Brain Imaging and Alzheimer's Disease Prediction

Enhanced early detection of risk for Alzheimer's dementia and other forms of dementia is key to prevention and early intervention.

Brain imaging holds promise as a pre-clinical disease risk assessment tool in Alzeimer's dementia.

Dementia risk has been linked to several brain imaging abnormalities found with magnetic resonance imaging. These abnormalities have included atrophy of the brain hippocampus, medial temporal lobe as well as white matter hyperintensities.

A recent study from France examined whether brain MRI findings can improve Alzheimer's and other dementia prediction over conventional known risk factors.

Here are the key elements of the design of this study:
Subjects: French citizens 65 years and old living at home participating in a longitudinal study of dementia with interviews two, four, six and ten years after baseline interview
Brain imaging: 1.5 Tesla MRI with estimation of white matter lesion volume, hippocampal volume (right and left summed) and total brain volume
Dementia diagnosis: all subjects screened at each interview, with targeted neuropsychological testing and neurologist consensus assessment
Standard dementia risk model variables: age, gender, education, smoking status, alcohol use, functional daily living skills, cognition screening tests, cardiovascular disease, diabetes status, systolic blood pressure and apolipoprotein epsilon 4 status.

The research team found a statistically significant smaller hippocampal and total brain volume at baseline in those later developing dementia. White matter lesion scores showed a trend (p.076) with later dementia.

However, adding the imaging data to the standard dementia risk model did not add statistically to the predictive power for all-cause dementia to the model.

The baseline imaging in this study took place around the year 1999 to 2000. Since then, more specific brain imaging tools targeted towards Alzheimer's have emerged including amyloid plaque markers. 

These enhanced imaging tools may have better power at adding power to our prediction models.

Readers with more interest in this research study can access the free full-text manuscript by clicking on the link in the citation below.

Photo of meerkats from the Cincinnati Zoo are from the author's files.

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Stephan BC, Tzourio C, Auriacombe S, Amieva H, Dufouil C, Alpérovitch A, & Kurth T (2015). Usefulness of data from magnetic resonance imaging to improve prediction of dementia: population based cohort study. BMJ (Clinical research ed.), 350 PMID: 26099688

Brain Volume Differences in ADHD Normalize By Adulthood

Brain volume differences in ADHD have been documented in some childhood studies.

ADHD symptoms diminish with maturation in many but not all individuals. It is unclear whether this improvement in symptoms is also related to maturation of brain regions.

A recent study from the Netherlands provides some answers on this issue. A. Marten H. Onnink and colleagues performed a structural MRI study of 119 adults with ADHD compared to a group of controls.

This study is important because it examined effects of gender, comorbid depression and treatment history on key brain regions including the basal ganglia, amygdala and hippocampus.

The key findings from this study include the following:

• Women with adult ADHD showed no differences from controls on brain volume measures
• Men with adult ADHD showed reduced right caudate volumes and these volumes were negatively correlated with current hyperactivity symptom scores
• Comorbid major depression in adult ADHD was linked to smaller hippocampus volumes. ADHD without a history of depression was not linked to any differences in hippocampal volumes

A history of major depression in ADHD subjects was common (37% of men and 52% of women). Additionally, this sample high rates of current stimulant use (69% of the sample).

The authors note their study found essentially no link between adult ADHD and brain volumes. The only exception was the finding of reduced right caudate volumes in men with ADHD. 

The authors also note:

"Although male and female adults with ADHD have similar phenotypic features in terms of symptom rating and comorbidity patterns, the gender-specific finding for caudate nucleus volume suggests that partially distinct neurobiological deficits underlie ADHD in males and females."

Structural brain measures are only one element of brain imaging in ADHD and other disorders. In my previous posts, I reviewed studies linking ADHD with functional connectivity (white matter) deficits in both children and adults.

Studies of neural networks in ADHD continue to be an important area for future research. Understanding network abnormalities will be key in understanding the pathophysiology of the disorder.

Readers with more interest in this topic can access the free full text manuscript by clicking on the PMID link in the citation below.

Figure is from a screen shot of the basal ganglia from the iPad app 3D Brain. It illustrates the brain caudate region found to be reduced in adult men but not women with ADHD.

Follow the author on Twitter @WRY999.

Onnink AM, Zwiers MP, Hoogman M, Mostert JC, Kan CC, Buitelaar J, & Franke B (2014). Brain alterations in adult ADHD: effects of gender, treatment and comorbid depression. European neuropsychopharmacology : the journal of the European College of Neuropsychopharmacology, 24 (3), 397-409 PMID: 24345721