What is Isolated Cortical Venous Thrombosis?
Isolated cortical venous thrombosis (ICVT), or cortical vein thrombosis, is a special type of brain vein clot and a rare cause of stroke. In simple terms, ICVT occurs when a blood clot forms within the vein system of the brain’s outer layer, called the cortical vein system. However, these clots do not involve the larger veins in the protective layers of the brain, called dural sinuses.
The veins that can be affected include the surface brain veins, like the superficial middle cerebral vein, and deeper brain veins, like the vein of Galen.
ICVT can cause a range of symptoms such as headaches, sudden seizures, changes in consciousness, and specific neurologic weaknesses. If ICVT is not correctly treated, it can lead to a brain infarction (blockage of blood supply causing death of brain tissue), hemorrhage (bleeding), or herniation (shift of brain tissues).
It’s also noteworthy that ICVT is a relatively uncommon cause of stroke, accounting for only approximately 6.3% of all cerebral venous and sinus thrombosis (brain vein and sinus blood clots) cases.
What Causes Isolated Cortical Venous Thrombosis?
There are multiple risk factors for ICVT, a type of blood clot in the brain, which usually stem from conditions that make your blood more likely to clot. Certain deficiencies, such as shortage of proteins C and S, antithrombin, or the presence of certain gene variations can all increase blood clotting. High levels of homocysteine, factor VIII, and fibrinogen can increase the risk as well.
There are also certain conditions that you can develop, as opposed to being born with, which make your blood more likely to clot. This includes cancer, use of oral contraceptives, certain cancer drugs, being pregnant, taking estrogen supplements or hormone replacement therapy, having a disorder where you produce too many blood cells, or having a history of specific types of blood clots, like deep vein thrombosis or pulmonary embolism (blood clots in the deep veins of your legs or in your lungs, respectively).
Interestingly, recent research suggests that infection with SARS-CoV-2, the virus that causes COVID-19, can increase the risk of developing ICVT. This is because the virus can cause low oxygen levels in your blood, which can lead to an increase in blood thickness, activating pathways in your body that lead to excessive clotting, and consequently increasing the risk of developing conditions like blood clots in your veins, pulmonary embolism, and serious widespread clotting in your body.
Risk Factors and Frequency for Isolated Cortical Venous Thrombosis
ICVT, a type of cerebral venous and sinus thrombosis, represents just 6.3% of all such conditions, and less than 1% of all cerebral infarctions. A comprehensive review of 47 case reports and case series noted that the average age at diagnosis was 41, with women making up 68% of patients.
Generally, conditions like cortical vein thrombosis, isolated cortical vein thrombosis, and cerebral venous thrombosis tend to affect younger patients compared to those with arterial strokes. Women also have a higher risk compared to men. More studies are required to understand ICVT better, as it’s not often diagnosed and additional patterns need to be identified.
- Only 6.3% of all cerebral venous and sinus thrombosis is from ICVT.
- ICVT forms less than 1% of all cerebral infarctions.
- Based on a review of 47 cases, the average age of ICVT patients was 41.
- 68% of the diagnosed ICVT patients were women.
- Conditions like cortical vein thrombosis, isolated cortical vein thrombosis, and cerebral venous thrombosis typically affect younger patients than arterial strokes.
- Women run a higher risk of these conditions than men.
- More investigations are needed as ICVT is rarely diagnosed.
Signs and Symptoms of Isolated Cortical Venous Thrombosis
Intracranial venous thrombosis (ICVT) is often seen in younger individuals, both males and females, who have certain risk factors. Women are more at risk if they are pregnant, use oral contraceptives, or have an infection. Men are more likely to get it if they have a history of increased tendency of the blood to clot, due to either genetic or acquired reasons. People with ICVT mainly report new headaches, seizures, or specific neurological shortcomings.
It’s important to note that not all these patients will show increased pressure within the brain. They could show either generalized seizures or specific ones along with speech difficulties, weakness on one side of the body, visual field loss, and other peculiar neurological issues. These signs should make doctors think about ICVT as a possible diagnosis. These patients often show motor and sensory shortcomings. The most common symptom is a headache, which sometimes is the only symptom they present. The onset of this headache can vary between patients; some experience a slow increase over several days, while for others, it might be sudden and severe.
Patients who have a history of headaches or migraines accompanied by auras should be asked to compare the current headache with previous ones for any significant difference. ICVT should be considered if there is any new headache differing from their usual pattern, new seizures, quick onset of brain disease symptoms, or specific symptoms that don’t typically align with stroke patterns and are accompanied by a new headache.
Testing for Isolated Cortical Venous Thrombosis
If your doctor suspects a medical condition called Intracranial Cerebral Venous Thrombosis (ICVT) due to your symptoms and physical examination, the next step is immediate brain imaging. There are no lab tests that can specifically identify ICVT, so the diagnosis is usually confirmed through special types of brain imaging scans: Magnetic Resonance Imaging (MRI) and Magnetic Resonance Venography (MRV). If these machines aren’t available, then a Computed Tomography (CT) scan with CT Venography (CTV) can be used as an alternative.
Among these, an MRI paired with MRV is considered the most reliable method for spotting ICVT. In simple terms, a clot, if present, will show up as a dark spot within a vein in the brain only on MRI scan. If this clot is found within the sinuses, then another condition called cortical venous thrombosis may be considered.
Certain signs on your brain scans can potentially help doctors make this diagnosis. For instance, a symptom known as the “cord sign” seen on a CT scan without contrast might tip doctors off to the presence of cortical venous thrombosis. This “cord sign” appears as a bright cord-like image within a vein in the protective coverings of the brain called dural venous sinus.
Even though standard lab tests by themselves cannot diagnose ICVT, they can indeed help predict the course of the disease and guide treatment. Patients with ICVT and a higher likelihood of a clotting disorder should undergo tests to check for genetic causes. It may be beneficial to have a screening for lack of proteins C and S, antithrombin, and presence of certain variants in the prothrombin and factor V Leiden genes, which are all associated with increased likelihood of blood clotting. Doctors might also consider running checks for autoimmune disorders such as lupus anticoagulant and antiphospholipid syndrome, which are known to cause blood clots.
Treatment Options for Isolated Cortical Venous Thrombosis
The main goal for treating ICVT, which is a type of blood clot in the vein of the brain, is to clear the blocked blood vessel and stop the clot from spreading. This is usually done through blood-thinning medicines injected under the skin called low molecular weight heparin (LMWH) or heparin given directly into the veins. LMWH is usually the top choice. However, recent brain bleeding, very high blood pressure, bleeding disorders, and stomach ulcers may prevent the use of these medications. For patients with chronic kidney disease, the medication can build up in the body, so heparin may be a better option.
If a patient shows signs that the brain is being squeezed due to increased pressure, they should be seen by a neurosurgeon, and possibly have a procedure to relieve that pressure. If symptoms continue to worsen even with LMWH or heparin, removing the blood clot mechanically or using drugs to dissolve it may be discussed.
When dealing with ICVT, there’s a chance of encountering increased pressure within the brain. Patients might need to be admitted to a neuro-intensive care unit at this time. Here, the brain’s pressure can be frequently monitored, and methods like raising the head of the bed, giving medications to reduce brain swelling, and adjusting the patient’s breathing can be used. An IV steroid medication called dexamethasone is not recommended. Patients who initially came with seizures, swelling, stroke, or bleeding should be given preventative seizure medication.
Seizure medications levetiracetam or valproate are typically the first choice. After the patients are stabilized and sent home, they may continue on medicines like warfarin or dabigatran, which help prevent blood clots, for at least three months to avoid further ICVTs.
What else can Isolated Cortical Venous Thrombosis be?
ICVT, or Intracranial Venous Thrombosis, can sometimes first appear as a severe headache. It’s really important to perform an imaging test to help tell ICVT apart from other conditions such as subarachnoid hemorrhage, meningoencephalitis, or a brain tumor. It’s also necessary to check if the severe headache might be due to a serious infection affecting the brain function; this is particularly important if the patients are exhibiting fever, an increase in white blood cells, and a positive blood culture test.
In some cases, ICVT might be the first sign of a condition that makes blood clot more easily. Here are some conditions that must be considered:
- Vasculitis syndromes (inflammation of blood vessels)
- Primary or secondary thrombocytosis (high platelet count)
- Polycythemia vera (a type of blood cancer)
- Antiphospholipid syndrome (disorder of the immune system)
- Systemic lupus erythematosus (an autoimmune disease).
If ICVT is suspected or found, it could be beneficial for the patient to be tested for certain deficiencies and genetic variants such as protein C deficiency, protein S deficiency, antithrombin deficiency, G20210 prothrombin gene variant, and factor V Leiden thrombophilia, as these can increase the risk of developing blood clots.
What to expect with Isolated Cortical Venous Thrombosis
In simple terms, ICVT tends to have a positive outcome. According to a review of 325 cases, over 90% of the patients showed significant improvement at the time of leaving the hospital or during the first year of follow-up. This included complete recovery or noticeable improvement in their condition.
It’s worth mentioning that most patients saw their symptoms getting better before any improvements showed up on brain scans. In the review, the mortality rate during hospital stays was 3.0%.
Lastly, patients who were treated with blood-thinning medications for up to six months experienced complete or partial recovery of symptoms. This highlights the effectiveness of these anticoagulant treatments for ICVT.
Possible Complications When Diagnosed with Isolated Cortical Venous Thrombosis
: Complications associated with ICVT (Intracranial Venous Thrombosis) can range from blood clot formation in the veins (venous infarction) to bleeding (hemorrhage), and an increase in damaging fluid accumulation (vasogenic edema) in the brain. A severe complication it can lead to is a dangerous shift of brain structure (transtentorial herniation) that may result in death. In cases where this is suspected, a lifesaving procedure called hemicraniectomy, which involves removing part of the skull, might be needed.
Risk of having seizures also tends to be higher in patients who already experience seizures, have a history of them, or have existing brain concerns such as localized swelling (focal edema), lack of blood flow (ischemia), or bleeding related to stroke (hemorrhagic infarcts). As a rare occurrence, some patients could also experience severe vision loss.
Issues to be aware of include:
- Blood clot formation in the veins
- Bleeding
- Increase in damaging fluid accumulation
- Dangerous shift of brain structure that can lead to death
- Possibility of needing a lifesaving procedure to remove part of the skull
- Higher risk of seizures, especially for those who already have them or have existing brain issues
- Potential severe vision loss
Preventing Isolated Cortical Venous Thrombosis
The medical team should ensure that patients are knowledgeable about the factors that can increase their likelihood of developing ICVT, a type of blood clot in the brain. Patients with conditions that make their blood more likely to clot, such as deficiencies in proteins C and S, antithrombin, a prothrombin gene variant known as G20210, and a condition known as factor V Leiden thrombophilia, should be aware of their increased risk.
Regularly keeping in touch with a primary care doctor and a blood specialist (hematologist) can help manage these risks. Patients with cancer should also understand that their disease can elevate their risk of blood clots too, possibly leading to ICVT. Patients taking certain medications – including birth control pills, cancer treatment drugs, estrogen supplements, and hormone replacement therapy – are also more prone to getting blood clots.
Moreover, if you’ve previously had a pulmonary embolism (a blood clot in your lungs) or deep vein thrombosis (a blood clot in a deep vein, usually in your leg), your risk is higher. For patients with several of these risk factors, it’s crucial that the healthcare team provide thorough guidance on the pros and cons of starting treatment, keeping in mind their medical history.
