As CTE progresses, it can cause memory loss, impulsive and erratic behavior, balance difficulties, impaired judgment, and behavioral disorders including aggression, depression, and increased suicidal tendency. Eventually, CTE progresses to the onset of dementia. A similar accumulation of tau protein has also been observed in the brains of Alzheimer's patients. Symptoms of CTE can appear months or years after the brain trauma, and a definitive diagnosis of CTE can only be made after death by analyzing brain tissue during an autopsy. The CDC estimates that up to 3.8 million concussions occur each year, with approximately 10 percent of high school athletes suffering from post-concussion syndrome. The trauma is also often repeated: an athlete who suffers a concussion is four to six times more likely to suffer a second concussion. How these episodes of trauma progress to CTE is not well understood, and there is currently no cure. After the article's publication in July 2005, Omalu was informed by the Neurosurgery editorial board that the NFL's Mild Traumatic Brain Injury (MTBI) Committee was asking for a retraction. Omalu instead went ahead to examine Terry Long, another former football player who had committed suicide at age 45, and discovered the same accumulation of tau proteins. His follow-up article in Neurosurgery was published in November