Neurotrauma: 2022 update

Abstract

The year 2021 was highlighted by many notable advancements in the field of neurotrauma and associated neuropathology. After a thorough review of the new literature, we call attention to what we feel are among the most impactful studies and publications. In brief, 2021 was marked by published consensus papers related to the diagnosis of chronic traumatic encephalopathy (CTE) and its clinical counterpart, traumatic encephalopathy syndrome. There was also progress toward our understanding of the impact of traumatic brain injury (TBI) on the general population, and how strongly CTE pathology may, or may not, commonly underlie long term clinical sequelae following TBI. Next, a critical new study has identified that acetylated tau protein, which has been found to be increased in the brains of Alzheimer's disease and CTE patients, can be induced by TBI, is neurotoxic, and that its reduction via already-existent therapeutics is neuroprotective. There are also several important updates that pertain to military and blast TBI, particularly as they pertain to establishing causality of interface astroglial scarring. In addition, and for the first time, a specific signature for diffuse axonal injury has been identified in ex vivo tissues using multidimensional magnetic resonance imaging, providing promise for the clinical diagnosis of this lesion. Finally, several important radiologic studies from 2021 have highlighted long-standing structural reductions in a number of brain regions following both mild and severe TBI, emphasizing the need for neuropathologic correlation. We end by highlighting an editorial piece discussing how TBI is portrayed in entertainment media and how this impacts public perception of TBI and its consequences.

Keywords: Chronic traumatic encephalopathy; Diffuse axonal injury; Interface astroglial scarring; Multidimensional MRI; Tau; Traumatic brain injury.

Figure 1. Comparison of chronic traumatic encephalopathy (CTE) and sulcal tau astrogliopathy.

A and B (black bars are 900µm and 200µm, respectively): pathognomonic CTE lesion with tau aggregates in neurons (and glia) around small blood vessels at the depth of a sulcus, with tau pathology not restricted to superficial cortical layers. C and D (black bars are 600µm and 200µm, respectively): in contrast, glial tau aggregates in a sulcal depth without perivascular predilection and limited to superficial cortical layers is not diagnostic for CTE, but is rather most fitting of tau astrogliopathy.

Figure 2. Comparison of ferret brain with human and other animal species.

Though relatively small, ferret brains show striking structural similarities with that of primate and human brains, particularly relative to the brains of rodents which themselves are lissencephalic, lack clear grey-white matter interfaces, and have substantially less white matter.