What are the neurodegenerative diseases associated with generalized slowing on electroencephalogram (EEG)?

From the Guidelines

Neurodegenerative diseases associated with generalized slowing on electroencephalogram (EEG) include Alzheimer's disease, Parkinson's disease, Lewy body dementia, frontotemporal dementia, and Huntington's disease, as supported by recent studies such as the 2020 acr appropriateness criteria® dementia 1. These conditions typically show diffuse slowing of brain electrical activity, with increased theta and delta waves replacing normal alpha rhythm. This EEG pattern reflects widespread neuronal dysfunction and loss of synaptic connections that characterize these disorders. The degree of slowing often correlates with disease severity and cognitive impairment, with Alzheimer's disease showing progressive slowing from mild to severe as the disease advances 1. Some key points to consider in the diagnosis and management of these conditions include:

• The importance of clinical diagnosis and interpretation of EEG findings alongside clinical findings, neuropsychological testing, and neuroimaging
• The role of protein aggregation (amyloid, tau, alpha-synuclein, or huntingtin) and subsequent neurodegeneration in disrupting normal cortical and subcortical neural networks
• The potential for fluctuating EEG patterns and periodic sharp waves in Lewy body dementia, as well as more frontal slowing patterns in Parkinson's disease
• The need for ongoing monitoring and assessment of disease progression, given the expected quadrupling of dementia prevalence by 2050 1.

From the Research

Neurodegenerative Diseases with Generalized Slowing

• Neurodegenerative diseases, such as Alzheimer's disease, can cause generalized slowing of cognitive function and activities of daily living 2, 3.
• The diagnosis of neurodegenerative diseases can be challenging, especially in early phases or atypical variants, and requires a comprehensive clinical approach, including neurofunctional imaging and diagnostic tests 4.
• Rapidly progressive dementias are a group of heterogeneous disorders that can cause dementia over weeks or months, and early and accurate diagnosis is essential for treatment 5, 6.
• The aetiologies of rapidly progressive dementias include immune-mediated, infectious, and metabolic encephalopathies, as well as prion diseases and atypically rapid presentations of more common neurodegenerative diseases 6.

Clinical Approach to Diagnosis

• The clinical approach to diagnosis of neurodegenerative diseases involves a comprehensive assessment of cognitive impairment, including established clinical criteria and diagnostic tests such as neurofunctional imaging 4.
• The diagnostic validity of a given investigation must be estimated by comparing the results obtained from "true" criteria to the "gold standard" or reference test 4.
• Clinical patient follow-up, creation of a data bank, and use of computer-aided diagnostic algorithms can provide solutions to the problem of diagnosis 4.

Treatment Options

• Treatment options for neurodegenerative diseases, such as Alzheimer's disease, include cholinesterase inhibitors, such as donepezil, which can provide small benefits in cognitive function, activities of daily living, and clinician-rated global clinical state 2, 3.
• High-dose steroid therapy may be used in the context of therapy and diagnosis in clinically ambiguous cases of rapidly progressive dementias 6.
• Early and accurate diagnosis is essential for treatment of rapidly progressive dementias, as many of the etiologies are treatable 5, 6.