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K Rezai

Publications and source records attributed to K Rezai.

7 recordsLinked to original sources
PubMed1992

Hypofrontality in neuroleptic-naive patients and in patients with chronic schizophrenia. Assessment with xenon 133 single-photon emission computed tomography and the Tower of London.

The "hypofrontality hypothesis" has been supported by many neuroimaging studies, but not all, perhaps because of heterogeneity of samples. The present study examined three different samples that permitted assessment of a variety of confounders, such as effects of long-term treatment, chronicity of illness, and presenting phenomenology: (1) 13 neuroleptic-naive schizophrenic patients, (2) 23 nonnaive schizophrenic patients who had been relatively chronically ill but were medication free for at least 3 weeks, and (3) 15 healthy normal volunteers. Regional cerebral blood flow was measured using single-photon emission computed tomography with xenon 133 as the tracer. The control condition consisted of looking at undulating colored shapes on a video monitor, while the experimental task was the Tower of London. We observed the Tower of London to be a relatively specific stimulant of the left mesial frontal cortex (probably including parts of the cingulate gyrus) in healthy normal volunteers. Both the neuroleptic-naive and the nonnaive patients lacked this area of activation, as well as a related one in the right parietal cortex (representing the circuitry specifically activated by the Tower of London). Decreased activation occurred only in the patients with high scores for negative symptoms. These results suggest that hypofrontality is related to negative symptoms and is not a long-term effect of neuroleptic treatment or of chronicity of illness.

Adult↗
PubMed1992

Abnormal captopril renogram in a patient without renovascular hypertension.

Captopril renal scintigraphy is a well-known noninvasive tool in the diagnosis of renovascular hypertension. The authors present a case of a patient with malignant hypertension whose captopril renal scintigraphy suggested bilateral and equal renovascular hypertension. His renal angiogram, however, demonstrated no renal artery stenosis or abdominal aortic atherosclerotic disease. False-positive captopril renal scintigraphy has been reported but can usually be attributed to the patient's hypotensive episode after captopril administration, volume or salt depletion, or chronic glomerulonephropathy. This patient demonstrated mild blood pressure changes after captopril administration and was not volume or salt depleted. His creatinine was 1.6 mg/dl on admission but demonstrated appropriate renal function on subsequent noncaptopril renal scintigraphy.

Captopril↗
PubMed1992

Coronary artery disease and cardiac events with asymptomatic and symptomatic cerebrovascular disease.

BACKGROUND AND PURPOSE: The purpose of this study was to evaluate the prevalence of coronary artery disease and coronary events during follow-up in patients with asymptomatic carotid stenosis, transient ischemic attacks, or small strokes. METHODS: We prospectively studied 60 consecutive patients with thallium-201 scintigraphy followed by coronary arteriography according to an established protocol. RESULTS: The 201Tl testing was abnormal in seven of 15 patients (47%) with asymptomatic carotid stenosis and in 19 of 44 patients (43%) with transient ischemic attacks or small strokes (p greater than 0.05). In 33 patients with no history of coronary artery disease, 11 (33%) had reversible 201Tl defects. In 26 patients with a history of coronary artery disease, 15 (58%) had reversible and/or fixed defects (p = 0.054 compared with patients with no history). A history of peripheral vascular disease was the only risk factor significantly associated with an abnormal 201Tl test (p = 0.032). Coronary artery stenosis of greater than 50% was identified in one or more vessels in 14 of 15 patients undergoing coronary arteriography. Over a mean follow-up period of 311 days, four patients (7%) developed new onset of angina. There were four coronary events among 14 patients (29%) with both a reversible area on the 201Tl and abnormal coronary arteriography. In comparison, there were only four coronary events among 46 patients (9%) without reversible defects on the 201Tl studies (p = 0.055). CONCLUSIONS: Our study demonstrates that one third of patients with no history of coronary artery disease had an abnormal 201Tl test and that nearly one half of patients with either symptomatic or asymptomatic cerebrovascular disease had abnormal 201Tl tests. Patients with a reversible 201Tl defect and significant stenosis by coronary arteriography were at higher risk for subsequent cardiac events. These findings demonstrate the utility of screening patients with asymptomatic and symptomatic cerebrovascular disease for cardiac disease.

Adult↗
PubMed1992

Image processing for the study of brain structure and function: problems and programs.

Fundamental problems in the analysis of functional and structural imaging data include data transport, boundary identification (including manual tracing, edge detection, and tissue segmentation), volume estimation, three-dimensional reconstruction and display, surface and volume rendering, shape analysis, and image overlay. These problems require that research investigators have access to suitable methods of image analysis, implemented on a set of software programs, in order to conduct neuroimaging research. The authors describe a group of software programs designed to provide a comprehensive solution for these problems.

Brain↗
PubMed1992

MR imaging and HMPAO scintigraphy in conjunction with balloon test occlusion: value in predicting sequelae after permanent carotid occlusion.

OBJECTIVE: Permanent occlusion of the internal carotid artery may be required for en bloc resection of a neck tumor or to treat certain aneurysms. The risk of ischemic infarct is usually assessed with carotid balloon test occlusion and concurrent distal arterial pressure measurement. However, up to 20% of patients who tolerate the test occlusion have delayed neurologic sequelae. We propose enhanced MR imaging and hexamethylpropyleneamine oxime (HMPAO) scintigraphy to detect subclinical signs of ischemia and hypoperfusion as adjuncts to the balloon test occlusion to identify patients at risk for delayed sequelae. SUBJECTS AND METHODS: We prospectively examined 12 patients referred for balloon test occlusion of the carotid artery. Serial measurements of distal occluded internal carotid pressure were recorded. 99mTc-HMPAO was injected IV after 2 min of asymptomatic test occlusion, and single-photon emission computed tomographic (SPECT) data acquisition was done 1-6 hr later. Contrast-enhanced MR imaging was performed 1-8 hr after completion of the 30-min test occlusion. Signs of decreased perfusion or ischemia on these tests were compared with the mean distal arterial pressure and neurologic status of the patient during test occlusion. RESULTS: Seven (58%) of 12 patients had abnormal findings on HMPAO scintigraphy or contrast-enhanced MR imaging. Only one patient had neurologic deficits that corresponded to abnormal MR enhancement. The other 11 patients (92%) remained asymptomatic during the 30-min test occlusion. Of these 11 asymptomatic patients, five (45%) had areas of decreased perfusion on scintigraphy and three (27%) had abnormal MR contrast enhancement suggesting residual focal ischemia as a result of the test occlusion. Mean arterial pressures in the distal occluded artery did not correlate well with the imaging results. CONCLUSION: HMPAO scintigraphy can show clinically silent areas of decreased perfusion, while enhanced MR shows signs of acute ischemia (i.e., significant hypoperfusion) associated with asymptomatic balloon test occlusion. Theoretically, such patients would be at increased risk for permanent sequelae after permanent carotid occlusion.

Adult↗