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Deep Brain Stimulation: A Sci-Fi Miracle Cure?

By Rhoda Frost

Photo credit: Pixabay

Can we believe the hype? It sounds like something in the realms of sci-fi movie imaginings: electrical stimulation of the brain resulting in incredible transformations for patients and dramatic reductions in symptoms. Enter deep brain stimulation (DBS), a treatment proven to be efficient in Parkinson’s disease and other movement disorders, [1] which is now being trialled on a wider scale in a range of neurological and psychiatric disorders. But has this ‘wonder treatment’ been pushed too far? [2] And is it really as good as we think it is?

What is DBS?

Chances are that you might not have heard of it, so let me explain – what actually is DBS? [3] The patient will first have a brain scan, to work out where the electrodes will go. The electrodes are then inserted into these areas through small holes drilled into the skull. A wire runs from the electrodes, down to the chest or abdomen, where a pulse generator is inserted under the skin. The electrodes themselves are made up of different sections, each of which can be programmed to give out stimulation at different frequencies to the surrounding brain tissue. This is (so I’m told) a straight-forward, safe procedure, which is relatively easy to perform, and which requires only a short recovery time post-op. What conditions has it been used in, and what are the results?

DBS was initially shown to be effective in movement disorders like essential tremor, Parkinson’s disease, and dystonia, [1] and indeed these are the only diseases in which the technique has been absolutely proven to work, and where health care services would offer this treatment in a fairly routine way. Incredible videos exist of patients who were incapacitated by their motor disorders, now able to walk around normally and perform intricate tasks (I’m serious, Google it), and without the side effects of some of the medical treatments they had previously relied on.

For a new treatment to become available in the medical world, it needs to go through several stages of trials to prove that it is safe and effective. DBS has gone through these processes for movement disorders and Parkinson’s, but as its spectrum of possible uses widens, trials are now looking at how DBS could be used to treat conditions like Alzheimer’s, [4,5] Tourette’s syndrome [6] and epilepsy. [7] There are reports of brain tissue growing back in Alzheimer’s patients, dramatic reductions in tics in Tourette’s, and nearly 10-fold decreases in the frequency of seizures in epilepsy sufferers, but these studies have mostly only looked at a very small number of people. For trials to really prove anything there needs to be a large ‘sample size’ (the number of people in the study), so we can make proper conclusions about the treatment. So, without the large-scale trials into these uses of DBS, these case reports are not worth much. Scientific papers may show the safety, and hint at the effectiveness, of its use in these diseases, but trials have been too small to really show anything even remotely concrete.

Broadening the DBS scope even more, there have been trials into conditions like depression, [8,9] OCD, [10] anorexia, [11] obesity, [12] chronic pain [13] and addiction. [14,15] Some authors have even suggested that it could be used to ‘cure’ personality issues, such as psychopathy. Again, the trials looking at this have had very small sample sizes, although the dramatic case changes some of them describe may offer hope for future successful trials. It seems in many ways like there is no end to the potential uses scientists could dream up for DBS, and they certainly seem determined to test it in a wide variety of diseases and conditions.

Photo credit: Pixabay

What does it do to the brain?

The short answer is: we don’t entirely know. It had been assumed that DBS just suppressed the level of electrical activity in the brain structures near where it was situated, by inhibiting the neurons (brain cells) there. Now however, it seems like there is more going on. [3] DBS appears to have different effects on different types of cells, and on different parts within cells, with some areas being activated and others being inhibited. The electrical stimulation being given to the neurons seems to change the way they release chemical messages (neurotransmitters) into the brain to communicate with other cells. But surely, so long as it works we don’t need to know the exact mechanism… right?

Potential pitfalls

We need to realise just how sensitive a structure the brain is, to be able to fully appreciate what we are doing. There are around 86 billion [16] neurons in the brain, and they are all arranged precisely to control almost every area of our lives – our behaviour, emotions, memory, movement, speech, and relationships with others (and I could go on). We don’t fully understand how the brain works, nor do we understand exactly which characteristics are controlled by which area of the brain. Blundering in with our electrodes, we may not know exactly what structures we are interfering with, and as so much of the way we are is determined in the brain, DBS could have wide-ranging effects we cannot predict. Possible personality changes, and even inducing severe depression [17] are just two of the pitfalls we could encounter. It has been reported that patients can feel a strange sense of unfamiliarity, like they are not really ‘themselves’ [18] while stimulation occurs, although the reliability of this statement is debatable. If this is true, however, and such extreme personality changes can and do occur, then it raises another issue – if a DBS patient commits a crime while stimulation is switched on, which they would not have done before treatment, who is to blame? [19]

What do we make of all this?

Clearly there are many areas of this topic which are still up for debate, both ethically and scientifically. I wouldn’t claim to have all (or any) of the answers, but I think the potential benefits here could be huge. Regrowth of brain tissue in Alzheimer’s disease? That’s amazing! A cure for heroin addiction? Incredible! Let’s not run away with ourselves. For Parkinson’s and motor disorders, DBS is and continues to be an amazing treatment. For all other applications, let’s hold fire and wait for some real results from the researchers.


References

  1. G. Deuschl et al., N. Engl. J. Med., 2006, 355, 896-908
  2. New Scientist, available from: https://www.newscientist.com/article/mg22830440-500-deep-brain-stimulation-a-wonder-treatment-pushed-too-far/ [accessed 23/12/15]
  3. B. Ford, Encyclopedia of Movement Disorders, 2010, 277-282
  4. A. Laxton and A. Lozano, World Neurosurg., 2013, 80, S28.e1–S28.e8
  5. T. Shankar, et al., Brain Stimulation, 2015, 8, 645-654
  6. A. Fraint and G. Pal, Front Neurol., 2015, 6, 170
  7. K. Vonck et al., Annals of Neurology, 2002, 52, 556-565
  8. H. Mayberg et al., Neuron, 2005, 45, 651-660
  9. A. Lozano et al., Biological Psychiatry, 2008, 64, 461-467
  10. B. Nuttin et al., Lancet, 1999, 354, 1526
  11. N. Lipsman et al., Lancet, 2013, 381, 1361-1370
  12. R. Kumar et al., Ann. Neurosci., 2015, 22, 181–188
  13. S. G. J. Boccard, E. A. C. Pereira and T. Z. Aziz, J. Clin. Neurosci., 2015, 22, 1537-1543
  14. J. Voges et al., World Neurosurg., 2013, 80, S28.e21-S28.e31
  15. H. Zhou, J. Xu and J. Jiang, Biological Psychiatry, 2011, 69, e41-e42
  16. F. Azevedo et al., J. Comp. Neurol., 2009, 513, 532-541
  17. B. P. Bejjani et al., N. Engl. J. Med., 1999, 340, 1476-1480
  18. M. Unterrainer and F. S. Oduncu, Scientific Contribution, 2015, 18, 475-485
  19. L. Klaming and P. Haselager, Neuroethics, 2013, 6, 527-539


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