Chronic Traumatic Encephalopathy (CTE)

Definition

Chronic Traumatic Encephalopathy (CTE) is a progressive neurodegenerative disease associated with repetitive head impacts (RHI), such as those experienced in contact sports or military service. It is characterized pathologically by the perivascular accumulation of hyperphosphorylated tau protein in neurons and astrocytes at the depths of the cortical sulci.

Early Manifestations in Young Athletes

Recent studies (McKee et al., 2023) have shown that CTE can begin much earlier than previously recognized:

  • Prevalence: 41.4% of brain donors under age 30 with a history of RHI showed diagnostic changes for CTE.
  • Severity: Most young cases are mild (Stages I or II).
  • Associated Features: Cavum septum pellucidum, ventricular enlargement, and thalamic notching.

Symptoms

Informant-reported symptoms in young athletes, regardless of pathologically confirmed CTE status, include:

  • Cognitive: Executive dysfunction.
  • Behavioral: Impulse control issues, apathy.
  • Mood: Depression and irritability.

Mechanisms

  • Tauopathy: Primary pathological driver. Unlike Alzheimer’s, CTE tau accumulation is uniquely perivascular.
  • T-cell Infiltration: Tau pathology (but not amyloid) appears to recruit T-cells to affected brain regions, suggesting an adaptive immune component. (See: Microglia-T cell Interaction)
  • Hippocampal Sclerosis & TDP-43: RHI is also linked to hippocampal sclerosis and TDP-43 inclusions, which may co-occur with or be exacerbated by CTE tau pathology (Nicks et al., 2023).