Talbot J D, Villemure J G, Bushnell M C, Duncan G H
Centre de recherche en sciences neurologiques, Université de Montréal, Québec, Canada.
Somatosens Mot Res. 1995;12(2):115-26. doi: 10.3109/08990229509101503.
The medial prefrontal cortex has been implicated in pain perception by recent anatomical, physiological, and functional imaging data demonstrating that frontal and anterior cingulate cortices receive inputs related to nociception; neurosurgical case reports suggest that lesions involving these areas may specifically reduce the affective or emotional component of chronic intractable pain. We examined this hypothesis more closely by assessing psychophysical ratings of (1) warmth, pain intensity, and unpleasantness evoked by phasic thermal stimuli, (2) tolerance to tonic cold stimuli, and (3) perceived intensity of visual stimuli, both before and after neurosurgical lesions of the fiber tracts connecting the frontal lobes to subcortical structures. A 22-year-old male, with no history of chronic pain, underwent psychophysical testing 3 days before, 5 days after, and 6 months after receiving bilateral lesions of the anterior internal capsule (aIC), performed as treatment for obsessive-compulsive disorder. In each session, the patient rated the intensity and unpleasantness of 5-sec cutaneous heat stimuli (39-47 degrees C); pain tolerance was measured by means of a cold-pressor test (hand immersion in 1 degrees C water). The patient was able to differentially rate the intensities of heat stimuli during both pre- and postsurgical testing sessions (p < 0.001). However, he rated heat stimuli as less intense 5 days after surgery than during presurgical testing (p < 0.001), with significant decreases in both pain intensity (p < 0.005) and unpleasantness (p < 0.05). Likewise, the patient described the cold-water immersion as less painful following surgery, although his tolerance times were substantially shorter than those of the presurgical evaluation. Ratings of visual stimulus intensity did not differ across the pre- and postsurgical testing periods, suggesting that changes in pain perception were not related to attentional or cognitive deficits. Magnetic resonance imaging 5 days following surgery revealed bilateral lesions and edema centered in the aIC, with some edema in the left frontal lobe. Those 6 months later showed substantially smaller lesions involving less than half of the aIC and no edema; pain ratings and cold-water tolerance measured at that time indicated a substantial return toward the patient's presurgical values. These data suggest that blocking subcortical input to the anterior cingulate and frontal cortices reduces both the perceived intensity and the unpleasantness of noxious stimuli; reduced cold tolerance times--in the face of decreased pain perception--may reflect a disinhibition of cortical control on spinal reflexes.(ABSTRACT TRUNCATED AT 400 WORDS)
近期的解剖学、生理学及功能成像数据表明额叶和前扣带回皮质接收与伤害感受相关的输入，内侧前额叶皮质与疼痛感知有关；神经外科病例报告显示，涉及这些区域的损伤可能会特异性降低慢性顽固性疼痛的情感或情绪成分。我们通过评估以下方面的心理物理学评分来更深入地研究这一假设：（1）阶段性热刺激诱发的温暖感、疼痛强度和不愉快感；（2）对持续性冷刺激的耐受性；（3）连接额叶与皮质下结构的纤维束进行神经外科损伤前后视觉刺激的感知强度。一名22岁无慢性疼痛病史的男性，在接受双侧内囊前肢（aIC）损伤以治疗强迫症之前3天、之后5天和6个月接受了心理物理学测试。在每次测试中，患者对5秒的皮肤热刺激（39 - 47摄氏度）的强度和不愉快感进行评分；通过冷加压试验（将手浸入1摄氏度的水中）测量疼痛耐受性。患者在手术前和手术后的测试中都能够区分热刺激的强度（p < 0.001）。然而，他在术后5天对热刺激的评分低于术前测试（p < 0.001），疼痛强度（p < 0.005）和不愉快感（p < 0.05）均显著降低。同样，患者称术后冷水浸泡的疼痛感减轻，尽管他的耐受时间比术前评估时大幅缩短。视觉刺激强度的评分在手术前和手术后的测试期间没有差异，这表明疼痛感知的变化与注意力或认知缺陷无关。术后5天的磁共振成像显示双侧损伤和水肿集中在aIC，左侧额叶也有一些水肿。6个月后的成像显示损伤明显变小，累及不到一半的aIC且无水肿；当时测量的疼痛评分和冷水耐受性表明已大幅恢复到患者术前的值。这些数据表明，阻断前扣带回和额叶皮质的皮质下输入会降低有害刺激的感知强度和不愉快感；在疼痛感知降低的情况下，冷耐受时间缩短可能反映了皮质对脊髓反射的抑制解除。（摘要截断于400字）
