Uniform qualitative electrophysiological changes in postoperative rest tremor.

Ablation and deep brain stimulation (DBS) can treat pharmacologically uncontrollable tremor. Here, we compared the postoperative electrophysiological changes in resting hand tremor after 32 ablations and 12 DBS implantations in patients with severe tremor-dominant idiopathic Parkinson's disease (PD) and essential tremor (ET). Short- and long-term accelerometric data were acquired after surgery and were compared to the preoperative tremor. After effective surgical treatments, significant rest tremor reduction and increase in both frequency and approximate entropy (ApEn) were detected in all PD cases, irrespective of the type and target of intervention. However, the long-term effect of DBS implantation on tremor reduction was significantly better compared to that after ablative treatments. In cases of thalamotomy, the postoperative increase in frequency and ApEn was significantly larger in essential tremor compared to PD, suggesting that the etiology of tremor may influence the size of the similar changes. However, cases where clinical tremor re-emerged 6 to 12 months after the surgery, no change in frequency and ApEn was detected on the second postoperative day, despite an initial tremor reduction and clinical improvement similar to the effective operations. Our results suggest that uniform postoperative changes in rest tremor and the increase in frequency and ApEn could be due to attenuation of pathological oscillators and might be immediate indicators of the effectiveness of neurosurgical treatments relieving tremor.