Just after New Year’s Day in 2013, I was asked by a local news station about a story in the mainstream media involving a “blood clot in the brain.” At-the-time Secretary of State Hillary Clinton had fallen and hit her head, and this was followed soon afterwards by a diagnosis of a blood clot “in the vein between the brain and…skull,” according to this news article. I recognized over the following week while the story played out in the news that, while Clinton’s clot was not the same thing as one might think of an ischemic stroke, there was little understanding outside of the medical community of how her neurological issue differed from the large majority of blood clots in the brain. I even received several questions about it from patients, the most common one being – did Hillary Clinton have a stroke? And my answer was – not exactly.
Ischemic strokes, as we think of them, involve an obstruction in an artery that is preventing oxygen-rich blood from reaching its target destination within the brain. Arteries can be blocked by blood clots, plaque accumulation within the wall of the vessel, a torn lining in the wall of the artery (dissection), or even overgrowth of cells within the blood vessel wall (hyperplasia). Veins, on the other hand, drain blood away from the brain and back to the heart once the oxygen has been extracted from it. Veins of significant size in the brain are called venous sinuses, as they are structured more like collecting pools for the drainage of blood that is no longer rich in oxygen. A clot that occurs in one of these venous sinuses are known as a cerebral venous sinus thrombosis (CVST). It is much less common to develop an obstruction blocking blood flow in one of the brain’s veins than it is within an artery. According to the scientific statement published by the American Heart Association/American Stroke Association in 2011, only 0.5 to 1 percent of strokes result from a blood clot in a cerebral vein.
People might be familiar with the concept of a venous clot, such as in a leg if one sits in a car or on an airplane for a prolonged period of time. However, venous clots can occur anywhere in the body, including in the brain.
Various factors may lead to increased risk of clotting in one of the venous sinuses or in a cerebral vein. It is important to understand that in all of us, our blood is in a constant state of flux. Just as the American government is set up with checks and balances such that the branches can more-or-less keep each other in check, our blood has millions of molecules pushing it towards clotting, and millions breaking down clots. We need to clot so we do not hemorrhage. Yet, our blood needs to be able to flow to our organs, and if it can’t because of extensive clotting then heart attacks, strokes, and other catastrophes develop.
There are certain genetic mutations that can cause blood to clot more readily, such as the factor V Leiden mutation or the prothrombin mutation. There are people who lack certain proteins that assist with breaking down clots, and in the absence of these proteins clots are more likely to develop. Deficiencies of protein C and protein S are two of the more common examples of this. Autoimmune disorders can increase the risk for clotting in general, such as can be seen with lupus and antiphospholipid antibody syndrome. The use of certain types of birth control pills can cause elevated risk of CVST, as can pregnancy, because elevated estrogen levels have been associated with thrombosis. Cancers and systemic infections/sepsis can cause massive hemorrhaging or diffuse clotting. Significant concussions or skull fractures can also result in CVST.
The most common initial symptoms of CVST are headache, visual changes, and/or seizure. A headache that continues to escalate for days to weeks, especially in a patient taking birth control pills, who is pregnant, or who has a history of abnormal clotting should undergo MRI of the brain. Standard MRIs are sensitive enough to detect most CVST, but if there is any question an MR-venogram or a CT-venogram of the head should be performed. If CVST is identified, the treatment is an anticlotting medication. Warfarin is the most common medication used for this, although rivaroxaban (Xarelto), apixaban (Eliquis), and dabigatran (Pradaxa) have been used more recently as off-label agents. In pregnant patients, enoxaparin (Lovenox) is typically used because it is thought to be safe (pregnancy Category B). Warfarin is known to cause birth defects (pregnancy Category X), and the effects of the other oral agents on fetal development is unknown at this time. Warfarin can be used safely in breastfeeding mothers once the baby is delivered.
In my experience, patients with CVST do very well clinically once started on an anticlotting therapy, especially if the clot is identified early. Secretary Clinton’s treating physician claimed in this news article that she had a clot in the transverse sinus. The nice thing about transverse sinuses is that there are two of them, and when one is blocked due to the presence of clot, blood is usually still able to drain from the brain. Her physician also noted that she had a deep venous thrombosis (DVT) in the 1990s, suggesting she might be at risk for clots. If people are at particular risk for clot formation, being dehydrated does not help (Clinton was reported to have influenza during that time), as the blood becomes more concentrated. While he described the condition as “potentially life-threatening,” in the dozens of transverse sinus thromboses I have treated, none of these patients have died, and the recovery is very favorable. Even patients with very large superior sagittal sinus thromboses do very well typically if recognized early and started on therapy.
When making a determination about whether a patient has had a stroke if an artery is blocked, we require that some degree of damage has occurred in the brain before calling it a stroke. If there is no damage and the patient has no lingering symptoms in this scenario, then the diagnosis of a TIA, or transient ischemic attack, is made. In the case of CVST, if diagnosed and treated early and lacking any evidence of damage to the brain, it probably should not be labeled as a stroke either. While it may be convenient to throw all CVST cases in the “stroke” bucket, many of these patients will not sustain permanent brain injury, and will go on to lead productive lives without lingering evidence that such an event ever occurred. So did Secretary Clinton have a stroke? I stand by my answer of – not exactly.
Would I expect something like this in Secretary Clinton’s medical history to prevent her from carrying out the duties of the presidency if she is elected in November? No more than migraines would have stood in Michele Bachmann’s way in 2012, or than atrial fibrillation would have prevented Bill Bradley from performing presidential tasks. By the time adults reach their 50s or 60s, it is almost an inevitability that a health condition of some sort will be present. If we want candidates for president in near-perfect health, we could change our laws and elect a very young person as our commander-in-chief, but then we lose the presence of life experience.