It’s the first time the snake parasite has been seen in a human, let alone a brain.
Do you think it makes sense to run all kinds of tests and scans whenever someone comes in with a headache? It’s often impossible to be certain about the underlying illness so doctors have to make educates guesses. If it’s probably a mundane problem, they’re not going to continue digging just in case the patient might have a never-seen-before worm in their brain.