Objective: To investigate changes in local field potential (LFP) activity of the posterior subthalamic area (PSA) in patients with essential tremor (ET) during wakefulness and sleep.

Background: Continuous deep brain stimulation (DBS) in the PSA has shown a remarkable therapeutic effect on tremor symptoms in patients with ET and other forms. Increasing evidence shows that this form of DBS exhibit in some patients a subsequent decline in efficacy possibly due to tolerance development. Hence, we recommend a switching off during nighttime, which has to be performed manually. Since closed-loop stimulation systems for adaptive DBS in Parkinsons disease are being discussed, one could speculate that this technique could be helpful to avoid tolerance by automatic switch off during sleep. Therefore, analyzing LFP of PSA at different consciousness level -from wakefulness to the different sleep stages- might enable an automatic detection of actual sleep stage to switch off the stimulation while sleeping.

Methods: We collected LFP data of two ET patients (patient A, female, age 70, disease duration 57 years; patient B, male, age 63; disease duration 38 years) via an fully implanted DBS system capable of recording LFP with implanted DBS lead (Activa PC+S®, Medtronic Inc., Neuromodulation, Minneapolis, USA) in chronic implanted state. LFP were acquired over a period of 45 seconds every 12 minutes throughout the night simultaneously with a continuous polysomnography (SOMNOscreen™ plus, SOMNOmedics, Randersacker, Germany) and the DBS turn off. The LFP intervals were correlated with the actual sleep stage according to the AASM-classification.

Results: Both patients showed changes in the PSA-LFP power spectrum distribution during different sleep stages. Most interestingly, we observed a marked reduction of the high-beta-band (20-30 Hz) activity and a concurrent increase in theta-band activity during slow wave sleep in both patients. In patient A, we were also able to capture multiple rapid-eye-movement phases. In this case, a recovery of beta-band-activity and a further increase in the theta-band occurred.

Conclusions: In this study we have identified LFP changes in the high-beta and theta-band during deep sleep in ET patients as a possible marker which might be useful in adaptive DBS.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/local-field-potential-changes-during-sleep-in-the-psa-of-patients-with-essential-tremor/