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Biomedical subjects

B McClarty

Publications and source records attributed to B McClarty.

9 recordsLinked to original sources

Structural brain changes in PTSD. Does trauma alter neuroanatomy?

Although the impetus for studying hippocampal morphology and functioning in PTSD was the finding that stress could result in hippocampal damage in rodent and primate models, it is far from proven that the findings to date in PTSD represent defects that have been caused by trauma. It is equally possible that the findings represent a preexisting anomaly which might serve as a risk factor for the development of PTSD following trauma exposure. To resolve this dilemma, it is necessary to study persons at high risk for trauma (e.g., soldiers) prior to trauma exposure and ag in after exposure. Such methods will permit the determination not only of whether trauma alters hippocampal morphology, but also, if so, of whether this effect is limited to persons with PTSD. At the present time, the field would be well advised to proceed vigorously but with appropriate caution along these lines of research. As just outlined, sample sizes have been small, and potentially confounding variables have abounded in most studies. The next few years of research may well continue to replicate the finding of abnormal hippocampal morphology in PTSD. However, it would not be surprising to find that other brain regions are also involved and that these represent part of a broader risk spectrum for the development of psychopathology under stress. Until these issues are clarified, the neuroanatomical findings to date in PTSD should be viewed as tentative, tantalizing, and in need of additional study.

Brain↗

Hippocampal volume in women victimized by childhood sexual abuse.

BACKGROUND: Several prior studies have found reduced hippocampal volume in victims of psychological trauma with post-traumatic stress disorder (PTSD). We were interested to determine if this finding was evident in women who were victimized by severe sexual abuse in childhood. METHODS: In this study, hippocampal volume was measured using quantitative magnetic resonance imaging (MRI) in 21 women who reported being severely sexually abused in childhood and 21 socio-demographically similar women without abuse histories. RESULTS: Women who reported sexual victimization in childhood had significantly reduced (5% smaller) left-sided hippocampal volume compared to the non-victimized women. Hippocampal volume was also smaller on the right side, but this failed to reach statistical significance. Left-sided hippocampal volume correlated highly (rs = -0.73) with dissociative symptom severity, but not with indices of explicit memory functioning. CONCLUSIONS: These findings, which are generally consistent with prior reports of reduced hippocampal volume in combat veterans with PTSD, suggest that diminished hippocampal size may be either a consequence of trauma exposure or a risk factor for the development of psychiatric complications following trauma exposure. The observed relationship between symptom severity and hippocampal volume suggests that mesial temporal lobe dysfunction may directly mediate certain aspects of PTSD and dissociative disorder symptomatology.

Adult↗

Influence of magnetic resonance imaging on diagnosis and therapeutic intention.

RATIONALE AND OBJECTIVES: We assessed the contribution of magnetic resonance (MR) imaging to diagnostic and therapeutic decision making. METHODS: In a before-after observational study, we collected information from clinicians before and after patients were given MR examinations. We studied 406 cases selected from consecutive referrals to a single MR imaging facility in Manitoba between November 1, 1991, and October 30, 1992, for diagnosis of suspected brain, spinal column, or large-joint disorder. We examined changes in diagnoses, changes in clinician diagnostic confidence, and changes in therapeutic intentions after MR examinations. RESULTS: Overall, MR imaging findings contributed to a change in referring physicians' diagnoses or diagnostic confidence in 76% of the cases. Referring physicians reported a change in provisional diagnosis in 42% of the cases. In 67% of these cases, the referring physician's provisional diagnosis was ruled out by normal examination findings; in the remaining 33% of the cases, an alternate diagnosis was offered by the consulting radiologist. In the 58% of the cases in which the provisional diagnosis was not altered by MR imaging findings, clinical confidence in the provisional diagnosis increased in 46% of the cases and decreased in 12% of the cases. Management plans were reported to be altered in 54% of the cases; in 24% of the cases, therapeutic intentions changed from lower to higher levels of intervention. CONCLUSION: Although MR imaging had a substantial influence on clinicians' decisions concerning diagnoses, the influence of MR imaging findings on therapeutic decision making, and therefore on patients' health status, was more moderate.

Brain Diseases↗

A simplified method for measuring cerebral blood flow with xenon-enhanced computed tomography.

The measurement of cerebral blood flow using the xenon-enhanced computed tomography (XECT) technique requires that the build-up of xenon in both brain tissue and end-tidal expired air be determined as a function of time. Monitoring of the former is carried out using CT scanning and the latter, most often, using a thermoconductivity analyser or mass spectrometer. This paper examines the possibility of greatly simplifying the XECT technique by eliminating the need for either thermoconductivity analyser or mass spectrometer. In the proposed approach, the patient's expired air is channelled through the scan field using a flexible plastic tube and sampled by the CT scanner in conjunction with the build-up of xenon in brain tissue. Phantom measurements have demonstrated the ability of the CT scanner to detect variations in the xenon concentration in expired air while computer simulations have shown that errors arising as a result of the proposed methodology are small compared to other inherent sources in the XECT technique.

Brain↗

Routine contrast enhancement for cranial magnetic resonance imaging: an analysis of its diagnostic value in adults.

This study evaluated the diagnostic value of contrast enhancement in consecutive adults referred for cranial magnetic resonance imaging (MRI). All of the 112 participating patients underwent two sets of studies, first without and then with a contrast medium. Three neuroradiologists independently reviewed the information for each patient. Contrast enhancement contributed diagnostically useful information in 75% of cases: in 4% because undiagnosed lesions became apparent, in 26% because more information was obtained regarding the size, extent or margins of a lesion and in 45% because the lack of contrast enhancement in the area of interest allowed more confident exclusion of disease in patients with compelling clinical findings or demonstrated the nonaggressive nature of a lesion apparent with unenhanced MRI. The authors conclude that contrast enhancement is diagnostically useful for most patients referred for cranial MRI. Although the proportion of cases in which contrast enhancement was useful was much higher than in previous studies conducted in the United States, the authors believe that this finding is due to the high prevalence of disease in the population referred to this Canadian MRI centre.

Adult↗

Quantitative computed tomography of the brain with xenon enhancement: a phantom study with the GE9800 scanner.

A recently proposed application of quantitative computed tomography is in the study of cerebral blood flow and partition coefficient using stable xenon as a freely diffusible, radio-opaque tracer. Central to the method is the calibration factor describing the relationship between CT number and xenon concentration in the brain. In this paper we examine the influence of temporal fluctuations, kVp, radial position and beam hardening on this calibration factor through the analysis of a series of phantom measurements. We conclude that under clinically realistic conditions and with correlations for temporal fluctuations, the error associated with the calibration factor is less than 2%. Furthermore, errors of this magnitude translate into errors of less than 3% in derived blood flow and partition coefficient values obtained using xenon-enhanced computed tomography.

Brain↗

The role of noise in the measurement of cerebral blood flow and partition coefficient using xenon-enhanced computed tomography.

Monte Carlo simulations have been used to study the accuracy which can be expected in the quantification of blood flow and the partition coefficient using xenon-enhanced computed tomography in the presence of noise. We have demonstrated that the markedly asymmetric frequency distribution of estimates increases in size rapidly with an increase in the standard error of the input CT data. On the basis of our results, we recommend that controllable sources of noise (eg. CT number drift) be corrected and that estimates be obtained by averaging CT data and then fitting, rather than averaging blood flow and partition coefficients derived from individual pixels, as the latter procedure results in the introduction of considerable bias.

Administration, Inhalation↗

Multiple intracerebral arteriovenous malformations. A case report and literature review.

The presence of multiple intracerebral arteriovenous malformations (AVMs) in a single patient has only been very rarely reported. We present a patient with three separate angiographically demonstrable intracerebral AVMs, all of which were radiologically demonstrated and surgically removed without residual neurological deficit. A literature survey was conducted and all the previously described cases of multiple intracerebral AVMs are discussed, along with the potential diagnostic and therapeutic implications.

Abnormalities, Multiple↗