Relative rCBF Research Articles

An Analysis of Regional Cerebral Blood Flow in Impulsive Murderers Using Single Photon Emission Computed Tomography

The authors explored differences in regional cerebral blood flow in 11 impulsive murderers and 11 healthy comparison subjects using single photon emission computed tomography. The authors assessed subjects at rest and during a computerized go/no-go concentration task. Using statistical parametric mapping software, the authors performed voxel-by-voxel t tests to assess significant differences, making family-wide error corrections for multiple comparisons. Murderers were found to have significantly lower relative rCBF during concentration, particularly in areas associated with concentration and impulse control. These results indicate that nonemotionally laden stimuli may result in frontotemporal dysregulation in people predisposed to impulsive violence.

The regional cerebral blood flow pattern of the normal human brain and its factor structure

The regional cerebral blood flow (rCBF) pattern of the normal human brain was drawn, and its structure was studied. Relative rCBF estimates for 66 regions of interest (cerebral anatomical-functional areas) were obtained using positron emission tomography in 158 healthy subjects aged 18–49 years. The rCBF rate variation range was 89–121% of the rCBF rate averaged over all regions of interest, taken as 100%. The rCBF rates were the highest (>115%) in the paracentral lobule, precuneus, insular cortex, primary visual cortex, and Broca’s area and the lowest (<95%) in the mediobasal regions of the temporal gyri and caudate nuclei. Analysis of the factor structure of the resultant pattern made it possible to classify cerebral anatomical-functional areas according to a predominant effect of one of the following factors on the interdependence between rCBF rates: (1) cytoarchitectonic characteristics; (2) the functional state of the cortex during quiet wakefulness; or (3) the brain vascular region to which the area belongs. The obtained pattern should be taken into account in both mapping of the functions of a normal brain and clinical diagnosis.

Medial frontal cortex perfusion abnormalities as evaluated by positron emission tomography in women with climacteric symptoms

To identify functional changes in the brains of women with climacteric symptoms. Images of regional cerebral blood flow (rCBF) were compared statistically between women with and women without symptoms to identify changes in rCBF. Results may provide a better understanding of the neural basis of the symptoms, which are divided into three symptom clusters: vasomotor, psychological, and somatic. The study participants consisted of 12 women with moderate to severe climacteric symptoms (age 47.5 +/- 5.9 years, mean +/- SD) and 7 women with no symptoms (control group; age 49.6 +/- 4.2 years, mean +/- SD). The study participants were patients at a menopause clinic, and the latter were healthy volunteer nurses and hospital staff. Climacteric symptoms were evaluated by an assessment of the severity of 17 symptoms immediately before positron emission tomography examination of rCBF. The symptoms had been used previously to generate the Kupperman Kohnenki Shogai Index, a modified Kupperman Menopausal Index adapted to Japanese women. rCBF was measured by positron emission tomography with the CO2 dynamic inhalation method. Reductions in relative rCBF in the patient group were observed in the bilateral rectal gyrus and in the left subcallosal gyrus on a voxel-by-voxel basis as compared with the control group. The present study revealed reductions in relative rCBF of the prefrontal cortex of Japanese women with moderate to severe climacteric symptoms. This area is close to that previously addressed in studies of familial bipolar depression and familial unipolar depression, although our participants did not satisfy criteria for depression. This reduction of rCBF may be related to the three climacteric symptom clusters, but further studies are needed for evaluation of its significance. Our results should stimulate investigations into the positron emission tomography rCBF change of these women as to the integration of multiple entities in climacteric symptoms.

Regional cerebral blood flow in Alzheimer’s disease: Comparison between short and long-term donepezil therapy

Treatment with donepezil improves cognitive function of patients with Alzheimer's disease (AD) when compared to a placebo-controlled group. The purpose of this study was to investigate changes in regional cerebral blood flow (rCBF) of AD patients in short-term and long-term treatment with donepezil. rCBF was measured by N-isopropyl-p-123I-iodoamphetamine (IMP) autoradiography method. CBF measurements were performed in 17 AD patients before treatment and after 3 months (short-term therapy) and 1 year (long-term therapy). Regions of interest were set at cerebral cortex and cerebellar hemisphere. We used absolute CBF and relative CBF expressed as ratio to cerebellar CBF. Significant increases in relative rCBF were noted in the frontal, parietal and temporal lobes at the end of short-term therapy. rCBF was decreased after the long-term therapy, whereas rCBF was still increased to a slight extent, as compared with the pre-treatment levels. Absolute rCBF showed minimal change and a tendency to decline. Relative rCBF significantly increased in the short-term donepezil therapy, while following the long-term therapy, rCBF decreased to the pre-treatment level.

Effects of antidepressant treatment with rTMS and fluoxetine on brain perfusion in PD

Although depression is highly prevalent in Parkinson disease (PD), little is known about the neural correlates associated with depression and antidepressant treatment in PD. To examine the effects of fluoxetine and repetitive transcranial magnetic stimulation (rTMS) on regional cerebral blood flow (rCBF) using SPECT in patients with PD and depression. Twenty-six patients were enrolled into two groups: One received active rTMS and placebo medication and the other sham rTMS and fluoxetine 20 mg/day. Brain SPECT was performed at baseline and after 2 and 8 weeks. Changes in rCBF were compared across timepoints and correlated with clinical scores. In addition, baseline rCBF of these patients was compared with that of 29 healthy, age-matched subjects. At baseline, patients with PD and depression showed significantly lower rCBF in the left prefrontal cortex, posterior cingulate gyrus, left insula, and right parietal cortex when compared with healthy controls. Both treatments induced significant clinical improvement and increases in rCBF in the posterior cingulate gyrus and decreases in rCBF in the right medial frontal gyrus. These changes were significantly correlated to the clinical outcome. Furthermore, the comparison between these two treatments revealed that whereas rTMS treatment was associated with an increased perfusion in the right and left prefrontal cortex, fluoxetine treatment was associated with a relative rCBF increase in the occipital lobe. Depression in patients with Parkinson disease is correlated with a dysfunction of the frontal-limbic network that can be modulated by two different antidepressant therapies.

Effects of dose‐dependent levels of isoflurane on cerebral blood flow in healthy subjects studied using positron emission tomography

In this study, we tested the hypothesis that escalating drug concentrations of isoflurane are associated with a significant decline in cerebral blood flow (CBF) in regions sub-serving conscious brain activity, including specifically the thalamus. Nine human volunteers received three escalating drug concentrations: 0.2, 0.4 and 1.0 MAC end-tidal inhalation. During waking, baseline and the three levels of sedation, aO PET scan was performed. Isoflurane decreased the bispectral index (BIS) values dose-dependently. Cardiovascular and respiratory parameters were maintained constant over time. No significant change in global CBF was observed. Throughout all three MAC levels of sedation, isoflurane caused an increased regional cerebral blood flow (rCBF) in the anterior cingulate and decreased rCBF in the cerebellum. Initially, isoflurane (0 vs. 0.2 MAC) significantly increased relative rCBF in the medial frontal gyrus and in the nucleus accumbens. At the next level (0.2 vs. 0.4 MAC), relative rCBF was significantly increased in the caudate nucleus and decreased in the lingual gyrus and cuneus. At the last level (0.4 vs. 1 MAC), relative rCBF was significantly increased in the insula and decreased in the thalamus, the cuneus and lingual gyrus. Compared with flow distribution in awake volunteers, 1 MAC of isoflurane significantly raised relative activity in the anterior cingulate and insula regions. In contrast, a significant relative flow reduction was identified in the thalamus, the cerebellum and lingual gyrus. Isoflurane, like sevoflurane, induced characteristic flow redistribution at doses of 0.2-1.0 MAC. At 1 MAC of isoflurane, rCBF decreased in the thalamus. Specific areas affected by both isoflurane and sevoflurane included the anterior cingulate, insula regions, cerebellum, lingual gyrus and thalamus.

Effect of Benzodiazepine Hypnotic Triazolam on Relationship of Blood Pressure and Paco2to Cerebral Blood Flow During Human Non-Rapid Eye Movement Sleep

We sought to clarify the effect of short-acting benzodiazepine hypnotic on the relationship of arterial blood pressure and arterial partial pressure of carbon dioxide (Paco2) to regional cerebral blood flow (rCBF) during human non-rapid-eye-movement (non-REM) sleep. Nine young normal volunteers were treated in a randomized, crossover design with triazolam or placebo and underwent positron emission tomography at night. During wakefulness and stage 2 and slow wave (stages 3 and 4) sleep, we measured mean arterial blood pressure (MAP), Paco2, and absolute CBF. With triazolam compared to placebo, MAP reduced gradually. During stage 2 sleep, Paco2 increased and whole-brain mean CBF decreased. With triazolam, relative rCBF of the left orbital basal forebrain decreased more during stage 2 than slow wave sleep, whereas absolute CBF of the occipital cortex and cerebral white matter remained constant. During triazolam-induced stage 2 sleep, absolute CBF of the cerebral white matter correlated more strongly to both MAP and Paco2 than during placebo sleep and also correlated more strongly to both MAP and Paco2 than absolute CBF of the occipital cortex. In the frontal white matter, during triazolam-induced stage 2 sleep compared to wakefulness, absolute CBF was significantly better correlated to MAP, but not to Paco2. During triazolam-induced stage 2, the cerebral white matter may receive a modulated CBF regulation having the strengthened relationship of Paco2 to CBF and, more locally, the frontal white matter may depend precariously on CBF regulation.

Decreased cerebral blood flow of the right anterior cingulate cortex in long-term and short-term abstinent methamphetamine users

Background The aim of the current study was to explore changes of relative regional cerebral blood flow (rCBF) in short-term and long-term abstinent methamphetamine (MA) users. Methods Relative rCBF in 40 abstinent MA users and 23 healthy comparison subjects was compared by the technetium-99m-hexamethyl-propylene amine oxime ( 99mTc-HMPAO) single photon emission computed tomography (SPECT). Relative rCBF in areas that were found to differ significantly was also compared in groups of MA users with short-term (<6 months) and long-term (≥6 months) abstinence. Results MA users showed decreased relative rCBF in the right anterior cingulate cortex (Brodmann area 32) relative to healthy comparison subjects. Long-term abstinent MA users had significantly greater rCBF than short-term abstinent MA users. Conclusions We report that abstinent MA users have decreased rCBF in the anterior cingulate cortex with smaller relative decreases in subjects with prolonged abstinence.

An fMRI investigation of memory-related medial temporal lobe activation in mild cognitive impairment prior to dementia

sessed by single photon emission computed tomography (SPECT). Methods: A community sample of 1708 dementia-free individuals aged 65 years and over was examined by neuropsychological testing in an epidemiological survey. 117 subjects underwent magnetic resonance imaging (MRI) and SPECT with Tc-ethylcisteinate dimer. Subjects were classified into four groups (normal and 3 subclasses for MCI) based on the neuropsychological test. After an MRI-based correction for partial volume effect, differences in relative regional cerebral blood flow (rCBF) across groups were evaluated on a voxel-based basis using an analysis of covariance with age and education as covariates. Conclusions: Out of 117 subjects, 84 were classified as normal, 22 as having MCI-amnestic, 7 as MCI-single nonmemory domain, 4 as MCI-multiple domains slightly impaired, respectively. Subjects with MCI-amnestic showed significant relative rCBF reduction in the bilateral temporoparietal cortices, precuneus, cerebellum and right insula as compared with normal controls. Reduced rCBF were found for MCI-multiple domains slightly impaired in the bilateral anterior cingulate, superior and middle frontal gyrus, left temporoparietal cortex and right parahippocampal gyrus. For the MCI-single nonmemory domain, decreased rCBF were also shown in the bilateral temporoparietal regions and right parahippocampal gyrus. These results were thought to be consistent with the previous reports on MCI and early AD. Temporoparietal hypoperfusion were considered to be most common among subclassifications of MCI.

Regional cerebral blood flow deficits in mild Alzheimer's disease using high resolution single photon emission computerized tomography

In spite of its wide availability, single photon emission computerized tomography (SPECT) scanning is uncommonly used in the assessment of Alzheimer's disease (AD) and related dementias. In light of recent advances in scanning protocols and image analysis, SPECT needs to be re-examined as a tool in the diagnosis of dementia. A total of 18 subjects with early AD and 10 healthy elderly control subjects were examined with high resolution SPECT during the performance of a simple word discrimination task. SPECT images were coregistered with individual magnetic resonance imaging scans, allowing delineation of predetermined neuroanatomical Regions of Interest (ROI). There was a gradation of regional cerebral blood flow (rCBF) values in both groups, with the lowest values being in the hippocampus and the highest in the striatum, thalamus and cerebellum. Compared to healthy controls, AD subjects demonstrated lower relative rCBF in parietal and prefrontal cortices. Analysis of individual ROI demonstrated bilateral reduction of rCBF in prefrontal poles, posterior temporal and anterior parietal cortex, and unilateral reduction of rCBF in left dorsolateral prefrontal cortex, right posterior parietal cortex and the left cingulate body. There were no significant differences for hippocampal, occipital or basal ganglia rCBF. Discriminant function analysis indicated that rCBF in the prefrontal polar regions achieved the best classification of cases. SPECT has utility in the diagnostic assessment of AD if standardized and semiquantitative techniques are used.

Brain processing of tonic muscle pain induced by infusion of hypertonic saline

Most of the previous studies on the effects of pain on Regional Cerebral Blood Flow (rCBF) had been done with brief cutaneous or intramuscular painful stimuli. The aim of the present study was to investigate the effect on rCBF of long lasting tonic experimental muscle pain. To this end we performed PET investigations of rCBF following tonic experimental low back pain induced by continuous intramuscular infusion of hypertonic (5%) saline (HS) with computer controlled infusion pump into the right erector spinae on L 3 level in 19 healthy volunteers. Changes in rCBF were measured with the use of 15O labelled water during four conditions: Baseline (before start of infusion), Early Pain (4 min after start of infusion), Late Pain (20 min after start of infusion) and Post-Pain (>15 min after stop of infusion) conditions. Results of SPM analysis showed relative rCBF increase in the right insula and bilateral decrease in the temporo-parieto-occipital cortex during initial phase of painful stimulation (Early Pain) followed by activation of the medial prefrontal region and bilateral inhibition of insula, anterior cingulate and dorso-lateral prefrontal cortex mainly in ipsilateral hemisphere during Late Pain conditions. The results show that longer lasting tonic experimental muscle pain elicited by i.m infusion of HS results in decreases rather than increases in rCBF. Possible explanations for differences found in rCBF during tonic hypertonic saline-induced experimental muscle pain as compared with previous findings are discussed.

Exposure to pulse‐modulated radio frequency electromagnetic fields affects regional cerebral blood flow

We investigated the effects of radio frequency electromagnetic fields (RF EMF) similar to those emitted by mobile phones on waking regional cerebral blood flow (rCBF) in 12 healthy young men. Two types of RF EMF exposure were applied: a 'base-station-like' and a 'handset-like' signal. Positron emission tomography scans were taken after 30 min unilateral head exposure to pulse-modulated 900 MHz RF EMF (10 g tissue-averaged spatial peak-specific absorption rate of 1 W/kg for both conditions) and sham control. We observed an increase in relative rCBF in the dorsolateral prefrontal cortex on the side of exposure. The effect depended on the spectral power in the amplitude modulation of the RF carrier such that only 'handset-like' RF EMF exposure with its stronger low-frequency components but not the 'base-station-like' RF EMF exposure affected rCBF. This finding supports our previous observation that pulse modulation of RF EMF is necessary to induce changes in the waking and sleep EEG, and substantiates the notion that pulse modulation is crucial for RF EMF-induced alterations in brain physiology.

Findings of brain 99mTc-ECD SPECT in high-functioning autism-3-dimensional stereotactic ROI template analysis of brain SPECT-

The aim of this study is confirmation of an abnormal regional cerebral blood flow (rCBF) pattern in high-functioning autism (HFA). Confirmation of an abnormal rCBF pattern in HFA may be useful for elucidate of its pathophysiology and a differential diagnosis, such as with attention-deficit/hyperactivity disorder (AD/HD). Brain 99mTc-ECD SPECT was performed in 16 cases of HFA. The HFA group consisted of 16 cases of HFA. They were all male, with an IQ of 76-126. They had normal brain MRI findings, and had an age of 9-14 years. We examined abnormal rCBF in HFA by comparing the results to those in the control group. The control group consisted of 1 male and 4 females cryptogenic epilepsy patients with normal intelligence. They have no problems in learning at school or mental or behavioral traits. They had normal brain MRI or SPECT findings, and had an age of 7-15 years. 3-dimensional stereotactic ROI template (3DSRT) was used to analyze SPECT data. We calculated the 'relative rCBF (%)' (RI count of each segment x 100/Sum of RI count of the corresponding hemisphere), and compared the values between the two groups. We found a significantly low 'relative rCBF (%)' in the left temporal region in the HFA group. We also calculated the 'L/R ratio' (the 'relative rCBF (%)' of a segment on the left side / the 'relative rCBF (%)' of the corresponding segment on the right side), and compared the value for each segment between the two groups. There were no significant differences in any segments between the two groups. We also checked for differences in the 'relative rCBF (%)' between segments on the right side and corresponding segments on the left side in both the HFA and control groups. We found significant right < left perfusion in the angular region and significant left < right perfusion in the pericallosal, thalamus, and hippocampus region in the HFA group. We also found significant right < left perfusion in the temporal region in the control group. Significant hypoperfusion in the left temporal region due to an unidentified underlying brain pathology and abnormal laterality in the angular, temporal (lack of right < left perfusion), pericallosal, thalamus, and hippocampus regions may influence the symptoms of autism.

Effects of subanaesthetic and anaesthetic doses of sevoflurane on regional cerebral blood flow in healthy volunteers. A positron emission tomographic study

We tested the hypothesis that escalating drug concentrations of sevoflurane are associated with a significant decline of cerebral blood flow in regions subserving conscious brain activity, including specifically the thalamus. Nine healthy human volunteers received three escalating doses using 0.4%, 0.7% and 2.0% end-tidal sevoflurane inhalation. During baseline and each of the three levels of anaesthesia one PET scan was performed after injection of . Cardiovascular and respiratory parameters were monitored and electroencephalography and bispectral index (BIS) were registered. Sevoflurane decreased the BIS values dose-dependently. No significant change in global cerebral blood flow (CBF) was observed. Increased regional CBF (rCBF) in the anterior cingulate (17-21%) and decreased rCBF in the cerebellum (18-35%) were identified at all three levels of sedation compared to baseline. Comparison between adjacent levels sevoflurane initially (0 vs. 0.2 MAC) decreased rCBF significantly in the inferior temporal cortex and the lingual gyrus. At the next level (0.2 MAC vs. 0.4 MAC) rCBF was increased in the middle temporal cortex and in the lingual gyrus, and decreased in the thalamus. At the last level (0.4 MAC vs. 1 MAC) the rCBF was increased in the insula and decreased in the posterior cingulate, the lingual gyrus, precuneus and in the frontal cortex. At sevoflurane concentrations at 0.7% and 2.0% a significant decrease in relative rCBF was detected in the thalamus. Interestingly, some of the most profound changes in rCBF were observed in structures related to pain processing (anterior cingulate and insula).

An fMRI study on autobiographical memory retrieval

Autobiographical memory is a memory for events and issues related to oneself and may be differently structured from other memories. To clarify the difference, we investigated an fMRI study of activated regions in the human brain in autobiographical memory retrieval. Each subject experienced two types of tasks, TASK1 and TASK2. In TASK1, the subject was requested to read a brief sentence in which an episode in his/her own past was described, then to silently make an image of the situation in his/her mind. In TASK2, in contrast, the subject was requested to read a sentence describing the other person's episode, and to make its image. The block-designed fMRI measurement was performed in three conditions: TASK1 vs. REST where the subject laid at rest, TASK2 vs. REST, and TASK1 vs. TASK2. Both in TASK1 vs. REST and in TASK2 vs. REST, increasing relative regional cerebral blood flow (rCBF) was observed in the striate cortex, the supplementary motor area, the frontal eye field, the frontal association area, and the cerebellum. The area of activated regions in autobiographical memory retrieval was larger than that in nonautobiographical memory retrieval. In the comparison of TASK1 vs. TASK2, relative rCBF increased in the frontal association area and inferior parietal lobule. The result in the TASK1 vs. TASK2 condition shows the possibility that the neural activity in the prefrontal area is specifically related to an ecphory of autobiographical information.

PET Measurement of rCBF in the presence of a neurochemical tracer

Functional neurochemical imaging can indicate neurotransmitter release by detecting changes in receptor occupancy. A dual tracer positron emission tomography (PET) technique is presented here to extend such studies by simultaneously measuring changes in regional cerebral blood flow (rCBF). This would permit correlations of task or drug induced changes in rCBF and neurochemical function. In this proposed method, the rapidly varying signal from a blood flow tracer is distinguished from the slowly changing signal due to a long-lived neurochemical tracer. As a proof of principle, baseline studies were carried out in rhesus monkeys. Two monkeys were anesthetized with isoflurane, and [ 18 F ]fallypride ( t 1/2=110 min), a dopamine D2 receptor antagonist, was injected. Starting 99–137 min after injection, PET images were acquired every 10 s while the blood flow tracer [ 17 F ]fluoromethane ( t 1/2=65 s) was administered by inhalation in a repeating pattern of 45 s on/45 s off. The observed time–activity curves for 2 ml brain regions were fit with a three compartment lung–body–brain model of fluoromethane kinetics with whole brain perfusion fixed. Comparing consecutive 6 min scans, reproducibility of relative rCBF and striatal [ 18 F ]fallypride concentration were 9 and 8%, respectively.

Effects of 1-Hz repetitive transcranial magnetic stimulation on acute pain induced by capsaicin

The aim of this study is to investigate the efficacy of 1-Hz repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex (M1) on acute pain induced by intradermal capsaicin injection and to elucidate its mechanisms by single-photon emission computed tomography (SPECT). We compared time courses of a subjective scale of pain induced by intradermal capsaicin injection in seven normal subjects under three different conditions: rTMS over M1, sham stimulation, and control condition (natural course of acute pain without any stimulation). In ten normal subjects, using SPECT, we also studied differences in regional cerebral blood flow (rCBF) after capsaicin injection between two conditions: rTMS over M1 and the control condition. rTMS over M1 induced earlier recovery from acute pain compared with the sham or control conditions. Under rTMS over the right M1 condition compared with the control condition, the SPECT study demonstrated a significant relative rCBF decrease in the right medial prefrontal cortex (MPFC) corresponding to Brodmann area (BA) 9, and a significant increase in the caudal part of the right anterior cingulate cortex (ACC) corresponding to BA24 and the left premotor area (BA6). A region-of-interest analysis showed significant correlation between pain reduction and rCBF changes in both BA9 and BA24. We conclude that rTMS over M1 should have beneficial effects on acute pain, and its effects must be caused by functional changes of MPFC and caudal ACC.

Voxel- and VOI-based analysis of SPECT CBF in relation to clinical and psychological heterogeneity of mild cognitive impairment

This study aimed to explore the heterogeneity of mild cognitive impairment (MCI) and detect differences in regional cerebral blood flow (rCBF) and cognitive function between progressive mild cognitive impairment (PMCI) and stable mild cognitive impairment (SMCI) in order to identify specific changes useful for early diagnosis of dementia. SPECT was performed in 82 MCI subjects and 20 controls using Tc-99m hexamethylpropyleneamine oxime. Cognitive functions were tested in five domains which included episodic memory, semantic memory, visuospatial function, attention, and general cognitive function. After the initial examination, MCI subjects were clinically followed for an average of 2 years. Twenty-eight subjects progressed to dementia and were defined as PMCI at baseline and 54 subjects remained stable and were defined as SMCI at baseline. The baseline rCBF and cognitive function of PMCI, SMCI, and controls were compared. PMCI had decreased relative rCBF in the parietal lobes and increased relative rCBF in prefrontal cortex compared to SMCI and controls at baseline. The cognitive function of PMCI was more severely impaired compared to SMCI with respect to episodic memory and visuospatial and general cognitive function. Both SPECT and neuropsychological tests had moderate discriminant function between PMCI and SMCI at baseline with the area under the receiver operating characteristic (ROC) curve at 75–77%. The combination of these two methods improved the diagnostic accuracy with the area under the ROC curve at 82–84%. Semantic memory and attention were negatively correlated with left prefrontal relative rCBF among the study population. The results show that the clinical heterogeneity of MCI is reflected in different patterns of psychological and CBF changes. Combined SPECT investigation and neuropsychological testing might predict the future development of dementia in patients with MCI.

Regional Cerebral Blood Flow Patterns and Response to Donepezil Treatment in Patients with Alzheimer’s Disease

We attempted to identify the characteristic patterns in regional cerebral blood flow (rCBF) of patients with Alzheimer’s disease who responded to donepezil therapy. Sixty-one patients treated with donepezil were divided into two groups (responders and nonresponders) on the basis of changes in their Mini Mental State Examination (MMSE) scores from baseline to study endpoint. We analyzed single-photon emission computed tomography data (SPECT) at baseline using three-dimensional stereotactic surface projections and compared differences in rCBF between the two groups. Statistical maps showed a significantly lower rCBF of the lateral and medial frontal lobes in the nonresponders than in the responders. There was a significant inverse correlation between the relative rCBF reduction in the frontal lobe and the MMSE change. These results suggest that frontal function, as assessed by SPECT, affects the patient’s response to treatment with donepezil. Measuring rCBF may aid in the selection of possible treatment responders.

Analgesia by electrostimulation of the trigeminal ganglion in patients with trigeminopathic pain: a PET activation study

Electrostimulation of the trigeminal ganglion (TGES) has shown good results in treatment of trigeminopathic pain in selected patients. To map the mechanisms of TGES analgesia, we determined changes in relative regional cerebral blood flow (rCBF) in ten patients with trigeminopathic pain using positron emission tomography. The patients were scanned before stimulation (habitual pain), after short-term stimulation (1 min, stTGES) and after long-term stimulation (ltTGES). Highly significant pain alleviation was reported after ltTGES. Relative rCBF changes after stTGES, which was without significant pain relief, were attributed mainly to intrinsic TGES effects. A statistical comparison of the subtraction images of ltTGES and stTGES disclosed significant rCBF increases after ltTGES in rostral parts of anterior cingulate cortex (ACC) and neighboring orbitofrontal and medial frontal cortices. Regression analysis of rCBF changes and subjective ratings of pain revealed an inverse relationship in the ipsilateral rostral ACC, and only rCBF changes in the caudal part of the contralateral ACC were consistent with the encoding of pain. The present study provides evidence for a pain modulating role of the rostral ACC, critically important in electrostimulation-induced analgesia, and identifies the caudal ACC as a region encoding pain sensation.