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Arch Neurol. 2002;59:907-908.

Reasoning
Shuren and Grafman (SEE ARTICLE) provide a thoughtful review of our current understanding of the cognitive basis of reasoning. Clearly, a better understanding of the basic mechanisms and subprocesses of reasoning should make it possible to evaluate reasoning abilities in different neurologic disorders.

Human Immunodeficiency Virus RNA Levels and Thinking
Ellis and colleagues (SEE ARTICLE) find that elevated human immunodeficiency virus (HIV) RNA levels in cerebrospinal fluid (CSF) (>200 copies/mL) predict subsequent progression to cognitive impairment. Monitoring CSF viral load and therapy to reduce HIV RNA levels in CSF may be of clinical value. Editorial comment is provided by Kenneth L. Tyler, MD, and Justin C. McArthur, MBBS, MPH. (SEE ARTICLE)

Is There an Active Infection by Human Herpesvirus 6 in Multiple Sclerosis?
Álvarez-Lafuente and colleagues (SEE ARTICLE) present persuasive data in support of the view that there is a an active human herpesvirus 6 variant A infection in a statistically significant number of patients with multiple sclerosis. The significance of this finding and its pathogenic significance are reviewed.

Table 2. HHV-6 DNA Prevalence in Serum*

Tau and Frontotemporal Dementia Revisited
Verpillat et al, (SEE ARTICLE) in their study of the largest series of patients with frontotemporal dementia (FTD), found that tau plays a primary role in the cause of this disorder. Further, their observations establish that the H1 haplotype of the tau gene and the 2 allele of apolipoprotein interact and increase the risk of FTD. These findings provide important new data to better understand the pathogenesis of this emerging, important class of the dementias.

Tau Gene Mutation and Pallidopontonigral Disease
Tsuboi and colleagues (SEE ARTICLE) report a missense mutation in exon 10 of the tau gene in an American and a French family. Affected members in both families had more clinical similarities than differences. The mutation described in these 2 families seems to have independent origins. Thus, this study is a unique genealogical and molecular genetic analysis.

Metabolic Changes in Alzheimer Disease
Chantal et al, (SEE ARTICLE) using magnetic resonance spectroscopy (MRS), have correlated regional cerebral metabolic alterations and neuropsychological dysfunctions in patients with early Alzheimer disease. A significant reduction of N-acetylaspartate/H₂O in the left medial temporal lobes correlated with a loss of verbal memory, among other findings. These MRS findings are a useful means of following the natural history of disease and provide a noninvasive means of quantitating change.

Familial Parkinson Disease in Spain
Hoenicka and colleagues (SEE ARTICLE) have searched for mutations in Park1 and Park5 genes and for new or described mutations in the Park2 gene in families with Parkinson disease in Spain. Six different mutations in the Park2 gene in 5 of the families with recessive inheritance are described, and 2 of these mutations, V56E and C212Y, have not been previously reported. The authors' observations provide important new phenotype/genotype correlations.

Oxidative Stress in Mild Cognitive Impairment
Praticò and colleagues (SEE ARTICLE) have studied levels of isoprostane, a specific marker of in vivo lipid peroxidation, in patients with mild cognitive impairment (MCI). Significantly higher levels of isoprostane in cerebrospinal fluid, plasma, and urine were found in patients with MCI compared with cognitively normal elderly subjects. Elevated levels of isoprostane may identify a subgroup of patients with MCI with increased lipid peroxidation, who are at increased risk for developing Alzheimer disease.

Intracranial Carotid Artery Dissection
Chaves et al (SEE ARTICLE) describe 10 patients with spontaneous intracranial internal carotid artery (ICA) dissection. They find that patients with ICA can have ischemic stroke with or without subarachnoid hemorrhage on initial examination, and intracranial ICA stenosis or occlusion should be considered in the differential diagnosis, especially in young patients. Importantly, some patients survive with mild or moderate deficits.

Daytime Sleepiness in Parkinson Disease
O'Suilleabhain and Dewey (SEE ARTICLE) report their experience with patients with Parkinson disease (PD) having excessive daytime somnolence. An increase in somnolence is found in patients with PD and is related to PD stage, levodopa dose, and the use of a dopamine agonist. Of interest, they find that most of the variability in sedation levels in PD as well as in control patients is due to as yet unidentified factors.

Intranasal Civamide in Cluster Headaches
Saper et al (SEE ARTICLE) describe their experience with intranasal civamide for treatment of episodic cluster headaches. Various headache parameters were evaluated and, in general, they concluded that intranasal civamide solution at a dose of 50 µg may have some effect in preventing episodic cluster headaches.

Echogenicity of the Substantia Nigra
Berg and colleagues (SEE ARTICLE) have studied the relevance of the sonographic phenotype of the substantia nigra in healthy adults. Postmortem studies show that the echogenicity of the substantia nigra is correlated with its iron content. Thus, these studies set the stage for the potential of transcranial sonography as a susceptibility marker for the development of nigral injury and increased iron content that can be detected early in life prior to the onset of Parkinson disease.