Neuroprotective Effects of Low-Intensity Pulsed Ultrasound in Chronic Traumatic Encephalopathy Induced by Repetitive Head Collisions: A Narrative Review.

The repeated head impacts experienced by athletes have attracted significant interest from both the public and the scientific community; however, the neurobiological effects following the games are not well understood. For example, a single football match carries the risk of repeated concussive and subconcussive head impacts, which can increase the risk of developing neurodegenerative diseases. Chronic traumatic encephalopathy (CTE) is one of the neurodegenerative conditions athletes often face or are unaware of. However, addressing the disease progression in CTE is difficult to determine due to several reasons, such as the failure to identify risk factors, difficulty in differentiating CTE from other neurodegenerative diseases, and the lack of a specific mechanism by which CTE leads to tau protein accumulation. In addition, CTE symptoms overlap with other neurodegenerative conditions, such as Alzheimer's disease (AD) and Parkinson's disease (PD), which poses a challenge to producing specific targeted therapy. In this case, ultrasound represents a promising non-invasive technique that enables clear visualization of brain structures and may modulate neuronal activity. The term ultrasound encompasses various modalities; for example, high-intensity focused ultrasound (HIFU) employs thermal energy to ablate cells, whereas low-intensity pulsed ultrasound (LIPUS) delivers mechanical energy that activates molecular signaling pathways to impede the progression of CTE. Therefore, the LIPUS application could potentially minimize the risk of damage in the surrounding tissues of the brain and reduce the disease progression in individuals with CTE. Nevertheless, limited studies have been reported in the literature, with a poor mechanistic approach. Hence, this review aims to highlight the molecular signaling pathways, such as AKT, MAPK, and ERK, affected by LIPUS and emphasize the need for additional research to clarify its mechanistic effects in CTE management. Ultimately, this review aims to contribute to a nuanced understanding of LIPUS as a therapeutic strategy in addressing the complexities of CTE and its associated neurodegenerative disorders.