Imaging pain in humans.
نویسنده
چکیده
Cerebral pain mechanisms are poorly understood when compared with the peripheral nervous system and spinal cord. Reasons for this have included a lack of suitable examination techniques, especially in humans. The recent availability of a number of relatively non-invasive methods that can produce images of functional brain activity has renewed interest in this field. Three of these techniques will be considered in detail; single photon emission computed tomography (SPECT), positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). These three techniques all provide indirect measures of local brain activity. There are other non-invasive techniques that directly detect magnetic and electrical neural activity. One of these, magnetoencephalography will be discussed briefly. These methods are compared in table 1. PET and SPECT use radionuclides to produce maps representing changes in regional cerebral blood flow (rCBF). By using radiolabelled ligands, PET and SPECT can also be used for in vivo studies of receptor distribution. PET, in particular, has been used to map opioid receptors. The evidence that links local blood-flow changes to increased neural activity is well established. Such an idea was first presented by Roy and Sherrington in 1890 [33] who proposed that increased neural activity released acid metabolites that produced local vasodilatation. More recent evidence suggests that nitric oxide may have a pivotal role in coupling rCBF to local brain activation [19]. These changes in blood flow occur rapidly and are extremely localized [29]. fMRI produces images based on changes in local blood oxygenation. The evidence that this is also linked to neural activity is reviewed elsewhere [5]. PET, SPECT and fMRI can all produce images of changes in rCBF during many types of neural activity and they have been applied to the problem of localizing brain areas associated with a variety of experimental and clinical pain conditions. There are, however, important limitations to these techniques. Temporal and spatial resolution are poor, measured respectively in tens of seconds and several millimetres at best. The final images are produced
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عنوان ژورنال:
- British journal of anaesthesia
دوره 75 2 شماره
صفحات -
تاریخ انتشار 1995