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

Abstract

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.

Intraoperative Localization of the Subthalamic Nucleus Using Long-Latency Somatosensory Evoked Potentials

“…Our intraoperative results suggest that the elicited LL‐SSEPs were generated within the STN, as also supported by our previous postoperative study addressing LL‐SSEPs within the STN of PD patients . In the case of the P80 such aspect was indexed by the highest amplitude attained by this component for a specific contact and its associated neuronal firing patterns.…”

“…In the present study, we investigated the clinical application of subcortical long‐latency (LL)‐SSEPs (latency >40 msec), namely the recently reported LL‐complex (P80, N100, P140, and N200) . Here, we report on the plausibility of utilizing LL‐SSEPs for intraoperative DBS target localization in the STN of PD patients by focusing on SSEP properties.…”

The Subthalamic Nucleus: A Hub for Sensory Control via Short Three- Lateral Loop Connections with the Brainstem?

“…These responses are suppressed by the ablation or cooling of the somato-sensory cortex [20]. Subthalamic somato-sensory responses were later confirmed in patients with Parkinson's disease in whom somato-sensory evoked potentials were recorded from the STN through DBS electrodes [23,24] and were used to optimize the localization of these electrodes within the STN [25]. Neurons in the STN have also been reported to be activated by visual stimulation in an oculomotor task in non-human primates [21] and 30 % (70/226) of STN cells recorded in freely moving rats exhibit short latency / short duration auditory responses to a tone or a white noise [22].…”

Subthalamic nucleus single-unit activity in humans with Parkinson's Disease encodes both the rate of change and the magnitude of force during a sustained grip-force task

“…The STN receives inputs from several frontal motor areas, including the primary motor cortex, and the supplementary motor area, as well as lesser inputs from the primary sensory cortex [19][20][21][22] . Sensory responses to light touch, passive movements [23][24][25][26][27][28][29][30] , and median nerve stimulation [31][32][33][34][35][36][37] have been noted with single unit recordings from subthalamic nucleus and other basal ganglia structures. Anatomical studies of the STN and its connectivity suggest a functional compartmentalization of the STN into motor and non-motor regions, and a more fine-grain division of the motor inputs from a variety of cortical source regions 38 .…”