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]
> -------------------------------------------------