Rome

A controversial experimental technique for treating certain psychiatric disorders is producing encouraging results, according to the neurologists who are testing it.

The technique, known as deep brain stimulation, uses an electric current from implanted electrodes to modulate brain function and has already raised ethical concerns (see Nature 417, 677; 2002).

But at the The Human Brain, an international conference held in Rome earlier this month, researchers said that the technique is showing promise. As a result, they pledged to set up an international collaboration to speed its development.

Volker Sturm: electrode therapy can help. Credit: FONDAZIONE SANTA LUCIA, ROME

At the meeting, neurosurgeon Volker Sturm of the University of Cologne presented data on 3 of the first 20 or so patients to have the therapy for obsessive-compulsive disorder. All showed improvements in their symptoms, he said. One patient, for example, who had been unable to look after her young son because of her compulsion to check repeatedly if he had been suffocated by his pillows at night, showed a marked reduction in her compulsion a few weeks after the treatment, Sturm said.

Bart Nuttin, of the Catholic University of Leuven in Belgium, published the first pilot study of four patients using this technique (B. Nuttin et al. Lancet 354, 1526; 1999), which has now been replicated at three centres in the United States. These centres plan to join several others in Europe to cooperate on optimizing the technique.

Ethical guidelines for the use of deep brain stimulation to treat psychiatric illness were published two months ago (B. Nuttin et al. Neurosurgery 51, 519; 2002). The technique has already been used to help hundreds of people with Parkinson's disease to move more normally, says Sturm, who has operated on over 200 Parkinson's patients.

The neural pathways that underpin obsessive-compulsive disorder are better understood than those of most psychiatric disorders, which means that very precise anatomical structures in the brain can be targeted by neurosurgeons. Some 15% of people with the disorder commit suicide, although prospects for patients who are resistant to drug or behavioural therapy have been improved by lesion of brain structures known as internal capsules. But such surgery is irreversible. “Deep brain simulation is theoretically preferable to lesioning,” says Nuttin. “An electrode can be switched off or removed.”

The international collaboration will seek to determine the most effective location for the electrodes and the optimal level of current. Most of the operations performed so far have placed electrodes in the anterior limbs of the internal capsules. Sturm places his electrodes in a nearby structure, the shell of the nucleus accumbens. “We have been able to use a much lower level of current than studies using implants in the internal capsules,” he says.

Neurologists do not understand how the technique brings obsessive-compulsive disorder under control. Suppression of obsessive symptoms can require weeks of stimulation, although a patient's mood can be altered within seconds. In contrast, the clinical improvement derived from the technique in Parkinson's patients is immediate.