Central Integration of Pain, Center for Neuroscience of Lyon, Inserm U1028 & University Claude Bernard Lyon 1, Bron 69677, France Servicio de Neurofisiologia Clinica, Hospital Universitari de Bellvitge, Barcelona S-08907, Spain Laboratoire d'étude des mécanismes cognitifs, Univ Lyon 2, Bron F-69676, France.
Pain. 2012 Jun;153(6):1244-1252. doi: 10.1016/j.pain.2012.03.004. Epub 2012 Apr 10.
Laser-evoked potentials (LEPs) are acknowledged as the most reliable laboratory tool for assessing thermal and pain pathways. Electrical stimulation with a newly developed planar concentric electrode, delivering stimuli limited to the superficial skin layers, has been suggested to provide selective activation of Aδ fibres without the inconveniences linked to laser stimulation. The aim of our study was to compare the scalp and intracranial responses to planar concentric electrode stimulation (CE-SEPs) with those of LEPs and standard somatosensory-evoked potentials (SEPs). Sixteen healthy subjects, 6 patients with intracortical electrodes, and 2 patients with selective lesions of the spinothalamic pathway were submitted to Neodymium:Yttrium-Aluminium-Perovskite laser stimulations, and electrical stimulations using standard electrodes or planar concentric electrodes (CE). In both healthy controls and epileptic implanted patients, CE- and standard SEPs showed significantly shorter latencies than LEPs. This is consistent with Aβ-fibre activation, peripheral activation time being unable to account for longer LEP latencies. In the patients with spinothalamic lesions, LEPs were absent after stimulation of the affected territory, while CE-SEPs were still present. For these 2 reasons, we conclude that the planar CE does not selectively activate the Aδ and C fibers, but coexcites a significant proportion of large myelinated Aβ fibres that dominate the ensuing cortical response. The use of CE-SEPs for the detection of spinothalamic system lesions is therefore not warranted; the planar electrode can, however, represent a useful tool to study nociceptive reflexes, which can be reliably elicited even in the presence of Aβ coactivation.
激光诱发电位（LEP）被认为是评估热和痛觉通路的最可靠的实验室工具。使用新开发的平面同心电极进行电刺激，可将刺激限制在浅层皮肤层，据称可选择性地激活 Aδ纤维，而不会带来激光刺激相关的不便。我们的研究目的是比较平面同心电极刺激（CE-SEP）与 LEP 和标准体感诱发电位（SEP）的头皮和颅内反应。16 名健康受试者、6 名皮质内电极患者和 2 名脊髓丘脑束选择性病变患者接受钕：钇：铝：石榴石激光刺激以及使用标准电极或平面同心电极（CE）的电刺激。在健康对照者和植入癫痫患者中，CE-SEP 和标准 SEP 的潜伏期明显短于 LEP。这与 Aβ 纤维激活一致，因为外周激活时间无法解释 LEP 潜伏期较长的原因。在脊髓丘脑束病变患者中，在刺激受影响的区域后，LEP 消失，但 CE-SEP 仍然存在。基于这 2 个原因，我们得出结论，平面 CE 不能选择性地激活 Aδ 和 C 纤维，而是共同兴奋大量占主导地位的有髓 Aβ 纤维，从而导致随后的皮质反应。因此，不能使用 CE-SEP 来检测脊髓丘脑系统病变；但是，平面电极可以作为研究伤害性反射的有用工具，即使在 Aβ 共同兴奋的情况下，也可以可靠地引发这种反射。
