Teaching Case

A 23-year-old female patient was admitted after a first seizure episode. She had a recent diagnosis of IV-stage nephroblastoma of the right kidney with pleuropulmonary metastatic disease (Fig. 1) and had started chemotherapy two weeks earlier. Metastatic CNS disease was suspected and CT and MR of the brain were requested.

Non-enhanced CT of the brain revealed a triangular-shaped left posterior temporal cortical and subcortical hypodensity-causing mass effect upon adjacent structures without midline displacement and a spontaneous hyperdensity in the ipsilateral sigmoid and transverse sinuses (Fig. 2). Contrast-enhanced CT showed mild cortico-pial enhancement with no further enhancement of the hypodense lesion and absent enhancement of the left jugular bulb (Fig. 3a and b).
On MR the lesion was hypointense on T1-weighted (T1W), hyperintense on T2-weighted (T2W) and FLAIR images (Fig. 4) and showed restricted diffusion of the cortex on diffusion-weighted images (DWI) (Fig. 5). Also noted was a spontaneous hyperintensity on plain T1W images in the left sigmoid and transverse sinuses and jugular bulb that showed absent flow on MR-venography (Fig. 6 and 7). There were no signs of haemorrhage. Post-gadolinium images demonstrated collateral cortico-pial hyperperfusion. No other anomalies were identified and metastatic disease was ruled out.

Cerebral venous thrombosis (CVT) is a rare form of stroke (0.5-1% of all strokes) that mainly affects young adults, especially women. [1-3]
CVT involves two pathophysiological mechanisms: thrombosis of the major cerebral sinuses, which causes intracranial hypertension because of impaired absorption of cerebrospinal fluid, and thrombosis of the cortical veins, leading to parenchymal congestion and breakdown of the blood-brain barrier that can damage brain tissue. [2, 4] Haemorrhagic transformation occurs in 30-50% of cases. [2]
Risk factors for CVT include oral contraceptives, coagulation disorders, puerperium and pregnancy, malignancies, trauma, and chronic inflammation or infection. [2, 4, 5]
The clinical presentation of CVT is highly variable, depending on the extent and location of thrombosis and the availability of venous collaterals. [2, 6] The most common symptoms are headache (usually severe), seizures and focal neurological deficits. [7] The latter two are suggestive of parenchymal abnormalities. [2, 3, 5] Hence, the diagnosis is difficult and relies on imaging, specifically on the demonstration of thrombi in the cerebral veins and/or sinuses by MR, MR-venography or CT-venography. [5, 7]
CT can be normal in up to 25–30% of cases and is inferior to MR in depicting brain parenchymal lesions. [2, 8] Unenhanced CT can demonstrate a spontaneous hyperdensity within the affected vein or sinus (the cord sign) or indirect signs such as brain oedema or infarction (Fig. 2). The classic finding of sinus thrombosis on CT-venography is the empty delta sign, a central filling defect (thrombus) with peripheral enhancement due to collaterals. [3, 6, 7]
Unenhanced MR detects intraluminal thrombi with variable signal intensity on T1W and T2W images depending on the time of onset (Fig. 6). Susceptibility-weighted sequences are useful in acute-stage thrombosis. MR-venography with time-of-flight sequences or contrast-enhanced MR-venography confirms absence of flow (Fig. 7), the latter with higher sensitivity especially for small veins thrombosis. [6] Findings of parenchymal lesions secondary to venous occlusion are similar to those of CT and DWI imaging can be helpful in this setting in the demonstration of additional acute infarctions (Fig. 5). [6, 7]
Prompt diagnosis and timely anticoagulant therapy with heparin are essential to reduce morbidity. [6, 8] Decompressive surgery is recommended in severe cases with impending herniation. [9]
Approximately 80% of patients recover without functional disability and the risk of recurrence is low. [3] Mortality is about 5-10%, associated with underlying diseases, particularly malignancies. [2]
CVT is an uncommon disorder with nonspecific clinical symptoms. Definitive diagnosis relies on a high degree of suspicion and brain imaging by MR, MR-venography or CT-venography. Early diagnosis and treatment are associated with a favourable outcome.