Senator John McCain was hospitalized Friday after a routine physical discovered a blood clot just behind his left eye.

The 80-year-old Arizona politician had a 5cm clot removed via a minimally invasive craniotomy with an eyebrow incision.

Though the surgery itself was not considered to be too intrusive, McCain's medical history and bouts of melanoma suggests that the clot could be the sign of a much more serious problem.

And after the Senator's confused questioning of ex-FBI head James Comey in June, a number of people have expressed concern for McCain's mental health and are wondering if the clot could have been affecting him in that way.

Friday's procedure was planned after the clot was discovered during a routine physical earlier in the week, according to a statement provided by his office.

Surgeons at the Mayo Clinic in Arizona went in just below McCain's left eyebrow to remove the clot. While they only had to open a small part of his skull, it was still a very serious procedure, and will likely result in a long recovery period.

On Friday afternoon, Senator John McCain had a two-inch (5-cm) blood clot removed from behind his eye via a minimally invasive craniotomy with an eyebrow incision

WHAT IS A CRANIOTOMY? THE PROCEDURE THAT SAW A PIECE OF MCCAIN'S SKULL REMOVED TO REACH THE PROBLEMATIC CLOT

Craniotomies are relatively straight forward procedures, according to Dr Babacar Cisse, a neurosurgeon at Weill Cornell Brain and Spine Center.

The surgeon goes in just under the eyebrow, and temporarily removes a piece of skull before taking out the clot. He or she would then put the piece of bone back and it would be fastened with titanium plates and screws.

A statement from the Senator's office said McCain is in 'good condition,' and that his surgeons reported that things went 'very well'. He is also said to be in good spirits, and recovering at home in Arizona until he is well enough to return to Washington.

Before any further information is released about the reason for the clot, McCain and his team of doctors are waiting for pathology reports.

The blood clot was likely tested for cancer markers and other abnormalities.

Recovery from that kind of surgery generally involves a number of different exercises, and doctors recommend that a patient avoid straining themselves in any way that could prevent healing for several weeks.

'A week is cutting it very close, but it is hard to tell because it is different for every person,' Dr Cisse told Daily Mail Online.

SENATOR MCCAIN'S HISTORY WITH MELANOMA: HOW THAT COULD HAVE CAUSED A BLOOD CLOT AND BE A SIGN HIS CANCER HAS SPREAD

The clot was discovered during a routine physical, which McCain goes in for relatively frequently due to his history with invasive melanoma.

Melanoma is a malignant form of skin cancer that develops in melanin cells, which makes peoples skin darker.

McCain first received treatment for a non-invasive melanoma in 1993, having one removed from his shoulder, then again in 2000 and 2002.

SENATOR JOHN MCCAIN'S HISTORY OF MEDICAL ISSUES Senator McCain has come under the spotlight on various occasions to answer questions about his mental and physical health, particularly when he ran for President in 2000 and then again in 2008. Both of the times he ran, McCain voluntarily released all information about his physical and mental health. That is because the 80-year-old politician has had multiple public and serious procedures in his lifetime. In August 2000, he was treated for invasive melanoma, and had to have a significant amount of skin on the left side of his temple removed. He had had other incidences of melanoma previously, but they were all surface level and thus less concerning. Throughout his adult life, the Senator has also had various orthopedic problems, primarily related to his time in the US Navy during the Vietnam War (pictured) Throughout his adult life, the Senator has also had various orthopedic problems, primarily related to his time in the US Navy during the Vietnam War. During the war his fighter jet was attacked by Vietnamese missiles. In the accident, he broke both of his arms, the right one in three places, and seriously broke his right leg right around his knee. He was then held and tortured there for five-and-a-half years as a prisoner of war. Since then, other than some trouble walking and brief bouts of dizziness, McCain has had no serious orthopedic issues. He has also had no psychological issues related to the imprisonment. In 2001, McCain had some inflamed tissue removed around his prostate when he noticed blood in his urine. However, since then, all scans are clear. Advertisement

In 2000 he also had an invasive melanoma on his left temple, just inches from where the clot was removed from on Friday, which could signify a recurrence in the cancer.

Additionally, this type of melanoma can cause brain bleeding, which could have caused the clot.

When the invasive melanoma was treated, surgeons removed a section of skin that was 2.2mm thick and 2cm across. They later went in and removed a 6cm patch of skin and part of his salivary gland to reduce inflammation, according to CNN.

If the clot was related to his skin cancer, it would be a intraparenchymal hematoma, Dr Cisse explained. That means it would be in the brain, and related to metastasized melanoma in the brain that caused bleeding.

'If this was the case, pathologists will be able to tell quickly because there will be tumor markers on the clot,' Dr Cisse said.

OTHER EXPLANATIONS FOR THE BLOOD CLOT: COULD IT HAVE CAUSED MCCAIN'S CONFUSED QUESTIONING OF JAMES COMEY?

However, the clot might not be related to melanoma at all, and could instead be the sign of a fall, a blow to the head, a stroke or just brain changes associated with aging.

'There are many types of blood clots and none are uncommon, so while his history with melanoma will cause doctors to look for cancer markers in his pathology report, there is a good chance it was caused by something else,' Dr Cisse explained.

Friday's procedure has led some people to question whether doctors specifically looked for clot on his left temple due to other symptoms, nameably mental health issues.

People first started questioning the Senator's mental capabilities at the beginning of June, when he appeared confused and at times nonsensical during his questioning James Comey.

McCain dismissed initial concerns by ensuring he had just stayed up too late the night before watching baseball.

However, his confusion could have been caused if a clot, called a subdural hematoma, was putting too much pressure on that part of his brain.

That kind of clot could have been happened after a fall or if the Senator was taking a blood thinner, Dr Cisse said. He also explained that the left side of the brain there is specifically related to tasks such as speaking and relaying messages.

'This type of clot is often found in older people, because they do experience worse falls, and are often on blood thinners for something else,' Dr Cisse explained.

'They can develop slowly, over weeks or even months, and sometimes do not have any symptoms. But, if they grow to a certain size, the pressure on the brain can cause pain and even confusion or difficulty with everyday tasks such as speaking or moving around in patients.'

Senator McCain has not previously disclosed whether he takes blood thinners.

At the beginning of June, McCain's confused and at time nonsensical questioning of James Comey led some people to express their concerns about the senator's mental health. However, he dismissed those worries by ensuring he had just stayed up too late the night before watching baseball

MCCAIN'S HISTORY OF HEALTH ISSUES RELATED TO AGE AND HIS TIME IN THE VIETNAM WAR

This procedure is not the first the Senator has had during his time as a politician, and it is certainly not the first time he has had to answer questions about his health.

Throughout his time in Washington, a lot of light has been shed on his past medical issues.

When he ran for president the first time in 2000 and the second in 2008, he voluntarily released all information about his physical and mental health, after being pressed for the fact that, had he been elected, he would have been the oldest president to take office.

In his past, McCain has had orthopedic problems, primarily related to broken bones when he ejected himself from his fighter jet while fighting in Northern Vietnam for the US Navy.

In his past, McCain has had orthopedic problems, primarily related to broken bones when he ejected himself from his fighter jet while fighting in Northern Vietnam for the US Navy

When he ejected himself, he broke both of his arms, the right one in three places, and seriously broke his right leg right around his knee.

He was then held and tortured there for five-and-a-half years as a prisoner of war.

Since then, other than some trouble walking and brief bouts of dizziness, McCain has had no serious orthopedic issues. He has also had no psychological issues related to the imprisonment.

In 2001, McCain had some inflamed tissue removed around his prostate when he noticed blood in his urine. However, since then, all scans are clear.

