123I-IPT brain SPECT study in essential tremor and Parkinson’s disease

Objective: To investigate nigral neuronal damage in patients with isolated postural tremor and those with postural and rest tremor without parkinsonism. Methods: Using [ 123 I]-N-(3-iodopropen-2-yl)-2β-carbomethoxy-3β-(4-chlorophenyl) tropane SPECT, we measured the basal ganglia-occipital cortex/occipital cortex ([BG-OCC]/OCC) uptake ratios in 21 control subjects and patients with isolated postural tremor (n = 9), postural and rest tremor (n = 6), and PD (n = 11). Results: In the patients with PD, the means (±SD) of the (BG-OCC)/OCC ratios of the ipsilateral (2.35 ± 0.37) and the contralateral (1.97 ± 0.33) sides to the more severely affected limbs were significantly lower than the mean of the bilateral (BG-OCC)/OCC ratios of the age-matched control subjects (3.83 ± 0.66). The mean (±SD) of the bilateral (BG-OCC)/OCC ratios of the patients with isolated postural tremor (3.60 ± 0.83) was comparable with that of the age-matched control subjects. However, the mean (±SD) of the bilateral (BG-OCC)/OCC ratios of the patients with postural and rest tremor (2.61 ± 0.18) was lower than that of the control subjects ( p Conclusions: Later in their clinical courses, some patients with postural tremor may acquire rest tremor in association with mild substantia nigra neuronal loss.