Tyramine neurotoxicity and first-pass brain technetium-99m-diethylenetriamine penta-acetic acid.

Tyramine induces coma in phenelzine-treated dogs with liver disease. The objective of the present investigation was to examine the influence of tyramine in these monoamine oxidase-inhibited dogs on the kinetics of Tc-99m-diethylenetriamine penta-acetic acid (Tc-99m-DTPA) during its first passage through the brain by nuclear imaging techniques. The study began with anesthetized mongrel dogs (n = 10) in a supine position over the camera detector. Data acquisition was started simultaneously after the rapid intracarotid injection of Tc-99m-DTPA (5 mCi) and 60 0.5-sec images of the brain were taken. Tyramine induced increased uptake with a concomitant impairment in the elimination of Tc-99m-DTPA from the brain of these phenelzine-treated animals with hepatic injury (n = 5) as compared to pretreated animals serving as a control group or phenelzine-treated animals without liver disease. This was accompanied by an appreciable reduction in hemispheric cerebral blood flow (50.5 +/- 19.3 vs. 110 +/- 16 ml/100 g/min), respectively. Increased cerebrovascular permeability of Tc-99m-DTPA and decreased cerebral blood flow occurred concomitantly with increased cerebrospinal fluid pressure and elevation in cerebrospinal fluid catecholamines of monoamine oxidase-inhibited animals with hepatic injury.

99mTc-sodium pertechnetate permeation into cerebrospinal fluid.

The integrity of the blood-brain barrier may be reflected by the blood and cerebrospinal fluid (CSF) if these two compartments are sampled at an appropriate interval after the administration of certain substances. After reading through the controversial literature, this study was undertaken to determine the frequency with which 99mTc-sodium pertechnetate entered the CSF to an abnormal extent, and to see whether this was related to any particular pathology. The plasma-to-CSF ratios were determined in 51 patients 4 hours following the intravenous administration of 0.5-10 mCi 99mTc-sodium pertechnetate. In 23 patients with active CNS tuberculosis, the mean value of the pertechnetate plasma-to-CSF ration was 32.12. In contradistinction, the plasma-to-CSF pertechnetate in 28 nontuberculous subjects was considerably higher (144.63). For the purpose of correlation, a 82Br partition test was also done on each subject 48 hours following the oral administration of NH82Br. The 48-hour study in each of these cases was generally in agreement with the pertechnetate studies: the plasma-to-CSF ratio mean value was 1.25 in patients with active CNS tuberculosis, while for the nontuberculous patients it was 3.32.

Pattern of radioactivity in the CSF after intravenous injection of 99mTc.

It has been shown that intravenously injected pertechnetate enters to CSF space and also that a transport of pertechnetate ions to the blood occurs when injected into the ventricles. Activity curves obtained by repeated samplings of CSF after intravenous injection of pertechnetate appears to differ at different levels of the intraventricular pressure but also in patients with different types of intracranial pathology, i.e. in patients with ventricular dilatation due to hydrocephalus and due to cerebral atrophy.

Penetration of 99mTcO4- into cerebrospinal fluid from blood on brain scintigraphy (author's transl).

It is well known that the permeability of the blood brain barrier and blood cerebrospinal fluid barrier changes more or less in various diseases of the central nervous system. At present, thee is no clinically available index which reflects the alteration of the permeability of the blood brain barrier and blood cerebrospinal fluid barrier. The brain scintiraphy is an examination which detects a breakdown in the blood brain barrier, its clinical usefullness is limited only in a localized and extremely pathological proces of the brain. In this report, a cerebrospinala fluid isotope measurement comined with the brain scintigraphy was presented as a clinical examination for blood brain barrier function. Thirty minutes prior to brain scintigraphy, potassium perchlorate (4 mg/kg) was given orally to reduce the accumulation of 99mTc04-in the choroid plexus and to minimize iradiation for tr other organs. Spinal tap was performed two hours after injection of 99mTc04- according to Haines's method...