Cerebral Sinus Thrombosis
(Dural Venous Thrombosis)
The brain contains large blood vessel-like structures that drain venous blood back to the heart. These are collectively known as "cerebral sinuses". There are nine of them total: the superior sagittal sinus, inferior sagittal sinus, a pair of transverse sinuses, a pair of sigmoid sinuses, straight sinus, cavernous sinus, a pair of superior petrosal sinuses, a pair of inferior petrosal sinuses, and the occipital sinus.
Just like other veins in the body, the cerebral sinuses can form blood clots (the technical term for a blood clot is actually a "thrombosis", hence the name). However, unlike blood clots that form in the veins of the upper and lower extremities, blood clots in the cerebral sinuses are relatively uncommon.
The exact cause of a dural venous thrombosis is not always discovered. However, there are numerous risk factors associated with their development. They include inherited defects in proteins responsible for blood clot formation. These defects are collectively known as "thrombophilias", which in Latin means "thrombus loving".
In addition, patients with a kidney condition known as nephrotic syndrome are at increased risk. In this condition patients piss out proteins responsible for keeping the blood clotting system at bay. The end result? An increased propensity to form unnecessary clots.
Infections such as mastoiditis and meningitis can cause inflammation of the sinuses, which can result in blood clot formation. Trauma to the head can also cause clot formation. In addition, that beautiful parasitic infection known as pregnancy (I joke of course!) also increases the risk of developing blood clots. On the flip side, many commonly used birth control pills, especially those containing estrogen, can also increase a person's risk.
Depending on the severity of the clot, everything from a mild headache (the most common presenting symptom) to death is fair game when it comes to cerebral sinus thrombosis. Patient's with severe headaches may also have associated nausea and vomiting secondary to elevated intracranial pressures. Decreased mental status (ie: confusion, coma, etc.) is also sometimes observed.
In terms of signs and symptoms, it is also important to remember that not all sinuses are created equal. For example, thrombosis in the superior sagittal sinus can present with leg weakness secondary to edema (ie: swelling) of the adjacent motor cortex.
If a clot forms in the cavernous sinus it may cause dysfunction of the third, fourth, fifth, and/or sixth cranial nerves. In addition, when blood "pools up" behind a clot in one of the venous sinuses it can cause increased swelling (aka: edema) in the surrounding brain tissue. If severe enough a venous stroke can occur, which can cause permanent neurological injury.
With todays modern imaging studies, MRI, and more specifically MR venography has become a crucial diagnostic aid in diagnosing and managing cerebral sinus thrombosis.
An example of an MR venogram is shown in the picture below. Other commonly used tests include traditional angiograms, in which radio-opaque dye is injected directly into the sinuses through catheters inserted in the groin. Finally, CT scans are also commonly obtained, especially to evaluate for possible co-existent hemorrhage.
Treatment is usually with a blood thinning medication known as heparin. It is delivered through an IV and helps prevent further clot formation. If a venous stroke is present the use of blood thinning medications must be weighed against the possibility of causing bleeding into the stroked brain tissue (ie: this is known as "hemorrhagic" transformation of a stroke). Aggressive hydration with normal saline is also often advocated.
Treating other underlying co-problems such as seizures and increased intracranial pressure is also an important part of managing patients with cerebral sinus thrombosis.
Cerebral sinus thrombosis is a blood clot in one or more of the large venous draining systems of the brain. They are uncommon and can present with everything from a mild headache to coma and death. Diagnosis is made most commonly with MRI. Treatment is based on preventing further clot formation with heparin and aggressive hydration.
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