fMRI in Fibromyalgia Syndrome and the response to milnacipran

A scientist from Pierre Fabre has used Functional magnetic resonance imagery to show that Fibromyalgia Syndrome patients treated with milnacipran exhibit a reduction in pain sensitivity and a parallel increase in activity in brain regions implicated in the descending pain inhibitory pathways .

Pharmaceutical firm Pierre Fabre originally developed milnacipran and sells the medication outside the United States. In the US, Milnacipran is marketed as Savella by Cypress Bioscience and Forest Laboratories. Savella was approved as a treatment for Fibromyalgia Syndrome by the American Food & Drug Administration (FDA) in January 2009 and was made available commercially in the US as a treatment for Fibromyalgia Syndrome at the end of April 2009.

Functional imaging has been used to study the response to pain in Fibromyalgia Syndrome (Fibro) patients. Functional magnetic resonance imagery (fMRI), which tracks local changes in blood flow, has a higher spatial and temporal resolution than other techniques such as positron emission tomography (PET) or single-photon emission tomography (SPECT). The speed of fMRI machines allow them to be used to track changes in real time, rather than taking a static snapshot, as with conventional MRI.

fMRI studies in Fibro patients suggest that similar levels of subjective pain result in similar central nervous system (CNS) activation in both Fibro patients and controls. For a similar stimulus, however, Fibro patients have a greater subjective sensation of pain.

This increased sensitivity is accompanied with a decreased activity in brain regions implicated in the descending pain inhibitory pathways, which would usually work to dampen pain signals.

The hypothesis that increased sensitivity to pain is due to decreased activity of the descending inhibitory pathways is supported by results with milnacipran. As a serotonin and noradrenaline reuptake inhibitor, milnacipran boosts levels of the neurotransmitters - serotonin & norepinephrine - involved in the descending inhibitory pain pathways.

Using fMRI, the study found that Fibro patients treated with milnacipran exhibited a reduction in pain sensitivity and a parallel increase in activity in brain regions implicated in the descending pain inhibitory pathways compared to placebo-treated patients.

References:

1. Mainguy Y. Functional magnetic resonance imagery (fMRI) in fibromyalgia and the response to milnacipran. Hum Psychopharmacol. 2009 Jun;24 Suppl 1:S19-23.