Al-Helli, OMAA; (2017) Anatomical and quantitative structural MRI studies in Parkinsonian disorders. Doctoral thesis , UCL (University College London).

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Abstract

The primary aim of this work is to investigate the value of quantitative magnetic resonance imaging (qMRI) metrics in patients with Parkinson’s disease (PD), progressive supranuclear palsy (PSP) and multi-system atrophy (MSA), and to investigate the potential role of these metrics in the diagnostic work-up of patients with Parkinsonian disorders. Chapter one discusses imaging theories and the clinical context of Parkinsonian disorders, summarizing their clinical features, imaging aspects, and the limitations of current imaging modalities. Chapter two is a methodological study of the imaging anatomy of the subthalamic nucleus (STN), a key structure in the pathogenesis of the disorders. Pre-operative stereotactic 1.5- T MR images—for patients with PD that underwent STN deep brain stimulation (DBS)—were studied. The distance between the anterior border of the mamillothalamic tract and the STN anteromedial border has shown to have minimal variation. This may help with more accurate localization of the STN on MRI for the work presented later in this thesis. Chapter three is a case study in which 1.5-T post-operative images, as well as 9.4-T postmortem MR images (of a patient who had had STN DBS), were studied. It is demonstrated that lead artifact location on postoperative MRI corresponded well with anatomical location on postmortem high-field imaging and histological examination. It helps in understanding the complex anatomy of the STN and its environs on MRI and histology. Using a 3-T MRI protocol, chapters four through six study fifty-nine subjects with PD, PSP, and MSA and control subjects at study-entry and at 6-16 month intervals thereafter using a region-of-interest (ROI) based method. They report T2 and T2* relaxation times in three key basal ganglia structures: the subthalamic nucleus (STN), the red nucleus (RN) and the substantia nigra (SN). T2 relaxation times are reduced in the STN ROIs of the PSP group when are compared to those from the control and the PD ones (p< 0.05). There is a significant correlation between age and T2 times in the control group (p <0.05). T2* and T2 relaxation times of the RN in the PD group are reduced (p <0.05) when are compared to those in the control group. In the SN of patients with PD and PSP, T2* times are reduced. There are no significant differences noticed in the longitudinal section of the work. The findings of the present studies suggest that T2 and T2* times of the STN, RN and SN may help in differentiating different Parkinsonian disorders from each other by measuring T2 and T2* times of the STN, RN and SN. qMRI may compensate for the lack of sensitivity and specificity offered by structural MRI when studying Parkinsonian disorders and may have the potential to provide insights into their pathophysiology.

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