Teaching Case

A 50-year-old lady presented with a 2 day history of headache, nausea and vomiting and right sided weakness. She had no significant past medical history. She was taking hormone replacement therapy. On examination she had 4/5 power on the right, brisk reflexes and impaired co-ordination.

Unenhanced CT head (Fig. 1) showed high attenuation (dense triangle sign) in the sagittal sinus suggesting dural sinus thrombosis. Following this the patient underwent CT angiogram, in the venous phase (Fig. 2) which demonstrated the empty delta sign.

Subsequent MRI (Fig. 3) showed acute venous infarction in the left parietal lobe.
On MRV (Fig. 4) there are extensive signal voids within the sagittal sinus, left transverse sinus and sigmoid sinus confirming the diagnosis and elegantly displaying the extent of the venous sinus thrombosis.

The patient was anticoagulated: initially with Enoxaparin and then Warfarin, with resolution of the symptoms over the following days.

MRV repeated after 2 months showed unequivocal excellent response to treatment.
The sinus thromboses had resolved and the sinuses had recannulated.

Cerebral venous thrombosis (CVT) presents with a wide variety of symptoms. Patients tend to be young and women are affected more than men [1-3]. Symptoms develop due to venous infarction, oedema and intracranial hypertension. They include headache, seizures, nausea, vomiting, focal neurology and reduced GCS. It is uncommon with an incidence of 3-4 per million per year [1] and accounts for less than 1% of strokes [3-4].

Risk factors include infection (local, such as sinusitis or mastoiditis, or systemic infection), prothrombotic diseases such as antiphospholipid syndrome, the oral contracteptive pill, hormone replacement therapy, pregnancy, trauma and inflammatory conditions [1, 3, 5].

Investigations include a full blood count and CRP, a clotting screen, a renal profile and specific tests to look for prothrombotic conditions. A normal D-dimer does not exclude a diagnosis of CVT [6].

Imaging is essential for the diagnosis. Unenhanced CT is often the first line investigation due to being readily available and its ability to discriminate between the wide differential diagnosis on presentation. Acute thrombus less than 2 weeks old is hyperdense. The “dense triangle” sign describes sinus hyperdensity due to thrombus [5, 7] and the “cord sign” linear thrombus within cortical veins [3, 5, 8]. If thrombus has been present for longer it will appear isodense [4]. Contrast CT shows the thrombus as a filling defect. The hallmark of CVT is the “empty delta” sign which is a triangular shaped enhancement with a low attenuating centre due to collaterals around the thrombus [3, 5, 7].

MRI/MRV is commonly performed to confirm the diagnosis or as an initial investigation in young or pregnant patients to avoid radiation from CT [4, 7]. Thrombosis may appear hyperintense on T1 and T2 weighted sequences replacing the signal void usually seen in the sinuses. MRV depicts an absence of flow [1, 3] and extent of thrombosis. Acute thrombus less than 5 days old may appear isodense on MRI. MRI is also useful to detect the consequences of the CVT such as oedema, venous infarction or haemorrhage [7].

CT venography is another option and has been shown to have similar accuracy to MRV [9]. It is useful in patients who have contraindications to MRI or when MRI/V is not readily available, but does have the disadvantage of ionising radiation [4, 8].

Treatment is anticoagulation for 3-6 months in patients with transient risk factors and lifelong for those with permanent risk factors [2].