I recently read a New York Times article that referenced the work of the late John Sarno, MD, a New York City physician who dedicated his career to one purpose: helping patients recover from back pain.
Sarno’s premise was that back pain resulted from suppressed rage, and the expression of pain in the back muscles was a way for the brain to avoid confronting the life conflicts responsible for a patient’s suffering. Sarno was confronted by a medical community that did not embrace the idea that back pain could result from psychological distress. Rather, physicians, for the most part, held strong beliefs that back pain was primarily the result of physical and structural injuries and compromises.
Now, over 40 years after Sarno’s book was first published, scientific study has led to a better understanding of not only why pain can emerge but why at times, it will linger, intensify, spread, and become persistent. When considered with an open mind, this research can help all of us understand the challenges we encounter when managing our patients’ persistent tooth pain, TMJ pain, or other orofacial pain problems.
To start, it is critical to understand that there are only three types of pain: nociceptive or somatic pain, neuropathic pain (episodic or continuous), and central-mediated or dysfunctional pain.
1. Nociceptive Pain
This type of pain is initiated by the activation of nociceptors (sensory receptors for painful stimuli) in somatic/visceral tissues that have sustained injury. Nociceptive means causing or reacting to pain. The cause of nociceptive pain comes from outside the nervous system (the somatic/visceral tissues), and the nervous system reacts to it.
Nociceptive pain is always accompanied by inflammation, which is a normal immune response that initiates the healing process when injury occurs. Due to the release of prostaglandins and bradykinin, nociceptive pain is intended to have a protective inhibitory influence. The pain experience is due to what’s called peripheral sensitization – an increase in the excitability of neurons in peripheral tissues.
Nociceptive pain is typically gone in a few days, weeks, or months – as long as the source of the injury is identified and stopped.
2. Neuropathic Pain
This type of pain results from abnormalities in neural structures, not in the somatic tissues where the pain is being felt. Neuropathic pain is not typically initiated by noxious stimulation of peripheral nociceptors but can be the result of an event such as surgery or treatment such as chemotherapy.
Neuropathic pain is what I call inside-out pain (normal somatic/visceral tissues and abnormal neural tissues). It is non-nociceptive pain because it comes from within the nervous system itself and has no other purpose but to make our patients miserable. Trigeminal neuralgia is a form of episodic neuropathic pain, and post-herpetic neuralgia and diabetic neuropathy pain are types of continuous neuropathic pain.
Essentially, in the case of neuropathic pain, the body’s alarm system has become over-sensitive and is firing in the presence of normal stimulation.
3. Central-Mediated or Dysfunctional Pain
With central-mediated or dysfunctional pain, there is no history of noxious stimulation or no peripheral pathology, no inflammation, and no damage to neural structures. Instead, it has its origin within the CNS. It lies within the complicated interaction between the brain (pain perception and response) and the brainstem (pain sensitivity). I call it interpretive pain because no pain exists unless the brain renders an opinion – there is no pain until the brain says so.
Central-mediated or dysfunctional pain complaints are no less real than the other two types of pain but require an assessment process and ultimately treatment that travels down different pathways.
Making The Diagnosis
If you keep the three pain types in mind, you’ll have a more reliable framework as you go about trying to understand why a patient in your care has pain that, despite your efforts, intensifies, spreads, and becomes persistent. It is possible, however, that somatic pain can transform into a neuropathic pain problem and prompt muscle guarding and spasm in somatic tissues.
These hints may be helpful as you work through making a diagnosis: if pain is present without an accompanying history that clarifies its onset and there are no objective examination/imaging/serology findings of tissue injury or disease, you can probably begin to rule out nociceptive pain.
To consider neuropathic pain as a diagnosis, your first order of business is to investigate the potential origin. Common origins include:
- Local nerve injury in the history (physical, surgical, chemotherapy, radiation, etc.).
- Upregulation of neurons and glial cells in the CNS as a result of nociceptive barrage from the periphery due to an extreme traumatic insult or ongoing insults.
- Loss of descending inhibitory modulation (the body’s everyday pain-blunting systems) due to chronic medical stress, emotional stress, PTSD, compromised sleep, early life traumas, etc. When deficient, normally-suppressed nociception is allowed to reach the higher centers and is perceived as pain.
Neuropathic pain cannot be considered unless you can make one of these connections in the patient’s history.
If your assessment has seemingly ruled out nociceptive and neuropathic pain, then you are left with central-mediated or dysfunctional pain as the likely diagnostic choice. A complete understanding of the patient’s medical, social, emotional, and trauma history is required to contemplate this diagnosis. It will also be necessary to try and understand why your patient’s pain-interpretive ability has been compromised, which will likely require collaboration with a pain-oriented mental health provider.
Although what the future will bring with regard to our ability to further help those suffering with persistent pain remains unclear, the controversial theories of clinicians like John Sarno will remain critical to stimulate the curiosity and debate necessary to push science forward.
The New York Times, “I Have To Believe Dr. Sarno’s Book Cured My Pain”
Dr. Sarno’s books on Amazon
My article, Diagnosing Orofacial Pain: Three Key Ingredients