Megan Brooks

Increased consumption of omega-3 polyunsaturated fatty acids (PUFA) correlate significantly with lower plasma levels of beta-amyloid 42 (Aβ-42) in elderly individuals without dementia, researchers found.

The association of higher omega-3 intake and lower plasma Aβ-42 they observed was independent of age, sex, ethnicity, education, and APOE genotype and has been “linked with reduced risk of incident Alzheimer’s disease (AD) and slower cognitive decline in our cohort,” they note.

The study, from Nikolaos Scarmeas, MD, MSc, associate professor of neurology, Columbia University Medical Center in New York City, and colleagues was published online May 2 in Neurology.

“We demonstrate here that there is an association between what we eat and levels of amyloid in our blood,” Dr. Scarmeas told Medscape Medical News. “The amount of omega-3 that we consume may relate to levels of amyloid in our system, an argument suggesting a possible direct relation with Alzheimer’s type of pathology,” he added.… [Continue Reading]

PET scanning is a powerful imaging technique that enables in vivo examination of brain functions. It allows for noninvasive quantification of cerebral blood flow, metabolism, and receptor binding. PET scanning helps in understanding the disease’s pathogenesis, making the correct diagnosis, and monitoring the disease’s progression and response to treatment.^[35]

PET scanning involves the introduction of a radioactive tracer into the human body, usually with an intravenous injection. A tracer is essentially a biologic compound of interest that is labeled with a positron-emitting isotope, such as carbon-11 (¹¹ C), fluorine-18 (¹⁸ F), or oxygen-15 (¹⁵ O). These isotopes are used because they have relatively short half-lives (from minutes to < 2h), allowing the tracers to reach equilibrium in the body without exposing the subjects to prolonged radiation.… [Continue Reading]

Single-photon emission computed tomography (SPECT) scanning uses direct photon-emitting isotopes rather than radioisotopes. SPECT isotopes have an average half-life of 6-12 hours.

SPECT instrumentation is highly variable; therefore, use of a SPECT scanner with poor resolution can result in poor clinical performance. Positron-emission tomography (PET) scanning uses tracers that measure regional glucose metabolism (rCMRGlc). SPECT imaging is most commonly used for blood-flow measurement.

Early SPECT studies of blood flow replicated findings of functional reductions in the posterior temporal and parietal cortex. The severity of temporoparietal hypofunction has been correlated with the severity of dementia in a number of studies.… [Continue Reading]

Many studies have shown that cerebral atrophy is significantly greater in patients with Alzheimer disease (Alzheimer’s disease) than in persons without it. However, the variability of atrophy in the normal aging process makes it difficult to use MRI as a definitive diagnostic technique. (See the images below.)

Coronal, T1-weighted magnetic resonance imaging (MRI) scan in a patient with moderate Alzheimer disease. Brain image reveals hippocampal atrophy, especially on the right side. Axial, T2-weighted magnetic resonance imaging (MRI) scan of the brain reveals atrophic changes in the temporal lobes. Axial, T2-weighted magnetic resonance imaging (MRI) scan shows dilated sylvian fissure resulting from adjacent cortical atrophy, especially on the right side. Axial, T1-weighted magnetic resonance imaging (MRI) scan shows a dilated sylvian fissure caused by adjacent cortical atrophy. Axial, T1-weighted magnetic resonance imaging (MRI) scan shows bilateral cortical atrophy with accentuated cortical sulci; there is decreased involvement in the posterior aspect. Axial, T1-weighted magnetic resonance imaging (MRI) scan shows bilateral cortical atrophy with accentuated cortical sulci; there is decreased involvement in the posterior aspect.… [Continue Reading]

Alzheimer disease (AD) is a clinical diagnosis. However, ancillary imaging studies (eg, computed tomography [CT]; magnetic resonance imaging [MRI]; and, in selected cases, single-photon emission CT [SPECT] or positron emission tomography [PET]) and laboratory tests may be used. These tests help exclude other possible causes for dementia (eg, cerebrovascular disease, cobalamin [vitamin B12] deficiency, syphilis, thyroid disease).

Diagnostic criteria established by the National Institute on Aging (NIA) and the Alzheimer’s Association are intended principally to facilitate research. However, the NIA-AA also proposed “core clinical criteria” for diagnosis of mild cognitive impairment (MCI) by health care providers without access to cerebrospinal fluid (CSF) testing or advanced imaging.[51] The NIA-AA criteria for diagnosis of dementia due to AD are clinical, with biomarkers in an assisting, nonessential role.[52]

Depression is an important consideration in the differential diagnosis of Alzheimer disease (AD). The clinical manifestations of depression overlap with those of AD. In addition, an estimated 30-50% of AD patients have comorbid depression.[53]

Depression in patients with AD appears to differ from depression in cognitively intact elderly patients. Depression in AD more often features motivational disturbances (eg, fatigue, psychomotor slowing, apathy), whereas depression in geriatric patients without cognitive impairment tends to feature mood symptoms (eg, depressed mood, anxiety, suicidality, sleep and appetite disturbances).[53]

Commonly used instruments for assessing depression (eg, Hamilton Scale for Depression, Beck Depression Inventory, Geriatric Depression Scale) were designed for use in other patient populations and may be less reliable in patients with AD. Consequently, the National Institute of Mental Health has developed provisional diagnostic criteria for depression in AD.[53]… [Continue Reading]

Patients with Alzheimer disease (AD) most commonly present with insidiously progressive memory loss, to which other spheres of cognitive impairment are added over several years. This loss may be associated with slowly progressive behavioral changes. After memory loss occurs, patients may also experience language disorders (eg, anomia) and impairment in their visuospatial skills and executive functions.

Patients with mild AD usually have somewhat less obvious executive, language, and/or visuospatial dysfunction. In atypical presentations, dysfunction in cognitive domains other than memory may be most apparent. In later stages, many patients develop extrapyramidal dysfunction.

Substantially less common, but biopsy or autopsy-proven, presentations include right parietal lobe syndrome, progressive aphasia, spastic paraparesis, and impaired visuospatial skills, which is subsumed under the visual variant of AD.… [Continue Reading]