Study Links Neurodegeneration in Head Trauma and ALS

[David]

The following article is written by ALS Society of Canada's science writer, Katie Moisse, PhD.

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Study Links Neurodegeneration in Head Trauma and ALS

Nearly four years since researchers identified the mystery component of toxic protein aggregates in ALS and frontotemporal lobar degeneration (FTLD)-affected motor neurons as TAR DNA-binding protein (TDP-43), a new study has suggested the protein is a player in head injury too.

Repetitive head injuries, like those tolerated by boxers, football players and hockey players, can lead to chronic traumatic encephalopathy (CTE) — a condition marked by neurofibrillary tangles of tau protein and behavioral changes akin to those seen in frontal lobe dementia.

But Boston-based researchers have reported that TDP-43 also accumulates in CTE patients’ brain neurons, and, in some cases, motor neurons in the spinal cord. In their report, published August 18 in the online Journal of Neuropathology and Experimental Neurology, they provide evidence that trauma-induced CTE and changes in brain TDP-43 expression could lead to downstream motor neuron degeneration resembling ALS.
The 16-strong research team, led by Ann McKee, MD, from the Bedford Veterans Administration Hospital in Bedford, MA, measured tau and TDP-43 expression in post-mortem brain and spinal cord tissue from 12 former athletes with CTE. Three of the subjects — a professional boxer and two professional football players — were also diagnosed with ALS. Tissue from 12 people who were neurologically normal at the time of death and 12 people with sporadic ALS served as controls.

As expected, the researchers detected abnormal tau expression in brain neurons from all 12 CTE subjects. But they also observed it in spinal neurons in all eight of 12 cases for which spinal cord tissue was available. This is in contrast to the rare tau-positive motor neurons they observed in spinal tissue from only four of 12 normal controls.

Read the full article

 

[Al]

Q: I heard about a study published in August that suggests that head trauma might be a cause of ALS. Is this true?

A: There was a study published in the Journal of Neuropathology and Experimental Neurology and it got a lot of attention because the New York Times ran an article about the research (August 17, 2010). That article went so far as to say that the famous Yankees baseball player Lou Gehrig might not have had ALS after all. This, of course, created quite a stir among everyone from baseball fans to people with ALS, the healthcare community and organizations that support people with ALS.

The study reported that some professional athletes (football, boxing) who have had repeated head injuries and developed what’s called chronic traumatic encephalopathy (CTE) may develop ALS. This study, based on the examination of the brain and spinal cord at autopsy, indicated that some pathological features of CTE in the brain can extend to the spinal cord. However, there were problems with the way the findings were reported by the media. The sample size was very small: the study only involved 12 people with CTE, three of whom developed ALS many years after their athletic careers ended. The cases were chosen based on their history of repeated head trauma, with or without a recent diagnosis of ALS. So, it is not at all surprising that people who developed ALS and head trauma showed neuropathological changes of both ALS and head trauma.

The majority of people with head trauma do not develop ALS. Head trauma is not rare; there are about 300,000 cases of head trauma every year. But there are about 5,600 cases of ALS annually. People with CTE demonstrate cognitive decline, abnormal behavior and dementia—all features indicative of brain damage. ALS, a motor neuron disease, involves upper (brain) and lower (spinal cord) motor neurons that die, causing a loss of muscle function. CTE is not a motor neuron disease, and there is no clear-cut cause-and-effect relationship between CTE and ALS. Some large, population based studies have provided evidence that head trauma might be one of many contributing factors involved in sporadic ALS, but much more work needs to be done in this area.

People with ALS sometimes ask me if they could actually have CTE instead of ALS. It’s important to know that the two diseases manifest themselves differently. In ALS, people typically have a gradual progression of weakness, and in CTE, they frequently have signs of dementia, a Parkinson’s like syndrome and behavioral problems. To further complicate the discussion, some patients with ALS have a frontal lobe behavioral component to their illness (FTS). So the paper contributes to the legitimate scientific debate about the spectrum of ALS and motor neuron disease, and raises relevant questions about injury to the nervous system and the development of ALS. It does not purport to claim that Lou Gehrig did not have ALS.

If you would like to submit questions for a future Q & A, please send your questions to Amber Walters at [email protected]. Please understand that we won’t be able to address all questions and we won’t be able to respond to individuals personally.