Faculty Bibliography

Deep cerebral venous thrombosis is often a devastating condition associated with hemorrhagic infarction. We describe a patient who presented with acute micrographia and hypophonia as the sole manifestations of extensive deep venous sinus thrombosis

Synchronous gamma-band neural activity has been proposed as a mechanism for 'binding' sensory stimuli into unitary conscious representations. Previous auditory and somatosensory experiments indicate covariance between gamma-band activity and subjects' thresholds for identifying one vs two sensory stimuli. Using a 148-channel whole-head MEG system (4-D Neuroimaging), we investigated whether similar covariance between perceptual thresholds and gamma-band activity is evident when human subjects identify stimuli that separately activate cortical hemispheres. Subjects were stimulated with taps of 2 ms duration from 2 piezoelectric stimulators, each held between the thumb and index finger of each hand. Both hands were stimulated synchronously with one tap each, or the left hand tap preceded the right hand tap by 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, or 24 ms. After each trial, subjects indicated whether the taps overlapped in time (perceived as one event) or were consecutive (perceived as two events). Evoked magnetic responses were averaged, analyzed by FFT, Principal Component Analysis, and filtered in several frequency ranges (1-400, 15-100, and 20-50 Hz). Results indicate a psychophysical threshold of apprx12 ms. For stimuli perceived as simultaneous, a single 20-50 Hz response occurred in each hemisphere. For taps perceived as sequential, a second gamma-band response was most evident in the hemisphere contralateral to the first stimulus. This suggests that somatosensory stimuli are bound across cortical hemispheres with a time-course similar to that of stimuli bound within a hemisphere, thus supporting the hypothesis that gamma-band activity is a neurophysiological correlate of perceptual binding

BACKGROUND AND PURPOSE: Several issues regarding ethnic-cultural factors, sex-related variation, and risk factors for stroke have been described in the literature. However, there have been no prospective studies comparing ethnic differences and stroke subtypes between populations from South America and North America. It has been suggested that natives from Buenos Aires, Argentina, may have higher frequency of hemorrhagic strokes and penetrating artery disease than North American subjects. The aim of this study was to validate this hypothesis. METHODS: We studied the database of all consecutive acute stroke patients admitted to the Ramos Mejia Hospital (RMH) in Buenos Aires and to the Beth Israel Deaconess Medical Center (BIMC) in Boston, Massachusetts, from July 1997 to March 1999. Stroke subtypes were classified according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria. All information on patients (demographic, clinical, and radiographic) was recorded prospective to the assessment of the stroke subtype. RESULTS: Three hundred sixty-one and 479 stroke patients were included at RMH and BIMC stroke data banks, respectively. Coronary artery disease was significantly more frequent in BIMC (P:<0.001), whereas tobacco and alcohol intake were significantly more frequent in RMH (P:<0.001). Intracerebral hemorrhage (P:<0.001) and penetrating artery disease (P:<0.001) were significantly more frequent in the RMH registry, whereas large-artery disease (P:<0.02) and cardioembolism (P:<0.001) were more common in the BIMC data bank. CONCLUSIONS: Penetrating artery disease and intracerebral hemorrhage were the most frequent stroke subtypes in natives from Buenos Aires. Lacunar strokes and intracerebral hemorrhage were more frequent among Caucasians from Buenos Aires than Caucasians from Boston. Poor risk factor control and dietary habits could explain these differences