Mohammed, founder of Islam, is often described as having epilepsy. He’s even described as such on epilepsy information site epilepsy.com. The historical basis for such claims are almost certainly false, however, and first stem from a historian writing almost 200 years after the Prophet’s death.
The myth has been most comprehensively debunked by the respected American historian of medicine Owsei Temkin in his book The Falling Sickness: This History of Epilepsy from the Greeks to the Beginnings of Modern Neurology (ISBN 0801848490). To quote from p153…
As is to be expected, the positive bias of Islam was countered by an opposite bias in the Christian world. As to the origin of the diagnosis “epilepsy”, everything points to Christian Byzantium, an empire that was no only hostile to Islam but at frequent war with the Arabs. Less than 200 years after Mohammed’s death, the Byzantium historian Theophanes (died about 817) told a story which was bound to make Mohammed appear and fraud and to discredit the belief in his divine mission.
According to Theophanes, Mohammed had the disease of epilepsy. And when his wife noticed it, she was very much grieved that she, being of noble descent, was tied to such a man, who was not only poor but epileptic as well. Now he attempts to soothe her with the following words: “I see a vision of an angel called Gabriel and not being able to bear the sight of him, I feel weak and fall down.” But she had a certain monk for a friend who had been exiled because of his false faith and who was living there, so she reported everything to him, including the name of the angel. And this man, wanting to reassure her, said to her: “He has spoken true, for this angel is sent forth to all prophets”. And she, having received the word of the pseudo-prophet, believed him and announced to the other women of her tribe that he was a prophet. (Theophanes, 1007, Chronographia, vol. 1, p334)
The is the story which was accepted by Western historians, theologians and physicians. The story has all the earmarks of religious and political propoganda. Hence it was repudiated by Gibbon as “an absurd calumny of the Greeks”.
PDF of Owesei Temkin’s obituary.