SPECT trial helpssolve mysteryof fibromyalgia

Millions of adults who suffer from chronic pain may no longer need to bear the added burden of wondering if their discomfort originates from a condition called fibromyalgia rather than depression or anxiety.

French researchers have used SPECT to identify brain abnormalities that present physiological evidence of fibromyalgia.

Dr. Eric Guedj of the Service Central de Biophysique et de Médecine Nucléaire at Assistance Publique des Hôpitaux de Marseille and colleagues investigated the specific clinical correlate of functional abnormalities of the brain using a technetium-99m-labeled probe and SPECT in 30 women (J Nucl Med 2008;49:1798-1803). Patients were injected with cysteinate dimer labeled with Tc-99m and kept at rest for one hour in quiet surroundings with their eyes closed. Guedj and colleagues performed SPECT using a dual-head gamma camera equipped with fanbeam collimation in 64 projections through 360º of rotation.

Twenty fibromyalgia patients exhibited posterior hyperperfusion in the somatosensory cortex and hypoperfusion of the frontal, cingulated, temporal, and cerebellar cortices. While also noting distinct perfusion in fibromyalgia patients, Guedj and colleagues found a correlation between degree of perfusion and severity of pain.

Patients who experienced symptoms of fibromyalgia more intensely had higher blood flow to the parietal areas, which are known to discriminate pain intensity, as well as lower blood flow within anterior temporal areas, known to be involved with emotional aspects of pain.

Study subjects evaluated the severity of their symptoms using the Fibromyalgia Impact Questionnaire, a standardized, self-administered survey consisting of visual analog scales and questions regarding limitations on activities of daily living such as the number of days the subject was unable to work. Anxiety and depression levels were also assessed.

The FIQ total score correlated positively with perfusion of the bilateral superior parietal lobules, bilateral precuneus, left postcentral cortex, and right pre- and postcentral cortex. The FIQ total score correlated negatively with perfusion of a left anterior temporal cluster, including the inferior, middle, and superior temporal gyri, fusiform gyrus, and uncus.

Previously, researchers thought functional brain abnormalities for fibromyalgia were related to psychological or psychiatric symptoms, Guedj said.

“We showed in our study that the functional abnormalities observed were mainly related to disability and not to anxiety and depression status,” he said.