Electrical brain networks before and after transcranial pulsed shockwave stimulation in Alzheimer's patients

Abstract

Alzheimer's disease (AD) is a neurodegenerative disorder that dramatically affects cognitive abilities and represents the most common cause of dementia. Currently, pharmacological interventions represent the main treatment to deal with the symptoms of AD; however, alternative approaches are readily sought. Transcranial pulse stimulation (TPS) is an emerging non-invasive neuromodulation technique that uses short, repetitive shockwaves with the potential to provide a wide range of vascular, metabolic, and neurotrophic changes and that has recently been shown to improve cognitive abilities in AD. This exploratory study aims to gain insight into the neurophysiological effect of one session of TPS in AD as reflected in electroencephalographic measures, e.g., spectral power, coherence, Tsallis entropy (TE), and cross-frequency coupling (cfc). We document changes in power (frontal and occipital), coherence (frontal, occipital and temporal), and TE (temporal and frontal) as well as changes in cfc (parietal-frontal, parietal-temporal, frontal-temporal). Our results emphasize the role of electroencephalographic measures as prospective markers for the neurophysiological effect of TPS.

Keywords: Alzheimer’s disease; Coherence; Cross-frequency-coupling; Electroencephalogram, ultrasound, shock waves; Non-pharmacological, intervention; Power; Tsallis entropy.

Fig. 1

Protocol. EEG from 21 channels during resting state with predominantly eyes closed (at least 10 min) was performed directly or within 24 h before and after the first TPS session for each patient. TPS was applied with MR-neuronavigation and took around 45 min with navigation calibration

Fig. 2

Effect of one TPS session on EEG power. Individual effects (across channels) at frontal-complete, fronto-polar, occipital, temporal, and parietal regions are marked as significant differences (**) and statistical trends (*)

Fig. 3

Effect of one TPS session on coherence. Grand average coherence (across patients and channels) corresponding to regions occipital, temporal, parietal-frontal-complete, frontal-complete, parietal, parietal-fronto-polar, fronto-polar, parietal-temporal, and frontal-complete-temporal. Significant differences between conditions are indicated by the shadowed regions. Figure marked with significant differences (**)

Fig. 4

Effect of one TPS session on Tsallis entropy (TE). Individual effects (across channels) at occipital, frontal-complete, fronto-polar, temporal, parietal, and all channels. Figure marked with statistical trends (*)

Fig. 5

Effect of TPS on cross-frequency coupling (cfc) corresponding to regions parietal- fronto-polar, temporal, fronto-polar, temporal, frontal-complete-temporal, and parietal-temporal. Frequencies in which there is a significant cfc difference between pre and post TPS are highlighted in black for each considered region. Note that frequencies in the x-axis depict the modulating frequency within the range [1, 10 Hz] and those in the y-axis refer to the modulated frequency [20, 85 Hz]

Fig. 6

Summary of neurophysiological effect of one session of TPS. A Increase in power at occipital and frontal (theta-alpha, alpha–beta-gamma, and beta-gamma); B increase in coherence at temporal (alpha–beta) and decrease at occipital and parietal-frontal complete (theta); C increase in Tsallis entropy (TE) at fronto-polar and temporal regions; D changes in cross-frequency coupling (cfc) (parietal-fronto-polar, fronto-polar, temporal, frontal-complete-temporal, parietal-temporal)