What are the EEG findings in Creutzfeldt-Jakob disease (CJD)?

From the Guidelines

EEG findings in Creutzfeldt-Jakob disease (CJD) are characterized by periodic sharp-wave complexes (PSWCs) with a frequency of 1 Hz, which have a sensitivity of 64% and a specificity of 91%. These PSWCs are considered a typical EEG pattern for CJD and are often seen in the frontal regions, with a periodic, synchronous, biphasic or triphasic sharp wave pattern occurring at intervals of 0.5-2 seconds 1. The background activity may show progressive slowing and disorganization as the disease advances. Early in the disease, the EEG may only demonstrate nonspecific diffuse slowing, but as CJD progresses, approximately 60-80% of patients develop these distinctive periodic complexes.

Key EEG Findings in CJD

• Periodic sharp-wave complexes (PSWCs) with a frequency of 1 Hz
• Sensitivity of 64% and a specificity of 91% for PSWCs
• Background activity shows progressive slowing and disorganization
• Nonspecific diffuse slowing in early disease stages
• Development of distinctive periodic complexes in approximately 60-80% of patients as the disease progresses

Other EEG findings may include frontal intermittent rhythmic delta activity (FIRDA) and focal epileptiform discharges. These EEG patterns, particularly the PSWCs, are valuable diagnostic markers when combined with clinical features and other tests like CSF biomarkers (14-3-3 protein, tau protein) and MRI findings (cortical ribboning and basal ganglia hyperintensities) 1. However, variant CJD may not show the typical PSWCs, and some genetic forms of CJD may have atypical EEG findings, making correlation with clinical presentation and other diagnostic modalities essential.

Diagnostic Considerations

• Correlation with clinical presentation and other diagnostic modalities is essential
• Variant CJD may not show typical PSWCs
• Genetic forms of CJD may have atypical EEG findings
• Combination of EEG with CSF biomarkers and MRI findings is valuable for diagnosis

From the Research

EEG Findings in Creutzfeldt-Jakob Disease

• The EEG is an integral part of the diagnostic process in patients with Creutzfeldt-Jakob disease (CJD) 2
• Characteristic EEG changes in CJD include:
  • Diffuse slowing and frontal rhythmic delta activity (FIRDA) in early stages
  • Periodic sharp wave complexes (PSWC) in middle and late stages
  • Areactive coma traces or alpha coma in preterminal EEG recordings
• PSWC occur in about two-thirds of patients with sporadic CJD, with a positive predictive value of 95% 2
• PSWC tend to disappear during sleep and may be attenuated by sedative medication and external stimulation 2

Lateralized and Focal EEG Abnormalities

• CJD can present with lateralized or focal cortical syndromes with colocalizing EEG and MRI findings 3
• Lateralized or focal periodic sharp waves can occur in CJD, corresponding to the site of inoculation of the transmissible agent 2, 3
• FLAIR MRI images can reveal increased signal in the cortical ribbon and deep gray matter corresponding to the lateralized clinical and EEG findings 3

Myoclonus and EEG Correlates

• Myoclonus is a common finding in CJD, occurring in 50.4% of patients 4
• Myoclonus can be classified into different types, including periodic, rhythmic, and irregular, based on its electromyography (EMG) pattern and EEG correlates 4
• PSWC are present in almost all patients with myoclonic jerks, but are time-locked with EMG-bursts only in cases of periodic myoclonus 4

Early Evolution and Incidence of EEG Abnormalities

• PSWC can occur within 12 weeks of onset of clinical symptoms in 88% of patients with CJD 5
• Focal PSWC or amplitude asymmetries of PSWC can correspond to focal myoclonus or other focal neurological abnormalities in the early stages of CJD 5
• The presence of PSWC in association with clinical, biochemical, cerebrospinal fluid, and neuroradiological findings is diagnostic of CJD 5

Clinical Changes and EEG Patterns Preceding PSWC

• Clinical changes preceding the onset of PSWC include akinetic mutism, myoclonia, and exaggerated startle reaction 6
• FIRDA-like EEG activities can precede the onset of PSWC and should be regarded as compatible with CJD diagnosis 6
• The selection of EEG recording dates to detect PSWC should be guided by detailed information about movement disorders and conscious level 6