Local field potential oscillations of the globus pallidus in cervical and tardive dystonia

Background: Reports about neural oscillatory activity in the globus pallidus internus (GPi) have targeted general (GD) and cervical dystonia (CD), however to our knowledge they are nonexistent for tardive dystonia (TD). Methods: Local field potentials (LFPs) from seven CD and five TD patients were recorded intraoperatively. We compared LFP power in thetadelta, alpha and beta band during rest and sensory palmar stimulation (SPS) in patients with general anesthesia and local/analgo sedation. Results: We found prominent LFP power activity in thetadelta for both CD and TD. Unlike TD, a significant difference between rest and SPS was revealed for CD. Conclusions: Our data support the presence of LFP oscillatory activity in CD and TD. Thetadelta power modulation in the GPi is suggested as a signature for sensory processing in CD. (C) 2016 Elsevier B.V. All rights reserved

Long-Latency Somatosensory Evoked Potentials of the Subthalamic Nucleus in Patients with Parkinson’s Disease

<div><p>Somatosensory evoked potentials (SSEPs) are a viable way to measure processing of somatosensory information. SSEPs have been described at the scalp and the cortical level by electroencephalographic, magnetoencephalographic and intracranial cortical recordings focusing on short-latency (SL; latency<40 ms) and long-latency (LL; latency>40 ms) SSEPs as well as by deep brain stimulation (DBS) electrode studies targeting SL-SSEPs. Unfortunately, LL-SSEPs have not been addressed at the subcortical level aside from the fact that studies targeting the characteristics and generators of SSEPs have been neglected for the last ten years. To cope with these issues, we investigated LL-SSEPs of the subthalamic nucleus (STN) in twelve patients with Parkinson’s disease (PD) that underwent deep brain stimulation (DBS) treatment. In a postoperative setting, LL-SSEPs were elicited by median nerve stimulation (MNS) to the patient’s wrists. Ipsilateral or contralateral MNS was applied with a 3 s inter-stimulus interval. Here, we report about four distinctive LL-SSEPs (“LL–complex” consisting of P80, N100, P140 and N200 component), which were recorded by using monopolar/bipolar reference and ipsi/contralateral MNS. Phase reversal and/or maximum amplitude provided support for the generation of such LL-SSEPs within the STN, which also underscores a role of this subcortical structure in sensory processing.</p></div

Example of LL-SSEPs recorded with bipolar reference.

<p>Left: Phase reversal of the P80 at contact (0 vs. 1), Patient 9, right STN, ipsilateral MNS. Right: Phase reversal of the N100 at contact (2 vs. 3), Patient 2, left STN, contralateral MNS.</p

Patient Collective: m = male, f = female, Age (at the time of operation), Duration since diagnosis (number of years since disease diagnosis).

<p>Score of the motor part of the Unified Parkinson’s Disease Rating Scale (UPDRS) without medication: UPDRS <i>Off</i>, score of the motor part of the UPDRS with medication: UPDRS <i>On</i>. The UPDRS test was performed prior to surgery.</p

Long-latency somatosensory evoked potential (LL-SSEP) components corresponding to monopolar data: N denotes the number of nuclei with a referred wave, Latency (ms): Mean ± SD (range), Amplitude (μV): Mean ± SD (range).

<p>Long-latency somatosensory evoked potential (LL-SSEP) components corresponding to monopolar data: N denotes the number of nuclei with a referred wave, Latency (ms): Mean ± SD (range), Amplitude (μV): Mean ± SD (range).</p

Statistical comparison of mean latencies between the N18/20 in the present study and data reported in the literature revealed no significant difference (significance level of 0.05).

<p>N denotes the number of nuclei with occurrence of the N18/20, Latency (ms): Mean ± standard deviation (SD) (range), Amplitude (μV): Mean ± SD (range), NA “not available”. This finding provides support for the used methodology, namely forehead rather than linked earlobes/mastoids for monopolar reference and filtering methods (Notch and 40 Hz high cut-off), in eliciting somatosensory evoked potentials (SSEPs).</p

Zoom-in view of Fig 1 emphasizing the short-latency somatosensory evoked potential (SL-SSEP) component N20: Patient 4, right STN, monopolar reference, contralateral median nerve stimulation (MNS).

<p>Black: Contact 0, red: Contact 1, blue: Contact 2, green: Contact 3.</p