In December 2012, Hillary Clinton sustained a concussion. The secretary of state had become so dehydrated she fainted, hit her head, and, as a result, was brought to New York-Presbyterian Hospital for a follow-up MRI scan of her brain. Doctors discovered a blood clot inside a vein inside her skull and promptly prescribed blood thinners — which became the genesis of conspiracy theories about Clinton’s health as she runs for president of the United States.

Ultimately, Clinton was diagnosed with cerebral venous sinus thrombosis (CVST). Three out of every one million people will develop CVST, which is when a blood clot forms in the transverse sinus — a large vein that wraps around the inner wall of the skull. Because of the force from the fall, Clinton formed the rare clot behind her right ear, leaving her with (temporary) double vision and dizziness. Although Clinton’s doctors reassured the public she had not suffered from a stroke or neurological damage, others have continued to speculate on her physical health.

Recently, Republican nominee Donald Trump and his supporters have echoed conspiracy theorists circulating the idea that Clinton isn't in good health. Photos of falsified medical records came along with the rumors that described Clinton experiencing black outs, uncontrollable twitching, memory loss, and fatigue. In response, Clinton’s long-time physician Dr. Lisa Bardack released this statement:

“I have recently been made aware of allegedly ‘leaked’ medical documents regarding Secretary Clinton with my name on them,” Bardack said. “These documents are false, were not written by me and are not based on any medical facts. To reiterate what I said in my previous statement, Secretary Clinton is in excellent health and fit to serve as President of the United  States.”

While many false statements have perpetuated the rumors about Clinton’s condition in order to discredit her ability to serve as president — Trump said this week that she lacked the "mental and physical stamina" to fight ISIS — some health controversies remain. Sean Hannity, conservative talk show host and co-host of Fox News Channel’s show “Hannity,” is behind many of the conspiracy theories about Clinton’s health [see video].

In response, CNN host Brian Stelter said: “Let me be clear. That was reckless speculation by Sean Hannity. All of it. Hannity is not interested in the truth about Clinton's health. Conspiracy theories are so much more interesting than the truth. But the last time I checked, Fox still has the word ‘news’ in its name.”

Hillary Clinton's health has been brought into question, but according to science, the rumors don't hold any weight.Photo courtesy of Reuters/ Charles Mostoller

Clinton’s health has arguably become a political issue in the fight for the White House. Here are the symptoms that underlie the rumors— along with the facts.

Aphasia

Aphasia is a communication disorder that impairs a person’s ability to process language, speak, understand others, read, and write. According to the National Aphasia Association, the most commoncause of aphasia is stroke, which occurs in approximately 25 to 40 percent of stroke survivors. Although Clinton did not experience a stroke, there has been speculation based on how she speaks in interviews and in speeches.

“What about some of the weird pauses she has, the coughing fits she has?” Hannity said in an interview on Fox and Friends. “There are moments when I'm literally watching her and I'm thinking, The facial expressions are odd. They seem off.  Is it possible she had a stroke, or do you really believe it was a head injury, traumatic brain injury?”

Hannity questions if her doctors were lying. However, aphasia can also be caused by a head injury, which Clinton did experience in 2012. But the neurological disorder’s most symptomatic sign is a an individual’s “need to pause frequently to find words during a conversation that require a higher level of complexity and precision, but then have no apparent difficulties when exchanging small talk.” Aphasia sufferers speak with noticeable effort, in single words, short, fragmented sentences and often omit small words like “the,” “of,” and “was.”

But in Clinton’s speech on Donald Trump and national security, delivered June 2016, her language is far from small talk: “Donald Trump’s ideas aren’t just different – they are dangerously incoherent. They’re not even really ideas – just a series of bizarre rants, personal feuds, and outright lies. He is not just unprepared: He is temperamentally unfit to hold an office that requires knowledge, stability and immense responsibility.”

Clinton speaks with dexterity, while those with aphasia are frequently misinterpreted as though the speaker is psychologically ill or mentally challenged. Along with difficulty retrieving words, names, and appointments, aphasia sufferers often have a noticeable weakness or paralysis of the right leg and arm as a result of experiencing a stroke. Conspiracy theorists point to a photograph of Clinton leaning on a staffer to walk up the slippery staircase of a house. Experts do not consider this proof of aphasia nor is it a residual sign of a stroke.

Parkinson's Disease

Conservative media outlets have spun the theory that Clinton has Parkinson’s disease, a debilitating neurological disorder that affects roughly one million Americans. Clinton’s tendency to hold a microphone in her left hand while she holds her right hand to her chest has been highlighted by conservatives as a telling sign of the disease.

According to the Mayo Clinic, Parkinson’s disease is a progressive disorder that starts off with barely noticeable tremors in one hand and stiffness in the arms when walking. As symptoms spread to the rest of the body, the face may show little or no expression and speech becomes soft or slurred. Eventually posture is impaired and patients have difficulty blinking, smiling, and writing. Parkinson’s diseasecannot be cured, although medications can curb some of the most prominent symptoms — none of which Clinton has presented.

Seizures

In July 2016, footage of Clinton nodding her head up and down in an interview sparked rumors that she was experiencing a seizure on camera. The video clip went viral, and conspiracy theorists cited it as evidence that Clinton regularly suffers from seizures as a result of her concussion. Fox medical correspondent Marc Siegel suggested the movement was not voluntary and instead the result of brain damage, while others dismissed the video as evidence only of the desperation of Clinton health rumor-mongerers.

According to the Epilepsy Foundation, seizures can range from unpredictable, to episodic, brief, or stereotypic. While there can be jerking movements of an arm, leg, or entire body, it’s usually accompanied by falling, sleepiness, weakness, confusion, lip smacking, chewing, fumbling movements, and the inability to speak.

Clinton’s head motion was quickly followed by a response to a question in the impromptu interview, which is highly uncharacteristic for those experiencing a seizure. If Clinton were to have experienced a seizure as a result of her concussion, it would have been directly following instead of occurring four years later.