Cerebral Venous Sinus Thrombosis

CVST is an uncommon condition seen most frequently in women. There are many known precipitants, but relative dehydration is a frequent feature.

The cavernous sinus is the most commonly affected site, usually as a complication of infection of the middle third of the face.

The image on the right shows a CT demonstrating bi-frontal Peri-falcine infarction consistent with CVST (Day 5).

Presentation

Patients often present with sub-acute symptoms. The headache is usually diffuse, progressive and persistent and has often been present for over 48 hours. In 15% of cases, it is described as a ‘thunderclap’ headache. Seizures and focal deficits often occur.

Clinical Examination

There are often focal signs and papilloedema. Cavernous sinus thrombosis presents with:

• Reduced visual acuity
• Chemosis (conjunctival oedema)
• Proptosis
• Ophthalmoplegia (cranial nerves III to VI)

It is important to appreciate that a CT scan may appear normal, especially initially. If the diagnosis is suspected, an MRI scan must be obtained.

Unlike SAH, the prognosis is not directly related to the neurological status at presentation. A comatose patient may make a full recovery, whereas patients with few signs may deteriorate and die.

The mortality in patients diagnosed with CVST is approximately 15%. A similar number survive with persistent deficits.

Causes

Causes can be identified as infective or non-infective.

Infective causes include:

• TB
• Sepsis
• Endocarditis

Non-infective causes include:

• A dural puncture
• Neurosurgery
• Pregnancy and contraceptive use
• Severe dehydration
• Head injury

Learning Bite

The diagnosis of CVST should be considered in all patients with sub-acute onset headache presenting with a seizure. Contrast enhanced MRI or CT venogram are the imaging modalities of choice – however, CT venogram is often more accessible has a reported sensitivity of up to 100%.⁵