The usefulness of established molecular imaging/nuclear medicine approaches in identifying the “hows” and “whys” of brain dysfunction and its potential in providing immediately useful information in treating depression are emphasized in a study in the August Journal of Nuclear Medicine.
“Individuals in a depressed emotional state have impaired cerebral (brain) blood flow,” explained Omer Bonne, head of inpatient psychiatry and associate professor in the Department of Psychiatry at Hadassah-Hebrew University Medical Center in Jerusalem, Israel. “Clinical improvement in depression is accompanied by diverse changes in cerebral blood flow, according to whether patients are treated with medication or electroconvulsive treatment,” he noted. “We found that antidepressant medicines normalized decreased brain blood flow usually seen in patients with depression, while electroconvulsive treatment was associated with additional decreases in blood flow,” he reported. “Currently, clinical psychiatry is based almost solely on subjective observer-based judgment. Our findings suggest that objective imaging evaluations could support subjective clinical decisions,” he said.
Using SPECT (single photon emission computed tomography)—a molecular imaging/nuclear medicine procedure in which injected radiotracers are utilized to produce three-dimensional, computer-reconstructed images that reveal information about both structure and function—investigators confirmed already published findings that cerebral blood flow in depressed patients is lower than in healthy control subjects, especially in frontal, limbic and subcortical brain regions. “We wanted to see whether improvement in clinical depression is accompanied by changes—increases—in cerebral blood flow,” he said. “We found that cerebral blood flow increased only in patients whose depression improved. In contrast, cerebral blood flow remained unchanged in patients whose depressed condition persisted,” detailed Bonne.
Depression is a serious and debilitating—yet treatable—disease that affects every aspect of a person’s health. Estimates indicate that 19 million Americans are affected by depression each year, along with their family members, friends and co-workers. Depression may be related to a chemical imbalance in the brain that makes it hard for the cells to communicate with one another. A variety of antidepressant medications and psychotherapies are used to treat depression. Sometimes electroconvulsive therapy—applying an electric current briefly to produce a seizure—is useful, especially for those whose depression is severe or life threatening or for whom repeated treatment trials with antidepressant drugs failed.
“Interestingly, patients’ response to two different classes of antidepressant medicines that target different neurotransmitters is associated with a similar improvement in cerebral blood flow,” he noted. “However, cerebral blood flow continued to deteriorate in patients who responded to electroconvulsive therapy,” added Bonne, who helped implement functional brain imaging research in psychiatry at Hadassah. Israeli researchers studied 33 depressed patients and 25 healthy control subjects with SPECT and the radiotracer 99mTc-HMPAO.
“Our findings may aid in elucidating the mechanism of depression and its treatment,” said Bonne. “There may be more than one mechanism responsible for the development of depression and for mediating response to its treatment,” he added. Additional research could examine whether it’s possible to use functional imaging techniques to determine which patients would benefit from drug treatment and which would respond better to electroconvulsive therapy, explained Bonne. Future research should also examine the differences in brain blood flow in patients at later time points, he said.
Source : Society of Nuclear Medicine