I believe that parents, such as Bernie Rimland, have promoted our modern understanding of autism. Indeed, I have learned more about the clinical aspects of autism by reading autobiographical accounts than by reading medical textbooks. It is therefore unsurprising that throughout the years when diverging opinions regarding autism have erupted between physicians and parents, it is the latter’s point of view that has carried the day. It stands to reason that nowadays when a controversy arises I try to understand both sides of the argument before making an informed decision. In the present blog, I will risk wasting everybody’s time in discussing a subject that has been repeatedly broached in the literature and offer my own take on the role that mercury may (or may not) have on the genesis of autism from the perspective of a neurologist and neuropathologist. I won’t cover the MMR controversy because I have not found any credible evidence to support a role for the measles virus in autism.
The art of diagnosis requires that in order to define the nature of a given affliction in a patient we take a comprehensive look at the clinical history and presenting signs, symptoms, and laboratory results. This practice is all the more important in Neurology as the brain is a heterogenous organ and different conditions can target specific portions of the same. This has led some clinicians to elaborate the concept of pathoclisis or selective vulnerability of the brain for given insults. In similar fashion efforts at parcellating the brain into regions have also used regional vulnerabilities to injury. As expected, the resultant map called pathoarchitectonics, differs from other maps using cellular or chemical criteria in their parcellation schemes, i.e., cytoarchitectonics, chemoarchitectonics.
There are several distinguishing clinical features that define intoxication with organic mercury. This would be a person with visual deficits whose blindness is marked by a progressive concentric constriction of his/her visual fields. There are difficulties in standing and running. Hand movements may become clumsy. Overall movements of the extremities are jerky and broken down by irregular accelerations and decelerations. It may be difficult for affected individuals to reach for a target, and when the hand or finger approaches its aim it may develop a side-to-side rapid movement or tremor. This tremor may also involve the lips and tongue. Speech is interrupted by variable intonations. Some individuals may also present with motor or sensory findings due to involvement of peripheral nerves. The mental state may be marked by confusion. Neuroimaging methods will reveal cerebral atrophy, with areas of tissue attenuation in the brain regions that process visual information and coordination (cerebellum). Brains from mercury poisoned individuals coming to autopsy show diffuse loss of neurons throughout the cerebral cortex, most marked in the anterior portion of a fissure (calcarine) involved in vision. Another area of the brain, the cerebellum, seems to be specifically targeted with marked loss of a specific type of neuron called granule cell.
Personally, I would have never confused the clinical picture of mercury intoxication with autism. The symptoms, including the clumsiness, are widely different for both conditions (see https://corticalchauvinism.wordpress.com/2013/02/01/clumsiness-and-autism/). In mercury poisoning the brains get smaller and become atrophied with certain areas of marked susceptibility. Brains of autistic individuals, on average, tend to be bigger, specially depending on developmental age. Even in the cerebellum, where abnormalities have been found in both conditions, the type of cells affected is very different. In mercury it is the granule cell while in autism it is the Purkinje cells (probably due to hypoxia, more on a future blog). So, mercury intoxication provides a fingerprint for its involvement based on both clinical, laboratory and pathological data. This fingerprint is not present in autism.
Since most of the controversy about mercury involves thimersoal (a preservative found in vaccines), I would find a propo to cite a recent press release regarding the position of the American Academy of Pediatrics and the World Health Organization (http://pediatrics.aappublications.org/content/131/1/152):
“A draft treaty under consideration by the United Nations Environmental Program has been prepared to greatly reduce global health hazards from environmental mercury. In response to the draft treaty, the World Health Organization urges removal of a provision in the treaty that calls for a ban on thimerosal (which contains ethyl mercury) in vaccines, a position recently endorsed by the American Academy of Pediatrics (AAP) and the US Public Health Service (USPHS).”
“Removal of the ban on thimerosal-containing vaccines (TCVs) represents a significant reversal of the position expressed in an AAP/USPHS joint statement in 1999 that called for elimination of mercury in vaccines and the subsequent actions taken in the United States. Understanding the circumstances that led 14 years ago to the 1999 statement and the knowledge accumulated in these subsequent years can reinforce the importance of the 2012 AAP/USPHS position. AAP representatives and other members of national pediatric societies within the International Pediatric Association advocating for deletion of the provision banning TCVs need to know why the elimination of thimerosal was initially called for in 1999 but is no longer indicated.”
This whole controversy is no longer about mercury and autism but about the lives of innocent individuals. Many people have died or suffered because of lack of vaccination. It should be clear by now that it is not the mercury in vaccines that causes autism.