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Background In the procedure of thalamotomy, we mark the targets by thalamic 13−27-Hz β-band and 3−7-Hz τ-range hyperactivities as representing parkinsonian rigidity and tremor, respectively. Aim We tested the validity of these thalamic markers in surgically treated non-parkinsonian patients with tremor of complicated pathophysiology. Methods As the cases with tremor, but no thalamic τ-range hyperactivities, we selected four of the 23 previously studied non-parkinsonian patients; examined the shoulder, neck, face and limb electromyograms, brain local field potentials, and multiple unit spikes; and rated the local field potentials in the bands of 3–7, 7–13, 13–27 and 27–80 Hz. Results Tremor rated as moderate in the present study was postural, kinetic, intentional, ballistic, or myoclonic, or of some combined nature with irregular rhythms at variable frequencies widely ranging in 1–13 Hz. Tremor accompanied motor hyperactivities and thalamic β-band hyperactivities, but not τ-range activities. The β-band hyperactivities and high neural noise occurred in the caudate nucleus, thalamic ventroanterior nucleus, nucleus ventralis lateralis and nucleus ventralis intermedius. The thalamic β-band hyperactivities were not accompanied by rigidity in three of the patients. The four patients were thus atypical when compared with the other non-parkinsonian and parkinsonian patients. Yet, thalamotomy alleviated tremor and concurrent motor hyperactivities. Conclusion Non-parkinsonian tremor in the four patients was related to β-band hyperactivities, and elevating neural noise in wide regions of the basal ganglia and thalamus. Thalamotomy was effective by eventually abolishing ventralis lateralis with β-band hyperactivities and high noise that was involved as a part of the widely distributed pathophysiology of these patients.

Background Parkinsonian thalamic 13- to 27-Hz (β-band) and 3- to 7-Hz (τ-range) hyperactivity is linked to rigidity and tremor, respectively, but not to bradykinesia. Aim To clarify the contributions of different types of thalamic activity to the progression of parkinsonian symptoms, we modeled a neural converter that translates thalamic activity into symptoms and examined its input-output relationship. Methods We scored pre- and postoperative rigidity, tremor, and bradykinesia as well as case-representative τ-range (Vτ) and β-band (Vβ) activity in 170 patients with Parkinson's disease. Results The relationship between abolished rigidity (dR) and Vβ was described by a hysteresis curve, which was simulated by two parabolas relating dR and Vβ to preoperative rigidity (preR) using the calculated time lag corresponding to 1.5 preR grades. The abolished tremor was linearly related to Vτ. The partly abolished bradykinesia was related to Vβ by hysteresis. Hysteresis in the dR-to-Vβ relationship was observed as a result of 11 patients with preR scores of 4. Their brain activity was generally low and similar to that of patients without rigidity. Conclusion In contrast to the direct correlation between Vτ and tremor, Vβ caused rigidity and, in part, bradykinesia via time-consuming processes, as demonstrated by the delayed parabola model. Patients with the severest rigidity showed a loss of thalamic activity and the spread of pathophysiological abnormalities in the neural circuitry beyond the thalamus with progressive age.

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.