beta-CIT SPECT demonstrates blockade of 5HT-uptake sites by citalopram in the human brain in vivo

The cocaine analogue 2-beta-carbomethoxy-3-beta-(4-iodophenyl)-tropane (beta-CIT) is a potent ligand for both dopamine- and serotonin uptake sites which in its 123I labeled form can be used for single photon emission computerized tomography (SPECT). It was demonstrated previously by SPECT-studies in non-human primates that 123I-beta-CIT binds to dopamine transporters in the striatum and to serotonin transporters in hypothalamus and midbrain. The aim of the present study was to compare 123I-beta-CIT binding in the brain stem of normal controls and a group of subjects under treatment with the selective serotonin reuptake inhibitor (SSRI) citalopram. 123I-beta-CIT-SPECT was performed in 12 depressed patients under 20 mg (n = 5), 40 mg (n = 6) and 60 mg (n = 1) citalopram daily, in one untreated depressed patient and in 11 controls at regular time intervals up till 24 hours p.inj. A highly significant reduction of beta-CIT binding was found in an area including mesial thalamus, hypothalamus, midbrain and pons in patients under citalopram compared to controls (44.1 +/- 14.4 vs. 82.3 +/- 18.6cpm's/mCi x kg body weight; specific binding 4 hrs p.inj.; p = 0.0001). No differences were seen between the high and low dose group and no changes were found in the striatum. 123I-beta-CIT binding in the brain stem and striatum in one untreated depressed patient fell within the range of control values. To our knowledge this is the first report directly demonstrating the effect of a selective serotonin uptake inhibitor in the brain in humans in vivo. SPECT measurements of serotonin uptake sites in patients with depression and other psychiatric disorders might provide better insights into the pathophysiology of these disorders and into mechanisms of drug action.

Technetium-99m-HMPAO SPECT imaging of cerebral blood flow during REM sleep in narcoleptics

This study was performed to demonstrate global and regional cerebral blood flow (rCBF) changes during rapid eye movement (REM) sleep in six patients with narcolepsy using SPECT and 99mTc-HMPAO.

METHODS

Global and hemispheric HMPAO uptake as well as regional (RI) and asymmetry indices were estimated and compared between polysomnographically verified sleep onset (SO)REM and wakefulness.

RESULTS

The estimated global HMPAO uptake did not differ between the two conditions indicating a similar overall cortical activity. During (SO)REM sleep, hemispheric HMPAO uptake as well as calculated RI, especially in the supratemporal plane, were significantly higher on the right side than contralateral. This indicates an initially right-sided cerebral activation and a special involvement of the right, nondominant hemisphere during dreaming which is responsible for visual-spatial perceptions. Furthermore, increased RI in superior parietal regions during sleep were evident and were explained by an activation of associative areas. In thalamic regions, decreased RI were found during sleep, which may reflect thalamic dysfunction.

CONCLUSION

A definite assignment of these CBF alterations to (SO)REM sleep might be problematic because of unstable boundaries between sleep stages in narcolepsy. On the other hand, specificity of such CBF changes for narcolepsy requires further study.

D2 receptor blockade by flunarizine and cinnarizine explains extrapyramidal side effects. A SPECT study

Twenty-six patients under treatment with the calcium channel blockers flunarizine (Fz) or cinnarizine (Cz) were examined-with single-photon emission computed tomography using [123I]iodobenzamide as a ligand. The striatal dopamine D2 receptor-binding potential was determined and found to be reduced by 14 to 63% (39.5 +/- 15.0%; p < 0.0001) in patients compared with age-matched control values. This reduction was larger in 12 patients with extrapyramidal symptoms and was only slowly reversible after discontinuation of treatment. Patients treated for > 6 months had significantly larger reductions than patients treated for a shorter period. Parkinsonian symptoms were only seen in patients older than 50 years. Our findings prove a neuroleptic-like action of Fz and Cz, which seems to be the major reason for their extrapyramidal side effects. Older age and long-term treatment are predisposing factors for these effects.

SPECT imaging of dopamine receptors with [123I]epidepride: characterization of uptake in the human brain

[123I]Epidepride is a new ligand for single photon emission computerized tomography (SPECT) that specifically labels D2-like dopamine receptors with very high affinity. Here, we report on the regional kinetic uptake of [123I]epidepride in the brain of 4 normal volunteers and 3 patients with choreatic movement disorders. In healthy subjects striatal activity peaked at 2.5 hours after injection of the tracer and decreased slowly thereafter. There were no significant differences between left and right brain hemispheres. Activity above background was also measurable in areas corresponding to the thalamus, temporal cortex and frontal cortex. The striatal to cerebellar ratio was about 14 after 2.5 hours and this ratio steadily increased with time. The striatal to cerebellar ratio was clearly reduced in all 3 patients with choreatic movement disorders (from about 14 in control subjects after 2.5 hours to about 7 in choreatic patients). [123I]Epidepride may be a useful SPECT ligand for studying D2 receptors in the living human brain because of its high target to background ratio, its high affinity and the possibility to investigate extrastriatal D2 receptors.

A study of acetazolamide-induced changes in cerebral blood flow using 99mTc HMPAO SPECT in patients with cerebrovascular disease

For semiquantification of SPECT studies we tried to calculate cerebral 99mTc-HMPAO uptake related to injected dose and estimated brain volume. The method was applied to SPECT investigations of 27 patients who had at least one ischaemic attack and a confirmed 80-100% stenosis of the corresponding internal carotid artery (ICA). Vascular reactivity was tested by parenteral administration of acetazolamide (AZ). Increase in HMPAO uptake after AZ was evident in both hemispheres, although the increase (AZ effect) was significantly lower in the affected hemisphere (+24% versus +28%). No interhemispheric uptake differences were seen in patients with largely normal SPECT studies, although local asymmetries in HMPAO deposition were visible. Patients with low density lesions on CT and with a well-demarcated lesion in the same location on SPECT revealed interhemispheric uptake differences, with lower uptake on the affected side. This was not due solely to alterations in the lesion, but also to reduced HMPAO uptake and AZ effect in the surrounding area. The AZ effect showed no correlation with angiographic findings, indicating no major haemodynamic influence of the ICA stenosis on cerebral hemisphere perfusion. Calculated cerebral HMPAO uptake changes after AZ administration were in good accordance with absolute cerebral blood flow measurements, and made interindividual comparisons possible. However, as changes in the area around an infarct or local reduction in vascular reserve may not be reproduced adequately by uptake calculations, visual inspection is still necessary.

Iodine-123-IBZM-SPECT: studies in 15 patients with pituitary tumors

Single photon emission computerized tomography (SPECT) using the Iodine 123 labeled dopamine D2 receptor antagonist S(-)Iodobenzamide [S (-)IBZM] was performed in 15 patients with pituitary tumors. Among them there were five prolactinoma patients with macroadenoma and two acromegalic patients with macroadenoma. Specific binding in the area of the adenoma was only observed in one subject, a macroprolactinoma patient, who was responsive to dopaminergic treatment. None of the other patients, among them one macroprolactinoma patient responsive to dopaminergic treatment showed specific binding in the area of the tumor. IBZM-binding in the striatum was found to be significantly lower in the group of pituitary tumor patients as compared to controls. The results show that D2 receptors in pituitary adenomas can be visualized using SPECT. However, the sensitivity of IBZM-SPECT appears to be too poor to visualize PRL- and GH- secreting macroadenomas in general.

Dopamine D2 receptor blockade and antimigraine action of flunarizine

We studied in vivo the influence of flunarizine on dopamine D2 receptors and investigated whether dopamine D2 receptor blockade is involved in its antimigraine action. Eleven migraine patients, treated with flunarizine, 10 mg per day, underwent single photon emission computer tomography (SPECT) using [123I] labeled iodobenzamide, a ligand with high affinity and high specificity for D2 receptors. There was a reduction of the dopamine D2 receptor binding potential in all patients compared to age-matched controls. The efficacy of flunarizine in migraine prophylaxis failed to correlate with the degree of the dopamine D2 receptor blockade. The antimigraine action of flunarizine may not involve antidopaminergic mechanisms.

Central nervous system function after cardiopulmonary bypass

In a prospective study, an elderly group of patients (n = 63, 47 male, 16 female, age 40-65 years) was examined before and after open-heart surgery under cardiopulmonary bypass: postoperatively, 19 patients (30%) showed no clinical neuropsychiatric symptoms, whereas in 35 patients (56%) mild or transient neurological signs and in nine (14%) severe neurological complications were found. The postoperative EEG changes were characterized by a slight delta-theta increase, an alpha decrease and a significant slowing of the dominant frequency from 9.7 to 9.3 Hz. In brainstem auditory evoked potentials no changes were found, and in somatosensory evoked potentials (median nerve) the latency of the early cortical component, N20, increased. Cardiovascular reflexes showed increased changes, similar to those found in autonomic neuropathies. In the neuropsychological test battery, the Visual retention test (Benton) and the Rorschach test showed slight postoperative improvement, whereas other psychometric variables (flicker fusion frequency, reaction time) did not change. Despite an improved operative technique some minor clinical and neurophysiological disturbances of the central nervous system remain. However, specific pre- or peri-operative risk factors for these postoperative disturbances or complications could not be identified.

SPECT imaging of dopamine and serotonin transporters with [123I]beta-CIT. Binding kinetics in the human brain

Single photon emission computerized tomography (SPECT) studies in non-human primates have previously shown that the cocaine derivative [123I]-2-beta-carbomethoxy-3-beta-(4-iodophenyl)-tropane ([123I]beta-CIT) labels dopamine transporters in the striatum and serotonin transporters in the hypothalamus-midbrain area. Here, we report on the regional kinetic uptake of [123I]beta-CIT in the brain of 4 normal volunteers and 2 patients with Parkinson's disease. In healthy subjects striatal activity increased slowly to reach peak values at about 20 hours post injection. In the hypothalamus-midbrain area peak activities were observed at about 4 hours with a slow decrease thereafter. Low activity was observed in cortical and cerebellar areas. The striatal to cerebellar ratio was about 4 after 5 hours and 9 after 20 hours. In 2 patients with idiopathic Parkinson's disease striatal activity was markedly decreased while the activity in hypothalamus-midbrain areas was only mildly diminished. Uptake into cortical and cerebellar areas appeared to be unchanged in Parkinson's disease. Consequently, in Parkinson's disease the striatal to cerebellar ratio was decreased to values around 2.5 after 20 hours. These preliminary methodological studies suggest that [123I]beta-CIT is a useful SPECT ligand for studying dopamine and possibly also serotonin transporters in the living human brain.

[The importance of magnetic field strength in the MR diagnosis of multiple sclerosis: a comparison of 0.5 and 1.5 T]

The value of magnetic resonance (MR) to establish the diagnosis of multiple sclerosis (MS) is well known. This study was undertaken to compare MR imaging of the brain of MS patients at high (1.5T) and mid (0.5T) field strength. 25 patients with MS underwent two consecutive MR studies within one hour, each consisting of axial proton density and T2-weighted spin-echo images. Lesions in the supratentorial white matter and corpus callosum and those in the brain stem and cerebellum were separately counted. At 1.5T significantly more lesions were seen than at 0.5T (p < 0.05). Although T2-weighted images at 1.5T added significant information compared to images obtained at 0.5T, in none of our 25 patients the diagnosis was missed at 0.5T. However, at 1.5T dissemination in space was better demonstrated, suggesting MR scanning with high field-units to be favourable in patients with clinically suspected MS.

Frontal DC potentials in auditory selective attention

Selective dichotic listening during periods of 35 sec was associated with negative shifts of the cortical DC potential. Amplitudes of negative DC potentials had maxima in frontal, in particular, in anterior frontal records. The temporal pattern of negative DC potentials was different between the fronto-lateral records of the two hemispheres: in records from the right side, DC potentials declined during the 35 sec observation period, whereas they remained sustained in those of the left side. Different instructions ("attend left ear," "attend right," "attend both") and different levels of pitch separation between deviants and standards had no effects on frontal negative DC potential shifts, which are discussed in terms of higher order control of selective dichotic listening.

SPECT and MR imaging in herpes simplex encephalitis

Two cases of necrotizing herpes simplex encephalitis (HSE) were investigated with 99mTc-hexamethylpropyleneamineoxime (HMPAO) SPECT and MR. The clinical course was compared with the neuroimaging results. In the acute stage, the increased HMPAO uptake matched the MR hyperintense signal in the limbic temporal lobe and in the basal ganglia. Protracted inflammation was accompanied by persistently high HMPAO uptake. The sequelae of HSE were characterized by decreased HMPAO uptake and postnecrotic widening of the temporal horns. The "limbic" pattern recognized in both SPECT and MR reflects the basic pathophysiology and neuropathology of HSE. Both methods may be useful in the diagnosis and follow-up of HSE.

[Neurologic and psychiatric complications after heart surgery]

In 63 patients undergoing heart operations with extracorporeal circulation (47 males, 16 females, mean age 54 years; coronary artery bypass in 38 cases, valvular surgery in the rest) postoperative neurological and psychiatric complications were evaluated. 18 patients (29%) had no complications, whereas 35 patients (56%) showed minor or transient neurological symptoms, and 9 patients (14%) exhibited severe symptoms. Nine of the patients had slight psychiatric disturbances (affective disturbances, disorientation). No correlation was found between risk factors (age, nicotine abuse, hypertension, hypercholesteremia, neurologic and cardiac history), intraoperative parameters (duration of extracorporeal bypass, aortic clamp time, deviation of mean arterial pressure), postoperative parameters (internal complications) and the complication rate. Therefore no predisposing factors could be identified.

The influence of temperature on somatosensory-evoked potentials during cardiopulmonary bypass

Somatosensory-evoked potentials (SEPs) after median nerve stimulation were recorded in 10 neurologically normal patients during cardiopulmonary bypass and hypothermia. In all patients the changes of the latencies (spinal N13, cortical N20 and N35) and the central conduction time during cooling, and the decrease in latencies during rewarming was described by a gamma function. The analytic discussion of pooled data of all patients led to another SEP-latency-temperature relationship than the observation of each single patient. In 6 of 10 patients there was found a maximum of latency increase before the minimal temperature was reached. The cooling and the rewarming curve had to be considered separately. Latency changes of SEPs during hypothermia are discussed as a very complex phenomenon influenced by many technical and patient factors. This reduces the value of SEPs as an index of central nervous system integrity during open heart surgery and hypothermia.

[Evoked potentials in the follow-up and prognosis of patients with craniocerebral trauma]

The aims of this study were to find a reliable way of establishing the prognosis for the final outcome in the first week after head injury, to show the correlation between abnormalities in evoked potentials (EP) and clinical coma score, and finally, to document EP results in patients with the clinical diagnosis of brain death. We examined 46 patients, 23 in different states of coma and 23 with bulbar syndrome (complete absence of cortical and brain stem function). In the group of comatose patients brain stem auditory EP (BAEP) and somatosensory EP (SEP) were recorded in the first 48 h, 3-5 days, 1 week and 4 weeks after the head injury. The depth of coma was scaled with a scoring system devised by the authors and with the Innsbruck coma scale. Outcome was evaluated with the Glasgow outcome scale after 3, 6, and 9 months. BAEP were recorded bilaterally after stimulation with clicks; SEP were recorded from the neck (C2) and the contralateral cortex (C3', C4') after electrical stimulation of the median nerve. Evoked potentials were scored according to a four-point scale from grade 1 (normal) to grade 4 (only component I present in BAEP or absence of cortical responses on both sides in SEP). We found a significant correlation between the mean SEP score of the first week and the Glasgow outcome of the 3rd month, but no significant correlation between the BAEP score of the first week and the Glasgow outcome. There was a significant correlation between SEP (BAEP) scores and the corresponding clinical score.(ABSTRACT TRUNCATED AT 250 WORDS)

Topographic brain mapping of EEG before and after open-heart surgery

The brain function of 60 patients undergoing open-heart surgery (36 patients receiving coronary artery bypass, 21 patients valve replacements, 3 both) was investigated before and 10 days after the operation utilizing topographic brain mapping of the electroencephalogram (EEG). The postoperative EEG changes were characterized by a slight delta-theta increase, an alpha decrease [especially in the fast alpha (10.5-13 Hz) band] and a beta increase in the relative power. The total power and the absolute power of the delta-theta, alpha and beta showed a decrease, the dominant frequency a significant slowing from 9.7 to 9.3 Hz. The centroid of alpha and beta activity decreased as well. These results are similar to findings obtained in patients with organic brain syndrome. The EEG changes were prominent over the left hemisphere, which may be of particular clinical relevance.