October 2010
Reck
C, Himmel M, Florin E, Maarouf M, Sturm V, Wojtecki L, Schnitzler A, Fink GR,
Timmermann L
Implantation of electrodes in the subthalamic nucleus (STN) for deep
brain stimulation is a well-established method to ameliorate motor
symptoms in patients suffering from Parkinson’s disease (PD). This study
investigated the pathophysiology of rest and postural tremor in PD.
In
14 patients with PD, we recorded intraoperatively local field potentials
(LFPs) in the STN (at different recording depths) and electromyographic
signals (EMGs) of the contralateral forearm. Using coherence analysis
we analysed tremor epochs both at rest and hold conditions in patients
of the akinetic-rigid or of the tremor-dominant PD subtype.
Data
analysis revealed significant LFP–EMG coherence during periods of rest
and postural tremor. However, strong differences between both tremor
types were observed: local maxima (cluster) of rest and postural tremor
did not match. Additionally, during rest tremor coherence occurred
significantly more frequently at single tremor frequency than at double
tremor frequency in tremor-dominant as well as in akinetic-rigid
patients. In contrast, during postural tremor in patients with
akinetic-rigid PD coherence was predominantly at double tremor
frequency.
The data suggest a specific topography of ‘tremor clusters’
for rest and postural tremor. Furthermore, we presume that the same
tremor mechanisms exist in patients with tremor-dominant and
akinetic-rigid PD, but to different degrees.
