Cerebral Uptake of MIBG: Adrenoceptors Visualized?

Radiolabelled metaiodobenzylguanidine (MIBG) localizes in adrenergic neurons. A study was carried out to evaluate the uptake of this radiopharmaceutical in cerebral tissues. Twenty-three patients with neural crest tumours, who had no evidence of central nervous system disease, were evaluated. Each patient underwent a diagnostic MIBG study, followed by a therapy dose with 131I-MIBG and subsequent scintigraphy. Focal uptake was seen in the cerebellum (CB), basal nuclei and thalamic region (BNTr), 24 and 48 h postinjection on the diagnostic images. The BNTr to cerebral cortex ratio ranged from 1.05 to 1.79. Uptake was also seen on the days 2, 3, 4 and 6 post-therapy images. Single photon emission computed tomography (SPECT) clearly outlined the uptake in the CB and BNTr. The BNTr to cerebral cortex ratio ranged from 1.10 to 1.85 and CB to cerebral cortex ratio from 1.18 to 2.01. It is hypothesized that the focal uptake observed in the CB and BNTr is due to adrenergic receptor binding. It is felt that SPECT with radiolabelled MIBG may prove to be a useful tracer for mapping the adrenergic receptors in the human brain.