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Robert cartman

Deep Brain Stimulation. (Intermittent Stimulation)

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My wife has tremor predominant parkinsons and consequently has a bi-lateral DBS to the STN. She recently underwent surgery to replace her Medtronic Kinetra which had a depleted battery with a Activa RC.

Because the IPG was changed (Kinetra replaced by Activa RC) Medtronics 'pocket adaptor' was required to be fitted.

After this procedure she has regained full control of the tremor on the left side, however control of the tremor on her right side is intermittent (It comes and goes without any obvious explanation) I think it is important to stress at this point that this is NOT the result of the tremor breaking through due to her being 'emotionally charged'.It happens when she is completly 'flat' emotionally. In addition the impedance level on contact 2 is high.

 

The question I would like to ask is;

Is it possible to determine precisely where the problem of intermittent stimulation is arising from without surgery. e.g. IPG, pocket adaptor, extension wire connector, set screw etc.and if it is how can it be done?

 

My wife's surgeon and programmer seems at a loss to know what to do. The surgeons answer is to replace the whole of the DBS system

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The most likely scenario we have seen in our clinic is that the two batteries are not equal and simply reprogramming higher or lower settings should capture the tremor.

 

The second thing we have seen is that during a replacement if the connector wire is replaced too, any tugging on the DBS lead can result in displacement from the target. This can be checked by an image and is much less likely.

 

One counterintuitive thing we have seen is the need to sometimes turn the voltage down instead of up.

 

Keep us posted.

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Dr. Okun,

 

I'd also be interested in an expert team's evaluation of the following aspects of the poster's question. If I understand correctly, this is one of those difficult long-term DBS diagnosis situations, which your hospital is proud to tackle.

 

1. Having seen the posting person's contribution to another forum, I believe that the main question is: what imaging tool would a good team need in order to test non-intrusively an intermittent current interruption at the IPG connector (loose contact at the setscrews) more than at the ear connector ... before exploratory surgery.

 

2. If it were a suspected hardware problem, what role can Medtronic play, including being requested to consult on its worldwide database of similar situations... and post-explant hardware tests.

 

3. If the new IPG were a dual Medtronic Activa PC or RC replacing say bilateral Kinetras, how would you expect the one new battery to share its load between the two sides ... say in voltage mode? Even considering that the new Activa RC IPG + Pocket Adaptor has a different loop impedance, and that the Activa has a different stimulation waveform.

 

Thank you

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The best way to check connectors is in a programming technique where impedences and currents can be checked. If abnormal we do plain X-rays in a shunt type series to search for the issue. If not visible, then sometimes the surgeon can try to replace the extension cable and also can test the lead by exposing the connector in the OR.

 

I am not aware of a specific role a company can play other than to give you numbers of reports...

 

There is a battery estimator tool available at http://mdc.mbi.ufl.edu/surgery/dbs-battery-estimator where you can enter the number of leads per battery and battery type and estimate. A similar estimate can be made by calling a company support line, or by calculating current density. There is an article just published in PLOS ONE this month on the topic. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0058665

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Dr. Okun

In order to give you a fuller understanding relating to this issue I think it will help if I briefly outline the course of events.

 

My wife who has tremor predominant parkinsons had bilateral DBS in the STN in October 2009 this was very sucessful and resulted in full control of her tremor in all limbs and also increased the effectiveness of her Ldopa.

In September 2012 she presented with full control of her tremor but with a totally flat Kinetra battery. She underwent surgery and the Kinetra was repaced with an Activa RC resulting in her regaining full control of tremor on her left side but experiencing intermittent tremor of her right side. At that time interrogating the impedances showed that all the left electrode impedances were elevated. As the only thing that had been altered was the battery and the new 'pocket adaptor' she underwent a second procedure and the battery was re explored and the 'pocket adaptor' was changed, however this did not affect the impedances which still registered high.

 

As a result of this she had a third surgical procedure in which her left electrode (3387) was replaced after which a check CT scan with the frame in place confirmed that the position of the electrode was unchanged. The majority of the impedance measurements came down with this replacement but the impedance measurements involving number 2 contact remained high and the surgeon accepted this. However my wife has not regained control of the tremor on her right side and has been left with a severe rest and postural tremor that is intermittent.

 

My wife has had several 'programming' sessions with individuals whom clearly do not have either the necessary knowledge, skill or time to capture any benefits. Therefore she has been left with a severe right sided tremor that is evident for longer and longer each day.

The surgeon's solution to this is to revise the left electrode (that he has only just unsucessfully revised, with the exception of the extension lead) and also put in a new thalamic electrode to target specifically tremor, clearly a drastic strategy that is not without risk .

 

The question I would like to ask is what would you do at your Hospital to solve this issue?

 

Thank You we appreciate your time

Robert Cartman

 

 

 

 

As my earlier posts indicate we feel a much better option would be to determine precisely where the problem is and

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My approach....

 

An evaluation that checks PD scales in all med and stim conditions, an MRI with a 3-D reconstruction of the lead, and programming to include checking thresholds for benefits and side effects at each contact. This comprehensive approach will help identify the problem and allow moving forward with options and a discussion of risks and benefits. That is my approach in our clinic. We have a specific clinic for DBS failures and have seen over 300 leads with issues.

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Dr. Okun,

We appreciate your swift response it is very helpful and if possible would be grateful if you could clarify a couple of points..

 

Firstly in your clinic specifically for DBS failures have you seen a problem similar to the one I have described?

Whereby high levels of impedance and 'intermittent stimulation' have caused problems with therapy immediately after a Medtronic Kinetra has been replaced by a Medtronic Activa RC using the Medtronic 'pocket adaptor' to allow for connection to the original extension lead.

 

Secondly, your approach advocates the use of an MRI scan to help determine the precise location of the problem, yet I have been led to believe by my medical team that an MRI scan is too dangerous for me due to having had DBS.

 

Is this not the case?

 

Thank you Robert Cartman

 

.

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First, I have seen the impedence issues you describe on a battery change but not right after a RC was placed.

 

The MRI issue has been published by many groups including an article in NeuroImage from NPF centers of excellence showing that it is likely ok (no adverse events) and citing thousands of scans in experience. The trick is having it done somewhere that has the safety guidelines implemented.

 

Hope that helps.

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Dr. Okun,

 

I hope you don't mind a technically oriented caregiver wishing to understand the tools and options that your team or others may have, beyond the generalities... for a desperate patient's case of therapy loss after IPG replacement, similar to the one originally posted.

 

In line with your 3-step procedure mentioned above, let's say that impedance testing of a Medtronic Activa RC (or PC if you have more experience with it) leads to a suspicion of open circuit ... not in the brain lead, not in the extension cord, but at the IPG connectors or pocket adaptors. The Medtronic implant manual (I found an online copy) is quite specific that over- or under-tightening of the setscrews may create intermittent symptoms... possibly due to a loose setscrew or maybe damage to the contact on the extension wire tip.

So, before surgical exploration, what non-invasive imaging tool and technique would allow your team, or expect of an expert troubleshooting DBS center, to visualy diagnose an intermittent loose contact at the IPG... maybe while asking the patient to move his / her body or hand-manipulating the subcutaneous IPG. I assume that any imaging, unless it involves radiation or EMI effects, would be recommended before another surgery.

 

I mean to ask this question constructively, being aware that individual teams have different tools and preferred techniques and available time at their disposal.

 

For comparison, would a more accurate image be necessary and available than the IPG scans published in:

1. Alesch F: Sudden failure of dual channel pulse generator. Mov Disord 2005;20:

2. Guridi J et al: Hardware complications in DBS: Electrode impedance and loss of clinical benefit. Parkinsonism and Related Disorders 18 (2012)

 

A similar question was posed on your forum on Apr 12 2012 regarding St. Jude's rechargeable Brio model for DBS (in Europe). Which was somewhat different in that low impedances were detected post-op ... and device warnings were published by FDA Maude and European medical device certification agencies.

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Thanks for the question. I can only post my own experience which is to obtain a plain film old fashioned X-ray and look for the disconnection or abnormality. If it does not reveal itself then usually surgery to check the connections and possibly replace the extension is the next step. If the problem persists then it may be necessary to replace the brain lead.

 

I will post in case someone else has a more sophisticated approach.

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