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NMDA‐Receptor Activity Visualized with (S)‐[ N ‐Methyl‐ 11 C]Ketamine and Positron Emission Tomography in Patients with Medial Temporal Lobe Epilepsy
Author(s) -
Kumlien Eva,
Hartvig Per,
Valind Sven,
Øye Ivar,
Tedroff Joakim,
Långström Bengt
Publication year - 1999
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1111/j.1528-1157.1999.tb01985.x
Subject(s) - ictal , positron emission tomography , temporal lobe , ketamine , nmda receptor , epilepsy , nuclear medicine , chemistry , magnetic resonance imaging , medicine , endocrinology , anesthesia , psychology , neuroscience , radiology , receptor
Summary:Purpose: To determine whether neurochemical activation of the N ‐methyl‐D‐aspartate (NMDA) receptor‐gated ion channel shows quantitative changes, measured as binding of 11 C‐labeled ( S )‐[ N ‐methyl]ketamine, in patients with medial temporal lobe epilepsy (MTLE). Methods: Eight patients with MTLE who were evaluated regarding epilepsy surgery underwent positron emission tomography (PET) with ( S )‐[ N ‐methyl‐ 11 C]ketamine. The presurgical investigations included magnetic resonance imaging (MR1), PET with 18 F‐fluoro‐deoxyglucose ( 18 FDG), and seizure monitoring by using video‐EEG. The uptake of ( S )‐[ N ‐methyl‐ 11 C]ketamine in the temporal lobe of ictal onset was compared with the contralateral side and correlated to changes in regional glucose metabolism measured by PET with 18 FDG. Results: ( S )‐[ N ‐methyl‐ 11 C]ketamine rapidly reached the brain, and high radioactivities were measured in the striatum, thalamic nuclei, and cortical regions. Overall the brain uptake and regional binding potentials of ( S )‐[ N ‐methyl‐ 11 C]ketamine were similar to measurements observed previously in healthy controls. However, 20 min after administration, when blood flow influence was negligible, a side‐to‐side comparison revealed a 9–34% reduction of tracer radioactivity in the temporal lobes of ictal onset. At earlier times, the differences in binding potentials were less pronounced, 9–21%. The magnitude and distribution of the reduction were similar to the metabolic pattern seen on PET scans with 18 FDG. Conclusions: Radioactivity uptake of intravenously administered ( S )‐[ N ‐methy]‐ 11 C]ketamine was reduced in temporal lobes of ictal in patients with TLE. This may reflect reduced NMDA‐receptor density, reduced perfusion, focal atrophy, or other factors.