Researchers noted that the development of a simple scale focused on abnormalities in dementia with Lewy bodies may help to further incorporate the EEG in clinical decision-making.
Data from a study examining biomarkers in patients with dementia with Lewy bodies (DLB) using electroencephalography (EEG) revealed that profound EEG abnormalities are already present in the prodromal stage of DLB and have both diagnostic and prognostic value.1
Researchers aimed to determine whether EEG differentiates the prodromal phase of DLB from other causes of mild cognitive impairment (MCI), as well as whether EEG is predictive for time to conversion from MCI to DLB by comparing its readings and the clinical follow-up of patients with MCI due to DLB (MCI-DLB) with those who have MCI due to Alzheimer disease (MCI-AD).
Led by Jessica J. van der Zande, MD, researcher, Alzheimer Center Amsterdam, VU University, the researchers compared 37 patients with MCI who developed DLB during follow-up or had an abnormal 123I-PF-CIT SPECT scan with 67 age-matched patients with MCI-AD. They assessed EEGs with a score of increasing abnormality (range, 1—5).
They found that visual EEG-scores were higher in MCI-DLB patients, with 60% (n = 22) of them scoring >2 compared to 8% (n = 5) of those with MCI-AD (P <.001). Additionally, normal rated EEG scores, having a severity of 1, were reported in 49% of the patients in the MCI-AD group compared to 16% of the patients with MCI-DLB (P <.01).
Several individual EEG measures—such as peak frequency, theta power, beta power and theta/alpha-ratio—showed the highest diagnostic accuracy for differentiating MCI-DLB from MCI-AD with areas under the curve (AUCs) of 0.94, 0.91, and 0.92, respectively. The visual measure of diffuse abnormalities reached an AUC of 0.84.
Van Der Zande and colleagues concluded that “different studies have not indicated the added value of EEG for the discrimination of DLB from AD, even in early stages. We have described 3 MCI-DLB patients with an initially normal 123I-PF-CIT SPECT scan, but clearly abnormal EEG, illustrating the added value in this specific group.”
Frontal intermittent delta activity (FIRDA) was observed in 22% of the MCI-DLB group but did not occur in the MCI-AD group. Lower peak frequency was observed in patients with MCI-DLB (7.5 Hz; interquartile range (IQR), 6.0—9.9) compared to those with MCI-AD (8.8 Hz; IQR, 6.8–10.2; P <.001).
Overall, there was more slow-wave activity in the MCI-DLB group. The patients with MCI-DLB had a higher global relative theta power (median of 0.32 [IQR, 0.18] vs 0.11 [IQR, 0.06]; P <.001), lower alpha-2 (0.05 [IQR, 0.04] vs 0.10 [IQR, 0.07]; P <.001) and beta power (0.08 [IQR, 0.06] vs 0.19 [IQR, 0.13]; P <.001) compared to patients with MCI-AD.
A total of 38 patients had sufficient data at follow up, with 23 (61%) of them converting to dementia. Follow-up duration did not differ significantly between converters (mean 3 years; range 0.5—8 years) and non-converters (mean 2.6 years; range 1–5 years; P = .84). Using Kaplan-Meier analysis, researchers found that the risk for rapid progression to dementia was related to an EEG severity score >2, diffuse abnormalities, a lower alpha-2 power, a lower peak frequency and a higher theta-alpha-ratio.
Both groups were well-matched for age, but the MCI-DLB group consisted of more male patients. Medication use and Mini Mental State Examination (MMSE) score were comparable between groups. Within the diagnostic cohort of MCI-DLB patients, 23 had 1 or more 123I-PF-CIT SPECT scans available, and the first scan was abnormal in 20 patients (87%). Additionally, 24% of MCI-DLB patients had a cerebrospinal fluid (CSF) tau/ amyloid beta (aß)-42 ratio >0.52, consistent with AD co-pathology.
Additional work published by van der Zande and colleagues earlier this year suggests that those with MCI‐LB also have distinct neuropsychiatric and cognitive profiles, with prominent decline in attention, compared with those who have MCI‐AD. Those results, they noted, point to the importance of early diagnosis due to the impact that symptoms already have in the prodromal stages of dementia with Lewy bodies.2
NeurologyLive recently spoke with James Leverenz, MD, director, Cleveland Lou Ruvo Center for Brain Health, Cleveland Clinic, who offered insight into the challenges that have plagued physicians in identifying biomarkers for Lewy body dementia.
1. van der Zande JJ, Gouw AA, van Steenoven I, et al. Diagnostic and prognostic value of EEG in prodromal dementia with Lewy bodies. Neurology. Published online July 7, 2020. doi: 10.1212/WNL.000000000009977.
2. van de Beek M, van Steenoven I, van der Zande JJ, et al. Prodromal Dementia With Lewy Bodies: Clinical Characterization and Predictors of Progression. Movement Disord. Published online February 11, 2020. doi: 10.1002/mds.27997.