by Thomas N. Ward, MD

Endogenous analgesia has been of interest for decades. More recently, attempts have been made to standardize the assessment of conditioned pain modulation (CPM) in individuals. Of particular relevance in Headache Medicine is the nature of CPM in patients with migraine and the precise nature of alterations in patients with episodic migraine (< 15 days per month) as opposed to those with chronic migraine (≥ 15 days per month). Also of interest, is the intermediate group known as “high frequency episodic migraine” (10-14 days per month). If certain characteristics/biomarkers can be identified it may make the identification of individuals at risk for worsening or improvement of their headache pattern possible and may allow individualized treatments (personalized medicine) based on those patterns.

CPM is the means of assessing endogenous analgesia. In the past, CPM studies suffered from lack of agreement on how best to assess it. More recently, CPM assessment has become more standardized allowing for potential uniformity and reproduction of studies from different laboratories and clinics. Prediction of response to treatment in various clinical situations has been published for other medical conditions. The study by Yuan will compare CPM in healthy controls with CPM in adults with chronic migraine. Calcitonin gene-related monoclonal antibody response and remote electrical neuromodulation (REN) response will be used to assess CPM.

Defective descending pain modulation has been proposed as one mechanism by which migraine “chronifies” (worsens).  Welch et al. years ago reported iron deposition in the periaqueductal gray with resultant damage to the descending system. If individual assessment of dysfunctional CPM is possible it may become possible to determine which therapies might work in patients with migraine and which would not, thereby allowing for efficient choice of treatments, maybe even identifying treatments which should be avoided due to potential adverse effects or lack of benefit.

 

---

References:

1. Yarnitsky D, Volokh L, Ironi A et al. Nonpainful remote electrical stimulation alleviates episodic migraine pain. Neurology 2017; 88(13): 1250-1255.
2. Yarnitsky D, Bouhassira D, Drewes AM et al. Recommendations on practice of conditioned pain modulation (CPM) testing. Eur J Pain 2015; 19: 805-806.
3. Kennedy DL, Kemp HI, Ridout D et al. Reliability of conditioned pain modulation: a systematic review. Pain 2016; 157: 2410.2419.
4. Welch KMA, Nagesh V, Aurora SK, Gelman N. Periaqueductal gray matter dysfunction in migraine: cause or burden of illness? Headache 2001; 41: 629-63