My bald spot has gone!
As you can see from the before and after pictures my hair has grown back and I no longer have a bald spot on the back of my head, just the usual gray hairs. I guess it was caused by a combination of being in the hospital bed, medication, stress and who knows what else.
I didn’t have to do anything special for it to grow back, other than not get stressed about it and I guess it took about 6 weeks to recover. A friend of mine (who’s a hairdresser) thought it might have been Alopecia, from the way it’s described this certainly seems possible, I’m just glad it’s back to normal.