EEG Abnormalities During Delirium as a Prodromal Feature of Dementia with Lewy Bodies: A Case Report

Abstract

Background: A 79-year-old woman was admitted to the Neurology Clinic of the University of Chieti-Pescara for a syncope. At admission, the occurrence of an acute stroke was ruled out. Her cognitive status was unimpaired. After three days from the hospitalization, the patient experienced an episode of mixed delirium.

Objective: The present case report shows a case of delirium-onset dementia with Lewy bodies (DLB) with a specific electroencephalographic (EEG) pattern from its prodromal stage.

Methods: Delirium was assessed by 4AT test. During the hospitalization, the patient underwent a quantitative EEG (QEEG) with spectral analysis. At six months from the episode of delirium, she was tested by neuropsychological evaluation, QEEG, and ¹⁸F-fluorodeoxyglucose PET/CT to assess the onset of a possible cognitive decline.

Results: At baseline, the QEEG exam showed a dominant frequency (DF) in the pre-alpha band (7.5 Hz) with a dominant frequency variability (DFV) of 2 Hz. This pattern is typical of DLB at early stage. After six months, she reported attention deficits in association with cognitive fluctuation and REM sleep behavior disorder. The neurological examination revealed signs of parkinsonism. Cognitive status resulted to be impaired (MoCA = 15/30). QEEG recording confirmed the presence of a DLB-typical pattern (DF = 7.5 Hz, DFV = 2.5 Hz). The ¹⁸F-FDG-PET/CT showed a moderate bilateral posterior hypometabolism (occipital and temporal cortex), with relative sparing of the posterior cingulate cortex compared to cuneus/precuneus (Cingulate Island sign), and mild bilateral hypometabolism in frontal regions (suggestive of a DLB diagnosis).

Conclusion: EEGs may represent supportive and validated biomarkers for delirium-onset prodromal DLB.

Keywords: Delirium; EEG; dementia with Lewy bodies; prodromal dementia.

Fig. 1

Representations of both CSA and ¹⁸F-FDG-PET/CT patterns. a) Patient CSA patterns from occipital derivation at both admission and 6-month follow-up visit (left), compared to a CSA 1 pattern of a normal control (right). b) Axial ¹⁸F-FDG-PET/CT images and semiquantitative data (Cortex ID software) at 6 months from the hospitalization. Brain ¹⁸F-FDG PET study showed a moderate reduction in radiopharmaceutical uptake in the parietal, occipital, and lateral temporal bilaterally, more evident in the left hemisphere. A mild hypometabolism was also evident in the prefrontal regions bilaterally, although not reaching the statistically significant threshold at semiquantitative analyses. The uptake was also reduced at the level of the precuneus, especially on the right side, and a normal uptake at the level of the cingulate was present, describing the Cingulate Island Sign. This hypometabolic pattern was suggestive of DLB diagnosis. CSA, Compressed Spectral Array; ¹⁸F-FDG-PET/CT, ¹⁸F-fluorodeoxyglucose positron emission tomography; R, right; L, left.