I-123-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 parkinsonis m. Methods: Using [I-123] -N-(3-iodopropen-2-yl)-2 beta-carbomethoxy-3 beta -(4-chlorophenyl) tropane SPECT, we measured the basal ganglia-occipital co rtex/occipital cortex ([BG-OCC]/OCC) uptake ratios in 21 control subjects a nd patients with isolated postural tremor (n = 9), postural and rest tremor (n = 6), and PD (n = II). Results: In the patients with PD, the means (+/- SD) of the (BG-OCC)/OCC ratios of the ipsilateral (2.35 +/- 0.37) and the c ontralateral (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 b ilateral (BG-OCC)/OCC ratios of the patients with isolated postural tremor (3.60 +/- 0.83) was comparable with that of the age-matched control subject s. However, the mean (+/-SD) of the bilateral (BG-OCC)/OCC ratios of the pa tients with postural and rest tremor (2.61 +/- 0.18) was lower than that of the control subjects (p < 0.05). The mean of the bilateral (BG-OCC)/OCC ra tios of the patients with postural and rest tremor was comparable with that of the side ipsilateral to the severely affected limbs of the patients wit h PD. However, it was higher than that of the side contralateral to the lim bs more severely affected by PD. Four of the six patients with postural and rest tremor had (BG-OCC)/OCC ratios lower than 2 standard deviations from the mean of the age-matched control subjects. Conclusions: Later in their c linical courses, some patients with postural tremor may acquire rest tremor in association with mild substantia nigra neuronal loss.