cerebral dural venous sinus thrombosis (CVST)

Introduction

thrombosis of the cerebral venous sinus is a rare, potentially life threatening condition which causes raised intracranial pressure (ICP)
adult prevalence is 3-16 cases per million population per year with 75% being female and mainly in young adults, presumably due to pregnancy and combined oral contraceptive pill (OCP) being the prime causative factors
in children, annual prevalence is around 7 per million children, some 40% of these occur in neonates, mostly in dehydrated, unwell neonates
first recognized as a cause of death in 1825, but pre-mortum diagnosis on clinical grounds occurred in the 1940's, but only became radiologically possible with the advent of venography in 1951

the cerebral venous sinuses (aka dural venous sinuses) drain blood from the brain into the internal jugular veins and differ from normal veins in that their walls lack a full set of layers (there is no tunica media, and instead are dura mater lined with endothelial cells).
they do not have venous valves
see also https://en.wikipedia.org/wiki/Dural_venous_sinuses

thrombophilic states
- pregnancy
- pueperium
- thrombophilia
- tamoxifen
- oestrogens such as combined oral contraceptive pill (OCP)
- homocystinuria
- dehydration - especially neonates
- Jak2 V617F somatic mutation even in the absence of polycythaemia rubra vera or essential thrombocytosis - said to be present in 7% of cases of cerebral venous thrombosis
- polycythaemia rubra vera
- paroxysmal nocturnal haemoglobinuria
- nephrotic syndrome
- neoplasia / cancer / tumours
- heparin-induced thrombocytopenia (HIT) (rare cause)
- thrombosis with thrombocytopenia syndrome (TTS / VITT / VIPIT) post-COVID-19 vaccine (rare and presents AFTER 72hrs post vaccination with Astra Zeneca Covid-19 vaccine but within 28 days)
general inflammatory processes
local infections
local trauma to the vein wall or local venous stasis
- direct trauma (eg. closed head injury that injures dura can thus injure venous sinuses which are lined be dura, thrombosis is especially likely if predisposed such as dehydrated)
- medical procedures of head and neck

headache
- present in 90%, may be of sudden onset but usually progressively worsens over several days
the elderly may not have headache but may present with delirium or decreased consciousness
usually, the headache is associated with other features which may include:
- stroke (CVA) due to venous infarction - this may have bilateral neurology
- seizures occur in 40% - mostly partial
- raised intracranial pressure (ICP)
  - headache worse when head is dependent
  - vomiting
  - delirium
  - decreased consciousness
  - papilloedema
  - high BP with slow heart rate
- cavernous sinus thrombosis (painful opthalmoplegia, chemosis, proptosis)
- intracerebral haematoma due to merging of petechial haemorrhages
- 10% develop pulmonary embolism (PE) from embolism of the thrombus
may have a raised D-Dimer pathology test but not excluded by a negative result

a negative D-Dimer pathology test when combined with absence of risk factors or other clinical features may suffice to sufficiently rule out acute CVST although there is currently inadequate evidence to support this and this needs further study
- D-Dimer is more likely to be “falsely” negative if:
  - CVST is more than 30 days old
  - isolated headache only
  - single sinus involvement
CT brain non-contrast to exclude other causes such as subarachnoid haemorrhage (SAH)
CT brain venogram (venous phase IV contrast scan)
- 75-100% sens and 80-100% spec.
- “empty delta sign” may be observed in 1st two weeks
- alternatively MRI venogram can be used

if evidence of possible raised intracranial pressure (ICP), treat this and consult with neurosurgery as may require emergent management such as acetazolamide, CSF shunt or optic nerve sheath fenestration
anticonvulsants for seizures
d/w neurosurgery on commencement of anticoagulation with heparin or enoxaparin if there is no haemorrhage on CT and no C/I to anticoagulation