There are definitely those with ASD who have experienced brain damage earlier in life, there is no denying this. And I can see the connection, but there is a flaw in assuming cause versus a link. It is well documented that we auties tend to have mothers with abnormal pregnancies, obstetric complications, and early illness. All these can have the potential to damage the brain, yes. However, I do not see this as a likely cause. Pure brain damage behaviorally is much different than ASD. Symptoms of ASD speak of alterations throughout the cortices and nuclei (i.e., most of the brain). Even hypoxia (loss of oxygen to the brain) does not destroy or affect the whole brain. There are areas which tend to be more affected by the hypoxia, more susceptible to hypoxic damage.
In addition, there are neuroanatomic traits seen within our brains involving what are called, "minicolumns". These are essentially columns of pyramidal cells throughout the cortex of the brain, lined somewhat like picket fences throughout the six layers. Specifically, it has been found that the width between minicolumns, the size of minicolumns, an increase in the total number of minicolumns, and the size of the cells are all affected. The progenitor cells (original mother cells) to these columns differentiate within the first ten weeks of foetal life, meaning that the number of these columns and cells within those columns are laid down pretty much right away during pregnancy. This implies that this minicolumn trait, linked with ASD-- autism and Aspergers alike-- is rooted in very early life and whether it's affected by the womb environment or genetics, it means that autism begins basically right away.
An increase in white matter is also found. However, this is not long-distance white matter but rather short-distance white matter. This is most likely due to the increase in cell columns; the more columns, the more necessary this short-distance connectivity.
There is also strong evidence that there are differences seen in the immune systems of those on the Spectrum as well. It is possible that various immune conditions are reacting or even triggered off sometimes by the vaccinations we now regularly receive in infancy these days. Although there is little link to the thimerosal, itself, but rather to the attenuated (weakened) viruses used within the vaccines themselves. It has been shown that viruses can often act as triggers for immune disorders and so suspicion has landed on the vaccine viruses themselves.
Seizures are also common. This is due to the nature of the minicolumns. When minicolumns are closer together, the GABA interneurons which mediate cell firing may be affected and do not regulate this firing as well. Hence, forest fires of seizure activity can occur. It is reported that up to 30% of auties will experience at least two seizures within their lifetime.
I for one do not believe that autism can be caused by brain damage. For anyone who knows brain anatomy and the nature of "damage" as well as the behaviors and cognitive processes which are integral to autism then this makes no sense whatsoever. However, there are likely reasons why we are more prone to brain damage, difficult births, etc., which are probably linked to our ASD. When one looks at brain damage and autism and finds the two occuring together, one needs to realize that this is simply a correlation, not a causation, and correlation cannot imply cause. In this case, I think that old addage is reliable because postmortem studies do not support brain damage as more than another trait, but not a causal link.
22 Jul 2007, 11:19 am
