The clinical case that made me become a neurologist was a patient with one of those weird clinical syndromes that are usually seen only in a textbook. I was a second year medical student on the stroke ward for the first time; there I met a woman who’d had a stroke in one of those strategic sweet spots that we sometimes see. She’d hit a part of the brain that affected her right visual field, meaning she couldn’t see the right half of the world, but she’d also hit a part of the corpus collosum, the huge tract of white matter that allows neurons in the left and the right hand to talk to each other.

The implications of this were clear as soon as my supervisor asked her to write a sentence. She did so, making a fully legible statement about the sky being blue on a piece of scrap paper.

My supervisor looked at me, as if to brace me for what was coming. “Can you read that, please?” he asked.

She couldn’t. For the life of her, she could not read the phrase she had written down not ten seconds before.

I’m a neurologist, so I know the substrate – her left visual field could see the letters, meaning her right brain could process the images, but because the corpus collosum was knocked out, the visual information couldn’t get to the language centre. The letters she herself had written could not be interpreted; with a blood clot to the brain and a stroke of bad luck, this high-functioning woman had become completely and utterly unable to read. The fact that she could still write seems an especially cruel irony, but that’s the way the brain works.

I write this because it makes me think of the importance of language – as a writer, it seems such a struggle to get the right word on the page, to make the plot flow and the dialogue natural and the characters believable. As a neurologist, I see the things that can happen to our language on a daily basis. The words stop coming out, or a word gets substituted for another, or a person’s speech and comprehension dissolves into gibberish. We have our terms for it – aphasia, alexia, agraphia – but the bottom line is that they all rob people of that ability to communicate, the very medium that those of us who write depend on.

It’s a sobering thing to think, that all of our stories and plots could be lost forever with just the right blow to the right neurons. Our writing, our words, are such impossible and fragile things, and that’s all the more reason to treasure them while we have them. I think about that a lot when I hear of people with language complaints at work – how I would cope, what I would do, if the ability to read or write or speak were suddenly robbed from me.

So, to be a bit of the nagging health advocate, stop smoking, watch your blood pressure, get exercise, treat your heart and blood vessels right. These things usually happen because of a lifetime of bad habits and it’s never too late to turn that around. And appreciate what you read, and what you write – because there may come a time, someday, when it becomes a lot harder to do so.