Cingulate island sign

Cingulate Island Sign

The cingulate island sign is a neuroimaging finding observed in patients with dementia with Lewy bodies (DLB). It is characterized by relatively preserved metabolism in the posterior cingulate cortex compared to the surrounding areas, particularly the precuneus and posterior parietal cortex, which show reduced metabolism. This pattern is typically identified using fluorodeoxyglucose positron emission tomography (FDG-PET) scans.

FDG-PET scan showing metabolic patterns in Alzheimer's disease and dementia with Lewy bodies

Pathophysiology

The cingulate island sign is thought to be a result of the differential involvement of brain regions in DLB. In this condition, the posterior cingulate cortex is relatively spared from the pathological changes that affect other parts of the brain, such as the precuneus and parietal lobe. This sparing is reflected in the preserved metabolic activity seen on FDG-PET scans.

The underlying mechanisms for this selective sparing are not fully understood, but it may be related to the distribution of Lewy bodies and the pattern of neurodegeneration in DLB. The presence of the cingulate island sign can help differentiate DLB from other types of dementia, such as Alzheimer's disease, where the posterior cingulate cortex is typically more affected.

Clinical Significance

The identification of the cingulate island sign is clinically significant as it aids in the differential diagnosis of dementia. Differentiating DLB from Alzheimer's disease and other dementias is crucial for appropriate management and treatment, as the therapeutic approaches and prognosis can differ significantly between these conditions.

In clinical practice, the presence of the cingulate island sign on an FDG-PET scan, along with clinical features such as visual hallucinations, parkinsonism, and cognitive fluctuations, can support a diagnosis of DLB. However, it is important to consider the entire clinical picture, as the sign is not exclusive to DLB and may not be present in all cases.

Imaging Techniques

FDG-PET is the primary imaging modality used to detect the cingulate island sign. This technique measures glucose metabolism in the brain, providing insights into the functional activity of different regions. In DLB, the posterior cingulate cortex shows relatively preserved glucose metabolism compared to the surrounding areas, which is indicative of the cingulate island sign.

Other imaging modalities, such as magnetic resonance imaging (MRI), may be used in conjunction with FDG-PET to assess structural changes in the brain, but they do not directly visualize the metabolic patterns associated with the cingulate island sign.

Related Pages

• Dementia with Lewy bodies
• Alzheimer's disease
• Positron emission tomography
• Cingulate cortex