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Biomedical subjects

L M Brass

Publications and source records attributed to L M Brass.

At least 19 recordsLinked to original sources
PubMed1992

New anatomical and functional imaging methods.

Powerful new methods for imaging both brain anatomy and brain function are appearing at an increasing rate. The modern era of minimally invasive, highly informative, neurological diagnostic imaging methods began with the introduction of x-ray computed tomography in the 1970s. More recently, positron emission tomography and single-photon emission computed tomography have been used extensively in research on normal and pathological brain function, and they are finding specific medical applications. Nuclear magnetic resonance methods are in widespread use for neurological diagnosis only a decade after they became available. Rapid development of new techniques based on the same principles, and implementable on clinical instruments with relatively minor modifications, will expand the range of nuclear magnetic resonance measurement capabilities considerably in the near future. These technological innovations and others yet to come have major implications for the practice of neurology. The most important one is an increase in relative value among clinical diagnostic skills of history taking and mental status examination, which will remain largely beyond the reach of technology.

Brain↗
PubMed1992

A study of twins and stroke.

BACKGROUND AND PURPOSE: Although there are strong genetic contributions to coronary artery disease, only a few studies have considered heritable influences on stroke. METHODS: We investigated the role of genetic factors in stroke using the Twin Registry maintained by the National Academy of Sciences-National Research Council. The registry includes 15,948 male twin pairs born between 1917 and 1927. In 1985, 9,475 twins responded to a mailed questionnaire, which covered vascular risk factors, cardiac events, and stroke. RESULTS: Analysis of twin pairs in which both responded to the questionnaire, and a question on stroke, indicated proband concordance rates of 17.7% for monozygotic pairs and 3.6% for dizygotic pairs (relative risk = 4.3; chi 2 = 4.94, df = 1; p less than 0.05). CONCLUSIONS: This nearly fivefold increase in the prevalence of stroke among the monozygotic compared with the dizygotic twin pairs suggests that genetic factors are involved in the etiology of stroke. The twin study paradigm holds considerable promise for identifying both genetic and environmental influences on stroke.

Cerebrovascular Disorders↗
PubMed1992

Proton magnetic resonance spectroscopy of cerebral lactate and other metabolites in stroke patients.

BACKGROUND AND PURPOSE: Proton magnetic resonance spectroscopy can measure in vivo brain lactate and other metabolites noninvasively. We measured the biochemical changes accompanying stroke in 16 human subjects with cortical or deep cerebral infarcts within the first 3 weeks after symptom onset, and performed follow-up studies on six. METHODS: One-dimensional proton spectroscopic imaging encompassing the infarct region was performed with a 2.1-T whole-body magnet using the stimulated echo pulse sequence and an echo time of 270 msec. RESULTS: All but one of the cortical stroke patients had increased lactate within or near the infarct. Persistently elevated cerebral lactate was documented in five of six cases studied serially as long as 251 days after infarction. N-acetylaspartate levels were decreased in most cortical strokes. Elevated lactate, accompanied by minimal reduction in N-acetylaspartate, was recorded in two of four patients in the first week following a small subcortical infarct. CONCLUSIONS: Long-term elevation of lactate commonly occurs after stroke. This lactate may arise from ongoing ischemia or infiltrating leukocytes, or it may be a residual of the lactate formed during the initial insult. The ability to observe stroke-elevated lactate pools at any time after lesion onset provides an approach to distinguishing among these possibilities in the future.

Aspartic Acid↗
PubMed1992

Spectroscopic imaging of stroke in humans: histopathology correlates of spectral changes.

Previous studies of human stroke by 1H nuclear magnetic resonance spectroscopy have shown elevation of lactate lasting 3 to 6 months. Complete metabolic turnover of the elevated lactate pool has been demonstrated 5 weeks after a stroke. Its cellular localization is among the first questions requiring clarification. Information pertinent to this question came to us from a patient with a 2-week-old stroke by 1H nuclear magnetic resonance spectroscopic imaging 1 week before his death led to neuropathologic examination of the brain. 1H spectra from voxels including the infarcts showed increased lactate and decreased N-acetylaspartate. Histopathology showed sheets of foamy macrophages in the infarct, but few neurons. Macrophage density ranged from 196 cells/mm2 near the surface of the infarct to 788 near its medial margin. Glial density was 500 to 800 cells/mm2. Lactate concentration in voxels including portions of the infarct was estimated at 7 to 14 mM. Voxels showing low N-acetylaspartate and high lactate on spectroscopic imaging were associated with histopathologic sections containing foamy macrophages. Brain macrophages--which begin to appear 3 days after infarction and gradually disappear over several months--could be a major source of elevated lactate signals that persist for months after stroke.

Brain↗
PubMed1992

Transient ischemic attacks in the elderly: diagnosis and treatment.

Transient ischemic attacks (TIAs) are the most reliable warning sign of impending stroke and are highly indicative of significant coronary artery disease. The history and physical examination may suggest the pathologic mechanism, an important clue to diagnosis and prognosis. Diagnostic testing is individualized but often includes ECG and cerebral contrast angiography. Exercise testing, echocardiography, ultrasound, CT, and/or MRI are sometimes indicated. The patient with recent TIAs may be hospitalized for acute management. Long-term treatment includes stroke risk factor modification, use of antiplatelet agents, and sometimes anticoagulant therapy. Selected older patients may be candidates for carotid endarterectomy.

Aged↗
PubMed1991

A prognostic system for transient ischemia or minor stroke.

OBJECTIVE: To build a prognostic system for patients with carotid transient ischemic attack or minor stroke. DESIGN: Inception cohort study with 2-year follow-up. SETTING: Urban community teaching hospital. PATIENTS: Eligible patients (n = 142), identified on a carotid ultrasound roster, had been hospitalized between 1984 and 1987 within 30 days of a first carotid transient ischemic attack or minor stroke. MEASUREMENTS: Stroke or death within 2 years. MAIN RESULTS: Three factors were associated with stroke or death: age of more than 65 years, diabetes, and hypertension. Based on regression coefficients, age of more than 65 years was assigned 3 points; diabetes, 3 points; and hypertension, 2 points. An initial prognostic system comprised risk groups 1 (0 points), 2 (1 to 5 points), and 3 (6 to 8 points). Outcome rates in the three groups were 2%, 31%, and 54% (P less than 0.0001), respectively. In an independent test sample, the corresponding outcome rates for the initial system were 12%, 21%, and 31% (P = 0.04). A final prognostic system, including two additional predictors (coronary heart disease [1 point] and the distinction between stroke and transient ischemic attack for the baseline event [2 points]), comprised risk groups 1 (0 to 2 points), 2 (3 to 6 points), and 3 (7 to 11 points). Corresponding outcome rates were 3%, 27%, and 48% (P less than 0.001) in the original cohort and 10%, 21%, and 59% (P less than 0.001) in the test cohort. CONCLUSION: For selected patients with carotid transient ischemia or minor stroke, five clinical features can be combined to stratify effectively the risk for a subsequent stroke or death.

Aged↗
PubMed1991

Localized proton NMR observation of [3-13C]lactate in stroke after [1-13C]glucose infusion.

To assess whether elevated lactate in stable stroke is being actively produced from blood glucose localized 1H NMR stimulated echo spectra were obtained from a patient in the region of a 32-day-old cortical infarct before and 60-100 min after infusion of [1-13C]glucose. Prior to the infusion the spectrum from the region of the infarct contained an elevated resonance from C3 lactate and a greatly reduced resonance from N-acetyl groups relative to an unaffected contralateral region. After the infusion two additional resonances were observed at 62 and -64 Hz relative to the unlabeled resonance of C3 lactate which were assigned on the basis of chemical shift and relative intensity to [3-13C]lactate. The [3-13C]lactate fractional enrichment in the infarct region was measured to be 32% which is within error one-half the average [1-13C]plasma glucose enrichment during the postinfusion NMR measurement. The result suggests that the stroke lactate pool was completely derived from infused glucose.

Blood Glucose↗
PubMed1991

Lhermitte's sign in a patient with herpes zoster.

A 34-year-old, previously healthy man developed herpes zoster (shingles) involving the C4 dermatome. This was accompanied by Lhermitte's sign, i.e. an electric shock-like sensation radiating from the neck to the sacrum, elicited by flexion of the neck. Lhermitte's sign resolved in this patient after several days, and probably reflected acute inflammation together with changes in sensory axon excitability. This positive manifestation of dorsal column dysfunction can be present in the absence of fixed neurological deficits, and can reflect dorsal column dysfunction caused by a wide spectrum (demyelinating, traumatic, compressive, toxic/deficiency, infectious and inflammatory) of etiologies.

Adult↗
PubMed1991

Middle cerebral artery blood velocity and cerebral blood flow in sickle cell disease.

To understand better the relationship between blood velocity measured by transcranial Doppler and cerebral blood flow measured by the 133Xe inhalation method, we examined 23 patients undergoing evaluation in the Comprehensive Sickle Cell Center at Columbia University. Blood velocity in the middle cerebral artery was directly related to cerebral flow (r = 0.77; p less than 0.05). A multivariate analysis in this sample made it possible to improve this correlation to account for more than 90% of the variability in cerebral blood flow by the use of transcranial Doppler measures of velocity and pulsatility along with the patient's age and hematocrit (r = 0.95; p less than 0.001). It is likely that the combination of Doppler and clinical or demographic variables in other diseases will similarly improve the quantitative estimation of cerebral blood flow.

Adolescent↗
PubMed1991

Family history in patients with transient ischemic attacks.

To determine the influence of family history on vascular disease, we surveyed hospital patients discharged with a diagnosis of transient ischemic attack. Of 117 respondents, 81 knew their family history for myocardial infarction and 81 knew their family history for stroke. Of 83 responding 43 reported a personal history of myocardial infarction, and of 85 responding 66 reported a personal history of stroke. As expected, there was an association between positive family and personal histories of myocardial infarction in younger (aged less than 70 years) patients (Fisher's two-tailed exact test, p = 0.014). This association was reversed for stroke (Fisher's two-tailed exact test, p = 0.017). Older (aged greater than or equal to 70 years) patients had a stronger association between positive family and personal histories of stroke; 14 (74%) of 19 older patients with a positive personal history of stroke had a positive family history of stroke. The reason for this reversal in the relation between family and personal histories of stroke compared with myocardial infarction may relate to the older age at onset of most strokes, differing stroke subtypes in older age groups, or lower rates of fatal myocardial infarction. This study suggests that familial factors may be important in some subtypes of cerebrovascular disease. Familial effects may be different in vascular diseases of the heart and brain.

Adolescent↗
PubMed1991

A methodological appraisal of research on prognosis after transient ischemic attacks.

We analyzed existing research on the prognosis of patients who have had a transient ischemic attack to identify studies that adhere to basic methodological principles and to identify underinvestigated questions. Studies were eligible for analysis if they were published in peer-reviewed journals after 1950, written in English, and included at least 50 patients with transient ischemia. Studies that included patients with stroke were included only if they reported outcome rates separately for the subgroup of patients with transient ischemia. All eligible studies were extracted by one investigator who recorded adherence to six key methodological principles. Among 60 eligible studies, 54 were observational cohort studies and six were randomized trials. Adherence to the six methodological principles was as follows: eight studies included an adequate description of diagnostic criteria and of procedures used to assure adherence to the criteria, 54 used appropriate end points, two assembled inception cohorts, 10 included an adequate description of end point surveillance, 22 adequately reported and analyzed censored patients, and 10 included a multivariate analysis for predictive variables. No study adhered to all six principles, but two adhered to the three most important ones (appropriate end points, inception cohort, and adequate reporting and analysis of censored patients). Aspects of prognosis after transient ischemia that have not been completely investigated include the severity of subsequent strokes and methods for estimating the outcome risk for individual patients. We conclude that only a few published investigations on prognosis after transient ischemia are methodologically complete. This finding helps explain why it is difficult to interpret many studies. Further research is needed and should target underinvestigated topics.

Cohort Studies↗
PubMed1991

A comparative study of the cerebrovascular complications of cocaine: alkaloidal versus hydrochloride--a review.

Cocaine, especially in its alkaloidal or "crack" form, has been increasingly associated with cerebrovascular disease. Before the crack epidemic, cocaine hydrochloride (HCl) was also implicated as a cause of stroke. However, less is known about the differences in stroke subtypes, age at stroke onset, or presence of underlying structural cerebrovascular disease with different forms of cocaine use. We compared 26 patients (previously reported) from our four institutions plus 16 cases reported in the literature of stroke associated with alkaloidal cocaine to 63 (57 reported in the literature and six not previously reported from our four institutions) cases of stroke associated with cocaine HCl. Ischemic and hemorrhagic strokes are equally likely after alkaloidal cocaine use, whereas cocaine HCl is more likely (approximately 80% of the time) to cause hemorrhagic stroke, with approximately half the intracranial hemorrhages occurring from ruptured cerebral saccular aneurysms or vascular malformations. The presence of an underlying cerebral aneurysm was more common among patients with cocaine HCl-associated strokes than alkaloidal cocaine-associated strokes. Cerebral infarction was significantly more common among the alkaloidal cocaine users than in all the cocaine HCl users, and this was also true when alkaloidal cocaine users were compared with parenteral cocaine HCl (intravenous and intramuscular) users. Only hemorrhagic stroke has been reported with intravenous cocaine HCl use. We conclude that the pathogenesis of cocaine-related stroke is heterogeneous, and depends, in part, on the form of cocaine used.

Administration, Intranasal↗
PubMed1990

Cerebrovascular complications of the use of the "crack" form of alkaloidal cocaine.

BACKGROUND AND METHODS: The use of cocaine, especially one of its alkaloidal forms ("crack"), has been increasingly associated with cerebrovascular disease. To clarify the clinical, radiologic, and pathological features of the events associated with cocaine use, we identified 28 patients at four medical centers who had stroke temporally related to the use of alkaloidal cocaine (during or within 72 hours of use). RESULTS: The 28 patients had the following types of cerebrovascular event: cerebral infarction (n = 18 [2 hemorrhagic; 1 fatal]) in the areas supplied by the middle cerebral artery (n = 10), anterior cerebral artery (n = 3), posterior cerebral artery (n = 1), and vertebrobasilar arteries (n = 4); subarachnoid hemorrhage (n = 5); intraparenchymal hemorrhage (n = 4); and primary intraventricular hemorrhage (n = 1). Eighteen patients (64 percent) had acute neurologic symptoms immediately or within one hour of using cocaine. Fifteen patients (45 percent) with either occlusive or hemorrhagic strokes had sever headache as an early symptom. Vasculitis was not suggested by radiography in any patient, nor was it identified on pathological examination in one patient who died. All the patients were young (mean age, 34 years; range, 23 to 49) and had no other apparent, direct cause of stroke. Other risk factors for stroke among the patients included mild mitral-valve prolapse (n = 4), hypertension (n = 4), cigarette smoking (n = 8), and regular alcohol use (n = 6). CONCLUSIONS: There is a strong temporal association of the use of alkaloidal cocaine with both ischemic and hemorrhagic cerebrovascular events. Cocaine-related stroke probably has many causes. A thorough history focusing on the use of cocaine and toxicologic screening of urine and serum should be part of the evaluation of any young patient with a stroke.

Adult↗
PubMed1990

Emotional facial paresis with striatocapsular infarction.

Emotional facial paresis (EFP) refers to hemifacial paresis of emotionally evoked or spontaneous smiling or weeping with preserved volitional movements of the face. The anatomical location for this phenomenon has been controversial. We report a 15-year-old boy with EFP. Follow-up MRI demonstrated infarction limited to the head of the caudate, putamen and anterior limb of the internal capsule on the contralateral side. This case lends support for selective damage at a striatal or capsular site in the production of EFP.

Adolescent↗
PubMed1990

Reversed intracranial blood flow in patients with an intra-aortic balloon pump.

As a preliminary investigation into the cerebral effects of mechanical cardiac assist devices, using transcranial Doppler ultrasonography I examined the basal cerebral arteries in three patients placed on an intra-aortic balloon pump. Unassisted systoles had normal blood velocities and waveforms. When the pump was in use, diastolic blood velocity during balloon inflation increased. As the balloon was deflated and intra-aortic pressure was dramatically lowered, diastolic blood velocity within the intracranial vessels decreased sharply. In two patients there was a reversal of blood flow in the middle cerebral, anterior cerebral, basilar, and vertebral arteries during late diastole. Although the clinical effects of cessation and reversal of blood flow in the cerebral circulation while on an intra-aortic balloon pump remain to be determined, transcranial Doppler ultrasonography appears to be a useful tool for measuring these hemodynamic effects. It may also be helpful in quantifying the effects of such pumps on cerebral blood flow and devising inflation/deflation timing sequences that maximize forward blood flow.

Arteries↗