It is an established fact that Muhammad had seizures, see  how this medical condition shaped Islam.

Muhammad and Temporal Lobe Epilepsy (TLE)

The Physical Effects of Muhammad's Ecstatic Experiences

Here is how Muhammad described his mystical experiences:

"The Revelation is always brought to me by an angel: sometimes it is delivered to me as the beating sound of the bell--and this is the hardest experience for me; but sometimes the angel appears to me in the shape of a human and speaks to me."

"Those who saw the Prophet (pbuh) in this state relate that his condition would change. Sometimes he would stay motionless as if some terribly heavy load was pressed on him and, even in the coldest day, drops of sweat would fall from his forehead" At other times he would move his lips.

Ibn Sa'd says, "at the moment of inspiration, anxiety pressed upon the Prophet, and his countenance was troubled"

"He fell to the ground like one intoxicated or overcome by sleep; and in the coldest day his forehead would be bedewed with large drops of perspiration.  Inspiration descended unexpectedly, and without any previous warning." 

"Then Allah's Apostle returned with that experience; and the muscles between his neck and shoulders were trembling till he came upon Khadija (his wife) and said, "Cover me!" They covered him, and when the state of fear was over"  and 

All these are symptoms of Temporal Lobe Epilepsy. The following is a partial list of the Temporal Lobe Seizure Symptoms & Signs as defined in  health.allrefer.com 

All the above symptoms were present in Muhammad during the moments that he was allegedly receiving revelations.

It is also interesting to note that Muhammad's hallucination was not limited to seeing the Angel Gabriel but he also claimed seeing Jinns and even in one occasion while praying in the mosque he started struggling with an imaginary person and later said "Satan came in front of me and tried to interrupt my prayer, but Allah gave me an upper hand on him and I choked him. No doubt, I thought of tying him to one of the pillars of the mosque till you get up in the morning and see him. Then I remembered the statement of Prophet Solomon, 'My Lord ! Bestow on me a kingdom such as shall not belong to any other after me.' Then Allah made him (Satan) return with his head down (humiliated)."

Muhammad's belief in Satan was such that he seemed to think that not even he is immune from his whisperings.

One of the embarrassing events in Muhammad's life occurred when Satan put words in his mouth.

Tabari says: "When the messenger of God saw how his tribe turned their backs on him and was grieved to see them shunning the message he had brought to them from God, he longed in his soul that something would come to him from God which would reconcile him with his tribe. With his love for his tribe and his eagerness for their welfare it would have delighted him if some of the difficulties which they made for him could have been smoothed out, and he debated with himself and fervently desired such an outcome. Then God revealed:

"By the Star when it sets, your comrade does not err, nor is he deceived; nor does he speak out of (his own) desire..."

and when he came to the words:

Have you thought upon al-Lat and al-Uzza and Manat, the third, the other?

Satan cast on his tongue, because of his inner debates and what he desired to bring to his people, the words:

"These are the high flying cranes; verily their intercession is accepted with approval.

The Quraysh left delighted by the mention of their gods. Amity was restored and the news of that reached the followers of Muhmmad who at his behest had migrated to Abyssina and some of them returned.  Muhammad realizing the consequence of this is giving up on his monopoly on God and the contradiction that it entails, claimed those verses and his Allah consoled him saying, "Never did We send a messenger or a prophet before thee, but, when he framed a desire, Satan threw some (vanity) into his desire: but Allah will cancel anything (vain) that Satan throws in, and Allah will confirm (and establish) His Signs: for Allah is full of Knowledge and Wisdom": 22:52  

In the Quran there are several mentions of Jinns. Surah 72 narrates a conversation between Jinns where they comment about the Quran, call it "a wonderful Recital" and convert to Islam. Their role is described as prying into the secrets of heaven and eavesdropping to the conversation of the exalted assembly. Which since the apparition of Muhammad, they found it filled with stern guards and flaming fires. "We used, indeed, to sit there in (hidden) stations, to (steal) a hearing;" Quran quotes one Jinn saying to others, "but any who listen now will find a flaming fire watching him in ambush. And we understand not whether ill is intended to those on earth, or whether their Lord (really) intends to guide them to right conduct".

It is not difficult to see that Muhammad suffered from Temporal Lobe Epilepsy. In fact TLE was just one of his ailments. The prophet suffered from other mental disorders and physical complications. I will speak about them in future. The real miracle is in the fact that a billion people follow a sick man for so long.  

 

 Understanding What Epilepsy Is & What It Causes the Brain To Do

Background: Temporal lobe epilepsy (TLE) was defined in 1985 by the International League Against Epilepsy (ILAE) as a condition characterized by recurrent unprovoked seizures originating from the medial or lateral temporal lobe. The seizures associated with TLE consist of simple partial seizures without loss of awareness (with or without aura) and complex partial seizures (ie, with loss of awareness). The individual loses awareness during a complex partial seizure because the seizure spreads to involve both temporal lobes, which causes impairment of memory.

TLE was first recognized in 1881 by John Hughlings Jackson, who described "uncinate fits" and the "dreamy state." In the 1940s, Gibbs et al introduced the term "psychomotor epilepsy." The international classification of epileptic seizures (1981) replaced the term psychomotor seizures with complex partial seizures. The ILAE classification of the epilepsies uses the term temporal lobe epilepsy and divides the etiologies into cryptogenic (presumed unidentified etiology), idiopathic (genetic), and symptomatic (cause known, eg, tumor).

Pathophysiology: Hippocampal sclerosis is the most common pathologic finding in TLE. Hippocampal sclerosis involves hippocampal cell loss in the CA1 and CA3 regions and the dentate hilus. The CA2 region is relatively spared.

For more information, see Pathophysiology in the article Seizures and Epilepsy: Overview and Classification.

Frequency:

In the US: Approximately 50% of patients with epilepsy have partial epilepsy. Partial epilepsy is often of temporal lobe origin. However, the true prevalence of TLE is not known, since not all cases of presumed TLE are confirmed by video-EEG and most cases are classified by clinical history and interictal EEG findings alone. The temporal lobe is the most epileptogenic region of the brain. In fact, 90% of patients with temporal interictal epileptiform abnormalities on their EEG have a history of seizures.

History:

Physical:

Causes:

Febrile seizures: The association of simple febrile seizure with TLE has been controversial. However, a subset of children with complex febrile convulsions appear to be at risk of developing TLE in later life. Complex febrile seizures are febrile seizures that last longer than 15 minutes, have focal features, or recur within 24 hours.