An electroencephalogram (EEG) is a non-invasive medical test that measures the brain’s electrical activity. Dementia refers to a decline in cognitive function that impacts daily life. This article explores how EEG is utilized in the assessment of dementia, providing insights into brain activity changes associated with various forms of the condition. While not a standalone diagnostic tool, EEG offers valuable information that complements other diagnostic methods in identifying and characterizing dementia.
Understanding Electroencephalography (EEG)
EEG operates on the principle of detecting electrical signals generated by brain cells. Small, flat metal discs called electrodes are strategically placed on the scalp, typically following a standardized “10-20 system” to ensure consistent placement. These electrodes capture the subtle voltage fluctuations produced by synchronized neuronal activity.
The collected electrical impulses are transmitted to a computer, which amplifies and records the data. The output appears as wavy lines, known as brain waves, representing the patterns of electrical activity. These brain waves are categorized by frequency, such as delta (0.5-3.5 Hz), theta (4-7 Hz), alpha (8-13 Hz), and beta (14-30 Hz). Different patterns correlate with varying states of consciousness, such as alertness, relaxation, or sleep.
Applying EEG in Dementia Assessment
EEG is a tool employed in the evaluation of individuals suspected of having dementia. It helps to rule out other conditions that might mimic dementia symptoms, such as delirium, depression, or seizures. The test can also provide insights into the physiological changes occurring in different types of dementia.
An EEG can assess changes in overall brain function or identify localized deficits. It is often considered part of a broader diagnostic workup, supporting the clinical assessment rather than providing a definitive diagnosis on its own. The non-invasive and relatively inexpensive nature of EEG makes it an accessible option for evaluating brain function.
Quantitative EEG (QEEG), a more advanced application, analyzes these recordings to measure specific aspects of brain function. This quantitative analysis can identify subtle abnormalities or patterns associated with neurological disorders. QEEG can aid in early detection of dementia signs and track the disease’s progression.
EEG Insights into Dementia Patterns
EEG can reveal distinct changes in brain wave patterns that are characteristic of various dementia types. In Alzheimer’s disease (AD), common findings include a generalized slowing of brain activity. This manifests as an increase in delta (0.5-3.5 Hz) and theta (4-7 Hz) power, coupled with a decrease in alpha (8-13 Hz) and beta (14-30 Hz) power. These changes reflect a shift of the brain’s electrical activity towards lower frequencies and a reduction in brain signal complexity and synchronization.
In Creutzfeldt-Jakob disease (CJD), a rapidly progressive dementia, the EEG often shows distinctive periodic sharp-wave complexes (PSWCs). These complexes typically occur at a frequency of about 1 Hz, appearing as periodic, synchronous, biphasic or triphasic sharp waves with intervals of 0.5-2 seconds. While the background activity may exhibit progressive slowing and disorganization as the disease advances, the presence of PSWCs is a highly suggestive, though not exclusive, finding for CJD.
Dementia with Lewy bodies (DLB) can present with a pattern of prominent slow-wave activity, including increased power in delta and theta bands, along with reduced power in alpha and beta bands. Frontal intermittent rhythmic delta activity (FIRDA) may also be present, which is uncommon in other forms of dementia. This distinction, along with the degree of reactivity to eye opening, can help differentiate DLB from other dementias.
EEG’s Role in a Comprehensive Diagnosis
While EEG provides valuable insights into brain function and can suggest certain types of dementia, it is generally not a standalone diagnostic tool. It is typically used in conjunction with other diagnostic methods to achieve a comprehensive diagnosis. These additional assessments include detailed cognitive evaluations, thorough neurological examinations, and various laboratory tests, such as blood work.
Neuroimaging techniques, like magnetic resonance imaging (MRI) and positron emission tomography (PET) scans, are also frequently employed to visualize brain structure and metabolic activity. EEG helps in ruling out other conditions that might present with similar symptoms, such as seizures or metabolic encephalopathies. The information from an EEG supports the overall clinical picture, contributing to a more accurate and nuanced understanding of a patient’s cognitive decline and its underlying cause.