TUTORIAL

Introduction

Vascular dementia is related to a number of distinct underlying diseases. Patients with hypertension, diabetes mellitus, and hypercholesteremia are more susceptible.

Multi-infarct dementia (MID) involves the large vessels and is due to multiple, large and discrete infarctions. A history of strokes, assymetrical neurological signs and pseudobulbar palsy are some clues that help in reaching the diagnosis of MID.

Subcortical arteriosclerotic encephalopathy (Binswanger's disease) involves the microcirculation, presents as white matter disease, and is attributed to atherosclerosis of penetrating cerebral arteries.

Imaging Findings

Characteristic findings in HMPAO-SPECT scintigraphy of multi-infarct dementia are multiple asymmetric perfusion defects, often involving the primary cortex and deep structures. CT and MRI also show multiple lesions.

 

Vascular dementias which involve subcortical structures are usually associated with diffuse and patchy patterns of reduced blood flow. Mixed patterns are often seen.

Differential Diagnosis

Alzheimer's dementia, which is far more common than multi-infarct dementia, must be ruled out before establishing the diagnosis of vascular dementia. Tc-99m-HMPAO SPECT is an accurate and useful modality in differentiating MID from Alzheimer's disease, when defects classically involve the temporoparietal cortex bilaterally, with sparing of primary motor and sensory cortex and deep structures. Clinically, the course of vascular dementia fluctuates between periods of improvements and deterioration, while a slow and progressive deterioration is often seen in Alzheimer's. Moreover, hypertension, which is common amongst patients with vascular dementia, is a rare finding in patients with Alzhiemer's disease.

References

1. Holman BL, Devous MD. Functional brain SPECT: the emergence of a powerful clinical method. J Nucl Med 1992; 33:1888-1904.
2. Harrison's Principles of Internal Medicine. McGraw-Hill. 12th edition pp 191.