10:49 25 October 02
Implanting electrodes into the brains of two patients has rid them of the symptoms of obsessive-compulsive disorder, researchers in France report.
Surgically implanted electrodes are used to treat the tremors associated with Parkinson's disease, though the method is reserved for only the most severe cases. But this study suggests that such "deep brain stimulation" could also be useful for treating behavioural problems associated with psychiatric disorders too.
Luc Mallet, Yves Agid and their colleagues from Hôpital de la Pitie-Salpêtrière in Paris had performed the surgery to treat Parkinson's symptoms. But the surgical team were unaware that two of their patients had obsessive-compulsive disorder (OCD) as well.
One patient, a 51-year-old woman, had suffered OCD for 33 years. She would repeatedly clean her home and rearrange shelves, claiming that she had a fear of being found dead in a dirty house. The second patient, a 50-year-old man, would check and recheck locks for up to three hours each day.
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Parkinson's disease
Deep brain stimulation
The Lancet
High frequency pulses
The research team implanted two small electrodes in each patient in a particular part of the basal ganglia. These are regions deep within the brain that help control movements. The electrodes produce high frequency pulses which are thought to disrupt the slower waves of nerve activity that drive tremors in Parkinson's patients.
Immediately after surgery, the patients both showed improvement in their Parkinson's symptoms, but much more marked improvements in their OCD symptoms.
It should not be a complete surprise that the two conditions are affected by the same surgery, suggests John Stein of Oxford University. "The basal ganglia are especially important for the internal generation of our actions, when there is no external stimulus," he says. This is exactly what is happening in OCD.
And researchers have already found that removing a tiny piece of brain tissue in the same part of the basal ganglia can alleviate OCD symptoms. "Ablation does more or less the same thing as stimulation," says Anne Morel of the University Hospital in Zurich. But electrical stimulation may be a better treatment, she suggests, because it can be stopped if the patient has any adverse reactions.
The researchers point out that OCD is a difficult condition to treat, and that perhaps electrode implants could be developed to help control it. But Agid cautions they must be certain that the treatment does not create any new problems.
Journal reference: Lancet (vol 360, p 1302)
Helen Phillips, Paris
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