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Biomedical subjects

David M Yousem

Publications and source records attributed to David M Yousem.

At least 19 recordsLinked to original sources
PubMed2006

Watershed strokes after cardiac surgery: diagnosis, etiology, and outcome.

BACKGROUND AND PURPOSE: Watershed strokes are more prevalent after cardiac surgery than in other stroke populations, but their mechanism in this setting is not understood. We investigated the role of intraoperative blood pressure in the development of watershed strokes and used MRI to evaluate diagnosis and outcomes associated with this stroke subtype. METHODS: From 1998 to 2003 we studied 98 patients with clinical stroke after cardiac surgery who underwent MRI with diffusion-weighted imaging. We used logistic regression to explore the relationship between mean arterial pressure and watershed infarcts, between watershed infarcts and outcome, and chi(2) analyses to compare detection by MRI versus CT of watershed infarcts. RESULTS: Bilateral watershed infarcts were present on 48% of MRIs and 22% of CTs (P<0.0001). Perioperative stroke patients with bilateral watershed infarcts, compared with those with other infarct patterns, were 17.3 times more likely to die, 12.5 and 6.2 times more likely to be discharged to a skilled nursing facility and to acute rehabilitation, respectively, than to be discharged home (P=0.0004). Patients with a decrease in mean arterial pressure of at least 10 mm Hg (intraoperative compared with preoperative) were 4.1 times more likely to have bilateral watershed infarcts than other infarct patterns. CONCLUSIONS: Bilateral watershed infarcts after cardiac surgery are most reliably detected by diffusion-weighted imaging MRI and are associated with poor short-term outcome, compared with other infarct types. The mechanism may include an intraoperative drop in blood pressure from a patient's baseline. These findings have implications for future clinical practice and research.

Aged↗
PubMed2006

Familial risk for Alzheimer's disease alters fMRI activation patterns.

Alzheimer's disease poses a looming crisis for the health care system as well as society in general. The low efficacy of current treatments for those already affected with this disease has prompted the suggestion that interventions might be more successful if they were applied before the development of significant pathology, that is, when individuals are clinically asymptomatic. Currently, the field requires a sensitive and specific diagnostic tool for identifying those individuals destined to develop this disease. As a first step, we present here an analysis of cross-sectional data for 95 asymptomatic offspring (50-75 years of age) of autopsy-confirmed late-onset familial Alzheimer's disease cases and 90 age-matched controls, studied with functional magnetic resonance imaging (fMRI) to investigate brain activation patterns. Analysis of activation in response to a paired-associates memory paradigm found significantly different patterns in these groups. At-risk individuals showed more intense and extensive activation in the frontal and temporal lobes including the hippocampus during memory encoding, an increase unrelated to the APOE epsilon4 allele. They also showed decreased activation particularly in the cingulum and thalamus during both the encoding and recall phases of the task. These results demonstrate that asymptomatic individuals, at genetic risk for development of late-onset Alzheimer's disease by virtue of familial clustering, show functional activation patterns distinct from those without such risk more than a decade before their parent's onset age. While longitudinal study is needed to determine whether these patterns, or a subset of them, are predictive of disease onset, these findings suggest that functional neuroimaging holds promise as a method of identifying pre-clinical Alzheimer's disease.

Age of Onset↗
PubMed2006

Findings on brain MRI from research studies of occupational exposure to known neurotoxicants.

OBJECTIVE: The expanding use of MRI in large-scale epidemiologic studies of CNS outcomes has led to increasing concern for the consistent handling of incidental findings. Our purpose is to identify the prevalence of incidental neuroradiologic abnormalities in an adult population with past occupational exposure to lead who underwent brain MRI as part of a large, longitudinal cohort study. MATERIALS AND METHODS: Structural MR images obtained for the research study were reviewed by a neuroradiologist on an ongoing basis for findings of clinical concern. The subjects were recruited as part of a longitudinal research study designed to examine the effects of past lead exposure on CNS structures. The cohort examined consisted of 589 men who previously worked at an organolead manufacturing facility and had a wide range of lead exposure durations and intensities. MR images were also reviewed from 67 population-based control subjects from the same study who had no history of occupational lead exposure. RESULTS: Incidental findings were detected in 84% (548/656) of research subjects. Of the 548 subjects with abnormalities, 30% (167) required no referral, 51% (280) required routine referral, 17% (93) required urgent referral, and 1.5% (8) required immediate referral. Incidental findings of all categories were observed in a larger percentage of older subjects, aged 60 years and above. Using multivariable logistic regression analysis, we found that age (p < 0.0001), but not lead history, was associated with an increased risk of incidental neuroradiologic abnormalities. CONCLUSION: In the population examined, there was a high prevalence of incidental brain and head and neck abnormality. Of particular concern were the serious health problems observed requiring urgent or immediate referral in 18.5% of the subjects. These findings underscore the need for radiologists to evaluate the anatomic images generated by research studies, particularly those with an older population base.

Adult↗
PubMed2005

Brain activation in offspring of AD cases corresponds to 10q linkage.

Previously, we reported evidence of genetic heterogeneity in late-onset familial Alzheimer's disease, based on sex of affected parent, demonstrating linkage to chromosome 10q, a region identified by other groups and implicated as a quantitative trait loci for Abeta levels, in families with an affected mother. Using functional magnetic resonance imaging and a memory encoding task, we now show differential brain activation patterns among asymptomatic offspring which correspond to the previous linkage finding. These results suggest the possibility that activation patterns may prove useful as a preclinical quantitative trait related to the putative familial late-onset AD gene in this chromosome 10 region.

Alzheimer Disease↗
PubMed2005

Accuracy of magnetic resonance imaging in predicting absence of fixation of head and neck cancer to the prevertebral space.

BACKGROUND: The purpose of this study was to determine the preoperative accuracy of preservation of the retropharyngeal fat plane on magnetic resonance (MR) images in predicting the absence of fixation or extension of head and neck carcinomas to the prevertebral space. METHODS: The MR images of 75 patients with T3 or T4 primary pharyngeal or laryngeal cancers seen over a 5-year period and treated at our Head and Neck Cancer Center were retrospectively reviewed. The MR images were independently and blindly evaluated by two head and neck radiologists for preservation of the retropharyngeal fat plane between the tumor and prevertebral musculature. In cases in which the fat was preserved, the prevertebral muscle complex was assessed for the presence of T2 hyperintensity and enhancement. All patients underwent panendoscopy, surgery, or both. RESULTS: Forty of 75 patients had preservation of the retropharyngeal fat plane between the tumor and the prevertebral compartment on T1-weighted images. In all 40 cases, the prevertebral muscles had a normal appearance on T2-weighted and enhanced MR images. Intraoperative assessment revealed absence of fixation of tumor to the prevertebral fascia in 39 of 40 cases, and these tumors were resectable. CONCLUSION: In patients with advanced head and neck carcinomas, preservation of the fat between the tumor and the prevertebral musculature on unenhanced T1-weighted images reliably predicts absence of prevertebral space fixation.

Adipose Tissue↗
PubMed2005

Effect of age on visuomotor functional MR imaging.

RATIONALE AND OBJECTIVES: We sought to determine the effect of age on functional MR imaging experiments performed with visual and motor stimulation. We hypothesized that there would be a diminution in the amplitude of fMRI activation with increasing subjects' age. MATERIALS AND METHODS: We used fixed effects models to study the amplitude of activation during a block design visuomotor task in three different age groups: old (mean: 75 years; standard deviation: 6 years), middle-aged (mean: 52 years; standard deviation: 9 years) and young (mean: 29 years; standard deviation: 5 years). Each group included 7 subjects. Regions of interest (ROI) were left primary motor area (LM1), supplementary motor area (SMA), and right and left occipital (RO, LO) visual areas. Individual subjects and group statistical parametric maps (SPMs) were generated for each ROI, and then the mean amplitude of activation was compared using the group analysis and t test. RESULTS: The young age group showed higher amplitude of activation than middle and old age groups in all ROI (P < 0.01 uncorrected). Unpaired two tailed t test results between the groups showed significant differences between middle and young, and old and young age groups in all ROIs (P < or = 0.05), with the exception of old and young age groups in RO region (P = 0.11). CONCLUSION: The group analysis, and unpaired t test results reveal higher amplitude of fMRI activation in the young versus the old and middle-aged groups.

Adult↗
PubMed2005

Clearing of red blood cells in lumbar puncture does not rule out ruptured aneurysm in patients with suspected subarachnoid hemorrhage but negative head CT findings.

BACKGROUND AND PURPOSE: In evaluating the results of lumbar puncture (LP), a decrease in the number of red blood cells (RBCs)/mm3 between the first and fourth tubes collected (clearing) has often been assumed to indicate a traumatic puncture rather than the presence of subarachnoid hemorrhage (SAH). We tested the hypothesis that, in the setting of severe headache, CSF clearing coupled with an unremarkable unenhanced CT scan was negatively predictive of the presence of aneurysm and could be used to reduce the need for conventional arteriography. METHODS: Cerebral angiography was performed to evaluate suspected SAH in 123 consecutive patients over 2 years at a university teaching hospital. Records of these patients were reviewed. Among the subset without SAH on CT scan, LP results were evaluated for clearing. Clearing was arbitrarily defined as a 25% reduction in RBCs between the first and fourth tubes. This subset's records were also reviewed for the presence of aneurysm at cerebral angiography or at follow-up 6 weeks later. Data were analyzed for correlation between clearing and aneurysm. RESULTS: Of the 123 patients whose records were reviewed, 22 did not show an SAH on CT scan. Of those 22 patients, eight had aneurysm at angiography and 14 did not. Clinical diagnoses in the other 14 included trauma, herpes meningitis, sickle cell disease, and cocaine use. CSF clearing was noted in 25% of those with an aneurysm (two of 8) and 21% of those without an aneurysm (three of 14). In the two cases with aneurysms, RBCs cleared from 3550 to 2550 (-28%) and from 24,686 to 17,842 (-28%), respectively. In the remaining six cases with aneurysms, RBCs increased a mean of 1370% between the first and fourth tubes (range, -22% to 7700%). Two of these six had a reduction that did not meet our criteria for clearing (-22% and -5.3%, respectively). In the 14 cases without aneurysms, RBCs increased a mean of 70% between the first and fourth tubes (range, -99% to 895%). In addition to the three of these 14 that met our criteria for clearing (-99%, -99%, and -43%), four cases had a reduction that did not (range, -0.7% to -14%). CONCLUSION: A 25% reduction in RBC concentration between the first and fourth tubes of CSF in patients with suspected SAH but negative CT findings occurs even in cases of ruptured aneurysms. Formal evaluation for the presence of an aneurysm is still necessary in this scenario.

Aneurysm, Ruptured↗
PubMed2004

Role of magnetic resonance neurography in brachial plexus lesions.

Magnetic resonance neurography (MRN) is a relatively new imaging technique that is highly sensitive in detecting lesions in the peripheral nerves. We studied six cases of brachial plexopathies in which MRN played a pivotal role in making the correct diagnoses. All patients had clinical, nerve conduction, and electromyographic findings consistent with brachial plexus lesions. Four patients had brachial plexitis and two had multifocal demyelinating neuropathy presenting as brachial plexopathies. MRN in all patients showed edema, thickening, and T2 hyperintensities localized to the brachial plexus region. We conclude that MRN is a useful technique in evaluating patients with brachial plexus lesions, particularly in cases of brachial plexitis, where conventional magnetic resonance imaging is generally normal.

Adolescent↗
PubMed2004

Age differences in orbitofrontal activation: an fMRI investigation of delayed match and nonmatch to sample.

Several investigations have suggested that the orbitofrontal cortex (OFC) may be particularly vulnerable to the effects of age-related changes. We recently reported behavioral data indicating greater age differences in orbitofrontal tasks when directly compared to tasks tapping dorsolateral prefrontal functions. The present study was designed to investigate the neural underpinnings of age differences in OFC functioning. Event-related functional magnetic resonance imaging (fMRI) was performed during delayed match and nonmatch to sample tasks, previously shown to differentially activate medial and lateral OFC in young adults. Sixteen healthy younger [age = 26.7(5.6)] and 16 healthy older individuals [age = 69.1 + 5.6] with similar levels of education and general cognitive functioning participated in the experiment. Participants chose the stimulus from a pair of stimuli matching a previously viewed target (match to sample) or chose the nontarget item (nonmatch to sample) depending upon a trial-specific instruction word. Consistent with previous studies, SPM99 analyses of the younger age group revealed activation for medial OFC regions during the match task compared to the nonmatch task and lateral OFC activation during the nonmatch task compared to the match task. In contrast, older adults showed prefrontal activation only during the match relative to the nonmatch task and posterior temporal and limbic involvement during the nonmatch relative to the match task. Between-group analyses confirmed within-group results suggesting differential age-related recruitment of prefrontal regions when performing match and nonmatch tasks. Results suggest that OFC recruitment during these cognitive tasks changes with age and should be evaluated within the context of other prefrontal subregions to further define differential age effects on frontal functions.

Adult↗
PubMed2004

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 valuable and relevant interpretation of neck scans in patients with laryngeal tumors. Critical factors include tumor volume; cartilaginous invasion; spread across supraglottic-glottic-subglottic boundaries; infiltration of preepiglottic, paraglottic, and pharyngeal planes; and nodal disease. MR imaging offers greater sensitivity to cartilaginous invasion than CT but shows a higher rate of false-positive studies. Direct coronal MR imaging is often valuable in assessing these issues.

Journal Article↗
PubMed2004

Correlation between the amplitude of cortical activation and reaction time: a functional MRI study.

OBJECTIVE: We sought to examine the correlation between reaction time and the amplitude of cortical activation during the performance of a visuomotor response-time task in a functional MRI (fMRI) experiment. We hypothesized that the fMRI blood oxygenation level-dependent (BOLD) amplitude may have a negative correlation with a subject's reaction time: the lower the amplitude within the cortical areas along the visuomotor pathway, the slower the response. A larger amplitude of the fMRI signal would reflect faster response times. SUBJECTS AND METHODS: During a single-event fMRI experiment, the reaction times (in milliseconds) of 32 right-handed subjects responding to a visual cue were recorded. Analysis of the single-event paradigm using Statistical Parametric Mapping (SPM99) was performed, activation maps were produced for each subject, and then a random effects group analysis was performed. The maximum amplitudes of cortical activation (percent signal change) in four activated cortical regions were estimated and tabulated. The regions of interest included were the right and left occipital visual cortices, the supplementary motor area, and the left sensorimotor area. Simple and multiple regressions were performed between the mean reaction times of the subjects and the BOLD amplitudes in each region of interest and for the composite region of interest. RESULTS: The results showed significant negative associations between the reaction times and maximum amplitudes in the right occipital, left occipital, and left sensorimotor area cortical regions (p < 0.05). However, no significant association was found between reaction times and the amplitude within the supplementary motor area. When the effects of age and sex on these associations were analyzed, we found that age had an impact on the results for individual regions of interest in the left occipital and left sensorimotor areas, but the composite amplitude of activation remained significantly correlated with reaction times. CONCLUSION: The degree of signal change in BOLD fMRI response of the right occipital, left occipital, and left sensorimotor areas reflects the speed of performance during the visuomotor response time task by the subject. Thus, the amplitude of activation can be used as one parameter to assess change in function.

Adult↗
PubMed2004

Imaging findings of CNS atypical teratoid/rhabdoid tumors.

Four patients with brain tumors were diagnosed with atypical teratoid/rhabdoid tumors and underwent CT and MR imaging. For all tumors, aggressive features were shown by imaging studies and included hydrocephalus, apparent invasion of the adjacent brain and dura, and marked mass effect. The striking heterogeneity of the atypical teratoid/rhabdoid tumor shown by imaging studies reflects the histopathologic complexity of these tumors, and awareness of atypical teratoid/rhabdoid tumor is important in making the correct diagnosis of this uncommon but probably underdiagnosed entity.

Adolescent↗
PubMed2004

Fluid-attenuated inversion recovery MR imaging and subarachnoid hemorrhage: not a panacea.

BACKGROUND AND PURPOSE: Subarachnoid hemorrhage (SAH) constitutes an important neurologic emergency. Some authors have suggested that fluid-attenuated inversion recovery (FLAIR) MR imaging can detect SAH that may not be apparent on CT scans but may be revealed by lumbar puncture. We sought to determine how often FLAIR MR imaging findings are positive for SAH in cases with negative CT findings and positive lumbar puncture results. METHODS: The CT scans and FLAIR MR images of all patients with suspected SAH during a 3-year interval (2000-2002) were retrospectively reviewed by a blinded reader. Among these cases, we identified 12 with CT findings that were negative for SAH, lumbar puncture results that were positive for SAH, and FLAIR MR imaging findings that were available for review. Eleven of the 12 patients had undergone FLAIR MR imaging within 2 days of CT and lumbar puncture. The 12 patients with negative CT findings were comprised of six male and six female patients with an age range of 7 to 69 years. We evaluated the true and false negative and positive FLAIR MR imaging findings for SAH by using the lumbar puncture results as the gold standard. The FLAIR MR imaging findings of 12 additional patients without SAH (as revealed by lumbar puncture) were used as control data for a blinded reading. RESULTS: For all 12 control cases without SAH, the FLAIR MR imaging findings were interpreted correctly. Of the 12 cases that had positive lumbar puncture results but false-negative CT findings for SAH, FLAIR MR imaging findings were true-positive in only two cases and were false-negative in 10. One of the two true-positive cases had the highest concentration of RBC in the series (365 k/cc), and the other had the second highest value of RBC (65 k/cc). CONCLUSION: FLAIR MR imaging cannot replace lumbar puncture to detect the presence of SAH. FLAIR MR imaging findings are infrequently positive (16.7%) when CT findings are negative for SAH. This is likely because there is a minimum concentration of RBC/cc that must be exceeded for CSF to become hyperintense on FLAIR MR images.

Adolescent↗
PubMed2004

Assessment of the neuroradiology fellowship match: year 3.

BACKGROUND AND PURPOSE: When the fellowship match for trainees entering neuroradiology programs was first proposed in 2001, the program directors in neuroradiology agreed to a 3-year trial utilizing the National Residency Match Program (NRMP) for selecting fellows. A decision as to whether to continue with the neuroradiology fellowship match was to be assessed at the 3-year mark in 2004. METHODS: A Web survey designed through the offices of the ASNR was distributed to neuroradiology fellowship program directors after the results of the most recent fellowship match were tabulated in June 2003. The questionnaire included items about the current sentiment about the fellowship selection process. RESULTS: Most (52 of 61 = 85%) neuroradiology program directors favored continuing the match system for selecting fellows. Most believed that the match 1) had little impact on their success in recruiting fellows (43 of 62 = 69%), 2) was fairly administered (100%), and 3) was appropriately timed from February to June in the third year of residency (56 of 65 = 86%). The number of candidates entering the neuroradiology match increased from 71 in 2001 to 124 in 2003. CONCLUSION: Support for continuing a match system for selecting fellows remains high (85%) among neuroradiology program directors. The system is considered fair and does not harm many programs. The recruitment of fellows to neuroradiology via the match has increased over the 3 years of its existence.

Fellowships and Scholarships↗
PubMed2004

CT-guided aspirations in the head and neck: assessment of the first 216 cases.

BACKGROUND AND PURPOSE: The growth of cross-sectional imaging has increased the detection of nonpalpable head and neck masses. We sought to determine the reliability of CT-guided fine-needle aspiration (FNA) over 216 consecutive cases. METHODS: We retrospectively reviewed histopathologic findings and notes from 216 consecutive head and neck CT-guided FNA procedures performed between 1993 and 2003. Types of needles used, passes required, lesion location, initial cytologic diagnosis, and final histopathologic or clinical diagnosis were reviewed. RESULTS: Diagnostic samples were obtained in 195 (90.3%) of the lesions, with 21 (9.7%) inadequate samples. A correct diagnosis was made in 191 cases (88.4%). Final FNA diagnosis was discordant in four (1.9%) specimens, with the parapharyngeal space and parotid gland having the highest rate of inaccuracy. The range in number of passes required for final diagnosis was one to six (mode, 2.0 passes per specimen; median, 2.0; mean, 2.6; standard deviation, 1.13). In 135 (63%) of 216 cases, definitive surgical pathologic results, including findings for the four discordant specimens, were obtained. Of the nondiagnostic specimens, six (29%) of 21 went to surgery, five (83%) of six were neoplastic, and one (17%) of six was fibrous tissue. The remainder underwent clinical and imaging follow-up. CONCLUSION: CT-guided FNA is a safe, well tolerated, and accurate for the diagnosis of head and neck lesions. In our series, the percentage of diagnostic samples obtained improved compared with prior reports. The low diagnostic error rate overall was possibly related to onsite evaluation by the cytopathologist and to improved FNA technique.

Biopsy, Needle↗