Exploring dopaminergic activity in ring chromosome 20 syndrome : a SPECT study

AIM: Several lines of evidence indicate that the dopaminergic system may play a role in the propagation of epileptic seizures and, indeed, DOPA metabolism impairment has recently been demonstrated in PET studies of ring chromosome 20 [r(20)] patients. We conducted a study looking for correlations between r(20) mosaicism, other clinical variables and both pre-synaptic dopamine transporter (DAT) expression and post-synaptic D2 receptor density. METHODS: Five patients with r(20) and epilepsy were enrolled in the study. DAT expression and D2 density were measured by single photon emission tomography (SPECT) imaging with 185 MBq of [¹²³I]ioflupane and [¹²³I]IBZM, respectively, on different days. Linear correlations between r(20) mosaicism, clinical variables and binding of [¹²³I]ioflupane or [¹²³I]IBZM were examined. RESULTS: A significant correlation between seizure frequency and r(20) mosaicism was detected (r=0.903, P<0.05), along with a negative correlation between r(20) mosaicism and binding of [¹²³I]ioflupane in the putamen and in the caudate nucleus (r=-0.692 and r=-807; P<0.05). Seizure frequency was positively correlated with post-synaptic D2 density (r=0.925, P<0.05). CONCLUSION: Striatal neurons are involved in r(20) epilepsy; the relationship found between r(20) mosaicism and DAT expression suggests that drugs acting on the dopaminergic system could have a place in the treatment of this rare form of epilepsy.