ABSTRACT
By the time Parkinson 's disease [PD] symptoms appear, the substantia nigra [SN] already has lost about 60% of dopaminergic neurons. So, with the advent of neuroprotective agents that could slow or prevent disease progression, it reinforces the need to define at-risk patients so that such a disease-modifying therapy could be initiated before the development of clinical dysfunction. However, there is a real clinical diagnostic problem in the differentiation between PD and essential tremor [ET] in the early stages of both disorders. To investigate the use of proton magnetic resonance spectroscopy [[1]H-MRS] as an objective diagnostic index in the differential diagnosis of PD from ET in the early stages of both disorders. This was a cross sectional study in which 20 patients with PD meeting the United Kingdom Brain Bank criteria for the diagnosis of idiopathic PD were recruited. They were Hoen and Yahr stage I to II. In addition, 20 patients with ET meeting the diagnostic criteria were also recruited. All patients underwent a routine MRI brain to exclude underlying pathology. Brain [1]H MRS was performed. The spectroscopic volume of interest was placed in the putamen, the temporal, and the cerebellar cortices. The metabolite ratios NAA/Cr NAA/Cho and Cho/Cr were determined. It was found that in comparison to the ET group, the PD group had significantly lower NAA/Cho ratio and higher Cho/Cr ratio in the putamen, and lower NAA/Cr and NAA/Cho ratios in the temporal region. On the other hand, ET group had significantly lower NAA/Cr and NAA/Cho ratios in the cerebellum than the PD group. The current study protocol that includes muti-regional [1]H-MRS assessment of the putamen, temperoparietal, and cerebellar cortices proved to be of considerable value in the differential diagnosis between PD and ET in the early stages of both disorders