Professional and Linguistic Assessments Board (PLAB) Practice Exam

What is the most likely cause of multiple sclerosis?

1. Bacterial infection

2. Methyl alcohol poisoning

3. Viral infection

4. Traumatic brain injury

The correct answer is: Methyl alcohol poisoning

The correct choice is based on the most widely understood pathophysiological aspects of multiple sclerosis (MS). Multiple sclerosis is primarily believed to involve an autoimmune response that leads to the demyelination of neurons in the central nervous system. While the specific cause of MS remains unclear, viral infections are considered significant risk factors that may trigger this autoimmune response. Among the options to consider, some viral infections, particularly the Epstein-Barr virus (EBV), have been strongly associated with an increased risk of developing MS. This association points to the idea that a viral infection can somehow lead to the breakdown of self-tolerance in the immune system, contributing to the development of MS. On the other hand, the other options—bacterial infection, methyl alcohol poisoning, and traumatic brain injury—are less connected to the etiopathogenesis of multiple sclerosis. Bacterial infections and traumatic brain injury lack direct links to the immune-mediated demyelination seen in MS. Methyl alcohol poisoning can cause neurological symptoms but does not relate to MS mechanisms. Thus, while the exact etiology of MS is still being researched, the connection between viral infections and the development of the disease is stronger than the other options provided.