Faculty Bibliography

The cerebral hemisphere contralateral to the preferred hand is generally dominant for learned representational motor acts, including those involving buccofacial muscles. It is generally also language-dominant. This buccofacial apraxia has, with rare exceptions, been associated with left hemispheric lesions in right-handers. We describe two patients with severe buccofacial apraxia caused by large middle cerebral artery territory infarcts in the hemisphere ipsilateral to the preferred hand and nondominant for language. Neither patient had aphasia or major limb apraxia. Computed tomographic scans in the first patient and neuropathologic examination in the second failed to reveal an abnormality of the hemisphere contralateral to the preferred hand. Hence, in some individuals, the hemisphere controlling skilled representational buccofacial movements may not be the one that is dominant either for handedness or for language

To determine whether the left space that is neglected after right hemisphere lesions is body centered or environment centered, we asked patients with right hemisphere stroke and normal controls to report the contents of spatial arrays of objects or words, either while seated or while reclining on their side. The reclining posture eliminated the alignment of the vertical axis of the body with the vertical axis of the environment. Patients made fewer reports to the body left, but also fewer reports to the environment left, independent of body position. This suggest that a cerebral hemisphere directs attention not only relative to the body midline axis, but also relative to an environmental reference frame

Eighteen patients with right hemisphere strokes and 10 age-matched normal controls were tested for visuospatial abilities and for recall of brief narrative passages. Visuospatial and verbal abilities were evaluated using an objective scoring protocol that quantified accuracy in reproducing individual details, appreciation of structural relationships, and the appearance of unwarranted intrusions. The right hemisphere damaged group was found to be impaired on all measures of verbal recall. Across subjects these defects, particularly the inability to abstract information from the narrative passages, correlated with the degree of constructional apraxia. Analysis of CT scans failed to define a discrete region of the right hemisphere selectively associated with either the visuospatial or verbal defects, but indicated that both are exacerbated by the presence of premorbid brain atrophy

A right-handed woman developed left homonymous hemianopia and left hemianesthesia from infarction due to right posterior cerebral artery occlusion. Ataxia of the left arm and leg was severe and was not improved by vision. The patient often interpreted spontaneous movements of the left arm as alien in origin. The ataxia may have been caused by a combination of sensory ataxia, resulting from right thalamic infarction, and crossed-optic ataxia, resulting from posterior disconnection of the hemispheres due to right temporo-occipital infarction. This opticosensory ataxia was associated with a new form of 'alien hand' syndrome

We measured the severity of left spatial neglect in 29 patients, 2 to 4 weeks after right cerebral infarction. The severity of neglect increased with both the size of the lesion and the degree of premorbid diffuse cortical atrophy. Recovery over 3 to 5 months from an initially moderate to severe neglect was less complete in patients with cortical atrophy. The importance of lesion size shows that spared areas of the right hemisphere limit the severity and duration of left neglect. The importance of premorbid atrophy suggests that the integrity of the left hemisphere is also essential

We studied two patients with impaired visual perception and imagery caused by bilateral posterior cerebral lesions. The first had prosopagnosia and achromatopsia, and the imagery disorder involved the description of objects from memory, especially faces and animals, and colors of objects. The second had visual disorientation; the imagery problem involved the description of spatial relations from memory. Impairments of visual imagery, like disorders of visual perception, can be dissociated. Object and color imagery may be dissociated from imagery for spatial relations. A given imagery deficit tends to be associated with the corresponding type of perceptual deficit

Three-dimensional magnetic resonance imaging (MRI) was used to study various aphasia and neurobehavioral syndromes due to embolic or thrombotic cerebral infarction. Two patients are presented to illustrate how MRI may complement, and sometimes improve on, CT for the in vivo demonstration of anatomic changes underlying said syndromes. MRI images were reconstructed at planes selected to match CT, and at coronal planes through the entire anteroposterior extent of the lesions. Both CT and MRI detected lesions; however, MRI provided better differentiation of gray and white matter. Coronal reconstructions aid in optimally visualizing the relationship of lesions to the opercular and perisylvian gyri. CT may be inadequate to define actual extent of lesions, whereas MRI may more clearly show that apparently subcortical lesions can, in fact, involve the cortex as well