The diagnosis may be suspected on the basis of the symptoms, for example the combination of headache, signs of raised intracranial pressure and focal neurological abnormalities, or when alternative causes of headache and neurological abnormalities, such as a subarachnoid hemorrhage, have been excluded. Imaging CT venogram showing a filling defect in the sagittal sinus (black arrow) A dural<unk>  sinus thrombosis of the transverse sinus. Greater on the right than left. There are various neuroimaging investigations that may detect<unk>  sinus thrombosis.<unk>  edema and<unk>  infarction may be apparent on any modality, but for the detection of the thrombus itself, the most commonly used tests are computed tomography (CT) and magnetic resonance imaging (MRI), both using various types of radiocontrast to perform a venogram and visualise the veins around the brain. Computed tomography, with radiocontrast in the<unk>  phase (CT venography or CTV), has a detection rate that in some regards exceeds that of MRI. The test involves injection into a vein (usually in the arm) of a radioopaque substance, and time is allowed for the bloodstream to carry it to the<unk>  veins – at which point the scan is performed. It has a sensitivity of 75–100% (it detects 75–100% of all clots present), and a specificity of 81–100% (it would be incorrectly positive in 0–19%). In the first two weeks, the "empty delta sign" may be observed (in later stages, this sign may disappear). The empty delta sign is characterized by enhancement of the dural wall without intra-sinus enhancement. Magnetic resonance venography employs the same principles, but uses MRI as a scanning modality. MRI has the advantage of being better at detecting damage to the brain itself as a result of the increased pressure on the obstructed veins, but it is not readily available in many hospitals and the interpretation may be difficult.<unk>  angiography may demonstrate smaller clots than CT or MRI, and obstructed veins may give the "corkscrew appearance". This, however, requires puncture of the femoral artery with a sheath and advancing a thin tube through the blood vessels to the brain where radiocontrast is injected before X-ray images are obtained. It is therefore only performed if all other tests give unclear results or when other treatments may be administered during the same procedure. D-dimer There is an association between the D-dimer blood test and<unk> . This association however is not strong enough to rule out the diagnosis alone. Further tests In most cases, the direct cause for the<unk>  sinus thrombosis is not readily apparent. Identifying a source of infection is crucial; it is common practice to screen for various forms of thrombophilia (a propensity to form blood clots).
Cerebral venous sinus thrombosis
Subarachnoid hemorrhage
Brain abscess
Cavernous sinus thrombosis
Amoebic brain abscess
Subdural empyema
Arachnoiditis
Pseudosubarachnoid hemorrhage