Age-related changes in regional cerebral blood flow during working memory for faces

Young and old adults underwent positron emission tomography during the performance of a working memory task for faces (delayed match-to-sample), in which the delay between the sample and choice faces was varied from 1 to 21 s. Reaction time was slower and accuracy lower in the old group, but not markedly so. Values of regional cerebral blood flow (rCBF) were analyzed for sustained activity across delay conditions, as well as for changes as delay increased. Many brain regions showed similar activity during these tasks in both young and old adults, including left anterior prefrontal cortex, which had increased rCBF with delay, and ventral extrastriate cortex, which showed decreased rCBF with delay. However, old adults had less activation overall and less modulation of rCBF across delay in right ventrolateral prefrontal cortex than did the young adults. Old adults also showed greater rCBF activation in left dorsolateral prefrontal cortex across all WM delays and increased rCBF at short delays in left occipitoparietal cortex compared to young adults. Activity in many of these regions was differentially related to performance in that it was associated with decreasing response times in the young group and increasing response times in the older individuals. Thus despite the finding that performance on these memory tasks and associated activity in a number of brain areas are relatively preserved in old adults, differences elsewhere in the brain suggest that different strategies or cognitive processes are used by the elderly to maintain memory representations over short periods of time.     

Effects of spinal cord ischemia on evoked potential recovery and postischemic regional spinal cord blood flow

The effects of spinal cord ischemia on spinal cord blood flow (SCBF) and somatosensory (SSEP) and motor (MEP) evoked potentials were investigated in a rabbit model of reversible spinal cord ischemia. Spinal cord ischemia was produced by balloon occlusion of the infrarenal aorta for 30, 60, and 90 min. SCBF, SSEPs, and MEPs were measured before, during, and 1 h after aortic occlusion. Aortic occlusion produced absolute ischemia of the caudal cord followed by hyperemia upon reperfusion. SSEP's and MEP's were obliterated during ischemia but demonstrated gradual albeit incomplete recovery following reperfusion with amplitude recovery inversely proportional to the duration of ischemia. Later peaks were more severely affected by a given period of ischemia than were early waves. In general, SSEP's were more resistant to ischemia than were MEP's although the differences were not significant.     

Diminished regional cerebral blood flow response to vibration in patients with blepharospasm

Mutations of the human Patched gene ( PTCH ) have been identified in individuals with the nevoid basal cell carcinoma syndrome (NBCCS) as well as in sporadic basal cell carcinomas and medulloblastomas. We have isolated a homologue of this tumour suppressor gene and localized it to the short arm of chromosome 1 (1p32.1-32.3). Patched 2 ( PTCH2 ) comprises 22 coding exons and spans approximately 15 kb of genomic DNA. The gene encodes a 1203 amino acid putative transmembrane protein which is highly homologous to the PTCH product. We have characterized the genomic structure of PTCH2 and have used single-stranded conformational polymorphism analysis to search for mutations in PTCH2 in NBCCS patients, basal cell carcinomas and in medulloblastomas. To date, we have identified one truncating mutation in a medulloblastoma and a change in a splice donor site in a basal cell carcinoma, suggesting that the gene plays a role in the development of some tumours.     

Assessment of thalamic regional cerebral blood flow in patients with cerebrovascular disease

The thalamus is believed to play an integrative role in the central nervous system. In the present study, thalamic rCBF was measured in 65 CVD patients and 15 normal volunteers by stable Xe/CT scanning. ROIs were chosen in the thalamic slice at a level 5cm over the OM line, and mean CBF was 7 cm over the OM line. The clinical factors focused on in multiple regression analysis were: age (A), sex (Se), stage from onset (St), lesion side (Sd); unilaterality or bilaterality, size (Sz) thalamic lesion (Tl). GCS (G), HDS-R (H); Hasegawa dementia score (revised), symptoms (Ss) such as anxiety, dizziness, head-headed feeling and headache, and neurological deficits (N). Each factor was graded and scored. Statistically, there was a significant correlation between thalamic rCBF (Y) and mean CBF (X) in the less affected hemisphere: Y = 1.82X + 2.2, r = 0.801, p < 0.001, n = 65. Multiple regression analysis of the thalamic rCBF revealed that the Sz factor was significant (p < 0.0001) on the lesion side: Y = 76.7-10.2Sz, r = 0.644, p < 0.001, n = 51, while the Se, Sd and St factors were significant (p < 0.005) on the less affected side: Y = 71.9 + 9.7Se-6.8Sd-5.0St, R = 0.585, p < 0.001, n = 65. The thalamic index (X), an indicator of thalamic atrophy, and thalamic rCBF were significantly correlated: Y = 28.7X + 10.2, r = 0.386, p < 0.001, n = 80. In conclusion, thalamic rCBF appeared to reflect the degree of organic changes and time course in the cerebral hemisphere, because factors such as size, sex and stage were statistically significant.     

Pathological regional cerebral blood flow in opiate-dependent patients during withdrawal: a HMPAO-SPECT study

Diabetic retinopathy is one of the most important causes of blindness. Diabetic patients do not attend outpatient clinics with the necessary regularity for an early diagnosis of the most severe forms of retinopathy. A program was planned to compare the efficiency of a 45 degrees non-mydriatic retinal camera with a Polaroid instant film versus biomicroscopy with a 78D lens and reverse image ophthalmoscope (standard method) in the diagnosis of the presence and evolutive degree of retinopathy. In a cross-sectional epidemiologic study a questionnaire was administered to 258 randomly selected diabetic patients, 129 with and 128 without retinopathy. Information was collected of demographics, visual acuity, diabetes and resources used with each method. The eye fundus with the poorest visual acuity was examined to determine the presence and evolution of retinopathy with the two diagnostic methods. The photographic method had an overall sensitivity of 91.1%, a specificity of 89.7% and a level of agreement of 82% with the standard method. A cost-effective analysis revealed a decrease of 35.7% in the cost per true positive case detected with the photographic methods versus the standard method. The 45 degrees non-mydriatic retinal camera had a similar efficiency to the standard method used in our setting for the diagnosis of diabetic retinopathy, which together with a lower cost per patient renders this method advisable for its use in medical settings that usually control for potential ophthalmologic complications resulting from diabetes mellitus.     

Increase of cerebral blood flow and improvement of brain motor control following spinal cord stimulation in ischemic spastic hemiparesis

A 64-year-old man had an ischemic stroke in the left parietotemporal cortical-subcortical areas. He developed a severe right spastic hemiparesis and dysphasia. An angiographic study showed left internal carotid artery occlusion and right internal carotid artery stenosis. A right internal endoarteriectomy was performed without any clinical improvement. After 1 year the patient was a candidate for cervical spinal cord stimulation (SCS) for the treatment of his spastic hemiparesis. An epidural electrode (Medtronic Sigma 3483) was positioned at the cervical level, mediodorsal to the cord. Clinical and neurophysiological studies (surface polyelectromyography, PEMG, for evaluation of brain motor control) were performed before and after 7 days of SCS (0.2 ms, 80 c/s, intensity for paresthesiae, continuous mode). A transcranial Doppler (TCD) study of both middle cerebral arteries (MCA) at rest and during SCS was performed on two occasions. SCS was followed by improvement of voluntary movement, decrease of spasticity and better endurance. The clinical findings were confirmed by the PEMG recordings. TCD examination showed an increase of flow velocities on both the right MCA (+43%) and the left MCA (+130%) during SCS. Such a TCD pattern, suggesting an increase of cerebral blood flow (CBF) during SCS, was reproducible. This case confirms efficacy of SCS in the treatment of ischemic hemiparesis and the increase of CBF following cervical SCS in man. The marked increase of CBF, particularly evident on the ischemic side, may play a role in mediating the improvement of motor control in our patient together with a possible arousal of the so-called 'sleeping neurons' of the penumbra zone.     

Viscoelastic relaxation and regional blood flow response to spinal cord compression and decompression

STUDY DESIGN: To better understand the relationships between primary mechanical factors of spinal cord trauma and secondary mechanisms of injury, this study evaluated regional blood flow and somatosensory evoked potential function in an in vivo canine model with controlled velocity spinal cord displacement and real-time piston-spinal cord interface pressure feedback. OBJECTIVES: To determine the effect of regional spinal cord blood flow and viscoelastic cord relaxation on recovery of neural conduction, with and without spinal cord decompression. SUMMARY OF BACKGROUND DATA: The relative contribution of mechanical and vascular factors on spinal cord injury remains undefined. METHODS: Twelve beagles were anesthetized and underwent T13 laminectomy. A constant velocity spinal cord compression was applied using a hydraulic loading piston with a subminiature pressure transducer rigidly attached to the spinal column. Spinal cord displacement was stopped when somatosensory evoked potential amplitudes decreased by 50% (maximum compression). Six animals were decompressed 5 minutes after maximum compression and were compared with six animals who had spinal cord displacement maintained for 3 hours and were not decompressed. Regional spinal cord blood flow was measured with a fluorescent microsphere technique. RESULTS: At maximum compression, regional spinal cord blood flow at the injury site fell from 19.0 +/- 1.3 mL/100 g/min to 12.6 +/- 1.0 mL/100 g/min, whereas piston-spinal cord interface pressure was 30.5 +/- 1.8 kPa, and cord displacement measured 2.1 +/- 0.1 mm (mean +/- SE). Five minutes after the piston translation was stopped, the spinal cord interface pressure had dissipated 51%, whereas the somatosensory evoked potential amplitudes continued to decrease to 16% of baseline. In the sustained compression group, cord interface pressure relaxed to 13% of maximum within 90 minutes; however, no recovery of somatosensory evoked potential function occurred, and regional spinal cord blood flow remained significantly lower than baseline at 30 and 180 minutes after maximum compression. In the six animals that underwent spinal cord decompression, somatosensory evoked potential function and regional spinal cord blood flow recovered to baseline 30 minutes after maximum compression. CONCLUSIONS: Despite rapid cord relaxation of more than 50% within 5 minutes after maximum compression, somatosensory evoked potential conduction recovered only with early decompression. Spinal cord decompression was associated with an early recovery of regional spinal cord blood flow and somatosensory evoked potential recovery. By 3 hours, spinal cord blood flow was similar in both the compressed and decompressed groups, despite that somatosensory evoked potential recovery occurred only in the decompressed group.     

A test-retest study of cerebral blood flow during somatosensory stimulation in depressed patients with schizophrenia and major depression

Six depressed patients with schizophrenia and 6 depressed patients with major depression were investigated before and during somatosensory stimulation (SS) with Tc-99m HMPAO SPECT. 8 controls were investigated only under resting conditions. The results can be summarized as follows: 1. Both psychiatric patient groups were hypofrontal (dorsolateral prefrontal cortex) compared to controls. 2. Hypofrontality was further enhanced by SS, significantly only in affective psychoses in the right inferior frontal lobe and in the right frontal hemisphere in total, in schizophrenia in the left dorsolateral prefrontal cortex. 3. Within the frontal lobes different regions were affected by SS in the two diagnostic groups. 4. In the right inferior parietal lobe SS response was significantly different in the two illnesses with schizophrenia showing a relative decrease, affective psychoses showing a relative increase of activity. 5. SS produced an increase of cerebral blood flow in subcortical regions (statistically significant contralateral to SS in thalamus and basal ganglia, ipsilateral to SS in cerebellum), a pattern which was common to all psychiatric patients. 6. Somatosensory cortex flow was not changed by SS. In conclusion, we could not fully confirm our hypotheses that similar blood flow abnormalities in different illnesses during SS are only caused by similarities in depressive psychopathology. Instead, depressed patients with schizophrenia were different from depressed patients with major depression in showing decreased activity in interrelating brain regions participating in an attentional network.     

Regional cerebral blood flow changes in chronic alcoholic patients induced by naltrexone challenge during detoxification

A follow-up study was performed with the aim to evaluate all individuals surgically treated by the uvulopalatopharyngoplasty (UPPP) or laser uvulopalatoplasty (LUPP) method from a whole county in Sweden, 1-8 years after surgery, by assessing snoring occurrence and daytime sleepiness, as experienced by the patients and their cohabitants. Questionnaires were mailed to all operated people (n = 457) and were returned by 91% (346 men, 69 women) preoperatively diagnosed as habitual snorers (n = 255), cases of obstructive sleep apnea syndrome (n = 110) and unspecified snorers (n = 48). In addition 345 bedpartners participated. For outcome of surgery, no significant differences in diagnoses or sex were found. Improvement in snoring occurrence was reported by 89.6% of the patients, confirmed by 92% of the cohabitants (r = 0.84, p < 0.01). The remaining snoring occurrence was significantly dependent on the surgical method and the time after operation. Excessive daytime sleepiness (EDS) was experienced by 73.3% of the patients compared to 67% reported by the cohabitants. Of 415 patients operated on, 18% were free from snoring and 25% were free from EDS. Individuals with a shorter time since surgery reported less snoring. The UPPP method gave a significantly better result than LUPP for the symptom 'snoring'.     

Spinal cord stimulation in chronic intractable angina pectoris: a randomized, controlled efficacy study

BACKGROUND: Spinal cord stimulation is known to be a successful treatment for chronic intractable angina pectoris. Its effect may be anti-ischemic. It is uncertain if the clinical effect is partly caused by a placebo effect of surgery for implantation of a stimulator. In this study, clinical efficacy is investigated, together with a possible placebo effect. METHODS AND RESULTS: Efficacy of spinal cord stimulation as a treatment for chronic intractable angina pectoris was studied for 6 weeks in 13 treated patients and 12 control patients with chronic angina. Assessments were exercise capacity and ischemia, daily frequency of anginal attacks and nitrate tablet consumption, and quality of life (perceived quality of life and pain). Compared with control, exercise duration (P =.03) and time to angina (P =.01) increased; anginal attacks and sublingual nitrate consumption (P =.01) and ischemic episodes on 48-hour electrocardiogram (P =.04) decreased. ST-segment depression on the exercise electrocardiogram decreased at comparable workload (P =.01). Anginal attacks and consumption of sublingual nitrates decreased (P =.01), perceived quality of life increased (P =.03), and pain decreased (P =.01). CONCLUSIONS: Spinal cord stimulation is effective in chronic intractable angina pectoris, and its effect is exerted through anti-ischemic action. Efficacy is unlikely to be explained as a placebo effect from surgery.     

Hypoxic-ischaemic encephalopathy is associated with regional changes in cerebral blood flow velocity and alterations in cardiovascular function

Pig-to-primate cardiac xenografts surviving beyond the period of hyperacute rejection succumb after 3-4 days to a secondary immunologic response characterized by xenograft infiltration with NK cells and macrophages. Circulating baboon mononuclear cells contain NK cell precursors which mediate lysis of porcine endothelium by two distinct mechanisms: antibody-dependent cellular cytotoxicity and lymphokine activation. IL-2 activated NK lysis of porcine endothelium was 2.4-fold stronger than lysis occurring following engagement of FcRIII by xenoreactive IgG. IL-2 augmented NK lysis involved interactions between CD2 and CD49d on baboon NK cells and their respective ligands on porcine endothelium, since NK lysis was reduced either by using Mabs against CD2, CD49d, or porcine VCAM, or by treating endothelial cells with PIPLC to cleave GPI-linked molecules. These results imply that interactions between accessory molecule receptor-ligand pairs on primate NK cells, macrophages and porcine endothelium are of critical importance in delayed xenograft rejection.     

Regional spinal cord blood flow in rats after severe cord trauma

Spinal cord blood flow (SCBF) was measured in 12 albino rats following acute cord injury produced by the extradural clip compression technique. Severe injury was produced with the clip compressing the cord with a force of 180 gm for 5 minutes, an injury previously shown to produce a severe functional deficit. Regional SCBF was measured 15 minutes, 2 hours, and 24 hours after injury by the 14C-antipyrine autoradiographic technique and a scanning microscope photometer. At 15 minutes and 2 hours, white and gray matter blood flow was severely diminished, and, at 24 hours, there was only minimal improvement. Focal decreases in blood flow were seen in white and gray matter for a considerable distance proximal and distal to the site of cord trauma. Thus, it has been confirmed in this model that severe cord compression injury produces severe posttraumatic ischemia in the cord which lasts for at least 24 hours.     

Transcutaneous electrical nerve stimulation in unstable angina pectoris

BACKGROUND: Silent ischemia is a strong predictor of unfavorable outcome in unstable angina pectoris. Dynamic continuous vector cardiography provides online detection of ischemic episodes. Transcutaneous electrical nerve stimulation (TENS) has been reported to have antianginal effects in patients with severe coronary artery disease and this is associated with a reduction in myocardial ischemia. The aim of the present study was to investigate the applicability of TENS in patients with unstable angina in the coronary care unit and the effects on vector cardiographic and biochemical markers of ischemia. METHODS: Thirty patients (14 in the TENS group and 16 in a placebo group) were included in a single-blind, placebo-controlled study after being admitted to the coronary care unit. Continuous vector cardiography, leakage of cardiac enzymes and consumption of analgesics were recorded for 24 h. RESULTS: TENS was well tolerated and did not interfere with standard treatment, although vectorcardiographic recording during actual stimulation was disturbed. There was a reduction in the number of silent ischemic ST change vector magnitude episodes (P = 0.02) and their duration (P = 0.01) in the TENS-treated group, and a nonsignificant reduction in the total number of ST change vector magnitude (painful plus silent) episodes (P = 0.09) and their duration (P = 0.05) and in leakage of cardiac enzymes (P = 0.12). There were no detectable differences in terms of episodes of pain leading to stimulation or consumption of analgesics. CONCLUSIONS: TENS seems to be a safe additional treatment in unstable angina pectoris and may reduce the number of ischemic events, by mechanisms apparently unrelated to the reduction of pain.     

Olfactory-evoked regional cerebral blood flow in Alzheimer's disease.

Olfaction is impaired in Alzheimer's disease (AD). It was hypothesized that AD would reduce olfactory-evoked perfusion in mesial temporal olfactory (piriform) cortex, where neuropathology begins. Seven AD patients and 8 elderly controls (ECs) underwent olfactory threshold and identification tests and olfactory stimulation during positron emission tomography. Odor identification was impaired in AD, but threshold was not. Olfactory stimulation in ECs activated right and left piriform areas and right anterior ventral temporal cortex. AD patients had less activation in right piriform and anterior ventral temporal cortex but not in the left piriform area. Although orbital cortex did not activate in ECs, there was a significant between-groups difference in this area. Right piriform activation correlated with odor identification. Impaired odor identification likely reflects sensory cortex dysfunction rather than cognitive impairment. Given olfactory bulb projections to the mesial temporal lobe, olfactory stimulation during functional imaging might detect early dysfunction in this region. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Myocardial turnover of endogenous opioids and calcitonin-gene-related peptide in the human heart and the effects of spinal cord stimulation on pacing-induced angina pectoris

OBJECTIVE: The authors determine if the intraoperative placement of paclitaxel powder in the subconjunctival space improves the outcome of glaucoma filtration surgery in rabbits. METHODS: A posterior lip sclerectomy was performed in the right eye of 24 New Zealand white rabbits. Before the conjunctiva was fully sutured, 8 mg of mannitol powder alone, or 8 mg of mannitol powder containing either 10 micrograms or 250 micrograms of paclitaxel, was placed in the subconjunctival space of six eyes each in masked fashion. An additional six animals were treated with episcleral application of a sponge soaked in a solution of 0.5 mg/ml of mitomycin C (MMC) for 5 minutes before the sclerectomy was performed. Intraocular pressure and bleb size were measured until the operation had failed or until the 7 weeks of observation had concluded. RESULTS: Both paclitaxel powder and MMC solution improved the outcome of filtration surgery in this model as measured by magnitude of intraocular pressure (IOP) lowering and duration of surgical success. No toxic effect of either drug was observed, although endophthalmitis was observed in eight animals followed for more than 3 weeks. CONCLUSION: The introduction of paclitaxel into the subconjunctival space at the conclusion of filtration surgery has an effect comparable to intraoperative MMC.     

Functional magnetic resonance imaging of regional cerebral blood oxygenation changes during breath holding

BACKGROUND and PURPOSE: Recently, noninvasive MRI methods have been developed that are now capable of detecting and mapping regional hemodynamic responses to various stress tests, which involve the use of vasoactive substances such as acetazolamide or inhalation of carbon dioxide. The aim of this study was to assess regional cerebral blood oxygenation changes during breath holding at 1.5 T. METHODS: In 6 healthy volunteers, T2*-weighted gradient echo images were acquired for a total dynamic scanning time of 10 minutes during alternating periods of breath holding and normal breathing at 40-second intervals after inspiration, at 30-second intervals after expiration, and at 18 seconds after expiration. To quantify the relative signal changes, 2.5-minute baseline image sampling with normal breathing was carried out. RESULTS: Repeated challenges of breath holding of various durations induced an overall rise in blood oxygen level-dependent (BOLD) signal intensities. In general, BOLD signal intensity increases were greatest in gray matter and nonsignificant in white matter. Depending on the breath-holding duration and techniques, BOLD signal intensity increases of all activated pixels varied from 0.8% to 3.5%. CONCLUSIONS: The present study demonstrates that cerebral blood oxygenation changes during breath holding can be detected by means of fMRI at 1.5 T. The breath-holding test, a short and noninvasive method to study cerebral hemodynamics with fMRI, could become a useful alternative to the acetazolamide or CO2 test.     

Cannabinoid-induced alterations in regional cerebral blood flow in the rat

A specific receptor for cannabinoids has been characterized at the pharmacological, molecular, and neuroanatomical level. However, less is known of the functional localization in the brain for the behavioral and physiological actions of these drugs. We have examined the effects of delta 9-tetrahydrocannabinol (THC) and its active metabolite 11-OH-THC on regional cerebral blood flow in the rat in order to determine functional CNS sites of action for the cannabinoids. Conscious rats were injected i.v. with one of four doses of THC (0.5, 1, 4, 16 mg/kg). 11-OH-THC (4 mg/kg), or vehicle 30 min prior to sacrifice. Regional cerebral blood flow was determined autoradiographically using the freely diffusible tracer method of Sakaruda et al. Changes in regional cerebral blood flow were observed in 16 of the 37 areas measured. Decreases in regional cerebral blood flow following THC were seen in such areas as the CA1 region of the hippocampus, frontal and medial prefrontal cortex, the nucleus accumbens, and the claustrum. Thresholds for these effects ranged from 0.5 to 16 mg/kg. Areas unaffected by THC include the medial septum, ventral tegmental area, caudate, temporal, parietal and occipital cortex, and cerebellum. These data indicate that THC and its active metabolite, 11-OH-THC, cause a heterogeneous alteration in the activity of specific CNS sites, many of which are involved in the characteristic behavioral actions of THC.     

PET regional cerebral blood flow change during working and declarative memory: relationship with task performance

Functional and anatomical relationships between working and declarative memory were investigated by contrasting regional cerebral blood flow (rCBF) change during standard working (Wisconsin Card Sorting Test, WCST) and declarative memory (Paired Associate Recognition Test, PART) tasks using identical stimulus-response modalities. The tasks and a resting baseline were administered to 30 participants (16 men, 14 women) during successive 10-min positron emission tomography 15O-water measures of rCBF. For both tasks, rCBF increased over baseline in inferior frontal and occipitotemporal regions, with more consistent dorsolateral prefrontal activation for WCST than PART. Additional orbitofrontal increases and dorsomedial decreases were seen for the PART. Activation patterns diverged when performance was considered. For the WCST, high performers activated dorsolateral and inferior frontal regions, whereas top PART performers activated only the occipitotemporal region. These results suggest operation of a frontotemporal network subserving both types of memory function that becomes more focal as performance increases.     

PET regional cerebral blood flow during working and declarative memory: Relationship with task performance.

Functional and anatomical relationships between working and declarative memory were investigated by contrasting regional cerebral blood flow (rCBF) change during standard working (Wisconsin Card Sorting Test, WCST) and declarative memory (Paired Associate Recognition Test, PART) tasks using identical stimulus-response modalities. The tasks and a resting baseline were administered to 30 participants (16 men, 14 women) during successive 10-min positron emission tomography –2–5O-water measures of rCBF. For both tasks, rCBF increased over baseline in inferior frontal and occipitotemporal regions, with more consistent dorsolateral prefrontal activation for WCST than PART. Additional orbitofrontal increases and dorsomedial decreases were seen for the PART. Activation patterns diverged when performance was considered. For the WCST, high performers activated dorsolateral and inferior frontal regions, whereas top PART performers activated only the occipitotemporal region. These results suggest operation of a frontotemporal network subserving both types of memory function that becomes more focal as performance increases. (PsycINFO Database Record (c) 2010 APA, all rights reserved)