Disrupted temporal lobe connections in semantic dementia. (1/70)

Semantic dementia refers to the variant of frontotemporal dementia in which there is progressive semantic deterioration and anomia in the face of relative preservation of other language and cognitive functions. Structural imaging and SPECT studies of such patients have suggested that the site of damage, and by inference the region critical to semantic processing, is the anterolateral temporal lobe, especially on the left. Recent functional imaging studies of normal participants have revealed a network of areas involved in semantic tasks. The present study used PET to examine the consequences of focal damage to the anterolateral temporal cortex for the operation of this semantic network. We measured PET activation associated with a semantic decision task relative to a visual decision task in four patients with semantic dementia compared with six age-matched normal controls. Normals activated a network of regions consistent with previous studies. The patients activated some areas consistently with the normals, including some regions of significant atrophy, but showed substantially reduced activity particularly in the left posterior inferior temporal gyrus (iTG) (Brodmann area 37/19). Voxel-based morphometry, used to identify the regions of structural deficit, revealed significant anterolateral temporal atrophy (especially on the left), but no significant structural damage to the posterior inferior temporal lobe. Other evidence suggests that the left posterior iTG is critically involved in lexical-phonological retrieval: the lack of activation here is consistent with the observation that these patients are all anomic. We conclude that changes in activity in regions distant from the patients' structural damage support the argument that their prominent anomia is due to disrupted temporal lobe connections.  (+info)

Pure anomic aphasia caused by a subcortical hemorrhage in the left temporo-parieto-occipital lobe. (2/70)

There have been few case reports of pure anomic aphasia and the underlying mechanism remains to be clarified. We report a patient in whom pure anomic aphasia was caused by subcortical hemorrhage in the left temporo-parieto-occipital lobe. Based on magnetic resonance images and cerebral blood flow imaging, the structural lesion underlying the pure anomic aphasia was thought to be located at the left temporo-occipital junction.  (+info)

Frontotemporal decreases in rCBF correlate with degree of dysnomia in primary progressive aphasia. (3/70)

Primary progressive aphasia (PPA) is an uncommon degenerative dementia characterized by gradual impairment of language function with initial sparing of the memory domain. Using semiquantitative 99mTc-hexamethyl propyleneamine oxime (HMPAO) brain SPECT as a measure of regional cerebral blood flow (rCBF), we investigated the relationship between reduced 99mTc-HMPAO uptake and the severity of dysnomia in PPA. METHODS: Seven right-handed patients with PPA had their dysnomia assessed by the Boston Naming Test (BNT), a subtest of the Boston Diagnostic Aphasia Examination. Neuroimaging studies, including 99mTc-HMPAO brain SPECT, CT, and MRI, were performed. Correlational analysis between reduced rCBF and BNT was performed. RESULTS: Brain SPECT showed a reduction in 99mTc-HMPAO uptake involving the frontal and temporal lobes in all 7 patients. CT and MRI showed mild to moderate cerebral atrophy in 4 patients. Low scores on the BNT correlated with low frontotemporal 99mTc-HMPAO (Spearman r = 0.97, P = 0.004) in the 5 patients with left-hemisphere involvement. CONCLUSION: Decreased rCBF to the frontotemporal region characterized the cerebral abnormalities associated with PPA. The finding of focal rCBF abnormalities in the right hemisphere of 2 right-handed women corroborates that PPA symptoms may arise from a "non-left-dominant"-hemisphere degenerative process. Our results support the usefulness of rCBF SPECT imaging as a diagnostic aid in PPA.  (+info)

Identification without naming: a functional neuroimaging study of an anomic patient. (4/70)

The neural correlates of identification and name retrieval have proved difficult to characterise because both occur highly automatically in normal language processing. Thus, although some evidence points to the left anterior temporal cortex (ATC) as a brain region underlying these functions, its relative role in semantic and lexical retrieval processes is still a matter of debate. Positron emission tomography (PET) was used to measure regional cerebral blood flow responses to famous and non-famous visually presented faces and buildings in a severely anomic patient and in six control subjects, while they were performing a same-different matching task. Because the patient was able to identify the stimuli that he could not name, it was possible to investigate whether the left ATC would respond when identification occurred without name retrieval. Both the patient and the controls activated the left ATC when famous stimuli were compared with non-famous stimuli. This result supports the hypothesis of a predominantly semantic function of the left ATC.  (+info)

The Gerstmann syndrome in Alzheimer's disease. (5/70)

BACKGROUND: It remains unclear from lesion studies whether the four signs of the Gerstmann syndrome (finger agnosia, acalculia, agraphia, and right-left confusion) cluster because the neuronal nets that mediate these activities have anatomical proximity, or because these four functions share a common network. If there is a common network, with degeneration, as may occur in Alzheimer's disease, each of the signs associated with Gerstmann's syndrome should correlate with the other three signs more closely than they correlate with other cognitive deficits. METHODS: Thirty eight patients with probable Alzheimer's disease were included in a retrospective analysis of neuropsychological functions. RESULTS: The four Gerstmann's syndrome signs did not cluster together. Finger naming and calculations were not significantly correlated. Right-left knowledge and calculations also did not correlate. CONCLUSIONS: The four cognitive functions impaired in Gerstmann's syndrome do not share a common neuronal network, and their co-occurrence with dominant parietal lobe injuries may be related to the anatomical proximity of the different networks mediating these functions.  (+info)

Development of selective verbal memory impairment secondary to a left thalamic infarct: a longitudinal case study. (6/70)

A 68 year old man suffered an acute dysphasic episode with persistent memory disturbance while taking part as a control in a longitudinal magnetic resonance imaging (MRI) study. A small new left thalamic infarct involving the mamillo-thalamic tract could be demonstrated on volumetric MRI, coinciding with the development of a selective verbal memory impairment. This suggests that lateralisation of cognitive processing of visual and verbal material exists at the thalamic as well as the cortical level. High resolution volumetric MRI may be helpful in demonstrating small subcortical infarcts that may not be seen using computed tomography or conventional MRI.  (+info)

Subcortical pathways serving cortical language sites: initial experience with diffusion tensor imaging fiber tracking combined with intraoperative language mapping. (7/70)

The combination of mapping functional cortical neurons by intraoperative cortical stimulation and axonal architecture by diffusion tensor MRI fiber tracking can be used to delineate the pathways between functional regions. In this study the authors investigated the feasibility of combining these techniques to yield connectivity associated with motor speech and naming. Diffusion tensor MRI fiber tracking provides maps of axonal bundles and was combined with intraoperative mapping of eloquent cortex for a patient undergoing brain tumor surgery. Tracks from eight stimulated sites in the inferior frontal cortex including mouth motor, speech arrest, and anomia were generated from the diffusion tensor MRI data. The regions connected by the fiber tracking were compared to foci from previous functional imaging reports on language tasks. Connections were found between speech arrest, mouth motor, and anomia sites and the SMA proper and cerebral peduncle. The speech arrest and a mouth motor site were also seen to connect to the putamen via the external capsule. This is the first demonstration of delineation of subcortical pathways using diffusion tensor MRI fiber tracking with intraoperative cortical stimulation. The combined techniques may provide improved preservation of eloquent regions during neurological surgery, and may provide access to direct connectivity information between functional regions of the brain.  (+info)

Viscosity and social cohesion in temporal lobe epilepsy. (8/70)

Clinical case reports suggest that viscosity, the behavioural tendency to talk repetitively and circumstantially about a restricted range of topics, is common in patients with temporal lobe epilepsy (TLE). Such patients are also reported to exhibit heightened levels of social cohesion, the tendency to become interpersonally "clingy". This "sticky" interpersonal style may be particularly common in TLE patients with a left sided temporal lobe seizure focus. To test this hypothesis, self-report and observer rating scales were developed to assess both viscosity and social cohesion. Subjects consisted of patients with right, left, or bilateral temporal lobe seizure foci, absence or primary generalised tonic-clonic seizures, psychiatric controls (panic disorder patients), and normal controls. Elevations on the viscosity scale were observed primarily in TLE patients with left or bilateral seizure foci. Viscosity scores also correlated with seizure duration and left handedness. No group differences were observed on the social cohesion scale. These findings are consistent with the hypothesis that viscosity results from subtle interictal language disturbances, although other pathogenetic mechanisms are discussed.  (+info)

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