Monday, September 24, 2012

Factors for Migraine Chronification: Central Sensitization


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I recently introduced a series of articles about the modifiable factors that may cause episodic migraines to become chronic. Today I'm breaking down the final modifiable factor, central sensitization, in more detail.

Researchers believe a phenomenon known as central sensitization may contribute to the transformation of migraine from episodic to chronic. Needless to say it is a complicated concept that is rather difficult to describe in layman's terms. 

The Basics of Central Sensitization

Central sensitization occurs after repeated experiences with pain. Specifically, chronic pain. It is a reaction to repeated activation of the nerves in the central nervous system that receive messages about pain. Over time, those nerves develop a memory for the experience of pain. The more often those nerves are activated, the stronger that memory becomes. This strengthened memory leads the nerves to react more strongly and effectively when they encounter the same stimuli in the future. 

People experiencing central sensitization will experience pain in the absence of any painful stimulation simply as a result of the strong memory of those nerves. This is because the central nervous system can change and amplify pain in such a way that the amount or intensity of someone's pain has no bearing on exposure to painful stimuli. 
 
Some information about how acute pain and chronic pain are different might be helpful to your understanding of central sensitization.
 
Acute pain is the day-to-day experience of pain that results from normal interactions with painful stimuli. Things like the pain from burning your hand cooking dinner or getting a paper cut. In this kind of situation pain is a warning system. It's the body's way of alerting you to a harmful situation. In the context of acute pain, it's helpful that the nerves that sense pain can build a memory of past exposure to pain because it helps us eliminate the danger faster. 

In contrast, chronic pain persists even when the nerves are not exposed to any kind of painful stimuli. It does not indicate the presences of disease or injury the way acute pain does. Since there is no dangerous situation to remove ourselves from there is also no easy way to eliminate the pain. Instead, it must be managed.

For information about the differences between acute and chronic pain, please read: 

How are Chronic Pain & Acute Pain Different?


Cutaneous Allodynia 

Central sensitization in migraineurs is often observed as cutaneous allodynia. In a nutshell, cutaneous allodynia is pain on the skin or scalp in the absence of exposure to something that causes pain. Many migraineurs find it painful to wash their hair, shave or wear a ponytail. This is due to cutaneous allodynia.

To learn more about cutaneous allodynia, please read: 

Migraine Comorbidities: Cutaneous Allodynia 

Researchers estimate as many as two-thirds of migraineurs experience cutaneous allodynia at some point during their migraine attacks. However, cutaneous allodynia is experienced more frequently by patients with chronic migraine than by patients with episodic migraine. There is no evidence that one causes the other. There is simply a correlation between the two. 


Preventing Central Sensitization


The main risk factors for central sensitization and cutaneous allodynia are high attack frequency, high pain intensity and high levels of migraine-related disability. All of these risk factors point toward the need for two main things: (1) appropriate treatment medications to abort and manage a patient's migraine attacks and (2) effective preventive therapy. 

While it is not possible to find effective treatment or preventive therapies for every single patient, there are many good options that will help the vast majority of patients. Knowledgeable headache disorders specialists who can provide them with this kind of effective management may help prevent the transformation of their episodic migraines into chronic status.


Do you have questions about central sensitization or any other topic in the Factors for Migraine Chronification Series? Please share them in the comments.

Related Posts:

Sources:
1. Woolf, Clifford J. "Central sensitization: Implications for the diagnosis and treatment of pain." Pain 2011; 152:S2–S15. http://www.rosslab.neurobio.pitt.edu/wp-content/themes/rosslab-theme/files/article_woolf.pdf. 2. Bigal, Marcelo E. and Lipton, Richard B. "Modifiable Risk Factors for Migraine Progression." Headache 2006; 46: 1334–1343. 3. Katsarava, Zaza; Buse, Dawn C.; Manack, Aubrey N.; and Lipton, Richard B. "Defining the Differences Between Episodic Migraine and Chronic Migraine." Current Pain and Headache Reports 2012; 16(1): 86–92. 4. Lipton, Richard B., "Tracing transformation: chronic migraine classification, progression, and epidemiology." Neurology 2009; 72: S3-7. 5. Gudin, Jeffrey A. "Expanding Our Understanding of Central Sensitization." Medscape Education, 2004. http://www.medscape.org/viewarticle/481798. Accessed September 15, 2012.

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DISCLAIMER: Nothing on this site constitutes medical or legal advice. I am a patient who is engaged and educated and enjoys sharing my experiences and news about migraines, pain and depression. Please consult your own health care providers for advice on your unique situation.