Younger patients with Parkinson’s Disease whose symptoms respond to levodopa are usually the best candidates for deep brain stimulation, a movement disorders expert has told ANZAN delegates.
Neurologist Dr Mark Simpson from the Auckland City Hospital in New Zealand told delegates that Parkinson’s Disease was a “disease of thirds”.
The first stage was the pre-symptomatic or ‘honeymoon’ phase where medications usually work quite well. Patients will typically move into the second stage where they develop motor fluctuations, before moving to a third stage involving increased disability and quality of life.
“The disease is a very dynamic process, every time you see a patient with Parkinson’s you need to think about where in the disease is that patient – because it varies from year to year – and if you only have 20 minutes to see that patient this is a tricky part of Parkinson’s disease,” he told delegates.
One of the main issues with levodopa was that it had a short half -life of 90 minutes which made it difficult for clinicians to manage patients’ symptoms, particularly when they were in the second and third stages of the disease.
But knowing which patients were good candidates for deep brain stimulation was often fraught with difficulty, Dr Simpson said.
“Not everyone with Parkinson’s needs DBS but about 10% are candidates… If you’re looking after patients with Parkinson’s Disease you probably should be referring some of them,” he said.
On the whole, younger patients were the best candidates for referral but there was no clear numerical age cut-off.
“The reason the younger person with Parkinson’s is going to be a better candidate for DBS is because they have many more years of motor fluctuations and dyskinesia – the middle third of the disease — and its those symptoms that respond best to DBS,” he explained.
However, he stressed that the disabling symptoms needed to occur despite best medical therapy which included sufficient levodopa, a trial of amantadine for dyskinesia and apomorphine.
Levodopa responsiveness is paramount
An important point to consider was that patients were only good candidates for DBS if their disabling symptoms responded to levodopa.
Dr Simpson noted that some symptoms responded better to the medication than others. For example, rigidity, bradykinesia and dyskinesia usually responded well but dementia/hallucinations, mood disorders, balance, tremor and falls less so.
“If someone is taking levodopa at the right dose but still has severe symptoms then they are not a good candidate for DBS” Dr Simpson told delegates.
Clinicians could determine levodopa responsiveness by withholding the medication overnight and measuring the ‘off’ state. The patient should then be given a 150% of the normal morning dose and the ‘on’ state should be measured.
Levodopa responsiveness could also be assessed by asking the patient to describe their early morning state, when they are at their best and worst.
He stressed that DBS was no better than levodopa at controlling symptoms, and this should be made clear to patients.
“You can make the point to the patient that DBS is not actually be better than LD and they will say, ‘why am I having it then?’ And I say, ‘because you don’t need to take DBS ten times as day, it will always be ‘on’, it will be ‘on’ in the morning, it doesn’t wear out (apart from battery replacements)'”.
DBS is not a cure
Dr Simpson added that it was important to communicate to patients that DBS was not a cure and did not help all aspects of the disease such as cognition, dementia, mood disorders, or autonomic failure.
He left delegates with an easy to remember mnemonic DBS-IN-PD, which he sometimes gives to patients :
D – does not cure
B – bilateral stimulation usually required
S – Smooths out motor fluctuations
I – improves tremor, rigidity dyskinesa
N- never better than LD
P – programming visits required
D – decreases medication in many, but not all