What is Cerebral Venous Thrombosis?
Cerebral venous thrombosis (CVT) is a rare condition where blood clots form in the brain’s veins, including dural sinuses, the channels that drain blood from the brain. This condition can lead to serious health problems and potentially life-threatening events. Symptoms of CVT can vary and include headaches, a condition called benign intracranial hypertension, which causes high pressure in the fluid around the brain, brain bleeding, localized brain function loss, seizures, unexplained changes in consciousness, and meningoencephalitis, an inflammation of the brain and the surrounding layer.
The diverse range of risk factors and changing symptoms make diagnosing CVT challenging. It’s quite usual to have a delay in diagnosis, as on average, it takes four days from the time symptoms appear to admission in the hospital, and then a further three days to get a diagnosis. That’s why if you have these symptoms, doctors need to be highly alert for this condition to make sure you are diagnosed and treated in a timely manner.
What Causes Cerebral Venous Thrombosis?
Many factors increase the risk of developing cerebral venous thrombosis, a condition where the brain’s veins become blocked by a blood clot. In more than 85% of those affected, at least one risk factor is identified, while over half of patients have more than one risk factor.
Cerebral venous thrombosis often occurs in conditions causing higher chances of blood clotting. Some examples include pregnancy, after giving birth, or those on birth control pills. According to a global research study on cerebral vein and dural sinus thrombosis (ICSVT), about 34% of patients with cerebral venous thrombosis had genetic and acquired blood clotting disorders.
Some people are born with a higher chance of developing blood clots due to inherited conditions like protein deficiencies, mutations in certain genes increasing clotting risk, and hyperhomocysteinemia, a condition where there is a high level of a particular amino acid in the blood.
Acquired thrombophilia, a condition increasing the risk of blood clots, can be suspected in patients with a history of nephrotic syndrome (which results in loss of antithrombin), a type of protein that helps control blood clotting or in those who produce antiphospholipid antibodies, another condition that increases clotting.
Other diseases and risk factors associated with cerebral venous thrombosis include chronic inflammatory diseases like lupus, inflammatory bowel disease, cancer, and vasculitis such as Wegener’s granulomatosis. Certain local infections like otitis (ear infection) and mastoiditis (infection in the skull), which can cause blood clotting of nearby sinuses, can also lead to cerebral venous thrombosis. Lastly, it can also occur due to head injuries, certain brain surgeries, direct injury to the sinuses or jugular veins (like during jugular vein catheterization), or even after a lumbar puncture, a procedure to collect spinal fluid for testing.
Risk Factors and Frequency for Cerebral Venous Thrombosis
Cerebral venous thrombosis, a rare brain disorder, occurs three to four times per million people each year. It’s more common in women than in men, mainly because of certain risk factors like the use of birth control pills and hormone therapy, and less commonly, pregnancy. Recent stats show that between 70% to 80% of this condition’s cases occur in women of childbearing age. However, this doesn’t apply to children or older individuals. During pregnancy, the condition occurs at a rate of about 12 out of 100,000 deliveries, slightly less than the rate of stroke during and after pregnancy.
- Cerebral venous thrombosis is a rare disorder happening three to four times per million each year.
- It’s more often seen in women than men, due to some women-specific risk factors.
- Use of birth control pills and hormone replacement therapy are some of these risk factors.
- Pregnancy is a less common factor.
- About 70% to 80% of cases happen in women of childbearing age.
- During pregnancy and just after birth, about 12 out of 100,000 deliveries are affected by this disorder, a number just below the rate of stroke in the same period.
Signs and Symptoms of Cerebral Venous Thrombosis
Cerebral venous thrombosis (a blood clot in the brain’s veins) can be difficult to identify due to its varying symptoms and rare occurrence. Symptoms can manifest suddenly or emerge slowly over time.
The most common symptom of cerebral venous thrombosis is a headache, which is reported by as many as 90% of patients with this condition. These headaches can affect the whole head or certain parts and might feel like migraines. However, they usually get worse over several days or weeks rather than improving with sleep. Some people might experience a severe, sudden headache, similar to what is seen in subarachnoid hemorrhages. These headaches might get worse with coughing, implying increased pressure in the brain.
This condition might also cause eye symptoms such as blurred or double vision when the brain pressure is extremely high. These symptoms might be seen with headaches. When examined, swelling of the optic disc may be revealed in the eye, a condition known as papilledema. If left untreated, this can lead to vision damage or even blindness. Remarkably, up to a quarter of patients with cerebral venous thrombosis might only have headaches without any other noticeable symptoms like brain deficits or papilledema which can make diagnosis even more challenging.
In addition, up to 44% patients with cerebral venous thrombosis experience focal neurological symptoms like muscle weakness including one-sided paralysis. Nonetheless, unlike arterial blood clots in stroke patients, these symptoms don’t usually only affect one specific region of the brain. Although less common, symptoms such as language difficulties and one-sided paralysis are unique to cerebral venous thrombosis.
Seizures can also be a part of this condition, seen in about 40% of patients. The most typical are localized seizures but these can potentially become more generalized, affecting the entire brain. In this context, cerebral venous thrombosis should be suspected in any patient presenting with a combination of headache, neurologic deficits, or new seizures. If a cerebral venous thrombosis affects the straight sinus, or in severe cases causes the blood clot to become a stroke (venous infarction), there can be deadly consequences such as brainstem compression leading to coma or death due to brain herniation.
Testing for Cerebral Venous Thrombosis
Cerebral venous thrombosis is a serious condition that can be hard to diagnose due to its wide range of symptoms. This condition should be suspected in young to middle-aged patients, especially those with risk factors such as recent childbirth, inherited or acquired blood clotting disorders, or strange neurological symptoms. Key signs to look out for include:
- People under 50
- Consistent, unusual headaches
- Changes in movement or feeling in certain areas
- Stroke-like symptoms, especially without usual stroke risk factors
- Seizures
- Conditions caused by increased pressure in the brain, like swelling of the optic disc (evidence of papilledema)
- Signs of multiple bleeding strokes (hemorrhagic infarcts) on a CT scan.
Important hints that could help in diagnosing this condition include symptoms developing slowly over time, affecting both sides of the body and happening alongside seizures.
Your doctor may also order blood tests to check your complete blood count, clotting time, electrolytes levels, as well as markers that indicate inflammation like C-reactive protein and sedimentation rate. It would be ideal if there was a simple test to rule out cerebral venous thrombosis without needing to do a imaging scan, such as the D-dimer assay. However, this test gives too many false negative results to be reliable.
Recent guidelines from the American Heart Association and American Stroke Association state that a negative D-dimer test can’t rule out cerebral venous thrombosis. If there is a cause for concern, an imaging scan will still be needed even if the D-dimer results are negative. However, using the D-dimer assay along with a clinical score board, based on symptoms such as seizures, known clotting disorders, contraceptive pill use, duration of symptoms, the intensity of the headache, and neurological deficits, can improve prediction.
Imaging tests used in this situation are different kinds of scans. Firstly, a CT scan might be done. This scan is quick, readily available and can show signs of a blood clot in the brain. Sometimes, it will show a rare sign of cerebral venous thrombosis called a ‘cord sign’ or a ‘dense triangle sign’. If these signs aren’t there, a CT Venography (CTV) might be used to help spot the blood clot.
Yet, the best way to diagnose cerebral venous thrombosis is with a scan called Magnetic Resonance Imaging (MRI) and Magnetic Resonance Venography (MRV). MRI is better than CT at spotting swelling in the brain caused by cerebral venous thrombosis. An MRI can also show different features based on the age of the blood clot, but this requires a detailed understanding of the scan changes.
If the MRI and MRV scans still leave the diagnosis unsure, an intra-arterial angiography could be done. This test provides a detailed view of the veins in the brain and helps spot normal variations in anatomy that can look like cerebral venous thrombosis. This test is especially useful in rare cases where the blood clot is in a brain vein without being in the sinus.
The most common sites for cerebral venous thrombosis to occur are in the superior sagittal sinus, followed by the transverse sinus.
Treatment Options for Cerebral Venous Thrombosis
When managing cerebral venous thrombosis, which is a blood clot in the brain, the first priority is to handle any immediate, dangerous symptoms like increased pressure in the brain, seizures, or coma. If a patient has seizures and brain imaging shows damage like bleeding or stroke, medication to treat and prevent further seizures should be started. In cases where the pressure inside the brain is increased, steps to reduce it like raising the head of the bed and administering certain medications (dexamethasone and mannitol) should be taken. The patient must be watched closely in an intensive care or stroke unit, and if their condition worsens, surgeons need to be consulted for a potential operation to relieve pressure.
Next, focus shifts to more specific treatments, including blood-thinning medications to prevent blood from clotting, certain procedures to dissolve clots, and surgery to remove clots.
There has been some controversy about using blood-thinning treatments because there is a risk of causing a cerebral infarct (a type of stroke) to bleed. However, studies have indicated that these treatments, even in patients with brain bleeding, are safe and effective. They prevent further blood clotting, reopen blocked veins, and may lessen the risk of serious complications like deep venous thrombosis and pulmonary embolism, which are other types of harmful clots. Blood-thinning medications should typically be started immediately after diagnosing cerebral venous thrombosis.
However, for some patients, blood-thinning therapy alone may not suffice, especially if their condition is deteriorating. In these cases, treatments aimed at dismantling the clot could be necessary. These include systemic thrombolysis (which involves injecting medication into the bloodstream) and catheter-directed thrombolysis (in which medications are delivered directly to the clot through a thin tube). These methods should be performed by experienced medical staff and should be reserved for patients whose condition is worsening despite the use of blood-thinning medications.
In more severe cases where neurological conditions are worsening despite the medical treatments, surgical removal of the clot might be necessary. In cases of large swelling or bleeding causing a risk of brain herniation (a life threatening condition where parts of the brain are squeezed), an early surgical procedure to alleviate pressure can improve clinical outcomes.
In addition to medical procedures and therapies, it’s also crucial to identify and manage underlying factors that contribute to cerebral venous thrombosis. For instance, women taking hormonal contraceptives should consider switching to estrogen-free alternatives. It’s also necessary to identify and manage any additional causes of increased blood clotting. Finally, follow-up imaging tests 3 to 6 months after diagnosis are recommended to check for recovery.
The overall quality and strength of these treatment recommendations are categorized differently by the European Stroke Organization, depending on factors such as available evidence or potential risks involved. These categories range from ‘very low’ to ‘moderate’ level of evidence and ‘weak’ to ‘strong’ strength of recommendations, indicating a need for further research and careful consideration in certain areas.
What else can Cerebral Venous Thrombosis be?
These are the possible conditions that could be considered when examining a patient’s symptoms:
- Abducens nerve palsy – weakness or paralysis of the sixth cranial nerve
- Blood dyscrasias – abnormal blood cells or proportions
- Cavernous sinus syndrome – a group of symptoms resulting from a disorder affecting the cavernous sinus in the brain
- Head injury
- Intracranial abscess – an accumulation of pus in the brain
- Neurosarcoidosis – a complication of sarcoidosis, a disease that causes inflammation in various organs
- Pediatric status epilepticus – a serious seizure disorder in children
- Pseudotumor cerebri – a condition that causes symptoms similar to a brain tumor, but no tumor is present
- Staphylococcal meningitis – a type of meningitis caused by staph bacteria
- Subdural empyema – an infection that leads to a buildup of pus between the brain and the outer covering of the brain
