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Types of Pain
Last updated: 09/14/2023
Key Points
- Chronic pain is complex and exists on a continuum but can be broadly categorized as nociceptive, neuropathic, and nociplastic.
- Neuropathic pain is from nerve injury and nociceptive pain is due to tissue injury. Nociplastic pain is caused by sensitization of the nervous system.
- Pain is complex and can often have multifactorial causes requiring a holistic evaluation and approach to treat effectively.
Introduction
- The International Association for the Study of Pain (IASP) defines pain as “an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.”1
- Pain often exists on a continuum but elucidating the primary etiology theoretically allows for more effective treatment rather than a symptom-based approach.2
- A broad classification for the types of chronic pain as defined by the IASP includes nociceptive pain, neuropathic pain, and/or nociplastic pain.1,3
- Neuropathic pain is defined as pain caused by damage or disease affecting the somatosensory nervous system.1,3
- Approximately 15-20% of chronic pain is neuropathic in origin and common examples include diabetic neuropathy, postherpetic neuralgia, radiculopathy, trigeminal neuralgia, etc.1
- Neuropathic pain is a clinical description (not a diagnosis) and is always a maladaptive response.3
- Nociceptive pain arises from actual or threatened damage to nonneural tissue and is due to the activation of nociceptors.
- This is the most common form of chronic pain that is expected after surgical and other traumatic injuries.1,3 Common examples include osteoarthritis, postsurgical pain, etc.
- Nociplastic pain arises from the abnormal processing of pain signals without any clear evidence of tissue damage or discrete pathology involving the somatosensory system.1,2
- Nociplastic pain can occur simultaneously with nociceptive pain. This category was previously known as functional pain syndromes. Common examples include fibromyalgia, irritable bowel syndrome, interstitial cystitis, etc.
Pathophysiology and Characteristics
![](https://www.openanesthesia.org/wp-content/uploads/2023/09/14/Types-of-Pain_table-1-lkbljy-e1694730550989.png)
Table 1. Characteristics of the different types of chronic pain
Approach to Treatment
- Pain is often multifactorial in nature and requires a thorough evaluation and multidisciplinary approach.
- Considerations include addressing individual needs as someone from a vulnerable population or barriers to access to care.
- Treatment options range and must be evaluated on an individual basis.
- Many meta-analyses have shown mixed results to different psychological, exercise, and complementary or alternative treatments.3
- Nociceptive pain is often most responsive to anti-inflammatory medications such as NSAIDs and acetaminophen.
- A treatment algorithm proposes the following model for neuropathic pain:4
- 1st line: TCAs, SNRIs, gabapentinoids, topicals
- 2nd line: Tramadol, or combination of 1st line therapies
- 3rd line: Specialist referral and potential SSRIs/anticonvulsants, NMDA antagonists, or interventional pain therapies
- 4th line: Neuromodulation
- 5th line: Low-dose opioids
- 6th line: Targeted drug delivery
Interventional Pain Management
- Interventional therapies include numerous treatments that have the potential to reduce pain, and are often performed under fluoroscopic or ultrasound imaging guidance.
- Examples include epidural steroid injections, facet joint blocks, radiofrequency ablations, sympathetic blocks, intrathecal drug pumps, and more.
- Regional anesthesia can be a diagnostic and therapeutic step leading to further interventional procedures.
- Epidural steroid injections involve steroid and local anesthetic injections into the epidural space to provide pain relief.
- Facet joint medial branch nerve blocks and radiofrequency ablation
- Lumbar facet joint pain can be temporarily relieved with intra-articular injections or medial branch nerve blocks and later denervation of nerves can provide longer-term relief.
- Sympathetic blocks for pain syndromes and specific conditions to produce short-term reduction in pain with examples including stellate ganglion blocks, celiac plexus blocks, and lumbar sympathetic blocks.
- Intrathecal drug delivery involves an implanted programmed pump that delivers medication (typically opioids, local anesthetics, or ziconotide) into the cerebrospinal fluid.
Neuromodulation
- Neuromodulation is another therapeutic modality used to manage chronic pain.5
- Mechanistically, neuromodulation techniques promote neuroplasticity to reduce pain.
- Targets for stimulation include pathways at the brain, spinal cord, nerve root, peripheral nerves, or at transcutaneous levels.
- The quality of evidence for these techniques are mixed with low-to-moderate quality reported in meta-analyses.5
- Spinal cord stimulation
- Interferes with pain propagation with an implanted pulse generator with many applications
- Leads placed in the epidural space
- Dorsal root ganglion stimulators
- These stimulators are similar to spinal cord stimulators but target a specific dorsal root ganglion to provide more localized therapeutic specificity.
References
- International Association for the Study of Pain Terminology Working Group. Definition of pain. IASP. Publish date 1994. Updated 2022. Accessed January 23rd, 2023. Link
- Cohen SP, Vase L, Hooten WM. Chronic pain: an update on burden, best practices, and new advances. Lancet. 2021; 397(10289): 2082-97. PubMed
- Fitzcharles MA, Cohen SP, Clauw DJ, et al. Nociplastic pain: towards an understanding of prevalent pain conditions. Lancet. 2021;397(10289):2098-2110. PubMed
- Bates D, Schultheis BC, Hanes MC, et al. A Comprehensive Algorithm for Management of Neuropathic Pain [published correction appears in Pain Med. 2023 Feb 1;24(2):219]. Pain Med. 2019;20(Suppl 1):S2-S12. PubMed
- Knotkova H, Hamani C, Sivanesan E, et al. Neuromodulation for chronic pain. Lancet 2021; 397(10289):2111-2124. PubMed
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