Cluster headache may be associated with obstructive sleep apnea, according to a study in the June 27 Neurology. Polysomnography of 25 adults showed a high rate of obstructed breathing in 80% of participants. Although the link between sleep apnea and cluster headache is unclear, the authors suggested that hyperapnea, large swings in intrathoracic pressure, abrupt changes in sympathetic tone, and (particularly) hypoxemia, "could trigger vascular changes thought to underlie cluster headache."

As many as 40% of patients with epilepsy may have been misdiagnosed, according to a report in the July 2000 Journal of the American College of Cardiology. Researchers at the Manchester Heart Centre in the UK evaluated 74 patients whose diagnosis of epilepsy was uncertain or whose response to antiepileptic treatment was poor. The head-up tilt test and the carotid sinus massage indicated that 41.9% of the patients had vasovagal syncope rather than epilepsy. Physicians should consider these evaluations to identify an alternative diagnosis in patients with apparent epilepsy and patients with convulsive blackouts, concluded the authors.

Memory impairment in the elderly is frequently due to Alzheimer's disease, according to a presentation by David Bennett, MD, at the World Alzheimer Congress 2000. Many people with mild memory problems who do not meet conventional criteria for dementia exhibit the pathology of Alzheimer's disease, he said. The number of people with Alzheimer's disease in the US, which is estimated at 4 million, may actually be much higher, he said.

Serologic evidence of chronic infection with Chlamydia pneumoniae is associated with the risk of ischemic stroke, according to a report in the July Stroke. Immunoglobin (Ig) A titers (which remain in the body for several days after C pneumoniae exposure) were more strongly linked to ischemic stroke than were IgG titers (which remain for several years) or IgM titers. Chlamydia pneumoniae may increase the risk of ischemic stroke through inflammation, suggested the authors. "The general idea is that infection with C pneumoniae may be another thing, just like cholesterol and homocysteine, that is associated with atherosclerosis," said lead author Mitchell S. V. Elkind, MD.

A new population of dopaminergic neurons has been identified in the striatum of patients with Parkinson's disease, according to a report in the July 1 Lancet. Compared with five age-matched controls, the 10 subjects with idiopathic Parkinson's disease showed more dopamine transporter neurons, with an average of 26 per 20-mm striatal section. The researchers, from Victoria, Australia, found 39.9% of dopamine transporter neurons in the putamen, 11.6% in the caudate nucleus, 16.3% in the globus pallidus externa, 6.2% in the globus pallidus interna, and 25.9% in the adjacent internal capsule and the ansa lanticularis. The 66,000 estimated neurons are sufficiently numerous to have an effect on dopaminergic function in the striatum, the authors wrote.

The risk-benefit ratio of treating non-dementia illness in patients with dementia should be carefully considered, according to a report in the June 28 JAMA. It is not known how impaired cognition will likely affect decision-making, reporting of adverse effects, and compliance, the authors noted. They cited a case wherein a woman with dementia and a fractured vertebra was prescribed an osteoporosis medication that had to be taken sitting upright and with a cup of water, as it could irritate the esophagus. Noncompliance led to esophageal ulceration, rupture, and erosion into a major vessel, causing death.

During the 10 years following diagnosis of Alzheimer's disease, costs of care incurred by women are higher than those incurred by men, according to a report in the June Journal of the American Geriatrics Society. Average 10-year costs for women were as high as $109,000, while costs for men were estimated at $67,000. Interventions that slow disease progression may affect community survival and health care costs, suggested the researchers. Women with Alzheimer's disease live longer with their disease than do men and have higher costs of care (both in the community and in institutions) associated with differences in use of institutional and medical care.

The risk of Alzheimer's disease, Parkinson's disease, and other common neurologic disorders may be lowered with adherence to a reduced-calorie diet, according to University of Wisconsin at Madison researchers. The genetic activity of mice that were fed a standard diet was compared to that of mice that were fed a calorie-reduced diet. The researchers reported in the July Nature Genetics that a reduced-calorie diet lowered activity of genes that encode inflammatory and free-radical—generated stress responses. The authors also suggested that mechanisms of aging in the brain are similar among mice, monkeys, and humans.

Amyloid plaques have been visualized in a living animal model in a Philadelphia study. According to a report in the June 20 Proceedings of the National Academy of Sciences, the amyloid-biding probe BSB crossed the blood-brain barrier of mice with Alzheimer's disease amyloidosis, and it labeled the senile plaques with high sensitivity and specificity. The researchers hope that the probe will be useful in clinical trials of therapies for Alzheimer's disease and that it can be used in antemortem diagnoses of Alzheimer's disease.

Retrograde axonal transport of herpes simplex virus (HSV) type 1 has been documented, according to a study in the July 5 Proceedings of the National Academy of Sciences. After being stripped of their envelopes, the HSV-1 particles were injected into the giant axon of a squid. The HSV-1 particles moved in a retrograde direction at 2.2 ± 0.26 µm/s. Although viral motility is not understood, the authors suggested that further study of retrograde transportation "should provide a powerful tool for the discovery of endogenous sequences on cellular components that recruit retrograde motor(s) for transport."

Depression may be a risk factor for stroke, according to a study in the July/August Psychosomatic Medicine. The National Health and Nutrition Examination Survey enrolled 6,095 stroke-free adults ages 25 to 74 in the early 1970s. Data collected from questionnaires that the participants completed during the 22-year follow-up indicated that there was a 73% increase of stroke in patients who reported high levels of depression and a 25% increase of stroke in patients who reported moderate levels of depression.

Neurons regenerated in the brains of mice in a study by researchers at Harvard Medical School. According to the report in the June 22 Nature, the researchers induced selected cells to undergo apoptosis. The presence of labeled BrDu (a marker of DNA replication), doublecortin (a protein expressed only by migrating neurons), hu (an early neuronal marker), and NeuN (a marker expressed by mature neurons) indicated that young neurons were developing and connecting with other neurons. The authors noted that they are not suggesting that apoptosis has a clinical application in the treatment of neurologic disorders, but that it is a means of examining the mechanism of neural regeneration.

Narcotic or alcoholic relapse may be a response to environmental cues, according to a report in the August Synapse. In a study of the molecular mechanism of craving, researchers at the University of Wisconsin Medical School injected rats with morphine once a day for 10 days. After the 10-day conditioning period, the rats behaved as if they had been injected with morphine when they were placed in the cage where they had received injections. The researchers also found that expression of the Fos gene increased in the limbic circuits and, surprisingly, in the prefrontal cortex. They noted that long-term changes may persist in the learning and memory systems of long-term drug users.

Comorbid Alzheimer's disease does not affect the outcome of stent surgery for idiopathic normal-pressure hydrocephalus, according to a report in the June Journal of Neurology, Neurosurgery and Psychiatry. Gait velocity and ambulatory index scores improved to a similar degree in patients with and without Alzheimer's disease, and no significant differences in postoperative psychometric changes or in urinary control were seen in the two groups.

—Kathryn Blair

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