A study of the medial temporal lobe in high-risk and established schizophrenia using T2 relaxometry

精神分裂症的神经发育模型表明，这种疾病与早期生活中出现的结构性大脑异常有关。这个模型预测，大脑的变化在精神分裂症发作之前就已经存在，而且不会改变。我们的研究支持这样一种观点，即损害从疾病开始就存在，然而，这种损害在后来发展为精神病的高危人群中并不明显。当这些患者在疾病发作后重新扫描时，他们表现出对精神分裂症症状至关重要的结构体积的减少。这一群体在精神病发作前缺乏结构变化可能有许多可能的解释。然而，可能是许多因素导致了精神分裂症患者颞叶的变化。因此，高风险受试者可能易受海马损伤，这种损伤在向精神病的过渡过程中变得明显。为了探索这一点，我们的研究将检查三组患者的海马体变化，并将其与匹配的正常对照组进行比较。患者群体为：(i)高危个体，（ii）首发精神病患者和（iii）慢性精神分裂症患者。这项研究将重新扫描高危人群，以检查他们精神病发作后海马的变化。T2弛缓测量是一种非侵入性的方法，用于检查精神分裂症患者从发病开始是否存在大脑变化。T2也将让我们检查高危人群，看看这些变化是否在发病前也很明显。使用T2，我们将能够检查这些结构变化的本质，并评估哪些过程是有证据的。我们的MRI发现对精神分裂症的神经发育假说提出了挑战。在这项研究中使用T2将允许对这些发现进行彻底的检查，并将对这一假设产生重大影响。

Neurodevelopmental models of schizophrenia suggest that this disorder is associated with a structural brain abnormality present from very early life. This model predicts that brain changes are present before the onset of schizophrenia, and do not change. Our work supports the idea that damage is present from the outset of illness - however, this damage was not evident in a high-risk group of individuals who later developed psychosis. When these patients were rescanned after the onset of the illness, they exhibited reductions in the volumes of structures that are regarded as critical to the symptoms of schizophrenia. The lack of structural changes in this group before the onset of psychosis may have a number of possible explanations. However, it may be that a number of factors produce the observed changes in the temporal lobe in schizophrenia. Thus, high-risk subjects may have a vulnerability to hippocampal damage that becomes apparent during the transition to psychosis. In order to explore this, our study will examine changes in the hippocampi in three groups of patients, and compare them with matched normal control subjects. The patient groups are: (i) individuals at high-risk, (ii) first-episode psychosis patients and (iii) patients with chronic schizophrenia. The study will rescan the high-risk group to examine hippocampal changes once they have become psychotic. T2 relaxometry is a non-invasive way to examine whether changes in the brain are present in patients with schizophrenia from the outset of illness. T2 will also let us examine the high-risk individuals to see whether such changes are also apparent premorbidly. Using T2 we will be able to examine the nature of these structural changes and assess what processes are in evidence. Our MRI findings present a challenge to the neurodevelopmental hypothesis of schizophrenia. The use of T2 in this study will allow a thorough examination of these findings and will have major implications for this hypothesis.