Ingestion of Common Chemicals Leads to Delayed Neurological Effects
Poisoning by common household or automotive substances like ethylene glycol, diethylene glycol, and methanol is correlated with delayed-onset nervous system damage. Symptoms often involve an impaired ability to control the muscles of the face. This development, among others which result from this poisoning, mirror the progression of Parkinson’s disease, a degenerative nervous system disorder that leads to loss of muscle control and slowed mental processes.
Ingestion of substances such as antifreeze and brake fluid has long been known to cause immediate symptoms such as seizures and vomiting, but it has been recently shown that patients who survive poisoning often develop neurological problems as well later on. In a research paper by Nandi J. Reddy, Madhuri Sudini, and Lionel D. Lewis at the Dartmouth-Hitchcock Medical Center, ethylene glycol, diethylene glycol, and methanol were investigated for their capacity to cause delayed nervous system damage.
Ethylene glycol is an ingredient in antifreeze which often leads to death when consumed due to its high toxicity. It acts as a central nervous system depressant, and has typically been associated with three distinct phases of poisoning. In the first stage, during the hours immediately after ingestion, patients often develop seizures and are at a high risk for death. In the second stage, after about twelve hours, respiratory symptoms begin. In the third stage, two to three days later, kidney failure develops.
The paper reviewed past cases on ethylene glycol ingestion and discovered that there is a fourth stage of poisoning, which starts five days to a several weeks after ingestion. This delayed stage is characterized by damage to the seventh cranial nerve, which is responsible for facial sensation and movement as well as taste.
This damage causes impaired speech and difficulty swallowing, symptoms which are remarkably similar to those of Parkinson’s disease. However, whereas damage from ethylene glycol poisoning is mostly localized to the face, Parkinson’s disease causes damage to other areas of the body as well.
Diethlyene glycol and methanol poisonings share an initial stage of high mortality followed by damage to the seventh cranial nerve. Their pathologies are also similar: in the body, these compounds are broken down by enzymes, forming intermediates which cause the symptoms to develop. What is amazing is that, regardless of their metabolism, each of the three compounds has a similar effect on the nervous system.
When asked for comments, author Lionel D. Lewis stressed that it is still unclear why the seventh cranial nerve is the most affected. The region of the brain usually responsible for delayed nervous system damage is the basal ganglia, clusters of cells that control voluntary motor function. Other disorders that involve the basal ganglia are Huntington’s disease, which leads to loss of muscle control and dementia, and Tourette’s syndrome, which leads to involuntary tics, and the disruption of movement and speech.
The paper demonstrates the need for further research on the precise mechanism by which ethylene glycol, diethlyene glycol, and methanol act on the brain. The symptoms produced are similar to those of other degenerative nervous system diseases, suggesting their better understanding might help in the understanding of these diseases as well.