three-month intervals will likely be needed to adequately address a patient’s suffering. But, this assumes that the WHY of the problem can be identified and controlled or eliminated. If not, the use of BOTOX® may need to continue, with concerns that will be discussed in Part 3.
Can BOTOX® Be Used to Treat Primary Neuropathic Pain Problems?
Since BOTOX® is being used for various nerve pain problems throughout the body, strategies to confront these problems in the trigeminal system have emerged. As a result, BOTOX® is now considered to address pain problems in the trigeminal system, which can be classified as:
- Primary Trigeminal Neuralgia: Unfortunately, the treatment results of primary trigeminal neuralgia (when an intracranial blood vessel compresses the trigeminal nerve) with BOTOX® and other neurotransmitters have been limited. Part of the problem most likely relates to recognizing that the symptoms of primary trigeminal neuralgia (and the location of the injections) are in the distribution of the peripheral nerve endings that supply the teeth and facial structures where pain is reported, not at the intracranial central origin.Although there is evidence that BOTOX® has a central inhibitory effect on pain as it reaches the central nervous system (CNS) via antidromic transport, there is doubt that this, by itself, is sufficient.
- Secondary Trigeminal Neuralgia: When a secondary trigeminal neuralgia is present as a result of intraoral trauma ( surgery/extraction of a tooth), for instance, though the injured nerve area may be identifiable and accessible, the paucity of research regarding the dosage of BOTOX® and the frequency necessary to address these problems remains a possible obstacle to achieving predictable results. As a result, this potential use of BOTOX® to achieve favorable results remains unclear. However, we continue to modify our protocols based on the feedback we are receiving from patients in our practice who have opted for this treatment.
- Idiopathic Trigeminal Neuralgia (whose cause is unknown): When a neuralgia results from unclear origins, the use of BOTOX® to ease symptoms is not a predictable treatment option.
Hopefully, in the future, there will be data to support a predictable regimen of care. When BOTOX® is used in our office to address these nerve problems, it is commonly accompanied by oral medications when possible.
What About the Use of BOTOX® for Neuroimmune Pain?
Though research has revealed that Botulinum neurotoxins (BoNT-A) can act as an analgesic by blocking the activation and release of neuroactive-pain-producing substances from glial cells (immune surveillance cells), no known applications are available to use this potential source of pain control.
One could envision, however, that if a sufficient amount of BOTOX® could be transported back to the CNS after a peripheral injection, this could potentially set the stage for the inhibition of spinal cord glia cells, which otherwise, when excited would release pro-inflammatory cytokines in the brain leading to the amplification of aches and pains. Presently, this remains theoretical.
Conclusion
What should be clear is that BOTOX® has the most significant potential for pain reduction in purely nociceptive/somatic muscle problems and those that have transformed into hybrid nociceptive/neuropathic problems.
In Part 3, I will discuss the common therapeutic protocol used for these problems and the potential for unfavorable side effects. Stay tuned.
To our colleagues: We eagerly seek your insights, reflections, and experiences as we explore this topic in depth. Please feel free to comment below with your thoughts.
* In this article, BOTOX® represents various neuromodulators.
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