Patients with acute neuropathic pain present a significant diagnostic challenge. Therefore, diagnostic criteria should reflect the mechanistic understanding of this pain and provide a framework for the research and treatment of complex acute neuropathic pain conditions.
Through a partnership of translations, innovations, opportunities, and networks for clinical trials of analgesics, anesthetics, and addiction (ACTTION), the U.S. Food and Drug Administration (FDA), the American Pain Society (APS), and the American Academy of Pain Medicine (AAPM), an expert working group, jointly developed the ACTTION-APS-AAPN Pain Taxonomy (AAAPT) for Acute Pain, which was published in Pain Medicine.
5 dimensions of pain
The AAAPT classifies acute pain in 5 dimensions: core criteria, common characteristics, modulating factors, effects and functional consequences as well as putative patho-psychological pain mechanisms. In short, the high-level characteristics of each of these dimensions are as follows:
Core Criteria: Defined by unpleasant sensory and emotional experiences associated with, or described in relation to, either actual or potential tissue damage; Pain that occurs within 30 days of a triggering incident that causes a neurological injury; Pain in a “neuroanatomically plausible distribution” compatible with a neurological injury; and pain associated with at least one physical examination finding either a sensory deficit or a sensory gain (e.g., allodynia, hypoalgesia, hyperalgesia).
Common characteristics: pain can occur anywhere in the body. It is usually described using the following terms: burning, shooting, tingling, electricity, or pins and needles.
Modulating factors: Pain can be modulated by the age or immune function of the patient, the presence of other disorders of the nervous system such as multiple sclerosis or Parkinson’s disease, genetic polymorphisms or psychosocial factors.
Effects and functional consequences: Pain is associated with poor physical function and affects emotional and social well-being, resulting in a decreased quality of life.
Possible Mechanisms: This category includes ectopic nervous system activity, peripheral and central sensitization, loss of descending inhibition, and neuroimmune interactions. Influences are likely to be genetic or epigenetic.
The group then applied the AAAPT criteria to three specific conditions that best “illustrate acute neuropathic pain” and demonstrate their scope: acute herpes zoster neuropathic pain, acute chemotherapy-induced neuropathic pain, and acute neuropathic pain after limb amputation. The diagnostic criteria for each disease across the 5 identified acute neuropathic pain dimensions are briefly described below.
Acute neuropathic pain related to herpes zoster
Core criteria include acute or subacute herpetic neuralgia, typically a few days before the onset of a dermatomal rash, at the time the rash appears, or shortly thereafter (within 30 days for acute or within 30 to 119 days for subacute) as a positive or negative sensory sign in the affected dermatome. No other condition could better explain the pain.
Pain can be described as continuous or intermittent, independent of the stimulus, or as an evoked stimulus, and dysesthesia or paresthesia can also be present.
Modulating factors are age, rash severity, presence of a painful prodrome, and immune status. The functional consequences range from insomnia and other activities of daily life to depression and impairments of social well-being to a reduced health-related quality of life.
This pain can be caused by a neural injury due to herpes zoster reactivation. A combination of mechanisms can be responsible for individual patient symptoms.
Acute neuropathic pain associated with chemotherapy
The core criteria include a history of receiving a neurotoxic chemotherapeutic agent, pain that occurs within 30 days of administration of this agent, a pain distribution that is neuroanatomically consistent with a neurological lesion, pain with at least one positive or negative sensory sign, and no other disease, doing this might better explain the pain. Pain can be present in the upper and / or lower extremities.
The pain can be modulated by the comorbid diseases, immune status, social and demographic factors, lifestyle and genetics of the patient. Functional consequences include difficulty with activities of daily living, disturbances in emotional and social well-being, and reducing the dose or stopping chemotherapy entirely.
Possible mechanisms are damage to neuronal DNA, mitochondria, endoplasmic reticulum and cell bodies in the axons of the ganglia of the dorsal root, as well as changes in the ion channels that lead to ectopic activity.
Acute neuropathic pain associated with limb amputation
Core criteria include a history of amputation, pain that occurs within 30 days of amputation, and pain that is felt in either the amputated limb or the stump of the amputated limb. No other diagnosis explains this pain better. Other common features include telescoping, or the feeling of limb shortening for phantom pain, and spontaneous stump movements for residual limb pain – both of which tend to lose weight over time.
The pain can be modulated by psychological factors such as depression, anxiety and post-traumatic stress disorder (PTSD), the frequency and severity of pre-amplification pain, and perioperative analgesia. The functional consequences include decreased patient satisfaction, decreased quality of life, increased need for postoperative medication, and progression to chronic pain after amputation.
Possible mechanisms are damage caused by the severing of peripheral nerves, which leads to ectopic discharge, central sensitization, and reorganization of the spine and supraspinal.
“Acute neuropathic pain is … different in time from, but closely related to, chronic neuropathic pain,” the researchers wrote. “The proposed AAAPT diagnostic criteria for acute neuropathic pain are designed to distinguish it from both chronic neuropathic pain and acute non-neuropathic pain. This reflects our current understanding of their unique mechanisms and clinical features.”
Additional studies on the mechanisms, pathophysiology and epidemiology of acute neuropathic pain are needed to “determine the reliability and validity of the proposed diagnostic criteria”.
“This proposed framework for understanding acute neuropathic pain in the context of other pain conditions may allow clinicians and researchers to improve the prevention, diagnosis, and management of acute neuropathic pain,” the researchers concluded.
Doshi TL, Dworkin RH, Polomano RC et al. AAAPT diagnostic criteria for acute neuropathic pain. Pain Med. Published online on February 12, 2021. doi: 10.1093 / pm / pnaa407
This article originally appeared on Clinical Pain Advisor