Wired for Parkinson’s


  • Health
  • Sunday, 17 Aug 2003

By HOOI YOU CHING

WHEN brain cells talk among themselves, it’s like listening to the radio with a really bad reception. It’s as though someone was trying to tune through as many radio stations as possible. That’s because when neurons in the brain fire messages to one another, they emit crackling ‘noises’ similar to radio static. 

But for brain specialists, the “noises” are music to their ears. By eavesdropping on these neural noises, coupled with sophisticated imaging and scanning techniques, they can accurately identify the part of the brain involved in the symptoms of Parkinson’s Disease (PD). 

In PD, these neural acoustics are heard in the basal ganglia, an area of nerve cells that is important for coordination of body movement. The symptoms of PD occur when cells in the substantia nigra die and consequently produce lesser amounts of dopamine. Dopamine is a chemical substance in the brain that is essential for normal movement of the body. 

Dr Chew Nee Kong...Parkinson's Disease is a medical condition that is commonlyunder-diagnosed.’

It is believed that the deficiency in dopamine levels results in hyperactivity of two structures in the brain that are known as the subthalamic nucleus (STN) and globus pallidus interna (GPi). When these sites are overactive, they trigger the symptoms of PD such as tremor (uncontrollable shaking of the hands and feet), rigidity (stiffness of body) and bradykinesia (slowness of movement). 

In addition to these classic symptoms, patients may suffer from stooped posture, a reduced facial expression, difficulty in speaking and postural imbalance. 

According to consultant neurologist Dr Chew Nee Kong, the symptoms of PD start slowly and insidiously. He blames the lack of awareness and general misconception of PD symptoms as being part of the normal ageing process for the delay in diagnosis. 

“In a study carried out on 153 patients who were treated at the University Hospital, it was found that the symptoms were already present for an average of 22 months before they sought medical advice. The early symptoms of PD, particularly slowness of movement, are mild and often attributed to the ageing process. Patients consult doctors only after the illness is at an advanced stage. 

“Secondly, PD is a medical condition that is commonly under-diagnosed. There are only about 30 neurologists who specialise in brain disorders in the whole country. Often, most patients are first seen by general practitioners who may not be familiar with the diagnosis of PD,” says Dr Chew. 

A person with PD will find performing the simplest of tasks a mission in frustration. As the illness progresses, their physical ability deteriorates. It is a daily struggle for PD sufferers who have to endure movement problems, embarrassing moments and a sense of helplessness. For example, drinking a glass of water is not as easy as a swig and swallow. As twitching hands and trembling fingers labour to bring the glass to the mouth, more water is poured on the body than into the mouth. Walking is accompanied by unsteady gaits that seem to take an eternity to reach short distances. Worse, when symptoms become so crippling, eventually some PD sufferers succumb to their illness. 

While no one knows the exact causes of PD, theories suggest it is caused by a combination of factors such as free radicals, certain chemicals and toxins in the environment and a genetic predisposition. 

Although a cure for PD has yet to be found, Dr Chew believes that early diagnosis markedly improves the quality of one’s life. More importantly, he advises individuals to consult a neurologist for proper diagnosis. 

“Neurologists are better trained to make a diagnosis and give treatment compared with general practitioners (GP). Most patients have difficulty getting access to neurologists because there are so few of them. Thus, it is best to get a referral letter from a GP in order to seek the immediate advice of neurologists. 

Dr Jaimie Henderson...'Clinicalresearch has shown significantimprovements in the physicalability of Parkinson's Diseasepatients treated with DBS witha 60% improvement in walkingand 70%reduction in rigidity.'

To make a diagnosis, the neurologist would first evaluate the medical history of the patient as certain medications may cause PD symptoms. 

“A diagnosis made by physical examination includes observing the patient’s movement – walking, writing, buttoning up the shirt and examination of the nervous system. Here, the neurologist attempts to look for physical evidence of brain disorders unrelated to but resembling PD. Unlike stroke, blood tests and brain scans are not necessary because these do not help in the diagnosis of PD. 

“The next step is to give a trial of levodopa for at least four weeks to monitor any response to the drug. A significant improvement in the patient’s symptoms supports the diagnosis of PD,” adds Dr Chew. 

To control the symptoms and progress of the illness, medications such as levodopa or L-dopa, botulinum toxin and dopamine agonists (bromocriptine, piribedil, pergolide) are prescribed to patients. 

According to Dr Chew, levodopa relieves all the three major symptoms of PD including bradykinesia, rigidity and tremor. 

“It acts by replacing the depleted dopamine in the brain. Once in the body, levodopa is converted into dopamine. The way the brain of PD patients needs levodopa is similar to the way a car needs petrol – a car can only move when there is petrol. PD patients need regular doses of levodopa throughout the day to keep ‘going’,” he explains. 

Unfortunately, 50% of patients treated with levodopa for between three and five years will experience short-lived clinical benefits, he observes. 

When medication is no longer effective in treating the symptoms, brain surgery is recommended. There are different types of brain surgery: transplantation, lesioning procedures and deep brain stimulation (DBS). 

According to Dr Chew, transplantation involves harvesting new brain tissues from human stem cells and replacing degenerated cells with “new” ones. However, he emphasizes that such treatment is still in its infancy. Furthermore, the use of stem cells from human foetus or pigs or cloning for that matter is mired in controversy. 

In lesioning procedures, the technique involves open brain surgery to permanently remove specific brain tissues. “These procedures are called thalamotomy, pallidotomy and subthalamotomy depending on the area of the brain that is operated upon. Surgery is usually performed on only one side of the brain. However, the physical disability of patients eventually affects both sides of the body. Thus, most patients will eventually need surgery on both sides of the brain. This is not so straightforward as surgery on both sides of the brain can lead to complications such as difficulty in speaking (slurred speech) and in swallowing food,” Dr Chew clarifies. 

Two decades ago, neurosurgeon Prof Alim Benabid and his team from Paris pioneered a procedure called deep brain stimulation (DBS), whereby electrical impulses are delivered to the thalamus, STN and GPi. DBS proved to be a better treatment as it effectively reduced PD symptoms without destroying cells as lesioning procedures would. 

At a recent public forum held at the Sunway Medical Centre, consultant neurosurgeon Dr Jaimie Henderson gave an overview on DBS. 

“Clinical research has shown significant improvements in the physical ability of PD patients treated with DBS with a 60% improvement in walking and 70% reduction in rigidity. Generally, patients can cut back about 40% to 60% on their medication after DBS. 

“With the help of a stereotactic head frame (a halo-type device secured to the head), data from MRIs and CAT scans is used to determine the location of the STN or GPi. After that, the patient is admitted into surgery.  

“The patient is conscious throughout the surgery. After the patient’s head is shaved, surgeons make an incision through the scalp and burrow a hole through the skull. A probe is placed into the brain – one tip within the brain substance and the other tip connected to an audio system. In this way, the surgeon can listen to the “noises” that originate from various types of brain cells. As the “excessive noises” of the STN and GPi are distinguishable from those from other parts of the brain, the probe helps us to identify the exact location of the STN and GPi.  

“The next step involves delivering electrical impulse through the probe into the STN or GPi. This has the effect of subduing the hyperactive STN or GPi and thus relieving all the symptoms of PD. The patient is asked to move the arms and legs. The instantaneous disappearance of the patient’s tremor and stiffness further indicates that the STN or GPi have been accurately targeted.  

“Finally, the probe is removed and replaced by a thin electrode. One end of the electrode is embedded in the STN or GPi, while the other end is attached to a wire that is threaded under the scalp and skin, along the sides of the neck and down to the chest. The wire is then connected to a pacemaker device that is implanted under the skin of the chest. The pacemaker contains a battery that delivers electrical currents to the STN or GPi, via the long wire. The patient can turn on and off the DBS system via remote control,” explains Dr Henderson, adding that the batteries in the pacemaker last an average four to five years. 

According to Dr Henderson, the DBS system is clearly a safer and more effective method of surgical intervention. 

“Compared to standard surgery where the outcome is irreversible, the electrode implants can be removed in the future if a cure for PD is found. In the old technique, there is greater risk of developing complications such as a stroke, haemorrhage, muscle stiffness and speech problems,” says Dr Henderson of the US-based Cleveland Clinic Foundation. 

Since the device can trigger metal detectors at airports, he advises patients to carry an identification card. Although the system doesn’t activate most electrical appliances, it can be affected by fridge door magnets. 

Although the DBS system is meant to enable patients to resume as normal as possible their daily activities, Dr Henderson warns that strenuous activities can damage the system. He cited an example of a patient who was playing golf when he inadvertently snapped the implanted wire and was forced to undergo a second surgery. 

But when do patients consider brain surgery? 

According to Dr Chew, patients most likely to benefit from surgery are those who have had initial good response to medication. “But when the disease has progressed to a point, usually five years of illness, where the patient has severe physical disability despite being on medication, then surgery is recommended. It is important to understand that brain surgery doesn’t cure PD. It basically increases the lifespan of patients as well as improves their quality of life. 

The decision to go for brain surgery such as DBS is not only about complications of surgery but the cost of surgery as well. 

“In Malaysia, the cost of the DBS system is about RM200,000 while the cost of pallidotomy is estimated to be only RM 4,000. Patients with DBS are also required to go for monthly check-ups to calibrate the device’s voltage and monitor their health. When the batteries run out, it’s another RM60,000 for cost of replacement. Cost is certainly an issue here since most patients are in their retirement years who draw small pensions. The Malaysian Parkinson’s Disease Association hopes that the health ministry can work together with hospitals to provide financial aid for needy patients,” he explains. 

The first DBS surgery was performed at Sunway Medical Centre (SMC) in February this year. Worldwide, about 20,000 patients have already gone through this procedure. 

For further enquiries, call the Malaysian Parkinson’s Disease Association (MPDA) at 03-20962246 or email: nkchew33@hotmail.com  

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