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Biomedical subjects

I Mena

Publications and source records attributed to I Mena.

At least 55 records · Page 3Linked to original sources
PubMed1993

Brain imaging in late-life schizophrenia and related psychoses.

Despite disagreements about nomenclature, patients who develop schizophrenic or schizophrenia-like symptoms in later life are often seen in clinical practice. Questions about the etiology of late-life psychotic disorders and about their similarities or differences from early-onset disorders remain unanswered. Neuro-imaging techniques have been used to study patients with late onset of psychosis, and in substantial subgroups of patients (from 25% to 100% in various studies) compared with age-matched control subjects, structural and functional abnormalities have been found. We review the literature on imaging in late-life schizophrenia and related psychotic disorders, and we present data from our own investigations of patients with these disorders. We discuss the potential usefulness of imaging evaluations in patients with late-onset disorders, and we offer suggestions for future investigations.

Aged↗
PubMed1993

Cerebral perfusion and neuropsychological consequences of chronic cocaine use.

Research indicates that cocaine significantly constricts the cerebral vasculature and can lead to ischemic brain infarction. Long-term effects of intermittent or casual cocaine use in patients without symptoms of stroke or transient ischemic attack were investigated. Single-photon emission computed tomography with xenon-133 and [99mTc]hexamethylpropyleneamine oxime, magnetic resonance imaging, and selected neuropsychological measures were used to study cerebral perfusion, brain morphology, and cognitive functioning. Patients were drug free for at least 6 months before evaluation. All showed regions of significant cerebral hypoperfusion in the frontal, periventricular, and/or temporal-parietal areas. Deficits in attention, concentration, new learning, visual and verbal memory, word production, and visuomotor integration were observed. This study indicates that long-term cocaine use may produce sustained brain perfusion deficits and persistent neuropsychological compromise in some subgroups of cocaine-abusing patients.

Adult↗
PubMed1993

Assessment of myocardial perfusion defect size after early and delayed SPECT imaging with technetium-99m-hexakis 2-methoxyisobutyl isonitrile after stress.

It is thought that the distribution of 99mTc-sestamibi undergoes minimal change during the first 4 hr after injection. Thus [99mTc] sestamibi unlike 201Tl should not demonstrate significant redistribution in ischemic myocardium. We tested this assumption by quantifying perfusion defect size in early and delayed clinical SPECT images obtained after exercise stress or after dipyridamole infusion using an automated algorithm. Twenty patients with coronary artery disease aged 55 +/- 10 yr (13 male and 7 female) underwent stress imaging. Technetium-99m-sestamibi was injected at peak exercise stress in 12 patients and after an intravenous infusion of dipyridamole in 8 patients; SPECT images were obtained 1 and 4 hr later. All patients underwent rest imaging with a second dose of 99mTc-sestamibi 1-3 days after the stress studies. Total left ventricular mass and left ventricular defect mass were quantified with an automated algorithm previously validated in animal and patient studies. Estimates of total left ventricular mass from studies obtained 1 hr after stress (341 +/- 90 g) were comparable to values obtained after 4 hr (336 +/- 89 g), with a correlation of r = 0.97; p < 0.0001. The left ventricular defect size 1 hr after exercise or dipyridamole infusion (149 +/- 74 g) was similar to that observed after 4 hr (151 +/- 73 g). The two measurements of hypoperfusion with stress were highly correlated (r = 0.91; p < 0.0001) and were significantly larger than the defect size at rest (121 +/- 70 g). These observations support the conclusion that 99mTc-sestamibi does not redistribute significantly in ischemic myocardium between 1 and 4 hr after injection.

Coronary Disease↗
PubMed1992

Regional xenon 133 cerebral blood flow and cerebral technetium 99m HMPAO uptake in unmedicated patients with obsessive-compulsive disorder and matched normal control subjects. Determination by high-resolution single-photon emission computed tomography.

We measured regional cerebral blood flow (rCBF) with the xenon 133 (133Xe) inhalation method and with regional cerebral uptake of technetium 99m d,l-hexamethyl propyleneamine oxime (99mTc-HMPAO) by single-photon emission computed tomography in 10 adult male patients with obsessive-compulsive disorder (OCD) and in 10 age-matched adult male normal controls. With the 133Xe method, there were no significant differences in cortical or basal ganglia blood flow between the patients with OCD and their matched controls. In the patients, there was a positive relationship between rCBF and the severity of both obsessive and compulsive symptoms (average r = .48). These rCBF findings were consistent with those of earlier reports of increased rCBF in patients with OCD who were undergoing imaginal flooding and who had exacerbation of symptoms following m-CPP administration. 99mTc-HMPAO is a lipophilic molecule that crosses the blood-brain barrier and is converted to a hydrophilic form that is trapped in the brain. The amount that is trapped is determined primarily by blood flow, but also by membrane permeability and kinetics of conversion of the 99mTc-HMPAO to the hydrophilic form. Compared with their matched controls, the patients with OCD had significantly increased 99mTc-HMPAO uptake in the high dorsal parietal cortex bilaterally, in the left posterofrontal cortex, and in the orbital frontal cortex bilaterally. Possible explanations include (1) increased rCBF that was not detected with 133Xe, (2) increased permeability of the blood-brain barrier and/or cell membranes, and (3) increased conversion and trapping of the lipophilic, injected form of 99mTc-HMPAO in these regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Emergency room evaluation of cocaine-associated neuropsychiatric disorders.

The widespread abuse of cocaine has produced an alarming number of cocaine-related emergency room visits in the last several years. The authors discuss the various issues involved in emergency rom evaluation of patients who abuse cocaine and manifest signs and symptoms suggesting neuropsychiatric disease. Appropriate triage is emphasized, and a discussion of impediments to the accurate assessment of these patients ensues. The unique features of cocaine-induced mood, psychotic, and organic disorders are then detailed and contrasted with other functional and organic disorders. Strategies for the emergency room treatment of patients exhibiting symptomatology consistent with cocaine intoxication and withdrawal are outlined. The issues of psychiatric comorbidity and dual diagnosis in the cocaine-abusing population are examined. In addition, the neurological complications associated with the use of cocaine are reviewed. Finally, emerging data from single photon emission computerized tomography (SPECT) analysis of cocaine abusers is reported.

Brain Damage, Chronic↗
PubMed1992

Effects of multiple injections of HCG on testis blood flow.

In attempting to determine whether or not multiple injections of human chorionic gonadotropin (hCG) augment testis blood flow, adult male rats were injected with three doses of 10 IU of hCG every other day and testis blood flow was determined on day 5, the day of the final injection. Testis blood flow (mL/100 g testis tissue/min +/- SEM) as measured by the 133Xe washout method increased from 10.8 +/- 1.3 to 20.4 +/- 4.5 (p less than 0.05) after the three doses of hCG. These observations suggest that multiple injections of hCG appear to have the same effect as a single dose of hCG in increasing testis blood flow. This supports the hypothesis that hCG should be administered to all patients undergoing orchiopexy in the hope that the increased perfusion of the gonad will make it less susceptible to ischemia during the surgical procedure.

Animals↗
PubMed1992

Neuropsychiatric effects of cocaine: SPECT measurements.

Cocaine causes serious neurologic and neuropsychiatric complications. Cocaine-induced seizures are common and appear to be due to the local anaesthetic actions of this compound. Cocaine induced stroke has varied mechanisms. With ischemic stroke there is severe vasospasm induced by rises in brain catecholamines. These changes can persist for many weeks and can be demonstrated using single-photon emission computerized tomography (SPECT). In many patients with psychiatric symptoms such as psychosis or mania, SPECT demonstrates similar changes in cerebral blood flow. In fact, some of the psychiatric symptoms induced by cocaine may be due to decreases in cerebral blood flow. In cocaine abuse, treatment strategies based on decreasing cerebral vasospasm need to be developed.

Bipolar Disorder↗
PubMed1991

Colonic motility and transit in health and ulcerative colitis.

Preprandial and postprandial colonic motility and transit (scintigraphy), with respect to the splenic flexure, were studied in 10 patients with ulcerative colitis and in 9 healthy subjects. The healthy subjects had a postprandial increase in intraluminal pressure that was significantly (P less than 0.03) greater in the descending colon than in other regions of the colon. In ulcerative colitis, the pressure was decreased in all regions compared with healthy subjects, with no significant pressure gradient among different regions. In normal subjects, transit was quiescent during fasting; eating stimulated both antegrade and retrograde transit. In ulcerative colitis, transit was variable before as well as after the meal. Both healthy subjects and patients with ulcerative colitis had more rapid emptying from the splenic flexure into the sigmoid than into the transverse colon. More frequent, low-amplitude, postprandial propagating contractions occurred in ulcerative colitis (P less than 0.05) than in healthy subjects. Propagating contractions were always antegrade and caused a rapid movement of the tracer into the sigmoid. In conclusion, ulcerative colitis is characterized by (a) decreased contractility, (b) increased low-amplitude propagating contractions, and (c) variable transit. These disturbances may accentuate the diarrhea in ulcerative colitis.

Adult↗
PubMed1991

Effect of eating on colonic motility and transit in patients with functional diarrhea. Simultaneous scintigraphic and manometric evaluations.

The aim of this study was to correlate colonic motility with transit in 8 patients with functional diarrhea compared to 12 healthy subjects. Intraluminal pressure was measured with perfused catheter ports in the transverse colon, splenic flexure, and descending and sigmoid colons. Transit of the luminal contents was measured by following the movement of 99mTC-diethylenetriaminepentaacetic acid instilled as a bolus in the splenic flexure. In patients with diarrhea, the intraluminal marker moved in and out of the transverse and sigmoid colon regions of interest during fasting, unlike healthy subjects, in whom the marker remained in the splenic flexure. After eating, radioactivity immediately increased in both the transverse and sigmoid colons in healthy subjects. In the patients with diarrhea, eating did not alter the marker movement into the different regions of the colon compared with fasting. Within 100 minutes of eating, the intraluminal marker almost disappeared from the regions of interest in patients with diarrhea. Postprandial colonic nonpropagating contractions increased in each region of the colon in healthy subjects; there was only a small postprandial increase in colonic motility in patients with diarrhea. However, the numbers of fasting and postprandial propagating contractions were increased in patients with diarrhea compared with healthy subjects (P less than 0.02). Each propagating contraction moved more tracer in patients with diarrhea than in healthy subjects (P less than 0.05). These studies suggest that (a) in patients with diarrhea, the fluctuation of marker in both transverse and sigmoid colons during the fasting and postprandial periods is associated with decreased nonsegmenting contractions and frequent propagating contractions; and (b) in healthy subjects, the intraluminal marker moved after eating because of a pressure gradient caused by nonpropagating contractions.

Adult↗
PubMed1991

Cisapride in children with chronic intestinal pseudoobstruction. An acute, double-blind, crossover, placebo-controlled trial.

To assess the effect of cisapride on gastrointestinal motility and gastric emptying in children with chronic intestinal pseudoobstruction, 20 children (mean age, 4.9 years; 14 female and 6 male) who required special means of alimentation or who had severe symptoms confirmed by diary during 2 weeks before the study were studied. A motility catheter with recording sites in the antrum and duodenum was placed on the first day of the study and remained in place until the end of the 5-day study. Cisapride (0.3 mg/kg PO t.i.d.) or placebo was given in double-blind randomized crossover fashion, with a 2-day "washout" interval. Antroduodenal motility was recorded on days 2 and 5. Recording consisted of 4 hours of fasting and 2 hours after a complex liquid meal labeled with 99mTc. Gastric emptying was assessed for 1 hour after the meal. Based on manometry, 16 patients had neuropathic and 4 patients had myopathic disorders. Cisapride had no effect on the discrete, qualitative abnormalities found in individual records. Cisapride increased the postprandial duodenal motility index from 1180 +/- 256 mm Hg/30 min after placebo to 2385 +/- 430 mm Hg/30 min (P less than 0.05) but had no significant effect on the antral motility index. Cisapride did not alter the profound delay in gastric emptying; time to reach 50% of initial activity (T1/2) was 105 +/- 20 vs. 93 +/- 19 minutes and percentage of retention after 60 minutes (R60) 56% +/- 4% vs. 58% +/- 4% in control vs. cisapride, respectively. In summary, in children with chronic intestinal pseudoobstruction, cisapride increased postprandial duodenal motility but did not improve gastric emptying.

Child↗
PubMed1991

Watershed infarcts, Tc-99m HMPAO SPECT and CT correlation. Case reports.

We report on the use of Tc-99m hexamethylpropylene amineoxime (HMPAO) in watershed infarcts in five patients who had focal neurologic symptoms. Good correlation between Tc-99m HMPAO and CT was found in two patients. In three patients only Tc-99m HMPAO SPECT in a watershed distribution showed a perfusion abnormality that explained the clinical findings. Tc-99m HMPAO SPECT may be more sensitive than CT in the detection of infarctions in the watershed distribution.

Adult↗
PubMed1991

Brain injury and cognitive function in late-onset psychotic depression.

Fourteen patients who developed a psychotic depression after age 45 were compared with 72 non-psychiatrically ill elderly control subjects using neuroimaging and neuropsychological (NP) tests. Despite the fact that the patients were not studied if they had an obvious dementia or neurological disease, structural brain abnormalities were found in approximately two-thirds of patients and in less than 10% of controls. The most common abnormality, subcortical white matter (WM) lesions, was thought to be vascular in etiology. Also, tumor and primary degenerative dementia were found more frequently in the patients. Compared to an age-, sex-, and education-matched control group, the patients performed more poorly on NP tests of frontal lobe, memory, and visual spatial abilities. Diagnostic evaluation of the patient with late-onset psychotic depression should include computed tomography or magnetic resonance imaging as structural brain abnormalities are common in these patients.

Age of Onset↗
PubMed1991

Frontal lobe degeneration: clinical, neuropsychological, and SPECT characteristics.

The clinical, neuropsychological, and cerebral blood flow characteristics of eight patients with frontal lobe degeneration (FLD) were studied. Social withdrawal and behavioral disinhibition were the earliest and most common clinical presentations, and psychiatric symptoms typically preceded the onset of dementia by several years. Neuropsychological testing showed selective impairment of frontal and memory tasks with relative sparing of attention, language, and visuospatial skills. Single-photon emission computerized tomography demonstrated frontal and temporal hypoperfusion with relative sparing of parietal and occipital blood flow. Previous studies suggest that the neuropathologic findings in patients with FLD are varied; some demonstrate frontal gliosis, neuronal loss, and Pick bodies while others show only gliosis and neuronal loss.

Aged↗
PubMed1991

An analysis of cerebral blood flow in acute closed-head injury using technetium-99m-HMPAO SPECT and computed tomography.

Technetium-99m-hexamethylpropyleneamine (HMPAO) SPECT and x-ray CT were compared in 15 patients with acute closed-head injury. There were 44 focal lesions in all. Fifteen (34%) lesions were seen on both x-ray and SPECT. Seventeen (39%) lesions were seen only on SPECT. Twelve (27%) of the lesions were seen on x-ray tomography only. Of the lesions seen on x-ray tomography but not on SPECT, two were subarachnoid hemorrhage, two were thin subdural hematomas, and eight were contusions. This study shows that SPECT can detect focal disturbances of cerebral blood flow that are not seen on x-ray tomography. It also suggests that there are two types of contusions: those with a decreased cerebral blood flow (i.e., detectable on SPECT) and those with a cerebral blood flow equal to that of the surrounding brain.

Acute Disease↗
PubMed1990

Comparison of thallium-201 and technetium-99m hexakis 2-methoxyisobutyl isonitrile single-photon emission computed tomography for estimating the extent of myocardial ischemia and infarction in coronary artery disease.

Single-photon emission computed tomography (SPECT) using thallium-201 (Tl-201) was compared with technetium-99m hexakis 2-methoxyisobutyl isonitrile (Tc-99m MIBI) in 24 patients with coronary artery diseaes. Patients exercised to the same work load as each isotope was studied. Normal and hypoperfused left ventricular mass was determined with an automated method. Estimated total left ventricular mass was similar for both stress/redistribution Tl-201 and stress/rest Tc-99m MIBI images. The mean estimated defect size in the redistribution Tl-201 images was 32 +/- 34.7 vs 33 +/- 38.4 g in the resting Tc-99m MIBI studies (difference not significant). The individual determinations of defect mass were highly correlated (r = 0.93; p less than 0.0001). Estimated defect size in the stress Tl-201 images (52 +/- 46.2 g) was significantly larger than the exercise Tc-99m MIBI estimates of defect mass (42 +/- 39.9 g; p less than 0.05). A linear correlation existed between stress thallium and technetium estimates of defect size (r = 0.85) but 15 of 24 Tc-99m MIBI defects were smaller than the Tl-201 defects. Partial redistribution of Tc-99m MIBI could explain the discordance. Stress Tc-99m MIBI SPECT defect size determined by visual interpretation or by the use of isocount analysis may be smaller than what is seen with stress Tl-201 SPECT.

Coronary Disease↗
PubMed1990

Postprandial colonic transit and motor activity in chronic constipation.

The aim of this study was to correlate colonic motility and transit in patients with constipation and symptoms of the irritable bowel syndrome. Studies were performed in 16 patients with constipation and compared with the results in 12 healthy subjects. Intraluminal pressure was measured with perfused catheter ports in the transverse colon, splenic flexure, and descending and sigmoid colon. Movement of the luminal contents was measured by following the movement of Technetium-99m-DTPA that was instilled as a bolus in the splenic flexure. In both healthy subjects and patients with constipation there was no movement of the intraluminal tracer and no increase in intraluminal pressure during fasting. After eating a meal, healthy subjects and one group of the constipated patients had an increase in the radioactive marker in the transverse colon (p less than 0.03) and in the sigmoid colon (p less than 0.03). The movement of the intraluminal contents was associated with a positive pressure gradient between the descending colon and the transverse and sigmoid colon. There was no retrograde movement of the intraluminal contents and no postprandial increase in intraluminal pressure in the second group of patients with constipation. In healthy subjects, propagating contractions, which were associated with the rapid movement of intraluminal contents, began 60 min after eating. There were no propagating contractions in patients with constipation. These studies suggest that (a) the movement of intraluminal contents in healthy and constipated patients is determined by the postprandial pressure gradients within the colon, and (b) the propagating contraction is necessary for a normal bowel habit.

Adult↗