The connection between brain injury and autism is somewhat vague. Does brain injury cause autism? Does autism cause changes in the brain? Or are the two related to a completely different disorder? Researchers -- and vaccine courts -- are still trying to figure it all out.
Many hypotheses have been put forth about what causes autism, and parents continue to reach out for explanations as to why and how their children developed autistic symptoms. Some wonder whether an injury during labor or early childhood could have permanently damaged the child's brain. The connection between the brain and autism is being studied vigorously in the hope that some clue will be discovered. But can brain injury cause autism? Or is autism caused by something unrelated to the structure of the brain? The answer is unclear.
Brain Injury at Birth
Brain injury to a baby during birth (or before birth to a developing fetus) has been suspected to lead to an increase in the chance of developing autism. The main cause of brain injury during birth is anoxia, which is when the brain is completely deprived of oxygen. Because the brain needs oxygen to survive and function at its highest capacity, anoxia can cause permanent brain damage and increase the risk of a child developing autistic symptoms.
Brain injury can happen prenatally as well. Terbutaline, an asthma medication, is used off-label as a medication to stall preterm labor. Terbutaline crosses the placenta and enters into the fetus, and the drug can potentially cause brain damage. As far back as 1995, the American College of Obstetricians and Gynecologists (ACOG) warned against using terbutaline for this reason, and the Food and Drug Administration (FDA) did the same in 1997. A 2011 study at Johns Hopkins Center for Autism and Developmental Disabilities Epidemiology (CADDE) compared twins born to mothers who had taken terbutaline to twins born to mothers who had not taken the drug. Researchers found that twins of mothers who had taken terbutaline had a significantly increased chance of developing autism. Although research has connected terbutaline and brain damage, as well as terbutaline and autism, it is has not found a direct connection between these two effects of terbutaline.
Mitochondrial Disease and Autism
The connection between mitochondrial diseases and autism has been under scrutiny in recent years. In people who have mitochondrial diseases, the mitochondria are unable to convert sugar and oxygen into energy efficiently, which can harm the brain. (The word "encephalopathy" means "brain damage.") Children with mitochondrial disease may have autism as well, although some only exhibit a few autistic symptoms, or in fact no autistic symptoms at all. More than just the comorbidity of these diseases, the two seem to be connected genetically. Some families that are predisposed to having mitochondrial disease are also predisposed to having autism, and both seem to be more prevalent in males. Some reports have studied the brain imaging of children with autism and found them to be consistent with mitochondrial dysfunction as well. However, that the two are connected has not yet been definitively proven.
Brain Injury and the Vaccine Debate
The question "Can brain injury cause autism?" is especially important in the vaccine debate. The Federal Vaccine Court has compensated over 600 parents who have claimed that their children developed encephalopathy -- the medical term for brain damage -- due to vaccinations. Children who have been diagnosed with autism, however, have not been compensated by the court, since the court has ruled that there is no proof that vaccines can cause autism. Many in the autism community, therefore, have encouraged others to claim that their child has encephalopathy and to stay away from the autism diagnosis until their case has been decided.
In 2010, the Hannah Poling case was the only one in which a child's autism diagnosis was accepted as a reason for compensation at the vaccine court. The court ruled that the vaccine had aggravated a mitochondrial disorder, which caused her to develop features of autism spectrum disorder. This landmark case tied together the concepts of brain injury, autism, and mitochondrial disorders, suggesting that the three may in fact be more strongly connected than is usually believed.
National Institute of Neurological Disorders and Stroke. "Mitochondrial Encephalopathies: Potential Relationships to Autism?" http://www.ninds.nih.gov/news_and_events/proceedings/20090629_mitochondrial.htm
Centers for Disease Control and Prevention. "Mitochondrial Disease - Frequently Asked Questions." http://www.cdc.gov/ncbddd/autism/mitochondrial-faq.html#relationship_encephalopathy
CBS News. "Vaccines, Autism and Brain Damage: What's in a Name?" http://www.cbsnews.com/8301-31727_162-20016356-10391695.html
Science Daily. "Brain Damage In Autism: Not What Scientists Once Thought." http://www.sciencedaily.com/releases/2001/01/010104071419.htm
Johns Hopkins Public Health. "Brain Storm." http://www.jhsph.edu/publichealthnews/magazine/archive/mag_fall04/brainstorm/page3.html
Carter Law Offices. "Autism and Terbutaline: Is There a Connection?" http://www.jcarterlaw.com/CM/Custom/Terbutaline-Brain-Damage-Autism.asp
Lawrence Day Law. "Anoxia (Lack of Oxygen to the Brain)." http://www.lawrencedaylaw.com/anoxia-lack-of-oxygen.html