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Subthalamic stimulation for Parkinson's disease: a new benchmark
  1. Paul Krack
  1. Movement Disorders Unit, Department of Psychiatry and Neurology, University Hospital Grenoble, France and Grenoble Institute of Neuroscience, Grenoble, France
  1. Correspondence to Professor Paul Krack, Service de Neurologie, CHU de Grenoble, BP 217, 38043 Grenoble Cedex 9, France; paul.krack{at}ujf-grenoble.fr

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Foltynie et al recently reported on the outcome of bilateral subthalamic stimulation (STN DBS) in Parkinson's disease (PD) using MRI-based targeting without microrecording and using one single trajectory per target, followed by immediate stereotactic MRI to verify targeting accuracy. The outcome in this series of 79 consecutive patients managed in the Unit of Functional Neurosurgery at the Queen Square in London is remarkable in terms of both safety and efficacy (see page 358).1

The leitmotif of this surgical school2 is that the first aim of elective functional surgery is not to harm, and so ventriculography was replaced by stereotactic CT early on,3 before moving to direct MRI-based targeting.4 Stereotactic imaging has become an integral part of the functional stereotactic procedure, performed under surgeons' direct supervision.1 Furthermore, the authors do not use microelectrode recording with multiple brain trajectories, in order to minimise the risk of brain haemorrhage.5 6 This is different from the practice in the vast majority of surgical centres that consider microrecording as a gold standard in order to optimise the precision of targeting.7–9

In the study by Foltynie et al, off-medication motor signs, as measured by the Unified Parkinson's Disease Rating scale (UPDRS), improved by 52%; l-dopa-induced dyskinesia improved by 52%; l-dopa equivalent dosage was reduced by 39%; and quality of life (measured with a disease-specific scale) improved by 18%.1 The outcome, based on these data, is in the upper range of published outcomes.10 What differs from the rest of the literature is that the surgical side effects were extremely low. The most relevant side effect was a decrease in speech intelligibility in a subpopulation of patients. There was no symptomatic or asymptomatic haemorrhage detected on systematic postoperative MRI, possibly related to the use of one single trajectory with a blunt macroelectrode. Intracerebral haematoma is the most dangerous complication occurring in 3–4% of the procedures across centres.10 11 Moreover, Foltynie et al report no infection compared with an average infection rate of 2–3% across centres.10 11 Thus, the overall risk/benefit ratio seems to be extremely beneficial in the hands of the London team. The motor outcome of PD surgery depends not only on the skills of the surgeons, but also on the skills of the neurologists involved in the selection of patients and in the postoperative management of medication and stimulation parameters.7 12 13 The study shows that direct MRI-based targeting of the STN doing without microelectrode recording is possible with a good outcome and very low morbidity.

The paper by Foltynie et al is also very timely because its outcome is in sharp contrast with the recently published report of the US Veterans Administration study. This multicentre study was run at seven Veteran Affairs and six affiliated university hospitals. It reported only 25% improvement of the UPDRS motor score in 147 PD patients with bilateral STN DBS, while 2% of cerebral haemorrhages (including one fatal) and 7% of infections were part of the surgical complications.9 This study illustrates that the mere use of microelectrodes is not sufficient to actually reach a target. A recent UK multicentre study in 174 PD patients with STN DBS reported an improvement in motor UPDRS of 36%. Complications included 2% of haemorrhages (including one fatal) and 9% of infections. The London group participated in this study highlighting the variability of outcome among centres.14 One may argue that these studies reflect the true outcome of STN DBS, as they are closer to a field study, including less experienced centres. More importantly, these studies were randomised controlled studies, as opposed to the retrospective study by Foltynie et al. However, other randomised controlled studies confirm the rule that the benefit of STN DBS in PD is predicted by the response of l-dopa,8 15 which is not the case with the above-mentioned recent studies.

Applying the highly complex technique of DBS is not like simply prescribing a drug which is given in the same way across patients. When starting a new surgical technique, learning curves seem ineluctable.11 However, suboptimal outcome from surgery in PD cannot be accepted as a death. The reasons for every single failure must be carefully analysed in order to be minimised subsequently. The outcome of surgical treatment depends on the training of both the surgeons and the neurologists, and the study by Foltynie et al convincingly illustrates the importance of a trained dedicated team. Foltynie et al's paper indeed shows an unprecedented risk/benefit ratio, thus providing a new benchmark for all centres involved in PD surgery.

References

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Footnotes

  • Linked articles 205542.

  • Competing interests PK received research grant and reimbursement of travel costs to scientific meetings from Medtronic, a manufacturer of DBS devices, and from the following manufacturers of antiparkinsonian drugs: Euthérapie, Novartis, GSK, Boehringer Ingelheim, Lundbeck. He has served on the Advisory Board of Novartis.

  • Provenance and peer review Commissioned; not externally peer reviewed.

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