Central sensitization: The key to chronic pain

Unlike acute pain, most chronic pain conditions are characterized by “central sensitization.” This is a process where the pain is encoded directly by the brain. The patient therefore may experience pain without any body injury or inflammation. There are no quick cures for central sensitization. It requires specific treatments often delivered repeatedly or over long periods of time.

Characteristic Features

In temporal summation, repeated stimulations at the same intensity cause build-up of pain over time, making it more painful with each stimulation

In spatial summation, painful stimulation in one area causes other areas around it to become more sensitive.

Risk

Given the severe sensitivity, some patients are not good candidates for invasive procedures which can trigger more pain.

Mechanisms

In the brain, neurons as the most important functional cells. But studies show that it is the support cells — the glial cells — that are pathologic in central sensitization.

Treatments

Because “central sensitization” is essentially the brain using the machinery for learning memory on pain signals, treating it involves helping the brain unlearn. This involves medications that work on memory like ketamine and memantine, glial-cell modulators like naltrexone. Just like learning which takes practice, repetition also helps the brain unlearn: repeat nerve blocks, peripheral nerve stimulators, and spinal cord stimulators are treatment options in some patients. Transcranial magnetic stimulation is an emerging treatment for this condition.