Alzheimer’s disease: new exploratory EEG study evaluates the neurophysiological effect of one TPS session

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Alzheimer’s disease: new exploratory EEG study evaluates the neurophysiological effect of one TPS session

Transcranial Pulse Stimulation (TPS) uses short, repetitive shock waves with the potential to provide a wide range of vascular, metabolic, and neurotrophic changes. Among the positive features of TPS are good spatial precision in the stimulation of brain regions and the possibility to reach deeper brain structures compared to other non-invasive brain stimulation techniques (TMS and tDCS), as well as the adaptability of stimulation parameters, which leads to individual and targeted patient treatments. One of the current scientific challenges is to gain a deeper understanding of the neurophysiological effects of the stimulation and the interaction between the sound waves generated by TPS and the tissue. 

The aim of a new exploratory study by Wojtecki et al. [1] was to use electroencephalographic (EEG) measurements to gain insight into the neurophysiological effect of one TPS session in Alzheimer’s disease (AD). The authors document changes in spectral power (frontal and occipital), coherence (frontal, occipital and temporal), Tsallis entropy (temporal and frontal) and cross-frequency coupling (parietal-frontal, parietal-temporal, frontal–temporal). The results emphasize the role of electroencephalographic measures as prospective markers for the neurophysiological effect of TPS. 

Methods
Ten Alzheimer patients (2 women, 8 men; age 69.2 ± 7.1 years) with mild (3), moderate (5), and severe (2) cognitive symptoms were recruited for EEG analysis. To measure the neurophysiological changes, EEG was recorded before and after the first session of a TPS treatment series. 

The TPS treatment protocol was 4 Hz, 0.20 mJ/mm2 by default. The stimulation protocol was similar to Beisteiner et al. [2], including the bilateral frontal cortex, bilateral lateral parietal cortex, and extended precuneus cortex. In difference to Beisteiner et al., the bilateral temporal cortex was also included. 

Results, discussion and conclusion
The authors documented various neurophysiological effects and significant changes after the TPS treatment: 

  1. Increase in power at occipital and frontal (theta-alpha, alpha–beta-gamma, and beta-gamma) 
  2. Increase in coherence at temporal (alpha–beta) and decrease at occipital and parietal-frontal complete (theta) 
  3. Increase in Tsallis entropy (TE) at fronto-polar and temporal regions 
  4. Changes in cross-frequency coupling (cfc) (parietal-fronto-polar, frontopolar, temporal, frontal-complete-temporal, parietal-temporal) 

In the discussion section of the paper, the authors highlight some of their findings to show that the significant changes and statistical trends after one TPS session might indeed suggest a direct or indirect biological effect on the brain and may be indicative of a positive effect provided by the stimulation. They particularly emphasize the reported effects on gamma oscillations, which might go beyond pure functional electrical networks. It has been described that increase of gamma power can be found after gamma-tACS (transcranial alternating current stimulation) in conjunction with decreased hippocampal beta-amyloid levels in AD [3]. Thus, TPS changes on gamma-networks should be observed with special interest as shock waves might affect the brains glymphatic clearance system. 

The authors conclude that their results support the role of one session of TPS in modulating oscillatory activity and connectivity of electrical brain networks with potential implications in cognitive functioning and modulation of plasticity. To clarify the prospect of EEG measures as neurophysiological biomarkers of TPS, future studies should consider the effects of TPS at different time points and after several sessions in relation to cognitive scores. 

Find out more about Transcranial Pulse Stimulation (TPS) with the NEUROLITH system.

Sources:
1. Wojtecki, L., Cont, C., Stute, N. et al. Electrical brain networks before and after transcranial pulsed shockwave stimulation in Alzheimer’s patients. GeroScience (2024). https://doi.org/10.1007/s11357-024-01305-x.
2. Beisteiner R, Matt E, Fan C, Baldysiak H, Schönfeld M, Philippi Novak T, et al. Transcranial pulse stimulation with ultrasound in Alzheimer’s disease—a new navigated focal brain therapy. Adv Sci. 2020;7:1902583. https://doi.org/10.1002/advs.201902583. 
3. Wu L, Cao T, Li S, Yuan Y, Zhang W, Huang L, Cai C, Fan L, Li L, Wang J, Liu T, Wang J. Long-term gamma transcranial alternating current stimulation improves the memory function of mice with Alzheimer’s disease. Front Aging Neurosci. 2022;15(14):980636. https:// doi. org/ 10. 3389/ fnagi. 2022. 980636.

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