A young woman recently came in for evaluation for evaluation of constant, daily headaches for the past month. She was known to be obese as well as pregnant, with no complications in her third trimester. The exam was notable for mild bilateral papilledema only. Formal visual field testing revealed enlarged blind spots in each eye. The scenario is concerning for idiopathic intracranial hypertension, previously known as pseudotumor cerebri.
One condition that can cause headache and increased intracranial pressure is dural venous sinus thrombosis – but how to evaluate the venous sinuses in pregnancy? Gadolineum contrast is strictly contraindicated, and radiation from CT should be avoided if possible.
The answer is – a time of flight magnetic resonance venogram, or MRV. The motion of flowing blood, either arterial or venous, causes ‘flow voids’, or areas which don’t create an imaging signal on MRI. These flow voids can be used to draw a ‘time of flight’ map of blood flow. As a result, we can get decent vessel imaging in pregnant patients or those who can’t get gadolineum contrast for other reasons, such as renal failure or allergy.