Neurophysiology and SPECT cerebral blood flow patterns in dementia

Area of Science:

• Neuroscience
• Gerontology
• Medical Imaging

Background:

• Alzheimer's disease (AD) and multi-infarct dementia (MID) are common causes of cognitive decline in the elderly.
• Distinguishing between AD, MID, and functional psychiatric illness is crucial for appropriate treatment.
• Neuroimaging and electrophysiological techniques offer potential biomarkers for differential diagnosis.

Purpose of the Study:

• To investigate the utility of electroencephalography (EEG) and single-photon emission computed tomography (SPECT) in differentiating elderly patients with AD, MID, and major depressive disorder.
• To correlate neurophysiological and perfusion imaging findings with specific dementia subtypes.

Main Methods:

• Patients diagnosed with AD, MID, or major depressive disorder (controls) underwent cognitive testing, EEG spectral analysis, visual evoked potentials (VEP), P300 recordings, and 99mTc HMPAO SPECT.
• Patients were categorized into AD-type (bilateral temporo-parietal deficits), MID-type (focal deficits), and control (normal perfusion) SPECT groups.

Main Results:

• The AD group showed significantly less alpha and more delta 2 power compared to the MID group. The MID group had lower alpha power than controls.
• Both AD and MID groups exhibited reduced alpha coherence and prolonged P300 latencies compared to controls.
• No significant differences were found in VEP P2-P100 latency differences between groups.

Conclusions:

• SPECT and EEG spectral analysis can help differentiate between AD, MID, and functional psychiatric illness in the elderly.
• Specific perfusion deficits and EEG alterations (alpha, delta, coherence, P300 latency) are associated with distinct dementia subtypes.