Brain Imaging in Diagnosis of Lewy Body Dementia

Brain image highlighting right insula implicated in DLB

Recent information has emerged concerning the suicide death of the comedian/actor Robin Williams.

Autopsy results have demonstrated that Robin Williams suffered from dementia with Lewy bodies (DLB).

This public case demonstrates the difficulty in making a correct diagnosis of DLB prior to the findings at autopsy.

In a previous post I reported on a screening tool for clinicians that appears to have some promise for screening for high-risk DLB patients.

In this post, I want to follow up on this topic by reviewing a recent brain imaging study that targeted patterns of brain cortical thinning in the dementias.

The key elements in the design of this research study included the following elements:

• Subjects: 28 subjects with prodromal DLB, 27 subjects with prodromal Alzheimer's disease (AD), 31 subjects with DLB, 54 subjects with AD and cognitively normal elderly adults.
• Brain Imaging: Structural magnetic resonance imaging (MRI) with a 3 Tesla scanner
• Statistical Analysis: FreeSurfer analysis of regional cortical thickness pattern across diagnosis groups

The key findings from the study included the following:

• DLB subjects showed distinct patterns of cortical thinning compared to AD
• DLB was associated with increased thinning of the right insular cortex
• AD was associated with left parahippocampal thinning and bilateral parietal lobe thinning
• In those with full dementia, AD subjects demonstrated more thinning in the enterorhinal cortex

The authors of this study note in the discussion section of the paper that the key finding is the finding of right insular cortex thinning in DLB. This finding may allow use of brain imaging as a sensitive addition to the use of clinical and neuropsychological assessment in elderly with early and later dementia.

This study will need to be replicated in additional independent samples. Some research groups may already have scan data that may be able to be analyzed in an attempt to replicate the current study.

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

Image of the right insular cortex is from a screen shot from my iPad using the Brain Tutor app.

Follow me on Twitter @WRY999

Blanc F, Colloby SJ, Philippi N, de Pétigny X, Jung B, Demuynck C, Phillipps C, Anthony P, Thomas A, Bing F, Lamy J, Martin-Hunyadi C, O'Brien JT, Cretin B, McKeith I, Armspach JP, & Taylor JP (2015). Cortical Thickness in Dementia with Lewy Bodies and Alzheimer's Disease: A Comparison of Prodromal and Dementia Stages. PloS one, 10 (6) PMID: 26061655

Brain Deficits in Visual Hallucinations

One the early things I was taught in my neuroscience training was that new-onset visual hallucinations need to be assessed for medical or "organic causes".

Auditory hallucinations were felt to be more characteristic of schizophrenia.

One medical disorder linked to visual hallucinations is dementia with Lewy bodies (DLB). 

DLB is second to Alzheimer's disease in producing neurodegenerative dementia. Visual hallucinations is a hallmark of DLB and is found in up to 70% of clinical samples with the disorder.

A recent study from France provides insight into the neuroanatomical correlates of visual hallucinations in DLB.

Researchers in this study used single-photon emission computed tomography (SPECT) in a group of 36 subjects with DLB who reported visual hallucinations.

This group of cases was compared to 30 subjects with DLD who did not report visual hallucinations.

Specific differences in blood flow were noted with visual hallucinations. Visual hallucinations subjects had diminished cerebral perfusion in the following regions.

• Left anterior cingulate cortex
• Left orbitofrontal cortex
• Left cuneus

Deficits in regional cerebral perfusion in several areas correlated with the severity of visual hallucinations:

• Bilateral anterior cingulate cortex
• Left orbitofrontal cortex
• Right parahippocampal gyrus
• Right inferior temporal cortex
• Left cuneus

The authors note the cuneus (also known as Brodmann's area 18). This region is known as a secondary visual integration area. Reduced blood flow to this region may contribute to visual processing errors and the subjective sensation of visual hallucinations. Perfusion deficits in more anterior regions may contribute to inability to recognize the visual hallucinations as abnormal.

This study is one of many emerging showing specific clinical features of neuropsychiatric disorders may relate to specific neuroanatomical deficits and impairment.

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

Image of left cingulate cortex is an iPad screen shot from the app 3D Brain from the author's files.

Follow the author on Twitter @WRY999

Heitz C, Noblet V, Cretin B, Philippi N, Kremer L, Stackfleth M, Hubele F, Armspach JP, Namer I, & Blanc F (2015). Neural correlates of visual hallucinations in dementia with Lewy bodies. Alzheimer's research & therapy, 7 (1) PMID: 25717349