What is the next most appropriate investigation for a patient with severe headache, blurry vision, and increased intracranial pressure, with a history of postpartum cardiomyopathy and chronic changes on CT (Computed Tomography) scan?

MRI Brain with Venogram

The next most appropriate investigation is MRI brain with venogram to exclude cerebral venous sinus thrombosis, which is mandatory in this clinical presentation of raised intracranial pressure. 1

Clinical Reasoning

This 39-year-old woman presents with a classic constellation of findings strongly suggesting idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri:

• Severe headache with blurry vision 1
• Markedly elevated opening pressure of 36 cm H₂O (normal <25 cm H₂O) 1
• Normal CSF composition (WBC 2, RBC 3, glucose 75% of plasma, no xanthochromia) 1
• BMI of 41 kg/m² (typical IIH patient profile: woman of childbearing age with BMI >30 kg/m²) 1
• Upgoing left plantar with easy fatigability (suggesting increased intracranial pressure effects)
• CT head showing no acute pathology 1

Why MRI Brain with Venogram is Essential

CT or MR venography is mandatory to exclude cerebral sinus thrombosis within 24 hours in all patients with suspected IIH. 1 This is a critical diagnostic step because:

• Cerebral venous sinus thrombosis can present identically to IIH with headache, papilledema, and elevated intracranial pressure 1
• The patient has significant risk factors for thrombosis: postpartum cardiomyopathy history (thromboembolism risk) and obesity (BMI 41 kg/m²) 2, 3
• Missing this diagnosis has catastrophic consequences including stroke, hemorrhage, and death 1
• Treatment differs fundamentally: anticoagulation for venous thrombosis versus medical management for IIH 1

Why Other Options Are Inappropriate

Ultrasound Doppler scan of the carotids is not indicated as this presentation suggests raised intracranial pressure, not carotid stenosis or anterior circulation ischemia. 1

Autoimmune screen would be premature before excluding structural causes; CNS vasculitis typically presents with focal deficits and abnormal CSF (elevated protein/cells). 1

CT arterial angiogram evaluates arterial pathology (aneurysm, vasospasm, stenosis) but this patient needs venous imaging to exclude sinus thrombosis. 1

Echocardiogram is not the next step despite her cardiomyopathy history, as her cardiac symptoms are not acute and ECG shows normal sinus rhythm; the neurological presentation demands urgent investigation. 2, 3

Critical Diagnostic Pathway

According to consensus guidelines for IIH investigation: 1

1. Urgent MRI brain within 24 hours (already done via CT, which showed no mass/hydrocephalus)
2. CT or MR venography mandatory within 24 hours to exclude cerebral sinus thrombosis ← THIS IS THE CURRENT STEP
3. Lumbar puncture (already performed, showing elevated opening pressure with normal CSF)

Common Pitfalls to Avoid

• Never assume IIH without excluding venous thrombosis first - this is a mandatory investigation per guidelines 1
• Do not be falsely reassured by normal CT head - venous thrombosis requires dedicated venography 1
• Obesity and postpartum state are risk factors for BOTH IIH and cerebral venous thrombosis - making venous imaging even more critical in this patient 1, 2
• The "chronic changes to right hemisphere" on CT require further characterization with MRI to ensure no underlying structural lesion 1

Next Steps After Venography

If venography is negative for thrombosis, this patient meets criteria for typical IIH and requires: 1

• Ophthalmology assessment for papilledema grading and visual field testing
• Weight loss counseling (only disease-modifying therapy)
• Medical management with acetazolamide if vision threatened
• Close monitoring for visual deterioration