John C. Adair

Right-left confusion in Gerstmann's syndrome: a model of body centered spatial orientation.

Gerstmanns syndrome encompasses the tetrad of finger agnosia, agraphia, acalculia and right-left confusion and is associated with lesions of the dominant angular gyrus. The localizing value of this syndrome has been questioned because multiple mechanisms can account for each of the components of the syndrome. We present the case of a man who developed Gerstmanns syndrome following a focal infarct of the left angular gyrus. The patients right-left confusion could not be accounted for by either an aphasia or a degraded body schema. A series of experiments that investigated the patients spatial mapping system by progressively restricting the degrees of freedom for spatial rotation revealed an isolated defect in deriving the relative position of an object along the horizontal axis. Defective horizontal mapping can account for the other components of Gerstmanns syndrome because they all share a common dependency on relative horizontal positioning.

Adynamic Aphasia: A Transcortical Motor Aphasia with Defective Semantic Strategy Formation

Adynamic aphasia is a form of transcortical motor aphasia characterized by sparse but otherwise normal spontaneous speech that may improve when concepts are introduced by external stimuli. Akinesia, impaired concept formation, inertia of concept generation, a defective semantic network, damage or impaired access to the verbal output lexicon, and defective semantic strategy formation have been proposed to account for this disorder. We studied a patient with adynamic aphasia and frontal lobe systems dysfunction due to bilateral striatocapsular infarctions. The patient was not akinetic but did demonstrate inertia of concept generation that could be overcome with prompting. However, prompting did not improve the number of concepts generated. He demonstrated a generally intact verbal lexicon and semantic network and normal lexical priming. However, his ability to sort closely related items into different classes without prior cuing regarding the nature of the classes was defective. Although his verbal memory was normal, he appeared to use a serial rather than a semantic strategy to recall items. Finally, despite normal lexical priming, he was impaired on a letter fluency task. These results most clearly demonstrate a defect in semantic strategy formation but indicate an additional and possibly related deficit in concept formation and a partial deficit in lexical strategy formation. All of these deficits appear to reflect impairment in the hierarchical organization of knowledge specific to the task at hand. This appears to be a key component of executive functions supported by frontal lobe systems.

Object and Action Naming in Alzheimer's Disease

We administered measures of object naming and action naming to matched groups of ten patients with Alzheimers disease (AD) and ten normal control subjects. AD patients were impaired in both object and action naming, with object naming impaired to a significantly greater extent than action naming. This difference remained after controlling for the effects of word frequency. We propose that the pattern of pathological changes in AD impairs both conceptual and lexical retrieval systems for objects but only conceptual systems for actions. The similar patterns of error during the two tasks suggest quantitative rather than qualitative differences in the breakdown of the two abilities.

Physostigmine pharmacotherapy for anomia

Abstract Cholinergic neurons may influence the neural networks that subserve language. To learn if chollnergic drugs enhance the ability of anomic aphasic patients to name objects, we conducted studies of physostigmine and lecithin in three patients with anomia due to focal brain lesions. The flrst patient studied was amnestic and anomic, and presumed to be cholinergic-deficient due to a basal forebrain lesion. In open and blinded trials confrontation naming improved consistently with treatment but other cognitive measures did not. We subsequently tested two additional anomic patients with lesions outside the basal forebrain. We found improvement in confrontation naming but not other measures of cognition or mood during open-label physostigmine treatment. Physostigmine appears to improve naming in patients with anomia.

Meperidine Neurotoxicity After Organ Transplantation

Meperidine neurotoxicity, characterized by recurrent convulsions, myoclonus, and asterixis, was diagnosed in an organ transplant recipient. Aside from cyclosporine toxicity, the literature regarding neurologic complications of transplantation contains limited reference to the neurotoxicity of therapy. The case reported illustrates how pharmacokinetic factors might render transplant patients particularly vulnerable to the neurotoxic side effects of certain medications, such as meperidine.

Rapidly Progressive Dementia: A Clinicopathologic Correlation

We evaluated a 66-year-old man with a rapidly progressive, akinetic-rigid dementia syndrome. Despite extensive testing, which included magnetic resonance imaging (MRI), we were unable to make the correct antemortem diagnosis. Autopsy demonstrated spontaneous progressive multifocal leukoencephalopathy. This report illustrates that even in the absence of characteristic MRI findings, this uncommon cause of dementia should be considered in the differential diagnosis of rapidly progressive, akinetic-rigid syndromes with dementia.