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David M Yousem

Publications and source records attributed to David M Yousem.

At least 37 records · Page 2Linked to original sources
PubMed2003

Correlation of functional MR imaging activation data with simple reaction times.

PURPOSE: To determine the relationship between subject reaction times (RTs) and activation volume in the brain during visuomotor functional magnetic resonance (MR) imaging. MATERIALS AND METHODS: Twenty-four subjects performed a simple RT task during single-event functional MR imaging, and RTs were recorded. The six subjects with the fastest RTs were designated the fast RT group, and the six subjects with the slowest RTs were designated the slow RT group. The data were processed with noncorrected height threshold (P <.001) for individual comparisons and corrected height threshold (P <.05) for group comparisons (t tests). The activation volumes in both occipital lobes, the left sensorimotor cortex, and the supplemental motor cortices were compared for the two groups. RESULTS: The mean RT +/- SD was 342 msec +/- 20.15 for the fast RT group and 475 msec +/- 36.17 for the slow RT group (P <.0001). More voxels of activation were seen in the fast RT group than in the slow RT group in the occipital lobes, left sensorimotor cortices, and supplemental motor cortices on individual and group maps. This difference was statistically significant in the left sensorimotor (P =.03) and left visual (P =.05) cortices. In the right visual cortex, a trend toward more activation in the fast RT group was noted (P =.15). There was a negative correlation between RTs and activation volume in the left sensorimotor cortex (P =.048). CONCLUSION: There was a greater activation volume in motor and visual cortices in the fast RT group than in the slow RT group.

Adult↗
PubMed2003

Lack of sex effect on brain activity during a visuomotor response task: functional MR imaging study.

BACKGROUND AND PURPOSE: As more individuals are enrolled in clinical functional MR imaging (fMRI) studies, an understanding of how sex may influence fMRI-measured brain activation is critical. METHODS: We used fixed- and random-effects models to study the influence of sex on fMRI patterns of brain activation during a simple visuomotor reaction time task in the group of 26 age-matched men and women. We evaluated the right visual, left visual, left primary motor, left supplementary motor, and left anterior cingulate areas. RESULTS: Volumes of activations did not significantly differ between the groups in any defined regions. Analysis of variance failed to show any significant correlations between sex and volumes of brain activation in any location studied. Mean percentage signal-intensity changes for all locations were similar between men and women. A two-way t test of brain activation in men and women, performed as a part of random-effects modeling, showed no significant difference at any site. CONCLUSION: Our results suggest that sex seems to have little influence on fMRI brain activation when we compared performance on the simple reaction-time task. The need to control for sex effects is not critical in the analysis of this task with fMRI.

Adult↗
PubMed2003

Cavernous carotid artery calcification and white matter ischemia.

BACKGROUND AND PURPOSE: The relevance of cavernous carotid artery calcification on unenhanced CT scans of the brain has recently been investigated against the backdrop of the widespread implementation of coronary artery calcification scoring. We sought to determine whether the degree of cavernous carotid artery calcification correlated with scores of white matter hyperintensity seen on MR images. In so doing, we sought to establish a relative risk for future stroke on the grade of carotid calcification. METHODS: Neuroradiologic findings in 187 patients who underwent CT and MR imaging examinations within 1 month of each other were retrospectively reviewed. The degree of circumferential calcification and thickness of calcification were graded for the cavernous carotid arteries on the basis of CT findings. Using the scale developed by the Cardiovascular Health Study, the white matter was graded for degree of disease on the basis of MR findings. Correlation tests and regression analyses were performed to determine the impact of age, race, and sex on results. RESULTS: Although the cavernous carotid calcification scores and the MR imaging white matter scores showed good correlation (P <.001), the effect was mediated by age. With age factored in as a covariant, no correlation was shown between CT calcification scores and MR imaging white matter scores. Sex had no effect, but African American study participants had worse MR imaging white matter scores than did white participants. CONCLUSION: After adjusting for age, cavernous carotid calcification grades and MR imaging white matter scores do not show a significant correlation. The relative risk for future stroke cannot be predicted from cavernous carotid calcifications.

Adult↗
PubMed2003

MR imaging characteristics of pilomyxoid astrocytomas.

BACKGROUND AND PURPOSE: Pilomyxoid astrocytoma (PMA) is a recently described tumor that typically occurs in the chiasmatic-hypothalamic region in young children and has unique histopathologic and clinical characteristics. These tumors have been previously diagnosed as pilocytic astrocytoma (PA). PMA appears to have a higher rate of recurrence and CSF dissemination than typical PA. METHODS: We analyzed MR findings in four patients with PMA and compared them with those of typical chiasmatic-hypothalamic PA. RESULTS: MR findings of PMA were chiasmatic or hypothalamic enhancing solid tumor with hydrocephalus, highly homogeneous T2 signal intensity that extended into the deep white and gray matter, and CSF dissemination. CONCLUSION: Larger series are needed before the MR imaging findings of chiasmatic or hypothalamic enhancing solid tumor with hydrocephalus, highly homogeneous T2 signal intensity extending into the deep white and gray matter, and CSF dissemination can be used in the differential diagnosis of such tumors.

Astrocytoma↗
PubMed2002

Laryngeal imaging.

Knowing the surgical options for treating laryngeal carcinomas and the factors that are used to select patients for radiation therapy leads to a more comprehensive interpretation of neck scans in patients with laryngeal tumors (Table 6). Critical factors include tumor volume; cartilaginous invasion; spread across supraglottic-glottic-subglottic [table: see text] boundaries; infiltration of preepiglottic, paraglottic, and pharyngeal planes; and nodal disease. MR imaging offers greater sensitivity to cartilaginous invasion than CT but leads to a high rate of false-positive studies, which decreases its overall accuracy. Thin-section CT with multiplanar capability is competitive with direct coronal MR scanning and benefits from high specificity and submillimeter section thickness, if multidetector units are employed. Overall, the head and neck radiologist plays an invaluable role in assessing the extent of disease and therefore influences the appropriate selection from the available treatment options.

Carcinoma, Squamous Cell↗
PubMed2002

Correlation of reaction time in and out of the functional MR unit.

RATIONALE AND OBJECTIVES: The authors performed this study to determine whether reaction times (RTs) recorded in the functional magnetic resonance (MR) imaging environment reflect the performance of the patient outside the imaging room. MATERIALS AND METHODS: Fifteen healthy control subjects (mean age, 61.6 years) performed a simple reaction time (SRT) task outside the MR magnet and a visuomotor response time task inside the magnet with use of block-design and event-related paradigms. For both behavioral and functional MR imaging tests, subjects tapped the right index finger upon the appearance of a visual cue. The mean RTs for out-of-magnet and functional MR imaging paradigms were compared. Results. There was a statistically significant difference in RTs between block-design and single-event paradigms (t = 3.458, P < .004). The RT values during functional MR imaging and SRT tasks did not show significant differences (.65 < P < .7, paired t test). However, no correlation was found in RT values between event-related (p = -0.004, P = .15) or block-design (p = 0.03, P = .13) paradigms and SRT data. With the block-design functional MR imaging paradigm, the RT was significantly faster (P < .0003) at the beginning of the session than the end, illustrating the effect of anticipation. CONCLUSION: Functional MR imaging RTs must be used to determine the correlation between subjects' performance and the volume of brain activation in a functional MR imaging experiment. The effect of anticipation should be minimized, which could best be achieved by using event-related paradigms.

Adult↗
PubMed2002

Impact of pager notification on report verification times.

RATIONALE AND OBJECTIVES: The purpose of this study was to assess the impact on times of verification (TOVs) by a pager notification system (PNS) that informs physicians when reports are available for signature. MATERIALS AND METHODS: An automated PNS was implemented in the authors' department in November 2000. Monthly report verification times of each physician were collected for 3 months in the years before and after initiation of the PNS. Radiologists enrolled in the PNS and those who were not were assigned into two groups for analysis. Mean TOVs for the two sets of 3 months and for the two groups were calculated and differences recorded. Two-tailed t tests were used to assess for statistical differences between the groups. RESULTS: Twenty-nine of 37 radiologists voluntarily enrolled in the PNS (group 1). Mean TOV was 26.75 hours (standard deviation [SD] = 17.76) for these physicians before and 14.48 hours (SD = 11.86) after the PNS was employed (P < .01). For those physicians who did not enroll in the PNS, mean TOV was 11.53 hours (SD = 5.55) before and 9.77 hours (SD = 9.86) after the PNS was employed (P = .33). Both the absolute and percentage reductions in TOVs were significantly greater for those physicians enrolled in the PNS than for those who were not (P = .035). Twenty-three of 29 (79%) physicians who used the PNS showed a reduction in their report turnaround times. CONCLUSION: Linking the PNS with the radiology information system to notify physicians of unsigned reports was effective in reducing report verification times.

Humans↗
PubMed2002

Effect of emergency department CT on neuroimaging case volume and positive scan rates.

RATIONALE AND OBJECTIVES: The authors performed this study to determine the effect a computed tomographic (CT) scanner in the emergency department (ED) has on neuroimaging case volume and positive scan rates. MATERIALS AND METHODS: The total numbers of ED visits and neuroradiology CT scans requested from the ED were recorded for 1998 and 2000, the years before and after the installation of a CT unit in the ED. For each examination type (brain, face, cervical spine), studies were graded for major findings (those that affected patient care), minor findings, and normal findings. The CT utilization rates and positive study rates were compared for each type of study performed for both years. RESULTS: There was a statistically significant increase in the utilization rate after installation of the CT unit (P < .001). The fractions of studies with major findings, minor findings, and normal findings changed significantly after installation of the CT unit for facial examinations (P = .002) but not for brain (P = .12) or cervical spine (P = .24) examinations. In all types of studies, the percentage of normal examinations increased. In toto, there was a significant decrease in the positive scan rate after installation of the CT scanner (P = .004). CONCLUSION: After installation of a CT scanner in the ED, there was increased utilization and a decreased rate of positive neuroradiologic examinations, the latter primarily due to lower positive rates for facial CT scans.

Cervical Vertebrae↗
PubMed2002

Diffusion-weighted imaging and apparent diffusion coefficient maps in a case of intracerebral abscess with ventricular extension.

Previous findings have demonstrated the diagnostic usefulness of diffusion-weighted imaging in depicting specific features of a brain abscess. We report a case of a cerebral abscess, which ruptured into the ventricular system, including its findings on both diffusion-weighted images and apparent diffusion coefficient (ADC) maps. Purulent material within the left lateral ventricle, similar to that of the central abscess cavity, was strongly hyperintense on diffusion-weighted images. However, variable signal intensity changes were observed on the ADC map; these probably corresponded to regional variation of the concentration of protein in the purulent material. In this case, both diffusion-weighted images and ADC maps were important and complementary in the evaluation of ventricular extension of an intracerebral abscess.

Aged↗
PubMed2002

MR imaging characteristics of cranial bone marrow in adult patients with underlying systemic disorders compared with healthy control subjects.

BACKGROUND AND PURPOSE: In young adults, hematopoietic bone marrow has usually converted to fatty marrow. Fat hyperintensity on T1-weighted MR images facilitates the evaluation of marrow abnormalities. Our purpose was to compare cranial marrow signal intensity patterns in adults with systemic disorders and in healthy subjects. METHODS: MR images in 25 adults with underlying systemic disorders (chronic anemia, lymphoma, leukemia, or other infiltrative processes) and 44 healthy aged-matched individuals were retrospectively reviewed. Calvarial and clival marrow signal intensity on sagittal T1-weighted images was graded relative to that of orbital fat, white matter (WM), and gray matter (GM). Marrow was classified as homogeneous (uniformly isointense), diffusely heterogeneous (mottled), or focally heterogeneous (generally isointense with a focal lesion). RESULTS: In 84% of the control subjects, bone marrow was iso- or hyperintense relative to WM. Patients had abnormal diploic (n = 22) or clival (n = 17) marrow; 22 had calvarial marrow that was hypointense relative to WM compared with that in seven healthy subjects (P <.001). Marrow hypointensity relative to WM was a sensitive (93%) and specific (86%) marker of pathologic abnormality. Although marrow hypointensity relative to GM was specific (96%), it was not sensitive (67%). Calvarial and clival marrow patterns, respectively, were homogeneous in 81% and 64% of control subjects and 76% and 60% of patients. Clival marrow intensity varied more than did calvarial intensity; therefore, clival criteria were less sensitive and accurate in systemic disease detection. CONCLUSION: Homogeneous diploic marrow hypointense relative to WM on non-contrast-enhanced T1-weighted images suggests an underlying systemic or hematologic disorder and requires appropriate clinical correlation and evaluation.

Adult↗
PubMed2002

Influence of imaging parameters on high-intensity cerebrospinal fluid artifacts in fast-FLAIR MR imaging.

BACKGROUND AND PURPOSE: High-intensity CSF artifacts at the basal cisterns on MR images are often seen when a fast fluid-attenuated inversion recovery (FLAIR) technique is used. We investigated the influences of four optional fast-FLAIR sequence parameters on the high-intensity CSF artifacts. METHODS: A total of 377 patients (age range, 1 week to 91 years; mean 40.6 years; 186 female, 191 male) were examined with axial fast-FLAIR images obtained (TR/TE(eff)/TI, 8800/133/2200) with a 1.5-T system during 6 months. The effects of the optional addition of inferior inflow saturation (thickness, 80 mm), section flow compensation, and tailored radiofrequency (TRF) pulses, plus the choice of interleaving acquisition factors of 2 or 3, were evaluated for the presence of high-intensity CSF artifacts on the fast-FLAIR images. Two radiologists independently reviewed the fast-FLAIR images in 76 patients; afterward, a single observer reviewed the remainder of the images. RESULTS: The interobserver agreement rate in 76 cases was more than 90%. The use of TRF and/or three interleaving acquisitions resulted in a substantial reduction in the incidence of high-intensity CSF artifacts from about 80% to 40% (P <.05, two-sample two-sided Z test). Inferior inflow saturation and section flow compensation did not significantly improve image quality (P >.05). The results were consistent with the image quality ranking obtained in five healthy volunteers. CONCLUSION: The appropriate choice of sequence parameters in fast-FLAIR imaging reduces the incidence of high-intensity CSF artifacts that are frequently encountered in the presence of rapid CSF flow.

Adolescent↗
PubMed2002

Intracranial hypotension as a cause of radiculopathy from cervical epidural venous engorgement: case report.

We describe the case of a 40-year-old man with spontaneous intracranial hypotension who presented with cervical radiculopathy associated with epidural venous engorgement. Epidural venous engorgement can occur secondary to intracranial hypotension and manifests intracranially as pachymeningeal venous engorgement. In the cervical spine, two cases of epidural venous engorgement due to intracranial hypotension have been reported in the literature, and neither patient presented with symptoms related to nerve compression. Epidural venous engorgement should be considered in the differential diagnosis of an enhancing epidural mass in the cervical spine. Diagnostic clues include sparing of the anterior midline and posterior aspects of the epidural space and, if present, pulsation artifact.

Adult↗
PubMed2002

Serial MR Imaging of Annular Tears in Lumbar Intervertebral Disks.

BACKGROUND AND PURPOSE: Annular tears of lumbar intervertebral disks are found in both symptomatic and asymptomatic persons; therefore, it is difficult to determine whether these findings indicate acute abnormality. Our purpose was to determine whether the MR imaging findings of tears (ie, hyperintensity and contrast enhancement) of the annulus fibrosus persist or resolve over time. METHODS: A radiologic database was searched for spinal MR imaging examinations noting annular tears. Eighteen patients were identified who had undergone more than one spinal MR imaging study. The images were reviewed for presence or absence of annular tears, defined as an area of hyperintensity on T2-weighted images or enhancement in the posterior annulus, separate from the nucleus pulposus. RESULTS: Annular tears were observed at 29 levels in 18 patients. Two tears developed during the follow-up interval. When contrast-enhanced images were obtained during serial examinations, 10 (100%) of 10 enhancing annular tears persisted on the follow-up contrast-enhanced T1-weighted images (mean interval, 17.2 months; SD, 12.3 months). High signal intensity on T2-weighted MR images was noted in 26 (96%) of 27 tears initially and persisted in 23 (88%) of 26 (mean interval, 21.9 months; SD, 15.0 months). CONCLUSION: Hyperintensity on T2-weighted MR images and enhancement of annular tears could not be used to determine the tears' acuity over the range of follow-up provided in this study.

Adult↗
PubMedDate not supplied

Dehiscence of the jugular bulb and vestibular aqueduct: findings on 200 consecutive temporal bone computed tomography scans.

OBJECTIVE: To determine the incidence of dehiscence between the vestibular aqueduct and the jugular bulb on computed tomography (CT) scans and assess its implication as a cause of dizziness or hearing loss. METHODS: Two hundred temporal bone CT scans were evaluated for the prevalence of dehiscence between the jugular bulb and vestibular aqueduct. Correlation of the imaging findings and clinical data was performed. RESULTS: A total of 11.5% of patients had dehiscence of the jugular bulb with the vestibular aqueduct; 75% of these cases occurred on the right side and in the setting of a high jugular bulb. Nine (39.1%) of 23 patients with dehiscence had dizziness, and 11 (47.8%) had hearing loss. The correlation between the incidence of dizziness, hearing loss, and dehiscence was not significant. CONCLUSION: The incidence of a dehiscent jugular bulb with a vestibular aqueduct is 11.5%. The prevalences of vertigo and hearing loss associated with this finding are 39.1% and 47.8%, respectively. The depiction of dehiscent jugular bulb-vestibular aqueduct should be considered with caution as the sole cause of symptoms.

Adolescent↗
PubMedDate not supplied

A prion disease--possible Gerstmann-Straussler-Scheinker disease: a case report.

A 50-year-old patient with a 6-month history of progressive cognitive and motor disability is presented. There were no myoclonic jerks on examination and no periodic sharp waves by electroencephalography. Imaging showed high signal on T2-weighted scans in the basal ganglia and posterior limbs of the internal capsules, with no restricted diffusion and parenchymal volume loss. A brain biopsy was performed. Western blot analysis revealed a protease-resistant prion protein fragment (PrP7-8), the molecular hallmark of Gerstmann-Straussler-Scheinker disease.

Blotting, Western↗