Thalamocortical dysrhythmia in patients with delirium: an EEG possible marker of prodromal dementia with Lewy bodies

Abstract

AbstractBackgroundEEG in DLB is characterized by pre‐alpha dominant frequency (DF) [6–7.5] Hz. The appearance of prealpha rhythm in the cortex is linked to a dysfunctional thalamocortical connection, the thalamocortical dysrhythmia (TCD). The hypothesis that TCD is implicated in DLB has been demonstrated by several structural, functional, and molecular imaging studies. TCD has been implicated in the appearance of altered conscious states, including fluctuating cognition and delirium, two clinical core features of DLB. Delirium can represent the onset of DLB and is listed among the symptoms of prodromal DLB. We aimed to assess specific QEEG abnormalities akin to those found in DLB, also in delirium, to detect a prodromal stage of DLB.MethodCross‐sectional multicentre cohort study and longitudinal prospective study, nested in the multicentre. rsEEG activity was compared in hospitalized patients with delirium vs. patients without delirium. In a subset of 23 patients, rsEEG was also recorded in patients with delirium at resolution of symptom and and at 1‐month follow‐up. DF and DF variability (DFV) were analysed. ResultCross‐sectional multicentre study: 65 subjects with acute delirium were matched for age/sex with 41 controls. Abnormal EEGs were found in 100% delirium patients vs. 34% no‐delirium patients. DF was lower in delirium group (p<0.001), which showed pre‐alpha DF; no‐delirium group had alpha DF. DFV was higher in delirium group (p<0.001). Single‐centre longitudinal study: After delirium resolution, 21 patients had EEG normalization and were cognitively unimpaired. 2 patients had abnormal EEG and were respectively diagnosed as DLB and MCI.ConclusionAcute delirium was characterized by pre‐alpha rhythm, expression of TCD. In most patients EEG normalized after resolution, making EEG a state marker of acute delirium, when the thalamocortical system becomes unstable, but it is still able to recover. TCD may become unrecoverable when the neurodegenerative process of DLB progresses.