Spinal cord pathology in chronic traumatic encephalopathy with motor neuron disease
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Chronic Traumatic Encephalopathy (CTE) is a neurodegenerative disease caused by repetitive head trauma and mild traumatic brain injuries (mTBIs) and has been associated with contact sports such as football, boxing, and ice hockey. CTE is a slowly progressing neurological disease that is often clinically associated with symptoms of memory loss, decline in cognitive function, behavioral changes such as increased impulsivity and aggression, and/or suicidal thoughts. Advanced stages of the disease present with more severe neurological changes such as dementia, speech and gait abnormalities, and parkinsonism. Amyotrophic Lateral Sclerosis (ALS, also known as Lou Gehrig Disease) is a progressive and fatal neurodegenerative disease characterized by motor neuron loss and corticospinal tract degeneration. While 90-95% of ALS cases are sporadic in nature, many genetic mutations have been identified that contribute to familial forms of the disease. The etiology of sporadic ALS is unknown but it is likely caused by a complex interaction of various genetic and environmental risk factors. Epidemiological evidence suggests that one such risk factor is brain trauma, the main risk factor associated with the development of CTE. In this study the spinal cord tissue of twelve athletes diagnosed with CTE who also developed a progressive motor neuron disease and showed symptoms of profound muscle weakness, atrophy, spasticity, and fasciculations several years before death was examined. The spinal cord tissue from these 12 CTE cases with motor neuron disease (CTE+MND) was compared to the spinal cord tissue of 10 sporadic ALS control cases. Results showed a difference in frequency of tau pathology between the two disease cohorts, as one-third of CTE+MND cases and none of the ALS cases showed tau immunoreactivity. In addition, TDP-43 immunoreactivity was present in every CTE+MND case but one and was present in all ALS cases. Motor neuron inclusions were positive for both FUS and p62 in both cohorts, and no distinct differences were observed cystatin C pathology. Overall, this suggests that the spinal cord inclusions in CTE+MND have a similar composition to sporadic ALS. However, there is an increased frequency of tau pathology in CTE+MND though this result did not reach statistical significance in this study.