I heard an archaeological podcast last evening that talked about new evidence related to Henry III. In his younger adulthood, he was very active in jousting and similar activities. It appears that at one of these events he was unseated from the saddle and his horse in turn fell on top of him.

It is speculated that he sustained a severe concussion and was unconscious for an extended period. His wife at the time (Ann Bolynn if I remember correctly from the program) was so distressed that she miscarried their child. It was the son Henry wanted (their second child together - first was a daughter). She was beheaded a year later.

The podcast report attributed his susceptibility to severe headaches in his later life to this incident.

@t1nick Yes it is also said that his sepsis, came from a wood splinter, which got into his leg while jousting, and which festered away over many years.