A brief history of brain surgery in Parkinson’s
Undergoing brain surgery may sound dramatic, but for around 300 people with Parkinson’s in the UK each year it is a lifeline that promises better symptom management and quality of life. We look back on how far research has come and current progress being made.
Surgery for movement disorders was pioneered in the early 1900s. At this time it wasn’t clear which areas of the brain were involved in the condition. Even in 1940 surgeons were attempting to cut away portions of the cerebral cortex (the crinkled outer layer of the brain responsible for memory, thought and consciousness amongst other things) to treat Parkinson’s with significant side effects.
It was an American neurosurgeon, Russel Meyers, who first focused on the basal ganglia, the area of the brain now known to be centrally involved in Parkinson’s. He performed surgery on one person with Parkinson’s to damage this specific brain structure. The results, reported in the 1940s, showed that the surgery improved tremor, rigidity and walking and underpin lesioning surgery that continues to be used today.
The basic principle of lesioning surgery is that as Parkinson’s causes some brain cells to be lost, specific areas of the brain become less active compared to other areas and this imbalance causes a tremor. But, by surgically targeting specific parts of the brain that are too active, it is possible to reestablish the balance in the brain and reduce tremor.
Other surgical lesioning treatments for Parkinson’s appeared in the 1950s. These involved:
- injecting alcohol to damage a specific part of the brain called the globus pallidus — surgery that targets this area of the brain is known as pallidotomy
- damaging a tiny part of the brain known as the thamalus — known as thalamotomy.
With surgery being found to relieve tremor and rigidity, although not without significant risks, thalamotomy became the most common surgical intervention for Parkinson’s with over 70,000 operations worldwide being counted by the mid 1970s.
Both thalamotomy and pallidotomy are still in use today however, they are now only used in rare cases. But research into lesioning has continued.
In the last few years, researchers have investigated using focused ultrasound, very high-frequency sound waves, to burn away specific brain cells deep inside the brain. This would make the lesioning surgery less invasive.
However, even with advances in lesioning techniques, this type of surgery still has drawbacks. It is permanent, cannot be fine-tuned over time, and most of the time can only be used on one side of the brain so cannot treat symptoms that affect both sides of the body.
It is because of these limitations that another type of surgery for Parkinson’s leads the way.
Stimulating the brain with electricity
Today, the most common type of surgery for Parkinson’s is known as deep brain stimulation (DBS). In DBS, very fine wires are carefully inserted into the brain to electrically stimulate particular groups of brain cells involved in controlling movement to adjust their activity.
But stimulating the brain with electricity is not a new idea. Indeed, in 46 AD Scribonius Largo, physician of the Roman emperor Claudius, describes using electric eels applied to the head to treat headaches. Needless to say, this isn’t recommended today.
It wasn’t until the 19th century that physicians started to investigate the potential of brain stimulation to treat neuropsychiatric disorders. And a brain stimulation therapy known as electroshock, introduced by Italian Neurologist Ugo Cerletti for the treatment of severe psychosis in 1938, was the first modern example of therapeutic application.
In the 1940s, this therapy became so popular that it was often performed on an out-patient basis. But electroshock was misused and abused, it was indiscriminately used on people who wouldn’t benefit from the therapy or in order to control "uncontrollable", often female, patients in mental institutions.
Today, the use of electroshock remains controversial and is often used only as a last resort. And while there is evidence showing it can be effective in the treatment of a very specific set of mental health disorders, there are still significant risks that are not fully understood.
But electroshock wasn’t the only type of brain stimulation being investigated and by the 1950s stimulation was successfully being used for pain control. The understanding of how this stimulation worked laid the foundation for new techniques of neurostimulation that are still in use today including transcranial magnetic stimulation, cortical brain stimulation, and deep brain stimulation (DBS).
Different types of brain stimulation
Transcranial magnetic stimulation is a non-invasive form of brain stimulation that involves placing a strong magnetic field over the skull causing very brief electrical stimulation of the nerves underneath. But while this technique has been approved to treat mental health disorders like depression and obsessive and compulsive behaviours in the US. In clinical trials for the treatment of Parkinson’s symptoms, including depression and problems with gait (walking), it has produced somewhat disappointing results.
Similarly, cortical brain stimulation, which involves surgically implanting electrodes on the surface of the brain, has yet to provide any robust, conclusive results for Parkinson’s. Instead, it is the brain stimulation approaches that require surgery to transplant electrodes deep into the brain, close to the areas that are affected by Parkinson's, which have shown great benefit.
Deep electrical stimulation of brain structures was originally introduced as a therapeutic option to treat behavioural disorders or chronic pain, but studies in the 1960s noted that while low-frequency stimulation (in the region of 5 to 10 Hz) could worsen tremor, high-frequency stimulation (50 to 100 Hz) reduced this symptom.
From brain chips to Parkinson’s treatment
The 1960s were an interesting time in brain stimulation research, and also marked a turning point in Parkinson’s management with the introduction of levodopa.
In 1963, there was a demonstration by a theatrical Spanish neuroscientist, José M. Delgadoof, that involved implanting a brain chip, a device containing radio-controlled electrodes, into the brain of a bull to stop it from charging at the press of a button. Read more about the use of brain chips on the National Library of Medicine website.
In the same year, Russian researcher Natalia Petrovna Bekthereva published the first report where implanted electrodes were used as a therapy for movement disorders in people. Natalia's report is available to read, in Russian, on the National Library of Medicine website.
But this paper, written in Russian, went largely unnoticed. And while DBS had found its clinical use for the treatment of pain, it wasn’t until 1991 that the first studies on the use of DBS to treat tremor emerged. Shortly after DBS was shown to be more effective than previous lesioning surgeries leading to a shift in the surgical approach to Parkinson’s.
Recent advances in DBS for Parkinson’s
Developments in DBS for Parkinson’s since the early 1990s have advanced our understanding of how electrodes placed in different parts of the brain can improve symptoms, reduce risks, and deliver more effective treatment.
In 2002, the Medical Research Council and Parkinson’s UK funded the largest and most comprehensive trial of deep brain stimulation to date, to understand the risks and benefits of this treatment compared to medication alone. The results, published in 2010, helped DBS become a mainstream treatment for people with Parkinson’s.
In the last decade, several randomized controlled trials have found that few treatments are as effective as DBS for controlling the troubling motor symptoms of Parkinson’s. These advances mean that today, approximately 300 people now undergo DBS in the UK each year and its impact for those individuals can be life-changing.
However, the therapy isn’t without limitations and challenges. DBS is highly effective in some patients but unsuitable in others. It cannot address all the motor symptoms of Parkinson’s and may even make some symptoms like speech worse. And while the risks are low, the invasive nature of this therapy means that they can be potentially serious and include infection and haemorrhage.
And so researchers continue to work to improve this therapy and make it more practical by extending the life of the implanted battery that powers the stimulator, designing smaller devices, integrating wireless technology, and developing more tailored and adaptive stimulation.
It is in this latter area that there have been the most recent developments which could revolutionise DBS as a treatment for Parkinson’s. Adaptive stimulation tries to overcome a feature of standard DBS which can be periodically adjusted but, for the most part, is provided constantly at the same level.
Adaptive DBS takes a step towards targeting the stimulation when it is required rather than providing it constantly at the same level. It works by measuring brain waves to adapt the stimulation to manage a person’s symptoms in real-time and researchers have started the first clinical trials.
Even more recently, studies have reported the potential of DBS to possibly slow the rate of progression of Parkinson’s, opening the door to testing the benefit of early DBS in Parkinson’s, and to improve some non-motor symptoms of the condition. Read more about the research into further benefits of deep brain stimulation.
Brain surgery has come a long way in 120 years since it was pioneered for movement disorders. Today countless researchers continue to dedicate their lives to improving the range and effectiveness of therapies available today to ensure more people have a better quality of life in the future. To keep up to date with the latest developments, and to hear about opportunities to take part in research to test new treatments, you can sign up to our Research Support Network.
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