Deep Brain Stimulation

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Mike Robins was diagnosed with Parkinson's disease 13 years ago. A successful businessman, his life was drastically changed when he had to deal with the constant tremors caused by the disease. Seven years ago, he was proposed a new treatment involving brain surgery called Deep Brain Stimulation (DBS) and was one of the first people in the world to undergo this procedure. It was successful and all the symptoms of the disease were eradicated. Today about 40,000 people have received DBS and although there is serious surgery involved, the positive results have encouraged researchers to look into how it could be used to treat other neurological diseases. DBSinvolves implanting one (or in some cases two) electrodes in certainareas of the brain. These are attached by wires to a pacemaker justunder the collarbone. The pacemaker controls the strength and rate ofhigh-frequency electrical impulses that are sent up wires embedded inthe neck to the electrodes. The impulses either completely stop orseverely reduce the activity in the area of the brain where theelectrodes are located. Theeffects of DBS can be dramatically displayed by watching Robins operatehis pacemaker. It can be turned on and off almost magically by holdinga magnet against the area of the chest where it is implanted. WhenRobins turns off his pacemaker he begins to shake and shudder down theright-hand side of his body. His speech becomes laboured and he isclearly stressed as he puts considerable effort in continuing to pacethe room as he did with such ease a few moments ago. Bringing themagnet to his chest again, his body relaxes and his breathing returnsto a normal rate as his pacemaker is reactivated. Photo courtesy of Medtronic, Inc Brain pacemaker: Similar to a cardiac pacemaker, this one sends electrical impulses to electrodes in the brain. In the case of Parkinson's disease, DBS stops the overactivity that causes muscle tremors and stiffness of limbs. These symptoms are caused by a lack of the neurotransmitter dopamine in the brain. Cells of the substantia nigra - an area of the brain just above the brain stem - normally make dopamine but Parkinson's causes these cells to die, resulting in a lack of dopamine. Since dopamine helps to regulate areas of the brain that control movement, like the thalamus, subthalamic nucleus and the globus pallidus, a lack of it causes some of these areas to go into overdrive. By targeting these areas, DBS can block the unwanted nerve traffic. Itmay sound like a miracle treatment, but DBS does involve major surgery.Most seriously, any brain surgery carries a risk of cerebralhaemorrhage - bleeding on the brain - and the impairment of other brainfunctions like speech and vision. With DBS surgery, there is the addedpossibility of the implant dislodging or becoming infected, the patientsimply not responding to the treatment and the need to undergo furthersurgery to replace the pacemaker about every four years when thebattery runs out. Interms of post-operative care, it can sometimes be hard to find anelectrical impulse with the right frequency and voltage for thepatient. And although DBS may permanently remove the symptoms ofParkinson's, it also ties the patient to permanent aftercare. Thereare other options for Parkinson's sufferers but these also have theirdrawbacks. Lesional surgery, in which the overactive areas of the brainare burned or cut, cannot be used for all patients since some aofthe brain are too sensitive to be treated in this manner. Drugs, manyof which mimic the effects of dopamine, can also be used and are asuccessful treatment for some patients, though they can lose theireffectiveness over time. Some patients suffer side effects from drugssuch as involuntary movements, nausea, hallucinations and irregularheartbeat depending on the class of drug being taken. About one in fivepatients do not respond to drugs at all, and these are the patientsmost likely to be considered for DBS.