'You think I'm mad?' – the truth about psychosomatic illness

Yvonne went blind overnight, Matthew couldn't walk, Shahina lost the use of her hand - but doctors found nothing wrong. Were they faking it, or was the mind playing tricks? A neurologist on her most intriguing cases

I was a junior doctor when I encountered Yvonne. She was 40 and worked in a supermarket. One Tuesday she was reorganising produce in a refrigerated unit while a colleague cleaned the glass. Yvonne turned to talk to her just as she released a small spray of window cleaner. Yvonne felt the liquid splatter on her face and a burning in both eyes. Another colleague led her to the bathroom and washed her eyes with water. Yvonne was taken by ambulance to hospital, where she was examined and had her eyes bathed. Her husband was called, and by the time he arrived she was feeling better. Her eyes were red and full of tears, but she could see normally and the pain had lessened. Her husband took her home.

He told her not to go in to work the next day, and during the morning Yvonne noticed her vision blurring. By lunchtime, she was struggling to read the digital clock. Her husband and children came home that evening and encouraged her to have an early night. When Yvonne woke up and opened her eyes, everything was black. She cried out for help and heard the noise of people entering the room, but could not see them. She was completely blind.

I noticed increasingly that when she spoke, she looked me in the eye. It was more than a glance; I felt our eyes connect

Do you really think my daughter could hold her hand like this for weeks? She's in pain. I know my own child

I can't believe it! I came to this hospital with muscle spasm and now I'm being told I'm doing it on purpose

Fantastic news: none of his tests had shown evidence of MS. I could see his face darken and his wife's eyes roll