The sophisticated science of brain scanning may be on the brink of revolutionizing the intuitive art of psychiatry, one of the few domains left in medicine in which a doctor’s educated guess is still the most common way to figure out what’s wrong
To be sure, brain scanning is still too young a science to be used for routine diagnosis of the most common psychiatric ills. But it is already proving invaluable in understanding the underlying abnormalities in a wide range of psychiatric disorders including obsessive compulsive disorder (OCD), schizophrenia, anxiety and depression.
Obsessive-compulsive disorder, for instance, which strikes roughly 8 million Americans, is a potentially disabling condition in which recurrent fears, images or impulses cause severe anxiety and drive people to repetitive behaviors such as compulsive hand-washing, arranging, checking or hoarding.
At the University of California, Los Angeles, doctors are experimenting with PET (positron emission tomography) scanning to predict which patients with OCD or major depression will respond to the anti-depressant drug, Paxil, and which won’t. (In PET scans, patients are given a radioactive form of the sugar, glucose; the color-coded images show, in real time, which areas of the brain are using the most glucose and are working hardest.)
One patient in the UCLA study, Marc Pincus, is a 41-year old office manager who used to wake up at night and feel he had to turn his head toward the clock exactly 19 times (once for each family member) within one minute to protect them from disaster. “If, by chance, the clock changed, I had to start again. So I didn’t get a lot of sleep,” recalls Pincus, who knew this was not protecting anyone but felt he had to do it anyway.
Just as Pincus’ initial PET scan predicted, he had a good response to Paxil. A second PET scan after several months on the drug showed the characteristic changes of a good response to the drug.
The lead researcher, Dr. Sanjaya Saxena, an associate professor at the UCLA Neuropsychiatric Institute, says that PET scans have “the potential to be used for identifying patterns of brain activity that predict response” to therapy for both OCD and depression, even though the scans confirmed that the underlying brain abnormalities in OCD and depression are different.
At Massachusetts General Hospital in Boston, Dr. Scott Rauch, director of psychiatric neuroimaging, has long been using PET and other scans in psychiatric illnesses. In OCD, he and his colleagues scan patients first, while they are resting, then they touch them with feared objects that induce obsessions.
“You see the circuitry light up,” says Rauch, noting that the abnormal brain circuits involve nerve pathways from the orbitofrontal cortex (behind the eyes) to the caudate nucleus (part of the basal ganglia) and thalamus, which lie deep within the brain.
Rauch and his colleagues have also shown that abnormal neural activity in the anterior cingulate portion of the OCD pathway can predict how well people with severe, intractable OCD respond to surgery in which doctors interrupt the pathways through tiny cuts.
Armed with patients’ scans, brain surgeons are now trying a potentially better approach – implanting permanent electrodes (brain pacemakers) into the abnormal brain tissue to modulate the abnormal electrical activity, a technique, called deep brain stimulation, already being used to treat Parkinson’s disease.
More than 15 patients with severe OCD have received the implants from doctors in a multi-center study based at the Cleveland Clinic in Ohio, Butler Hospital in Providence, R.I. and the University of Leuven in Belgium. The electrodes, made by Medtronic, Inc., can be turned up or down by the doctor, making the procedure is reversible – unlike traditional neurosurgery.
Dr. Ali Rezai, director of functional neurosurgery at the Cleveland Clinic, says patients who have had the electrodes implanted show an average 35.7 percent improvement in OCD symptoms. At Butler Hospital, Dr. Benjamin Greenberg, who heads the brain stimulation work in OCD, says that while longer follow up is needed, initial results seem “promising.” The researchers are also trying deep brain stimulation for intractable depression.
Elsewhere, researchers are using other types of scans to probe other psychiatric afflictions. At the National Institute of Mental Health, researchers have used MRI, or magnetic resonance imaging, to study ADHD, or attention deficit hyperactivity disorder in children. (In MRI, a magnet induces chemicals in the body to emit characteristic radio signals. These signals are converted into 3-D images that show the anatomical structure of the brain. No radioactive drugs are needed.) They found their brains to be 3 to 4 percent smaller than those of normal children.
Other researchers are using a variant of MRI called fMRI, or functional MRI, to study brain abnormalities in schizophrenia and other disorders. (Functional MRI provides a real-time image of the brain’s functions, not just structure, by tracking blood flow.)
At Johns Hopkins University, Dr. Rudolf Hoehn-Saric, a professor emeritus of psychiatry, is using fMRI to compare the brains of normal and anxious people. In tests involving listening to recordings of personal worries, people with generalized anxiety disorder, his research shows, have increases in activation in parts of the prefrontal cortex (the thinking part of the brain) and in parts of the emotional brain, or limbic system, including the hippocampus. But after seven weeks on the medication Celexa, an anti-depressant, the patients’ scans improved considerably, says Hoehn-Saric.
In fact, many of the drugs, like Celexa, that were originally designed to combat depression also seem to work for anxiety, which raises a question the imaging scientists haven’t quite answered yet.
“We know that anxiety and depression, while distinct syndromes, have certain common clinical features and both respond to similar drugs,” says Dr. Helen Mayberg, chair of neuropsychiatry at the Rotman Research Institute at the University of Toronto. “Interestingly, when we get to scanning, we can see at the brain level what might account for some of these similarities and differences.”
In other words, brain scans may never substitute for intuitive guesswork by a good psychiatrist. Nor should they. But they will undoubtedly be increasingly useful in helping doctors figure out which patients with severe psychiatric illnesses are most likely to respond to treatments.