Hyperdense sinus on CT Brain

A 25 yo female C/o headache.

Hematocrit 77.6%

Hb 26.7 gm%. 

Non contrast CT shows abnormal hyperdensity in the region of superior sagittal sinus; ' Cord sign' or ' Dense triangle' sign. No other parenchymal abnormality. 

MRI Brain shows abnormal high signal in the region of superior sagittal sinus with loss of normal flow voids implies to thrombosis as corresponding sinus not visualized on non contrast 2 D TOF MR Venogram. 

In this case based on hematocrit and non contrast CT findings the other closest differential is polycythemia. 
Features of polycythemia on NCCT head includes increase in attenuation of venous sinuses may not be as hyperdense as in this case but is primarily a reflection of hemoconcentration and attenuation of the hemoglobin protein. 
Hyperdensity in the region of dural venous sinuses is typically seen in cerebral venous sinus thrombosis. Cerebral venous thrombosis is a known complication of polycythemia and hypercoagulable states and hence both may coexist. so polycythemia may mimic cerebral venous thrombosis on CT and polycythemia may cause cerebral venous thrombosis.
MR venography is required to differentiate between the two and rule out CVT. 

Reference : J Pediatr Neurosci. 2010 Jan-Jun; 5(1): 27–29. doi:  10.4103/1817-1745.66679; Healy JF, Nichols C. Polycythemia Mimicking Venous Sinus Thrombosis. AJNR Am J Neuroradiol.2002;23:1402–3. [PubMed]