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• Subthalamic stimulation: double blind assessments
  Paul Krack
  Published on: 27 August 2004

• Published on: 27 August 2004

  Subthalamic stimulation: double blind assessments

  • Paul Krack
  • Other Contributors:
    • Pierre Pollak, Alim-Louis Benabid

  Dear Editor,

  Ford et al [1] report their experience with subthalamic nucleus deep brain stimulation (STN DBS) in advanced PD. In blinded reviews of videotaped neurological examination, off medication UPDRS III (motor) score improved by 26% (baseline 43.8, on stimulation at 12 months 32.3), which is much less than reported by other groups [2]. The authors believe that their more modest results represent a m...

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  Dear Editor,

  Ford et al [1] report their experience with subthalamic nucleus deep brain stimulation (STN DBS) in advanced PD. In blinded reviews of videotaped neurological examination, off medication UPDRS III (motor) score improved by 26% (baseline 43.8, on stimulation at 12 months 32.3), which is much less than reported by other groups [2]. The authors believe that their more modest results represent a more realistic estimate of the effect of DBS on PD because they used a double blinded evaluation of the motor UPDRS as their main outcome criterion.

  As the authors acknowledge, functional outcome of their patients was not improved and this is compatible with the modest improvement in motor score. The UPDRS II describes the impact of parkinsonian signs on activities of daily living. Whereas this score was improved by 60% with levodopa – thereby confirming that the patients had an excellent response to levodopa and indeed corresponded to the patient selection criteria generally accepted for this treatment - there was only a non significant 7% improvement with STN stimulation. This questions the value of DBS, because if activities of daily living cannot be improved, then it would not be worth taking the risks inherent to brain surgery.

  In our hands both activities of daily living and motor scores, using a non-blinded evaluation, were improved in parallel and to exactly the same extent (one year after surgery 66% improvement in UPDRS II, 66% improvement in UPDRS III, and 5 years on chronic STN DBS 49% improvement in UPDRS II versus 54% improvement in UPDRS III) [3]. We acknowledge that there may be a bias in a non-blinded assessment, but we assessed activities of daily living in the same way than Ford and colleagues and thus there should not be such a discrepancy in results. In the best responders to STN DBS, improvement is equivalent to that obtained with supramaximal doses of levodopa and some patients are able to discontinue this drug altogether [4]. If the response to STN DBS is way off the response to levodopa, then inadequacy of either the surgical technique or the postoperative neurological management should be suspected. In case of misplaced electrodes, re-operation might even be considered [5].

  Using evidence based medicine criteria, Ford et al have shown that in their hands, STN DBS has only a modest impact on off period parkinsonian motor symptoms and does not improve motor function. We do not believe that their results represent a more realistic estimate of the effect of DBS on PD than all other published series because their data greatly differ not only in the double blind evaluation of the UPDRS motor score but also in non-blinded assessment of several secondary outcome measures, including activities of daily living (UPDRS II), Schwab and England scale as well as postoperative decrease in dopaminergic treatment.

  References

  (1). Ford B, Winfield L, Pullman SL, Frucht S, Du Y, Greene P, Cheringal JH, Yu Q, Cote LJ, Fahn S, McKhann GM, Goodman RR. Subthalamic nucleus stimulation in advacnced Parkinson's disease: blinded assessments at one year follow up. J Neurol Neurosurg Psychiatry 2004;75:1255-9.

  (2). Deep-Brain Stimulation for Parkinson´s Disease Study Group. Deep- brain stimulation of the subthalamic nucleus or the pars interna of the globus pallidus in Parkinson´s disease. N Engl J Med 2001;345:956-63.

  (3). Krack P, Batir A, Van Blercom N, Chabardes S, Fraix V, Dowsey Limousin P, Benazzouz A, Lebas JF, Benabid AL, Pollak P. Five-year follow- up of bilateral stimulation of the subthalamic nucleus in advanced Parkinson's disease. N Engl J Med 2003;349 :1925-34.

  (4). Lang, A. E. and Widner, H. Deep brain stimulation for Parkinson's disease: patient selection and evaluation. Mov Disord 17, Suppl 3, S94- S101. 2002.

  (5). Batir A, Torny F, Fraix V, Krack P, Benabid AL, Pollak P. Improvement in parkinsonism by STN stimulation depends on electrode placement: Effects of reimplantation [abstract ]. Mov Disord 2004;19, Suppl 9:S260.

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  Conflict of Interest:
  None declared.

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