Analytical monitoring of brain activities for thalamotomy related with pathophysiology of parkinsonian motor symptoms

Background We monitor brain activities in thalamotomy for Parkinson's disease by a bipolar concentric microelectrode. Aim The present study aimed to standardize the quantitative monitoring for targeting and for pathophysiological analysis. Methods To show the process of data analysis, we selected 20 patients who gave informed consent for thalamotomy. The cases were divided into group I with rigidity, but no tremor (n = 10), and the group II with rigidity and tremor (n = 10). Most patients suffered from bradykinesia. We monitored the electromyograms of the neck and limb muscles. Brain activities were sampled as the electrode passed through the caudate and thalamic nuclei, divided into filtered local field potentials and multiple unit spikes, and rated at different depths by the summed periods in percent occupied by the component wavelets of field potentials at 3–7, 7–13, 13–27 and 27–80 Hz. Results Analysis was summarized by the depth distribution histograms of dominant wavelet compositions. The 13–27-Hz activities were exaggerated in the caudate, thalamic ventroanterior and ventrolateral nuclei. The 3–7-Hz activities time-locked with tremor were exaggerated in the nucleus ventralis intermedius. Group I cases showed little 3–7-Hz activities. Thermolesion in the thalamus with those highly-rated activities alleviated tremor and rigidity, but spared most bradykinesia. Conclusion The standardized analysis suggests that the thalamic 3–7-Hz and 13–27-Hz activities serve as the quantitative markers of pathophysiology representing tremor and rigidity, respectively.