technetium-tc-99m-exametazime and Hyperventilation

Mechanical hyperventilation is often instituted in patients with acute bacterial meningitis when increased intracranial pressure is suspected. However, the effect on regional cerebral blood flow (CBF) is unknown. In this study, we measured regional CBF (rCBF) in patients with acute bacterial meningitis before and during short-term hyperventilation. In 17 patients with acute bacterial meningitis, absolute rCBF (in ml/100 g min-1) was measured during baseline ventilation and hyperventilation by single-photon emission computed tomography (SPECT) using intravenous 133Xe bolus injection. Intravenous 99mTc-HMPAO (hexamethylpropyleneamine oxime) was subsequently given during hyperventilation. In 12 healthy volunteers, rCBF was measured by SPECT and 99mTc-HMPAO during spontaneous ventilation. Using standard templates to identify regions of interest (ROIs), we calculated rCBF in percentage of cerebellar (99mTc-HMPAO images) or mean hemispheric (133Xe images) flow for each ROI, the degree of side-to-side asymmetry for each ROI, and the anterior-to-posterior flow ratio. On 133Xe images, absolute rCBF decreased significantly during hyperventilation compared to baseline ventilation in all regions, but the relative rCBF did not change significantly from baseline ventilation (n=14) to hyperventilation (n=12), indicating that the perfusion distribution was unchanged. On 99mTc-HMPAO images (n=12), relative rCBF and the anterior-to-posterior flow ratio were significantly lower in patients than in controls in the frontal and parietal cortex as well as in the basal ganglia. Focal perfusion abnormalities were present in 10 of 12 patients. Regional cerebral blood flow abnormalities are frequent in patients with acute bacterial meningitis. Short-term hyperventilation does not enhance these abnormalities.

Topics: Adult; Aged; Aged, 80 and over; Blood Flow Velocity; Blood Gas Analysis; Brain; Cerebrovascular Circulation; Female; Humans; Hyperventilation; Image Processing, Computer-Assisted; Injections, Intravenous; Male; Meningitis, Bacterial; Middle Aged; Respiration, Artificial; Survival Rate; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon; Xenon Radioisotopes

The purpose of this study was to investigate the informative value of single photon emission tomography (SPECT) in relation to the pathophysiological functioning of the brain during absence seizures and the origin of ictal discharges in idiopathic generalized epilepsies (IGEs). Six patients with childhood absence epilepsy (CAE) were selected for the study and two consecutive SPECT sessions were performed concomitant with EEG recordings revealing normal results and during hyperventilation (HV) studies where the ictal discharges were induced either alone or accompanied by clinical absence seizures. All six patients had ictal discharges in their EEGs during HV and two of them also had clinical absences. SPECT findings during HV revealed an overall increase in the cerebral blood flow (CBF) with significantly higher values as compared to the baseline data. There was no indication for any focal origin in either the interictal or the ictal SPECT findings. Results of the study were supportive for the concept of subcortical origin for the absence seizures and they were also promising for the diagnostic value of ictal SPECT in epileptic cases with undetermined origin as to whether they were localization-related or generalized.

Topics: Adolescent; Brain; Case-Control Studies; Cerebrovascular Circulation; Child; Electroencephalography; Epilepsy, Absence; Female; Humans; Hyperventilation; Male; Radiopharmaceuticals; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

Hyperventilation is frequently used to prevent or postpone the development of cerebral edema and intracranial hypertension in patients with fulminant hepatic failure (FHF). The influence of such therapy on regional cerebral blood flow (rCBF) remains, however, unknown. In this study the CBF-distribution pattern was determined within the first 12 hours after development of hepatic encephalopathy (HE) stage 4 before and during hyperventilation. Ten consecutive patients (median age 48 [range 33-57] years) with FHF and 9 healthy controls (median age 54 [24-58] years) had rCBF determined by single photon emission computed tomography (SPECT) using intravenous injection of 133Xenon. For determination of high resolution CBF pattern, the patients were also studied with 99mTc-hexa-methylpropyleneamine oxime (HMPAO) in the hyperventilation condition. There was no significant difference in the rCBF distribution pattern during normoventilation as compared with hyperventilation. The anterior to posterior (AP) ratio was significantly lower in patients as compared with healthy controls. After hepatic recovery and disappearance of HE, 3 patients had restored normal rCBF distribution pattern as compared with healthy controls. We conclude that in sedated patients with FHF, a relatively lower rCBF is found in the frontal regions and in the basal ganglia as compared with posterior regions. This rCBF-distribution pattern was not aggravated during hyperventilation. It is speculated that this change of rCBF in patients with FHF may render the frontal brain regions more susceptible to hypoxia. The relative frontal rCBF decrease was shown to be reversible with hepatic recovery and alleviation of HE.

Topics: Adult; Alcohol Drinking; Basal Ganglia; Brain; Cerebrovascular Circulation; Female; Frontal Lobe; Hepatic Encephalopathy; Humans; Hyperventilation; Male; Middle Aged; Regional Blood Flow; Respiration, Artificial; Survival Rate; Technetium Tc 99m Exametazime; Time Factors; Tomography, Emission-Computed, Single-Photon; Xenon Radioisotopes

We report a pregnant 19-yr-old patient with moyamoya disease who had undergone bilateral superficial temporal artery to middle cerebral artery anastomosis and encephalomyosynangiosis at 8 yr with an uneventful postoperative course and who desired natural delivery after becoming pregnant at 18 yr. We determined her cerebral vascular reserve since natural delivery can result in decreased cerebral blood flow during labor. Technetium-99m-HMPAO brain SPECT, with hyperventilation challenge, was performed to assess cerebral vascular reserve since the stress of hyperventilation was thought likely to rehearse that of labor. The brain SPECT images, obtained using 333 MBq 99mTc-HMPAO, revealed maintenance of cerebral vascular reserve. In addition, whole-body images including the 27-wk-old fetus were obtained. These images demonstrated accumulation in the fetal liver. Natural delivery was, thus, considered indicated for this patient, who subsequently delivered a healthy baby girl. Technetium-99m-HMPAO brain SPECT with hyperventilation challenge was useful for estimating cerebral vascular reserve and for determining whether natural delivery was indicated for this patient with moyamoya disease.

Topics: Adult; Brain; Cerebral Revascularization; Cerebrovascular Circulation; Female; Humans; Hyperventilation; Moyamoya Disease; Natural Childbirth; Pregnancy; Pregnancy Complications, Cardiovascular; Radiography; Radiopharmaceuticals; Risk Factors; Stress, Physiological; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

A case with vasospasm of the right anterior cerebral artery induced by hyperventilation is presented. Consecutive Tc-99m HMPAO brain SPECT studies at rest and during hyperventilation greatly contributed to the quantitative evaluation of focal perfusion decrease in conjunction with contrast angiography. This technique seems to be useful for the detection of alterations in regional brain perfusion during short duration intervention.

Topics: Adult; Angiography, Digital Subtraction; Cerebral Angiography; Cerebrovascular Circulation; Electroencephalography; Female; Humans; Hyperventilation; Ischemic Attack, Transient; Organotechnetium Compounds; Oximes; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon

To study the pathophysiological mechanisms of hyperventilation-induced EEG showing, i.e., the so-called 'buildup' phenomenon, changes in regional cerebral blood flow (rCBF) were investigated before and during the phenomenon in a 16-year-old woman with headache, thought to be of neurotic origin, by subtraction technique of brain images with single photon emission computed tomography using technetium-99m hexamethyl-propyleneamine oxime (99mTc-HMPAO). The tracer uptake during buildup decreased by 31-42% as compared to baseline values at rest before buildup in all of the measured regions, reflecting a widespread reduction in rCBF. Gas analyses of arterial blood collected during buildup showed a decrease in PaCO2, and increases in PaO2 and pH with a slight decrease in blood pressure and an increase in pulse rate. These results directly demonstrate a close correlation between the hyperventilation-induced EEG and rCBF changes, suggesting that the buildup phenomenon results from cerebral ischemic change, presumably due to cerebral vasoconstriction caused by the PaCO2 decrease.

Topics: Adolescent; Brain; Cerebrovascular Circulation; Electroencephalography; Female; Humans; Hyperventilation; Organotechnetium Compounds; Oximes; Subtraction Technique; Technetium Tc 99m Exametazime; Tomography, Emission-Computed, Single-Photon