Striatal dopamine transporter changes in patients with essential tremor and idiopathic Parkinson's disease

ABSTRACT

BACKGROUNDS: There have been controversies about the association between essential tremor (ET) and Parkinson's disease. To examine the nigrostriatal dopaminergic neurons in patients with ET, we measured the striatal dopamine transporter levels with [123I] N-(3-iodopropene-2-yl)-2?-carbomethoxy-3?-(4-chlorophenyl) tropane(IPT) single photon emission computed tomography (SPECT). METHODS: This study included nine patients with postural tremor, six patients with postural and rest tremor, 11 patients with idiopathic Parkinson's disease, and 21 age matches controls. Using triple headed gamma camera, brain SPECT scans were performed at 115 and 120 minutes after the injection of 6.23?1.37mCi(range 5-10mCi) of I123 labeled IPT. We averaged two images. Regions of interest were drawn on the middle set image at the level of basal ganglia (BG) for each subject. Amounts of striatal dopamine transporter were measured by calculating the ratio between the average counts of the basal ganglia minus occipital cortex (OCC) and the counts of the OCC((BG-OCC)/OCC). RESULTS: The mean of (BG-OCC)/OCC ratios of 9 isolated postural tremor patients (3.60?0.83) was not statistically different from that of the controls (P>0.05). However, the mean of (BG-OCC)/OCC ratios of 4 patients with postural and rest tremor (2.61?0.18) was significantly lower than that of the controls (P<0.01). Four of the six patients with postural and rest tremor had mean ratios lower than 2.0 standard deviations from the mean of the controls. CONCLUSION: In their later clinical courses, some patients with postural tremor may develop rest tremor in association with a damage in the nigrostriatal dopaminergic system.