Benzodiazepine receptors and cerebral blood flow in partial epilepsy

Abstract

It was the aim of this study to compare benzodiazepine (Bz) receptor binding and cerebral perfusion in patients with partial epilepsy. Single photon emission tomography (SPET) studies with the flow-marker technetium 99m hexamethylpropylene amine oxine (99mTc-HMPAO) and with the 123I-labelled Bz-receptor ligand Ro 16-0154 (123I-Iomazenil) were performed in 12 patients with partial epilepsy, all with normal magnetic resonance imaging (MRI) and computed tomography (CT) scans. The SPET studies with 123I-Iomazenil were carried out 5 min and 2 h after injection. At 2 h the distribution of activity was very similar to the expected distribution of Bz-receptors in the human brain, known from positron emission tomography (PET) work and post-mortem studies. Early images showed a significantly higher tracer accumulation in the area of the basal ganglia, cerebellum, and naso-pharyngeal space. This finding is caused by non-specific binding and the contribution of the tracer in the blood pool in this phase. Also after 2 h p.i. of 123I-Iomazenil, 9 of the 12 patients showed a focal decrease of of Bz-receptor binding. Ten patients had focal flow abnormalities with 99mTc-HMPAO SPET. In 8 subjects impairment of flow was seen in sites of reduced 123I-Iomazenil uptake. 123I-Iomazenil is suitable for Bz-receptor mapping. In this series of patients, Bz-receptor mapping with SPET seems to offer no advantage over 99mTc-HMPAO in the detection of epileptic foci.

Right lower prefronto-parietal cortical dysfunction in akinetic catatonia: a combined study of neuropsychology and regional cerebral blood flow

“…SPECT imaging started with measurement of perfusion with 740 Mbq **mTc-ECD, which was given as a slow intravenous injection administered to the subject (eyes closed, 30 min of relaxation before injection) in a dimly lit, quite room as recommended by Bartenstein et al (1991). Imaging was started 60 min postinjection.…”

Rezeptordarstellung mit der Positronen-Emissions-Tomographie - Anwendung in Klinik und Forschung -

“…Zur In-vivo-Darstellung der Benzodiazepinrezeptoren stehen neben dem SPECT-Radiopharmakon 123 I-Iomazenil [24,25] eine Reihe von PET-Radiopharmaka zur Verfügung. Am häufigsten für klinische und wissenschaftliche Fragestellungen angewandt wird der Benzodiazepinantagonist 11 C-Flumazenil, dessen Synthese erstmals 1984 von Maziere et al [26] beschrieben wurde.…”

CPD – Education and Self-assessment: Functional imaging in epilepsy

“…Benzodiazepine receptors 123 I-Ro16-0154 ( 123 I-iomazenil) was shown to have intracerebral retention parallel to the known distribution of benzodiazepine receptors (BZR) in man 97 . In comparative studies of HMPAO and 123 I-iomazenil SPECT, most subjects show concordant regions of reduced uptake with both tracers; some studies show a small difference in sensitivity, a more marked reduction or a more restricted area of reduced tracer uptake with 123 I-iomazenil [98][99][100][101][102][103] . These studies suggest little advantage in imaging BZR over blood flow.…”