Tuesday, March 01, 2005

Implantable Devices for Major Depression

There already has been some media buzz, and a few blog posts, about the implantable vagus nerve stimulator. It first was developed as a treatment for epilepsy, and it is being investigated for the treatment-resistant depression. One blogger is neutral on the subject; another expresses a strong negative reaction -- which is refuted brilliantly in the comments. Similar devices are used for treatment of severe Parkinson disease. Business week online has a decent review (echoed on GNIF Brain Blogger) for non-technical or non-medical readers:
The use of implantable mini-generators is more widespread than you probably think. Already, 190,000 patients are wearing electrodes in their heads to control Parkinson's disease tremors or spinal-cord stimulators to relieve pain or prevent urinary incontinence. Some 30,000 have wires threaded to the vagus nerve in the neck to treat epilepsy, while 60,000 have microtransmitters in the inner ear enabling them to hear. These numbers are likely to grow -- and quickly. One of the most promising devices is a $15,000 neurostimulator for chronic depression from Cyberonics Inc., which the Food & Drug Administration conditionally approved on Feb. 2.
A couple of months ago, I reviewed the information available on the Internet about the use of the vagus nerve stimulator (the Cyberonics device) for the treatment of treatment-resistant depression. At this point, it sounds as though it could be useful to some people. Apparently, the FDA agrees, since they have indicated that they will approve the device for that indication. Clearly, though, the approval will be based upon the fact that the patients for whom it is intended will have failed many other available treatments. The vagus nerve goes down the neck and into the chest, so it isn't necessary to go into the skull to use it. Even so, implanting something metal inside your body is serious business. It would be hard to justify unless it either worked very reliably, or it is intended for patients who have not responded to multiple other treatments.

What I could find about the efficacy was not terribly impressive. That is why I say that it might be helpful for some people. Once all the efficacy data are available, I might be able to comment more enthusiastically.

Now, though, we hear of something new. This one, called Activa®, does go directly into the brain. Or, at least, it has wires that go into the brain. The device itself is implanted under the skin, at the base of the neck. They use the same device for severe Parkinson disease. That use is described here, at the Georgetown University Hospital site. They even have a video clip of a news interview with one of the patients.

Based upon prior studies (for example, 1 2 3 4), researchers suspected that the device also could be used to treat depression. They performed a pilot study, which is going to be published in the next issue of Neuron, (which is not up on their website, yet). From a press release:
Experimental electrode implant treatment shows promise for helping severely depressed Study experiments with surgically implanted electrodes in patients who were not responding to all other available treatments 28-Feb-2005 Toronto, CANADA – A team of Toronto researchers says it has obtained promising early results from a landmark surgical study of the use of deep brain stimulation (DBS) in severely depressed patients who were otherwise resistant to standard types of treatment.

Significant clinical response was seen in four of the six study patients with chronic stimulation of the subgenual cingulate region, with sustained improvement through six months to the study endpoint. While DBS in other brain areas has been used to treat disorders such as epilepsy and Parkinson's disease, this is the first report of DBS in the subgenual region for major depression. The technique involves high frequency electrical stimulation to a targeted area of the brain for the purposes of modulating that region's activity. The subgenual cingulate area was specifically targeted based on growing evidence of its critical role in depression. [...]

Dr. Mayberg cautions that the Cg25 DBS study is only a "proof of principle". It is the culmination of 15 years of research using brain imaging technology that has worked to characterize functional brain abnormalities in major depression and mechanisms of various antidepressant treatments.

The device sends electrical impulses to the subgenual cingulate region of the brain. This causes the neuronal activity there to decrease. Exactly how that would result in improvement remains to be seen. In fact, it remains to be seen whether more that four patients will respond to the treatment.

If the Activa device turns out to be effective for anywhere near 60% of the patients with treatment-resistant depression, it will be a major advance. It also will raise a fair amount of consternation among insurance company executives. Read it and weep:
The procedure involved Dr. Lozano drilling two holes about the diameter of a 5-cent piece into the skull with the patient awake and under local anesthetic. Guided by magnetic resonance imaging to confirm the precise anatomic location of the grey and white matter of area 25, he inserted two thin wires with electrode contacts down to the white matter tracts adjacent to the Cg25 area. The other ends of the wires were tunneled through to the lower neck area and hooked up to a pulse generator implant that directs an electrical current. The entire system, likened to a "brain pacemaker", is under the skin. Researchers determined the most efficacious voltage, pulse width and frequency for each patient and tracked their clinical response using positron emission tomography (brain imaging of cerebral blood flow activity) along with a comprehensive battery of neuropsychological tests. This tracking was done at baseline (pre-surgery) and at monthly intervals for 6 months.
The device itself will cost about $15,000. The news report of the study does not say how the candidates were selected. It would make sense, though, do do some kind of functional neuroimaging study to select the patients. Paying for all those scans would cost a bundle. Then, you have to use an MRI scan to figure out where to put the wires. You have to pay for the surgery, and you have to pay for follow-up. And the insurance company gets nothing back, after paying all that money. That makes for an adversarial situation.

Perhaps it is obvious, at this point, but I am going to say it anyway. This kind of thing is going to become more and more common. It may make the concept of private health insurance untenable. So obviously we need a national health program.

Wait! you say? Who wants the taxpayers -- those hard-working, compassionately conservative, long-suffering Americans, whose pockets get picked every April -- to pay for all this? You do, and here is why: The people who would be candidates for this are people who either cannot work, or who are working far below their potential. Many of them are getting social security disability. With the SSD and all their other benefits, housing subsidies, etc., they cost us, say, $25,000 per year. Take one of those citizens, treat them effectively, and they go back to work, making, say, $35,000 per year. The economic benefit is $60,000 per year, for the rest of their working lives. Over a 20 year period, that is $1.2 million dollars. Yeah, it's a back-of-a-envelope calculation, but it illustrates the point.

Pseudoethicists will cry out that the almighty taxpayer should not have to pay. But why should the insurance company pay? They get nothing back. Taxpayers don't get anything back, directly, but indirectly they get a million bucks. So which is ethical?

I suppose if you abolish social security, Medicaid, and housing subsidies, that would eliminate 40% of the value of the transaction. That makes it less appealing, but still a decent investment.

Like I said, more medical interventions are coming along, they will be expensive, and there isn't going to be any way to reduce the costs beyond a certain point. Sooner or later, insurance companies are going to have to become so selective about what they will pay for, that there won't be much point in having insurance. Individuals will go bankrupt, or just get sick and die, because of the cost of health care. The country will loose some of its most valuable resources: its people.

The notion that citizen X should not have to pay for citizen Y's medical treatment is appealing, on the surface, but it doesn't make sense once you admit that we all depend on each other in order to have decent lives. It may be true that person X, who lives in North Dakota, does not directly benefit if Ms. Schnitzel, who lives in Florida, gets treatment for her pneumonia. But that is a short-sighted, narrow-minded analysis. If the sum of all medical treatment provided in this country results in a reduction of infant mortality, is that worth anything to Mr. X? If the average span of productive work years per citizen is increased by 5%, is that worth anything? If we have more people working on inventing better inductive transconbobulators, or mousetraps, for that matter, rather than working on and off at various minimum-wage jobs, is that worth anything?

(Note: The Rest of the Story/Corpus Callosum has moved. Visit the new site here.)
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I see your point about the money issues and agree. I dont know if you have depression or any other disease, but are we here to lay dorminant? Meaning do we try nothing for these people? In your analysis it seems that there is a Darwinian attitude about this post. Anyway, the test subjects were all from Canada and not the U.S. So, I would not cry yet. And in Canada it's all free.

So, let's hope your dorminant state of humanity does not lead these potentially break-throughs come to America.
I see your point about the money issues and agree. I dont know if you have depression or any other disease, but are we here to lay dorminant? Meaning do we try nothing for these people? In your analysis it seems that there is a Darwinian attitude about this post. Anyway, the test subjects were all from Canada and not the U.S. So, I would not cry yet. And in Canada it's all free.

So, let's hope your dorminant state of humanity does not lead these potentially break-throughs come to America.
It is not free in Canada.
We pay taxes for equal health care for all Canadians.
And we are proud of the compasion of that fundamental Canadian right
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