Evidence for Subgroups of Fibromyalgia
Date: 11th May 2022 | By: Dr Lourdes Gaspar
To mark National Fibromyalgia awareness day (12th May 22) and raising awareness and information about the condition, we review a paper looking at the possibility of subgroups of Fibromyalgia Syndrome (FMS).
This is a fascinating study investigating the possibility of subgroups of fibromyalgia.Fibromyalgia has long been thought of as having altered pain processing within the central nervous system (see explanatory animation at ACTforPAIN.com) as the major pathological course. However it has been known that there may be changes in the small nerve fibres in the peripheral nervous system in some cases.
Skin biopsies (small section of skin) in some people diagnosed with fibromyalgia syndrome, have been shown to have a reduced density of small nerves fibres.
The relative importance of central nervous system (CNS) and peripheral nervous system (PNS) abnormalities in fibromyalgia is unclear at present.
This research group studied used functional MRI scans looking for changes in the brain matter in those patients diagnosed with fibromyalgia syndrome that have detectable abnormalities in the small nerves in the peripheral nervous system.
In the study brain scans were carried out on the following groups,
- “Normal patients”, do not have fibromyalgia called the “Normal control group”.
- Patients diagnosed with fibromyalgia with normal levels of small fibres in the PNS called “FMS normal PNS
- Patients diagnosed with FMS and shown to have reduced small nerve fibres in the PNS called “FMS abnormal PNS”.
The brains were analysed for cortical volume, for white-matter and for functional connectivity using functional MRI scans.
The studies found that those patients that both “FMS normal PNS” and “FMS abnormal PNS” had brain scans which differed from the “Normal control group”. In both types of the FMS subgroups, the scans showed a decrease in brain matter compared to the “Normal control group”.
However they found further changes between the two FMS groups.
The main findings were that the results showed that subgroup “FMS abnormal PNS” had greater alterations in the structure and functional connectivity compared to those with “FMS normal PNS”.
They concluded that this was the first study which demonstrated the differences between FMS subgroups with and without peripheral nervous system abnormality involvement.