Clinical Neurophysiology xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Clinical Neurophysiology journal homepage: www.elsevier.com/locate/clinph
Letter to the Editor Reply to ‘‘Motor cortex plasticity and excitability in Parkinson’s disease’’
Bareš et al. provided a quite nice, comprehensive but short, overview of the findings reported in the literature on a question whether intra-cortical facilitation (ICF) in Parkinson’s disease (PD) is impaired or not, and whether it changes in relationship with the levodopa treatment (Bareš et al., 2014). They particularly emphasized their two published studies where the issue was studied in more detail (Bares et al., 2003, 2007). In short, they found diminished ICF in PD patients compared to healthy controls (Bares et al., 2003, 2007), which became normalized after 6 and 12 months of levodopa treatment (Bares et al., 2007). However, as the authors do acknowledge, the PD patients in their studies, although levodopa naïve, were not anti-parkinsonian medication naïve. Moreover, in the 2003 study, the patients were studied while on medication. Thus, their findings cannot be directly compared with the findings from the Kacˇar et al. (2013) and Kojovic et al. (2012) studies where patients were anti-parkinsonian medication naïve. In both of these studies, no significant difference in ICF was found between PD patients and healthy controls. However, it has to be said that, besides the methodological differences between the studies, all of them were statically underpowered to be able to provide a conclusive proof for either of the opinions. More data is necessary to be gathered in order to understand the issue properly. Regardless of the aforementioned, the Bareš et al. letter requires an additional comment. It stresses the possibility of a certain general misreading of the Kacˇar et al. (2013) study findings. Namely, the main message of the Kacˇar et al. study was that some of the neurophysiological features of PD, which had been found previously in several studies on already treated PD patients, were
present in the medication naïve patients as well. In other words, those features seem to be neurophysiological markers of PD, present from the onset of the disease and potentially even before. The intention was by no means to suggest that medication and disease progression have no effect on the underlying physiological processes in PD. Acknowledgments This study was supported by project grants (#175012) from the Ministry for Education, Science and Technological Development of Republic of Serbia. References Bares M, Kanovsky´ P, Klajblová H, Rektor I. Intracortical inhibition and facilitation are impaired in early Parkinson’s disease patients – a paired TMS study. Eur J Neurol 2003;10:385–9. Bares M, Kanovsky´ P, Rektor I. Disturbed intracortical excitability in early Parkinson’s disease is L-DOPA dose related: a prospective 12-month paired TMS study. Parkinsonism Relat Disord 2007;13:489–94. ˇ ovsky´ P, Rektor I. Motor cortex plasticity and excitability in Parkinson’s Bareš M, Kan disease. Clin Neurophysiol 2014 [This Issue]. Kacˇar A, Filipovic´ SR, Kresojevic´ N, Milanovic´ SD, Ljubisavljevic´ M, Kostic´ VS, et al. History of exposure to dopaminergic medication does not affect motor cortex plasticity and excitability in Parkinson’s disease. Clin Neurophysiol 2013;124:697–707. Kojovic M, Bologna M, Kassavetis P, Murase N, Palomar FJ, Berardelli A, et al. Functional reorganization of sensorimotor cortex in early Parkinson’s disease. Neurology 2012;78:1441–8.
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S.R. Filipovic´ Department of Neurophysiology, Institute for Medical Research University of Belgrade, P.O. Box 39, 11129 Beograd 102, Serbia ⇑ Tel.: +381 11 2685788x104; fax: +381 11 2643691. E-mail address: sasa.fi[email protected]
http://dx.doi.org/10.1016/j.clinph.2014.02.008 1388-2457/Ó 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved
Contents lists available at ScienceDirect
Clinical Neurophysiology journal homepage: www.elsevier.com/locate/clinph
Letter to the Editor Reply to ‘‘Motor cortex plasticity and excitability in Parkinson’s disease’’
Bareš et al. provided a quite nice, comprehensive but short, overview of the findings reported in the literature on a question whether intra-cortical facilitation (ICF) in Parkinson’s disease (PD) is impaired or not, and whether it changes in relationship with the levodopa treatment (Bareš et al., 2014). They particularly emphasized their two published studies where the issue was studied in more detail (Bares et al., 2003, 2007). In short, they found diminished ICF in PD patients compared to healthy controls (Bares et al., 2003, 2007), which became normalized after 6 and 12 months of levodopa treatment (Bares et al., 2007). However, as the authors do acknowledge, the PD patients in their studies, although levodopa naïve, were not anti-parkinsonian medication naïve. Moreover, in the 2003 study, the patients were studied while on medication. Thus, their findings cannot be directly compared with the findings from the Kacˇar et al. (2013) and Kojovic et al. (2012) studies where patients were anti-parkinsonian medication naïve. In both of these studies, no significant difference in ICF was found between PD patients and healthy controls. However, it has to be said that, besides the methodological differences between the studies, all of them were statically underpowered to be able to provide a conclusive proof for either of the opinions. More data is necessary to be gathered in order to understand the issue properly. Regardless of the aforementioned, the Bareš et al. letter requires an additional comment. It stresses the possibility of a certain general misreading of the Kacˇar et al. (2013) study findings. Namely, the main message of the Kacˇar et al. study was that some of the neurophysiological features of PD, which had been found previously in several studies on already treated PD patients, were
present in the medication naïve patients as well. In other words, those features seem to be neurophysiological markers of PD, present from the onset of the disease and potentially even before. The intention was by no means to suggest that medication and disease progression have no effect on the underlying physiological processes in PD. Acknowledgments This study was supported by project grants (#175012) from the Ministry for Education, Science and Technological Development of Republic of Serbia. References Bares M, Kanovsky´ P, Klajblová H, Rektor I. Intracortical inhibition and facilitation are impaired in early Parkinson’s disease patients – a paired TMS study. Eur J Neurol 2003;10:385–9. Bares M, Kanovsky´ P, Rektor I. Disturbed intracortical excitability in early Parkinson’s disease is L-DOPA dose related: a prospective 12-month paired TMS study. Parkinsonism Relat Disord 2007;13:489–94. ˇ ovsky´ P, Rektor I. Motor cortex plasticity and excitability in Parkinson’s Bareš M, Kan disease. Clin Neurophysiol 2014 [This Issue]. Kacˇar A, Filipovic´ SR, Kresojevic´ N, Milanovic´ SD, Ljubisavljevic´ M, Kostic´ VS, et al. History of exposure to dopaminergic medication does not affect motor cortex plasticity and excitability in Parkinson’s disease. Clin Neurophysiol 2013;124:697–707. Kojovic M, Bologna M, Kassavetis P, Murase N, Palomar FJ, Berardelli A, et al. Functional reorganization of sensorimotor cortex in early Parkinson’s disease. Neurology 2012;78:1441–8.
⇑
S.R. Filipovic´ Department of Neurophysiology, Institute for Medical Research University of Belgrade, P.O. Box 39, 11129 Beograd 102, Serbia ⇑ Tel.: +381 11 2685788x104; fax: +381 11 2643691. E-mail address: sasa.fi[email protected]
http://dx.doi.org/10.1016/j.clinph.2014.02.008 1388-2457/Ó 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved
