Cognitive impairment is frequently observed in patients with MS [2] and changes in the GABAergic system have been associated with cognitive impairment in this population [3]. This study aimed to investigate GABA-receptor binding via [11C]FMZ PET. The optimal method of analysis was assessed for [11C]FMZ PET in MS patients and the GABA-receptor binding between CI and CP patients was compared.
MS patients (n=17: CI=11, CP=6) and healthy control subjects (n=11) underwent 60-minute dynamic PET, using plasma input data. Two models (1-tissue 2-rate-constant (1T2K); 2T4K) measured the influx rate and volume of distribution of 7 brain regions relevant for cognitive function. Akaike information criterion was used to determine the best-fitting model. Prof. Hanneke Hulst (Leiden University, Netherlands) presented the results.
By margins, the 2T4K model was preferred over the 1T2K model: in 55.6% of the analysed brain regions, the 2T4K model outperformed the 1T2K model. However, Prof Hulst argued that both models could reliably estimate radiotracer delivery. Mean perfusion rates were significantly lower for CI patients (0.29 μl/min−1) compared with CP patients (0.33) and healthy controls (0.33). The volume of distribution was higher in CP patients (5.73 ml of plasma/ cm3 of tissue) than in CI patients (4.95) and healthy controls (4.87). This implicates a higher GABA-receptor binding in CP patients compared with CI patients.