Biomedical subjects

Jonathan T Kleinman

Publications and source records attributed to Jonathan T Kleinman.

4 recordsLinked to original sources

PubMed2006

Right hemispatial neglect: frequency and characterization following acute left hemisphere stroke.

The frequency of various types of unilateral spatial neglect and associated areas of neural dysfunction after left hemisphere stroke are not well characterized. Unilateral spatial neglect (USN) in distinct spatial reference frames have been identified after acute right, but not left hemisphere stroke. We studied 47 consecutive right handed patients within 48h of left hemisphere stroke to determine the frequency and distribution of types of right USN using cognitive testing and MRI imaging. The distribution of USN types was different from the previously reported distribution following acute right hemisphere stroke. In this left hemisphere stroke population, allocentric neglect was more frequent than egocentric neglect.

Adult↗

PubMed2006

Restoring cerebral blood flow reveals neural regions critical for naming.

We identified areas of the brain that are critical for naming pictures of objects, using a new methodology for testing which components of a network of brain regions are essential for that task. We identified areas of hypoperfusion and structural damage with magnetic resonance perfusion- and diffusion-weighted imaging immediately after stroke in 87 individuals with impaired picture naming. These individuals were reimaged after 3-5 d, after a subset of patients underwent intervention to restore normal blood flow, to determine areas of the brain that had reperfused. We identified brain regions in which reperfusion was associated with improvement in picture naming. Restored blood flow to left posterior middle temporal/fusiform gyrus, Broca's area, and/or Wernicke's area accounted for most acute improvement after stroke. Results show that identifying areas of reperfusion that are associated with acute improvement of a function can reveal the brain regions essential for that function.

Aphasia, Broca↗

PubMed2006

Patients with diffusion-perfusion mismatch on magnetic resonance imaging 48 hours or more after stroke symptom onset: clinical and imaging features.

BACKGROUND: Abnormalities in diffusion-weighted (DWI) and perfusion-weighted (PWI) magnetic resonance imaging (MRI) are thought to reflect the presence of brain tissue at risk for ischemic stroke. Many patients with acute ischemic stroke have a mismatch pattern in which the PWI volume is larger than the DWI lesion. This mismatch typically resolves over 24-48 hours. Little is known about the presence of DWI-PWI mismatch in later stages of stroke. METHODS: This is a retrospective study of 122 patients admitted with a diagnosis of acute ischemic stroke who had DWI and PWI abnormalities on studies performed within 7 days of onset of symptoms. Patients were divided into two groups: those with MRI performed <48 hours and those with MRI performed >or=48 hours from onset of symptoms. RESULTS: Among 42 patients with MRI performed >or=48 hours after onset of stroke symptoms, 15 of 42 (36%) showed a mismatch pattern, compared to 45 of 80 (56%) in the <48 hours group (P < 0.05). Most of the patients in the >or=48 hours group with mismatch had large artery occlusive disease and many had neurological fluctuations. A subset of these patients were treated with induced hypertension and showed clinical improvement. CONCLUSIONS: Some patients have persistent DWI-PWI mismatch up to several days after stroke onset. Further studies are needed to determine if these patients should be candidates for reperfusion therapy.

Brain↗

PubMed2006

Neural correlates of modality-specific spatial extinction.

Sites of lesions responsible for visual, tactile, and/or motor extinction have not been clearly identified. We sought to determine the frequency of extinction in various modalities immediately after acute ischemic stroke, the rate of co-occurrence of extinction across modalities, and areas of infarct and/or hypoperfusion associated with each modality of extinction. A total of 148 patients with right supratentorial stroke were studied. In Study 1, 88 patients without hemiplegia, hemianesthesia, or visual field cuts were tested within 24 hours of onset for visual, tactile, and motor extinction, and underwent magnetic resonance diffusion and perfusion imaging. Associations between modality of extinction and areas of neural dysfunction (hypoperfusion/infarct) were identified. Of the 88 patients, 19 had only tactile extinction, 8 had only visual extinction, 12 had only motor extinction, 14 had extinction in two or more modalities, and 35 had no extinction. Tactile extinction was associated with neural dysfunction in the inferior parietal lobule; visual extinction was associated with dysfunction in the visual association cortex; and motor extinction was associated with neural dysfunction in the superior temporal gyrus. In Study 2, data from 60 patients who were excluded from Study 1 because of motor deficits were analyzed in the same way to determine whether frontal lesions contributed to visual or tactile extinction. Results again demonstrated that tactile extinction is associated with inferior parietal dysfunction, and visual extinction is associated with dysfunction of the visual association cortex. Potential accounts of the results, based on the "hemisphere rivalry" model of extinction and the limited attentional capacity model, are considered.

Aged↗