Nov 19 2010

Did Lou Gehrig have Lou Gehrig’s Disease?

Today I begin my day and a half of travel to get from CT to Sydney Australia for the the first TAM Australia event. Along the way I will stop off in Vancouver for a live show there, with special guest George Hrab and an appearance by Fraser Cain. Right now I am doing last minute packing and trying to remember the hundred things I need to bring along and have prepared before I leave. I will still be blogging over the two weeks that I will be out of the country – but I will probably keep a light blogging schedule, starting with today.

Here is just a quick item about Lou Gehrig’s disease – also known as motor neuron disease or amyotrophic lateral sclerosis (ALS). ALS is a neurological disorder in which the motor neurons progressively die off. There are basically two types of motor neurons – the upper motor neurons carry signals from the cortex of the brain down to the spinal cord. They synapse on the lower motor neuron which then carries that signal out of the spinal cord, through the peripheral nerve, and to the target muscle. There are interneurons that modulate function, but basically it’s a two-neuron system. In ALS both the upper and lower motor neurons die, that is the hallmark of the disease.

Actually ALS is a category of diseases, not one pathopysiological entity. There is familial ALS, about 20% of which is caused by a mutation in the SOD1 gene (for a protein that reduces oxygen free radicals). Sporadic ALS itself likely has multiple causes, all leading to the final common pathway of motor neuron death. While we know a lot about what is happening in ALS, we have not yet found the smoking gun (or guns) of the ultimate cause(s).

Epidemiology is often the first clue as to the cause of a disease. Here we don’t get many clues for ALS, the risk of which increases steadily as we age. It does not follow an infectious pattern, for example. There are a couple of regional populations at increased risk, such as natives of Guam, but this was explained as toxicity from eating fruit bats who in turn eat a local nut that contains a neurotoxin. But this only explains the Guam cluster. There are no other clearly predisposed groups that would provide a clue as to cause of other forms of ALS.

There are some possibilities, however. For example it is possible (although controversial) that there is a slightly higher chance of have been subjected to an electrical injury. It has also been proposed that the chance of having suffered a head injury or spinal cord injury is also greater among ALS patients.

Speculation about Lou Gehrig was started by this paper – Chronic traumatic encephalopathy: a potential late effect of sport-related concussive and subconcussive head trauma. The paper describes a distinct, if similar, syndrome of chronic brain damage from sports injuries. The questions is – did Lou Gehrig have true ALS, or did he have chronic traumatic encephalopathy secondary to his sports career (he did suffer multiple head injuries)? We will never know for sure, since he was cremated.

This story is a few months old – but I am blogging about it now because there is an update. A new editorial by ALS specialists argues that the claims in the original paper are not supported. They argue that the review of 12 patients did not provide evidence that traumatic encephalopathy (CTEM) can mimic the clinical findings of ALS, so if patients meet the well-defined clinical criteria for the diagnosis there is no reason to question it. Further, the CTEM patients they described mostly did not have the muscle changes seen in ALS and the three that did may have simply had trauma and ALS both.

I find their arguments compelling, but it still leaves open the question of whether or not prior head trauma is a risk factor for the development of ALS. And if it is – what does this mean for the pathophysiological cause of ALS (or one subtype of ALS).

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