Pathophysiology Clinical Question about the Brain

Question

A 65-year-old woman presents with a 1-hour history of right-sided weakness and aphasia. An immediate CT scan of the brain is negative.  

1. Where in the brain is the pathology?

Answer 1

The question is a bit vague, but the key is to understand the parts of the brain that control the functions in question.

It's also important to define the term "aphasia" - a broad definition would be dysfunction in producing and understanding speech (i.e. problems with processing language). However there's more than one type of aphasia, so the question could be elaborated to be more descriptive. Nonetheless, the relevant areas here are what are called Broca's area (located in the frontal lobe) and Wernicke's area (located mostly in the temporal lobe). Unlike many other brain structures, these areas are only found on one side of the brain - for most people it's the left side of the brain because most people are right-handed which is to say that the right side is the dominant side.

Lateralization is the key to understanding this question. Motor function of each side of the body is controlled by the motor cortex on the opposite side of the brain. The primary motor area is the pre-central gyrus - think of it like a headband arching over the top of the brain at the posterior end of the frontal lobe, at its border with the parietal lobe.

It's unclear what level of detail the question wants for the answer. In the broadest sense we can say that the injury is on the left side of the brain. Beyond that it's hard to say without more detail because the areas in question don't overlap and the type of aphasia isn't specified - one possibility is that there's blockage in the middle cerebral artery or some of its branches, but this vessel supplies a large area of the cerebrum including but not limited to the language centers and most of the pre-central gyrus.

So in summary I think you can say the pathology is expressed in the left side of the brain with complete confidence, followed by the middle cerebral artery with somewhat less confidence.

Feel free to ask your professor for more detail to demonstrate the depth of your understanding ;)