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.