The claims that the Prophet Muhammad suffered from epilepsy rests on a number of shaky assumptions not supported by medical research. They are based solely on the many different descriptions of his state during his reception of revelation. First, the Prophet first received revelation when he was forty years old. This would mean that the Prophet suddenly developed epilepsy later in life as it has never been reported that he suffered from such experiences before. This is highly unlikely from a medical perspective.

Moreover, epilepsy is seen as one way of explaining the Prophet’s visions and spiritual experiences. The Prophet was not reported to have suffered from any such physical or mental conditions except during his reception of revelation. This would mean that the Prophet’s "epilepsy" occurred only when he was inspired by verses from the Quran. This would be a medical anomaly as epilepsy is not consistently associated with such experiences.

Untreated epilepsy also leads to mental damage and difficulties. The Prophet Muhammad received revelation for twenty three years and it was never reported that his memory or mental faculties suffered in any way. The following hadith explains:

Narrated Jabir ibn Abdullah: That he heard Allah's Apostle describing the period of pause of the Divine Inspiration, and in his description he said, "While I was walking I heard a voice from the sky. I looked up towards the sky, and behold! I saw the same Angel who came to me in the Cave of Hiraa, sitting on a chair between the sky and the earth. I was so terrified by him that I fell down on the ground. Then I went to my wife and said, 'Wrap me in garments! Wrap me in garments!' They wrapped me, and then Allah revealed: "O you, (Muhammad) wrapped-up! Arise and warn...and desert the idols." (74:1-5) Abu Salama said....Rujz means idols." After that, the Divine Inspiration started coming more frequently and regularly. (Bukhari)

If we consider the entire life history of the Prophet, one sees very clearly the integrity and consistency of his personality and qualities. He transformed the belief, practice and mindset of a corrupt and backward people to a moral and civilized one. He became the father of a nation in a manner unparalleled in human history.

From his family life to his public persona, the details of his life were transparent. And what emerges from a fair-minded look at his personality is that all his achievements cannot be reduced to some single medical reason. Unlike many of the great figures of history, what the Prophet did, said and sanctioned is recorded authentically and even more so after he received revelation. Indeed the thousands of pages that have been written on his life reveal not a trace of erratic or irrational behavior.

The idea of the Prophet being an epileptic was first advanced by Orientalists whose arguments both from a scientific and historical view are very flimsy. Since then, the argument has been rehashed by propagandists and critics who care little for the basis of their claims. From the above, it is clear that when one looks fairly at the life of the Prophet, it is hard to take such an argument seriously.

I conclude by the following traditions of the Prophet of mercy (peace be upon him):

Narrated Ata ibn Yasar: I met Abdullah ibn 'Amr ibn Al-'As and asked him, "Tell me about the description of Allah's Apostle which is mentioned in Torah (i.e. Old Testament.") He replied, 'Yes. By Allah, he is described in Torah with some of the qualities attributed to him in the Quran as follows: "O Prophet ! We have sent you as a witness (for Allah's True religion) and a giver of glad tidings (to the faithful believers), and a warner (to the unbelievers) and guardian of the illiterates. You are My slave and My messenger (i.e. Apostle). I have named you "Al-Mutawakkil" (who depends upon Allah). You are neither discourteous, harsh nor a noise-maker in the markets and you do not do evil to those who do evil to you, but you deal With them with forgiveness and kindness..." (Bukhari)

Abu Tufail reported; I said to Ibn Abbas (Allah be pleased with them): I think that I saw Allah's Messenger (peace be upon him). He (Ibn Abbas) said: 'Give a description of him to me’. I said: ‘I saw him near al-Marwa on the back of a she-camel, and people had thronged around him. Thereupon Ibn Abbas said: It was Allah's Messenger (peace be upon him) for they (the Companions of the Holy Prophet) were neither pushed aside from him, nor were they turned away.’ (Muslim)

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https://islamstory.com/en/artical/3408691/Did- Muhammad-Suffer-From-Epilepsy?