The Pain Brain: Hippocampal Atrophy Found in Fibromyalgia

The Pain Brain: Hippocampal Atrophy Found in Fibromyalgia – Health Rising

Reductions in the volume of “gray matter” (the neuronal cell bodies and glial cells as opposed to the long nerve fibers) have been found in the insular, anterior cingulate cortices and the amygdala in the brains of FM patients.

Other issues have been found in the thalamus, the basal ganglia, the  parahippocampal gyrus,  the premotor cortex, motor cortex, the somatosensory cortices and the prefrontal cortex in the brain.

Other abnormalities have been found in the connections between various parts of the brain 

This Florida group was looking to add another brain region to the list: the hippocampus, a part of the limbic system that plays an important role in short-term memory (remember that?), long-term memory (generally thought to be intact) and “spatial navigation”.

The hippocampus isn’t directly involved in the production of pain but a breakdown in hippocampal functioning could lead to a “feed-forward” process that ends up disrupting the  limbic system and the pain networks in the brain.

Hippocampal problems could then conceivably result in discomfort, severe pain, anxiety and perhaps even the  mysterious and disturbing allodynia that some people with FM experience.

Because hippocampal atrophy is also present in depression and because depression is fairly common in fibromyalgia, the atrophy could have been due to depression.

Results

The hippocampus is made up of two hemispheres and hippocampal grey matter volumes were significantly reduced in both of them (p<.o8, p<.02).   Because the atrophy was independent of depression, it was coming from or contributing to fibromyalgia not depression.

A meta-analysis of magnetic resonance spectroscopy  findings concluded significant hippocampal NAA reductions are present in FM. A recent study linked cognitive problems in fibromyalgia with hippocampal dysfunction.

Glutamate/GABA and Nervous System Burnout

Nervous system “burnout” occurs when the excitatory part of the nervous system  triggers so much activity that nervous system cells get killed off.

Powered by glutamate and inhibited by GABA, several researchers have proposed that nervous system over excitation could be causing or contributing to the hypersensitive pain state found in FM.

Increased glutamate levels or ratio’s appear to be widespread in FM having been found in the insula, thalamus and posterior gyrus and have been linked to increased pain in several studies

Drugs that tamp down glutamate neurotransmission such as Lyrica, sodium oxybate and ketamine can be helpful for some patients.

A recent study suggested transcranial direct stimulation (tDS) reduces pain  in FM by reducing brain glutamate and increasing brain GABA levels.

Dietary glutamate (MSG), intriguingly, was associated with increased symptom severity in FM in one study

Here’s the PubMed study on glutmate:
http://www.ncbi.nlm.nih.gov/pubmed/22766026