麻豆传媒

SAN DIEGO -- A course of transcranial magnetic stimulation (TMS) helped about half of patients with binge/purge eating disorders to cut the frequency of such episodes significantly, a researcher said here.

Among 18 patients with diagnoses marked by bingeing and purging, nine showed at least 50% reductions in bingeing frequency and 10 had reductions of 50% or more in purgings, said Jonathan Downar, MD, PhD, of the University of Toronto.

Four of the patients showed complete resolution of bingeing a week after completing the 20-session TMS course, he said at a press conference at the Society for Neuroscience's annual meeting. And three of those patients were also no longer purging and in the fourth, purging frequency was cut by 92%.

Functional MRI brain scans showed that responders typically had poor connectivity between the frontal lobe and brain centers related to reward, craving, and emotional processing, whereas nonresponders had perhaps too much connectivity, Downar said.

In effect, he said, the responders "are missing a piece and we're filling it in" with TMS therapy.

"This is a very exciting area of research," said press conference moderator Fernando Gomez-Pinilla, PhD, of the University California Los Angeles.

He suggested that the relationship between eating and mood is bidirectional. "Do we have a mood problem because of what we eat, or is it just the opposite -- because we have mood disorders, we change our eating behavior? Maybe the answer is both. It makes the situation very complicated, because it's sort of a vicious circle that extends for life."

Downar, who administers TMS therapy at a depression clinic, first began investigating the treatment's potential in binge/purge disorders after discovering by accident that it essentially cured the condition in a 42-year-old woman with a long history of bulimia.

For the current study, he and his colleagues recruited 18 patients with mean pretreatment weekly frequencies of bingeing and purging of 11.44 (SD 10.11) and 14.94 (SD 16.46), respectively.

Nine of the patients had been diagnosed with the bingeing subtype of anorexia nervosa, eight had bulimia nervosa, and one had a diagnosis of "eating disorder not otherwise specified" that included binge and purge episodes. Patients had received prior medical and cognitive therapies without adequate responses.

TMS was administered in 20 sessions, directed to the dorsolateral prefrontal cortex, with scalp placement nearest to Talairach coordinates of x-0, y+30, z+30. Pulse frequency was 10 Hz, delivered at 5 sec on and 10 sec off, for 60 trains (total 3,000 pulses per hemisphere). Patients had sessions daily for 5 days each week for 4 weeks.

Of course, with approximately half of the patients showing clinically significant responses about half did not. Downar said that episode frequency for binging and purging worsened in two patients (not the same two in each symptom category). Most of the other nonresponders did show some minimal benefit.

The fMRI studies also included 18 age- and sex-matched controls to provide a reference for the connectivity findings in the patients, who were stratified according to response status.

In particular, the researchers examined connectivity from the dorsolateral prefrontal cortex to the striatum and midbrain, and from the subgenual anterior cingulate cortex (sgACC) to the striatum and midbrain.

Very different patterns were seen in responders and nonresponders in each case, with results in healthy controls somewhere in between. Overall, relative to controls, connectivity in treatment responders was blunted and was exaggerated in the nonresponders.

Specific brain regions showing reduced connectivity to the sgACC in the treatment responders included the dorsal raphe and bilateral amygdala. Downar said this was indicative of emotional lability, which could explain the "nervosa" elements attached to anorexia and bulimia.

He said it remains unclear how patients with the same clinical phenotype can show these opposing fMRI findings. He said calorie intake may play a role, as patients with eating disorders may not eat regularly despite abatement of their worst symptoms.

"We've had people who got better, and then they come back to us a few months later at a different time in their lives when they're not eating as much food and they're down to maybe 500 calories per day -- their brain is in starvation mode," he said. "Having a decent calorie intake may be important."

In depressed patients, he added metaphorically, "there are some people who are lacking in their brakes and others who are lacking in their accelerator. Their reward circuitry is just not pointing in the right direction. We think there is some other pathology in these nonresponders."

In the context of binge/purge disorders and excessive connectivity in the nonresponders to TMS, he said, "there may be people who can't think their way out of stress versus others who are actively thinking their way into stress."

"If that's the case, I can't fix it with a [magnetic] coil, for the same reason I can't use it to teach you Arabic or how to play the saxophone. You have to change the language of your thinking, as opposed to changing the volume."

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