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I certainly would appreciate if we could hear from Dr. Chris of BE his (always praised) comments about this new surgical technique . Cheers, Joao Paulo n cockle wrote: > The following was taken from a long article in New Scientist 26/2/00 > > MIEKO had no quality of life any more, says her surgeon Ali Rezai from > theCleveland Clinic in Ohio. For 15 years, she'd coped with Parkinson's > disease, but then her medication began to fail her, and she found > herselfalternating between the uncontrollable wild movements created by her > drugs and being locked motionless. > > For Antonia it was a different story. She had endured agonising pain around > her face for seven years since an operation to relieve the pressure of a > blood vessel against a nerve. Drugs did nothing. Last month, both found > instant relief when Rezai implanted a small electronic pace-maker-like > device deep inside their brains. > > Such devices appear to work by interrupting the excessive neuronal firing > that causes chronic pain or by smoothing out the strange rhythmical brain > activity that causes rigidity and tremors, much as a heart pacemaker > flattens the unusual beat rhythms of a fibrillating heart. They aren't a new > way of dealing with pain or Parkinson's disease stimulating the spine > tointerrupt pain signals was first used in the 1960s. But, if a > controversial new theory is correct, surgeons like Rezai may soon be getting > ready to fitthese "pacemakers" in a whole new group of patients with > psychiatric conditions such as obsessive compulsive disorder (OCD) and > depression, or desperately distracting sensations such as ringing in the > ears (tinnitus) or schizophrenic hallucinations. > > According to Rodolfo Llinas, a neuro-scientist at the New York > MedicalCenter, and Daniel Jeanmonod, a neurosurgeon at the University > Hospital inZurich, these conditions are united by a common feature. The > researchers believe that they are all characterised by strange, slow rhythms > of neuralactivity originating in a walnut-sized brain region called the > thalamus. > > This activity, they say, looks just as though one tiny part of the brain > has fallen asleep. The resulting disruption in the flow of signals to the > rest of the brain would produce the abnormal patterns of activity that > could account for bizarre perceptions and neurological symptoms as > wide-ranging as tinnitus and depression. Until recently, the thalamus was > considered to be no more than a simple relay station sitting at the top of > the brainstem, controlling the flow of information from our senses to the > brain's outer cortex. But interest in the region has grown since > neuroscientists discovered that when we're awake, it is working overtime, > passing on and modifying fast "gamma" rhythms of activity to the cortex that > seem to equate to conscious perception (New Scientist, 30 October 1999, p > 28). > > It's by no means a one-way flow of information. Within milliseconds of > receiving information from the thalamus, the cortex returns a signal > indicating which information might be worth dealing with. The thalamus > filters out what appears irrelevant and reinforces the relevant by sending > more signals back to the cortex. "You can't think thalamus without cortex, > or vice versa," says Jeanmonod, "It's a recurrent interplay between the > two." > > But it is not only the physical connections between the thalamus and cortex > that guide the passage of sensory infomation. The different activity > patterns of sleep or waking states are also important. Llinas describes the > thalamusas a "central switch" for sending the brain to sleep. When we fall > asleep,the thalamus lets very little information through. It becomes less > excitable,lowering its level of activity to a slow, rhythmical pattern > the"theta"and "delta" rhythms and effectively dis- connects us from > theoutside world. > > Llinas was one of the first to detect the switch from waking to sleeping > rhythms in individual thalamocortical neurons, back in 1982. He discovered > that the switch could be triggered by altering the chemi- calenvironment > orthe electrical charge of the outer membrane of the cell. More recently, he > wondered what effect switch- ing from fast to slow rhythms would have if it > occurred at the wrong time: "It would be like having one part ofyour > brainasleep," he says. But what would this then do to the cortex? Howmight > thisalter peo- ple's perceptions of the outside world, and theirhealth? > "Itwould be terrible if you got stuck in any one of thesesituations." > > One of the first groups of patients Llinas looked at with these ideas > inmindwere people with Parkinson's disease, who were experiencing limb > tremors. He noticed that their muscles were twitching in time to a theta > rhythm between three and six twitches every second. At the same time, he was > able to record electrical activity across the brain using a technique called > magnetoencephalography, or MEG, and found the same rhythmic activity > appearing in the areas of the cortex that were responsible for initiating > and sensing movement. He suspected that the rhythms originatedin theregion > of the thalamus connected to these cortical areas (Neurology^vol 46,p 1359). > > This set him wondering whether some- thing similar could occur in partsofthe > thalamus related to other areas of the ner- vous system, such asthevisual, > auditory and emotional areas, and not just in thoseregionsresponsible for > movement. > > Meanwhile, Jeanmonod had been recording electrical activity directly > inthebrains of patients with Parkinson's disease and chronic pain who > hadbeenreferred to him for brain surgery because they had failed to > respondtonormal drug treatment. > > Like many surgeons, Jeanmonod routinely destroyed small parts of > thethal-amus in order to bring Parkinson's tremors under contro a common > alternative to implanting a pacemaker. This approach was decades old,even > though surgeons had only the vaguest idea of how it could relieve > symptoms.The problem, however, was that some patients suffered severe side > effects,ranging from defects in language and analytical thinking to > paralysis, when surrounding brain tissue was damaged. Jeanmonod hoped that > by recording the activity in the thalamus, using tiny electrodes implanted > during exploratory surgery, he would be able to pinpoint exactly which areas > were abnormal, and so target his surgery more precisely. > > He found the sleep-like theta rhythms in the thalamus in patients with > Parkin- son's disease and chronic pain when they were awake. Just as Llinas > had suspected, Jeanmonod managed to pin the rhythms down to two neighbouring > regions of the thalamus, which together are responsible forpassing on > movement and pain sensa- tions. By destroying only the affected part of > thethalamus, Jeanmonod was able to considerably improve the outcome of his > surgery, and has now operated on more than 50 people with Parkinson's,and > more than 100 with chronic pain, using theta rhythms for guidance > ------------------------------------------------- > Nigel Cockle > 59 Norley Road, Cuddington, Northwich, Cheshire. CW8 2JY England > Tel +44 1606 882150 > Email [log in to unmask] > -------------------------------------------------