Spencer S S, Theodore W H, Berkovic S F
Department of Neurology, Yale University School of Medicine, New Haven, CT 06520, USA.
Magn Reson Imaging. 1995;13(8):1119-24. doi: 10.1016/0730-725x(95)02021-k.
MRI, PET, and SPECT are all used to image abnormalities in the epileptic brain. Comparison of the techniques is difficult because they measure different aspects of the epileptic process--structure, metabolism, and perfusion. SPECT is the only one that can be systematically applied during seizures, while all three are used to image interictal abnormalities. Literature review suggests that of interictal techniques, PET has the highest diagnostic sensitivity in temporal lobe epilepsy (TLE) (84% vs. 66% for SPECT, 55% for qualitative MRI, 71% for quantitative MRI) while SPECT has the highest sensitivity in extratemporal epilepsy (ETE) (60% vs. 43% for MRI and 33% for PET). The highest diagnostic sensitivity and specificity were achieved by ictal imaging with SPECT (90% in TLE, 81% in ETE). The techniques, however, were not always redundant. One reason for the wide discrepancy of results in TLE and ETE might be the differing pathologic substrates. A literature review of imaging findings associated with mesial temporal sclerosis (MTS), developmental lesion or tumor as the underlying abnormality associated with epilepsy supports this explanation. PET and MRI are much more sensitive to MTS than SPECT (100%, 95% vs. 70%). On the other hand, in developmental lesions the three techniques are equally sensitive (88-92%) and in tumors, MRI was most sensitive (96%) and SPECT least (82%). A study at NIH explains the differing sensitivities: using PET to measure both blood flow and metabolism revealed discrepant findings in the same patients. Preliminary evidence also indicates that the distribution of hyperperfusion on ictal SPECT can differentiate subtypes of TLE. Combining the results of refined imaging techniques holds great promise in epilepsy localization and diagnosis.
磁共振成像（MRI）、正电子发射断层扫描（PET）和单光子发射计算机断层扫描（SPECT）均用于对癫痫大脑中的异常情况进行成像。由于这些技术测量的是癫痫过程的不同方面——结构、代谢和灌注，因此很难对它们进行比较。SPECT是唯一一种可以在癫痫发作期间系统应用的技术，而这三种技术都用于对发作间期异常情况进行成像。文献综述表明，在发作间期技术中，PET在颞叶癫痫（TLE）中具有最高的诊断敏感性（84%，而SPECT为66%，定性MRI为55%，定量MRI为71%），而SPECT在颞叶外癫痫（ETE）中具有最高的敏感性（60%，而MRI为43%，PET为33%）。通过SPECT进行发作期成像可实现最高的诊断敏感性和特异性（TLE中为90%，ETE中为81%）。然而，这些技术并不总是相互冗余的。TLE和ETE结果差异巨大的一个原因可能是病理基础不同。对与内侧颞叶硬化（MTS）、发育性病变或肿瘤相关的影像学发现进行的文献综述，这些病变是与癫痫相关的潜在异常，支持了这一解释。PET和MRI对MTS的敏感性远高于SPECT（分别为100%、95%和70%）。另一方面，在发育性病变中，这三种技术的敏感性相同（88 - 92%），而在肿瘤中，MRI最敏感（96%），SPECT最不敏感（82%）。美国国立卫生研究院的一项研究解释了不同的敏感性：使用PET测量血流和代谢在同一患者中发现了不一致的结果。初步证据还表明，发作期SPECT上的高灌注分布可以区分TLE的亚型。结合精细成像技术的结果在癫痫定位和诊断方面具有很大的前景。
