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Dr. Okun

Post of the Week: New Study on Constant Current DBS

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Dr. Okun    409

Dear forum members this was published in Lancet Neurology online this week.

 

Lancet Neurol. 2012 Jan 10. [Epub ahead of print]

Subthalamic deep brain stimulation with a constant-current device in Parkinson's disease: an open-label randomised controlled trial.

Okun MS, Gallo BV, Mandybur G, Jagid J, Foote KD, Revilla FJ, Alterman R, Jankovic J, Simpson R, Junn F, Verhagen L, Arle JE, Ford B, Goodman RR, Stewart RM, Horn S, Baltuch GH, Kopell BH, Marshall F, Peichel D, Pahwa R, Lyons KE, Tröster AI, Vitek JL, Tagliati M; for the SJM DBS Study Group.

Source

Department of Neurology, Center for Movement Disorders and Neurorestoration, University of Florida College of Medicine, Gainesville, FL, USA.

Abstract

BACKGROUND:

The effects of constant-current deep brain stimulation (DBS) have not been studied in controlled trials in patients with Parkinson's disease. We aimed to assess the safety and efficacy of bilateral constant-current DBS of the subthalamic nucleus.

METHODS:

This prospective, randomised, multicentre controlled trial was done between Sept 26, 2005, and Aug 13, 2010, at 15 clinical sites specialising in movement disorders in the USA. Patients were eligible if they were aged 18-80 years, had Parkinson's disease for 5 years or more, and had either 6 h or more daily off time reported in a patient diary of moderate to severe dyskinesia during waking hours. The patients received bilateral implantation in the subthalamic nucleus of a constant-current DBS device. After implantation, computer-generated randomisation was done with a block size of four, and patients were randomly assigned to the stimulation or control group (stimulation:control ratio 3:1). The control group received implantation without activation for 3 months. No blinding occurred during this study, and both patients and investigators were aware of the treatment group. The primary outcome variable was the change in on time without bothersome dyskinesia (ie, good quality on time) at 3 months as recorded in patients' diaries. Patients were followed up for 1 year. This trial is registered with ClinicalTrials.gov, number NCT00552474.

FINDINGS:

Of 168 patients assessed for eligibility, 136 had implantation of the constant-current device and were randomly assigned to receive immediate (101 patients) or delayed (35 patients) stimulation. Both study groups reported a mean increase of good quality on time after 3 months, and the increase was greater in the stimulation group (4·27 h vs 1·77 h, difference 2·51 [95% CI 0·87-4·16]; p=0·003). Unified Parkinson's disease rating scale motor scores in the off-medication, on-stimulation condition improved by 39% from baseline (24·8 vs 40·8). Some serious adverse events occurred after DBS implantation, including infections in five (4%) of 136 patients and intracranial haemorrhage in four (3%) patients. Stimulation of the subthalamic nucleus was associated with dysarthria, fatigue, paraesthesias, and oedema, whereas gait problems, disequilibrium, dyskinesia, and falls were reported in both groups.

INTERPRETATION:

Constant-current DBS of the subthalamic nucleus produced significant improvements in good quality on time when compared with a control group without stimulation. Future trials should compare the effects of constant-current DBS with those of voltage-controlled stimulation.

FUNDING:

St Jude Medical Neuromodulation Division.

Copyright © 2012 Elsevier Ltd. All rights reserved.

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mickigarden    56

Dr. Okun, could you please explain how the new generator which was recently approved by the FDA is different from any previous generator. Thank you in advance. Micki

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Dr. Okun    409

The big difference is that it provides constant current instead of constant voltage.  The older generators use voltage and this can cause changes in the shape of the electrical field in the brain based on changes in brain tissue impedance.  So far studies have not shown constant current superior, but most devices will likely be made to support constant current in the future.

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mickigarden    56

Thanks for your quick response.  I am still somewhat confused regarding how it is  recharged.   I am afraid I don't understand the basic concept required to ask the right questions.  Is it rechargeable through the skin like a new generation IPhone? I am trying to decide which route to take as just had surgery done last week and presently awaiting implantation of generator.  Micki

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Dr. Okun    409

You are locked to get the generator that matches your lead.  Recharge-able or not is a different issue than constant current.

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Neftali    0

Dr Okun. Which is correct on bilateral DBS?

A) ALTERNATE FUNCTION ON ELECTRODES

B) SIMULTANEUS FUNCTION ON ELECTRODES

My father 74 yr old had a Dbs procedure on dec-16'. EP . Slow walk and speech problems. Since that datei cant see much changes. ¿could be somethig be wrong with position of electrodes? We arein Monterrey Mexico. Sorry about my English

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Neftali    0

Dr Okun. Which is correct on bilateral DBS?

A) ALTERNATE FUNCTION ON ELECTRODES

B) SIMULTANEUS FUNCTION ON ELECTRODES

My father 74 yr old had a Dbs procedure on dec-16'. EP . Slow walk and speech problems. Since that datei cant see much changes. ¿could be somethig be wrong with position of electrodes? We arein Monterrey Mexico. Sorry about my English

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Dr. Okun    409

Be careful as many patients actually worsen after bilateral DBS in walking and talking.  Sometimes it is a result of the surgery, but sometimes it is the programming or position of the lead.  These need to be carefully investigated.  In general DBS is not great for walking and balance though in some cases by improving on time, mobility also improves.

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janvier    3

Dear Doctor, I have bilateral STN implanted with LibraXP of St Jude. The battery has about 6 years of longevity according to St Jude. Now I see that after 2 years and 3 months it is exhausted. This is confirmed by the representatives of the company. With a normal usage of the battery for PD is this normal. The company gives all kinds of reasons for this. Is there a certain threshold of parameters like the current in miliampers, the frequency, the polarity, etc so that beyond that threshold this happens. Thanks.

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Dr. Okun    409

The battery life will depend on the parameters set on each device and on the battery itself.  If you want to share the contacts programmed and also the detailed parameters I can comment more.

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janvier    3

Here are the parameters:

Brain left side Electrodes used 1 and 2, bipolar stimulation, current 4.2 milli ampers.

Brain right side Electrodes used 2 and 3, bipolar stimulation, current 0.1 milli ampers.

Electrodes numbered as 0,1,2,3.

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Dr. Okun    409

The right sided lead is set very low and I would wonder why and if it may be sub optimally placed.  The left sided lead does not have particularly high settings for a bipolar configuration although some would say mildly high.  The company of the device (whichever one is the manufacturer) can estimate device longevity for you.  I would expect many years based on the above settings.  I didn't see the question on this thread but think that was what you were asking.  If not, feel free to follow-up.

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janvier    3

Indeed I have consulted the experts of the manufacturer which is St Jude and inquired about the longevity of the battery. They tried to contact the IPG via the patient device which indicated that the battery is exhausted. Then they tried with their own strong antenna which managed to communicate with the IPG. In this case they declared that the battery will be off very soon probably in  a few days or weeks. Now nearly 7 weeks have gone by and the battery is still functioning. I tend to think that there is a software error which is strongly denied by the company. For my part I am perplexed and do not now who to believe.

As to the low current on the right side of the brain before having the bilateral DBS, 10 years ago I had a unilateral VIM to stop the tremor on my left side. At that time there was absolutely no symptom on the right side of the body. In order to minimize the risk that additional electrode was left in place. Merely the existence of the electrode in VIM reduces the current to 0.1 and even the target electrode has been changed from 1-2 to 2-3.

As to my Neurosurgeon and neurologist they believe what the company says although in the publicity the company declares that LIbraXP has 40% longer life than all other batteries on the market.

Any advice is welcome.Thanks.

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janvier    3

Frustrating as it is, I have one remark. Although by various manufacturers such as Medtronic, St Jude the battery longevity is announced and claimed as 5 to 7 years, in certain countries this number is taken by default as 2 to 3  years especially from insurance point of view. It seems to be only low level battery consumption below a certain voltage level such as 3.6 mV reaches that target. However this is never openly declared by the suppliers nor confirmed openly by the Neurosurgeons. On the other hand even if this was done publicly I doubt very much whether it will have any serious impact on the number of DBS operations undertaken yearly in the world, because a well performed DBS affects the PD patient like a miracle.

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janvier    3

Further to this subject, I had the battery replaced by a rechargeable Brio model, which as St Jude claims will have a battery longevity of 10 years. The company's experts suggest that the IPG should be recharged as often as possible to have a good long life. This suggestion seems to be somewhat awkward and contrary to the common approach of running down the batteries supporting electronic devices until zero charge remains, at least twice a year. Considering the type of battery that must resist harsh environmental conditions and be very reliable, I assumed the suggestion of the company experts to be right. However I would like to get your opinion on this subject. Precisely cited: What kind of a battery recharging schedule are you advising to your patients? Is the idea of recharging as often as possible supported?

Dear Doctor, thanks or the response.

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Dr. Okun    409

Every battery design is different.  I have not used the Brio recharge-able so I would definitely suggest you call the technical helpline from the company and follow their advice,

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MurrayPD2    219

Dr. Okun,

 

I am scheduled next month for a DBS.  They are doing a bilateral lead insertion with me remaining unconscious.  They tell me the mapping system they have is shown to be just as effective as their previous wake surgeries. I am also told the surgeon will decide on STN or GPI placement based on my symptoms to make sure I benefit most.  The concern for STN is that is known for more cognitive/behavioral issues similar to what agonists can do.  I have learned agonists will cause problems for me.   So, now there is a worry that he will chose STN and I won't tolerate the side effects.  Any opinion on this?

 

The other concern of course the effects on speech and walking.  Is the risk greater or less for a 45 yr old male?  I assume that may be too subjective to many other things.  Just like everyone else, I am trying to assess my own risks. 

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Dr. Okun    409

This is a complex and tough question.  I can tell you how we do it as our own experience.  We have patients see neurology, neurosurgery, psychiatry, neuropsychology, PT, OT, speech and swallowing as well as social work.  We then sit and discuss the whole case as well as targets and approaches and symptoms as well as unilateral versus bilateral.  It is a complex discussion for each patient.  Good luck.

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