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Cerebral Venous Thrombosis

All organs require venous drainage and that includes the brain. Flow is high to match the high brain perfusion. Venous outflow from the brain is into a collection of different channels or sinuses and then into the internal jugular vein. Diseases and thrombosis of the veins are rare compared to the arterial supply. There are superficial veins which lie in the subarachnoid space and drain the cerebral cortex and empty into the venous sinuses. The higher areas of the cortex drain into the superior sagittal sinus (SSS) and the lower parts of the hemisphere into the transverse sinuses. Deep structures drain via a deep cerebral veins and eventually into the great cerebral vein. It eventually joins with the inferior sagittal sinus to form the straight sinus which drains into the left transverse sinus.

Anatomy of Venous drainage

CVT involves thrombosis of the intracranial veins and sinuses. It is an important cause of stroke that can be easily missed if not actively looked for. Increasing access to improved imaging has led to increased diagnosis of this condition. Venous thrombosis of the cerebral vessels is usually either due to localised infection e.g. mastoiditis or a systemic procoagulant condition. The CT may be normal or show infarction in a slightly odd non arterial distribution. Haemorrhage may also be seen. It most commonly involves thrombosis of in order of occurrence the superior sagittal sinus, Lateral sinuses, Straight sinus and Cavernous sinus.

The disease may present in many different scenarios. Not only to the stroke physician or neurologist but to obstetricians and oncologists and haematologists as well as general practitioners and physicians and in the younger patients and infants it presents to paediatricians. The presentation can be subtle. Where there is a venous prothrombotic state and new central neurology one should always ask - could this be venous thrombosis and if it enters the diagnostic differential then imaging should be seriously considered.

Location of thrombosis in declining Incidence
  1. Superior sagittal sinus
  2. Lateral sinuses
  3. Straight sinus
  4. Cavernous sinus

Venous thrombosis leads to increased venous pressure, oedema and venous infarction. Blood is forced out due to pressure rather than due to any vessel rupture. There is venous occlusion leading to back pressure but also reduced CSF drainage with increased ICP. Imaging has shown that there is both a degree of vasogenic and cytotoxic oedema. The typical procoagulant conditions, OCP, Pregnancy, hyperviscosity syndromes, smokers, Malignancy, labour, dehydration, ecstasy, Behcet's disease, Localised mastoid, ear or sinus infections need to be actively excluded. A cause is not always found.

CVT can sometimes occur as a cause of post LP headache. With a low pressure headache patients feel better lying down. With CVT there is little difference or the patient feels worse lying down.

If you don't think of it you can't diagnose it

Clinical Presentations

  • Focal neurology e.g. hemiparesis due to stroke (ischaemic or haemorrhagic)
  • Headache often localised, papilloedema
  • Headache is severe and dull and is worse when lying down or during valsalva
  • Thunderclap headache is seen and there may be coma and seizures
  • Present with Idiopathic intracranial hypertension
  • Encephalopathy with confusion
  • Cavernous sinus thrombosis - eye pain, diplopia, chemosis, proptosis
  • Jugular or lateral sinus clot can cause a pulsatile tinnitus
  • TIA like episodes

Investigations

  • D-Dimer A positive test supports the diagnosis but a negative test does not categorically exclude CVT and if clinical suspicion high then further imaging warranted. It is negative in 25% of cases.
  • Non contrast CT: May be normal or may show infarction or haemorrhagic infarcts not corresponding to arterial territory. CT with contrast shows increased contrast enhancement of falx and tentorium, Cord sign on non contrast CT due to fresh clot along falx, Subarachnoid blood may be seen.
  • CT with contrast: may show a Empty delta sign on CT with contrast identifying clot, CT with contrast or MRV can show empty delta sign and absence of flow in lumen of sagittal sinus occluded by venous clot.
  • MRI with Gradient echo and MRV: Can show extent of infarcts, haemorrhage and evidence of venous thrombosis, CSF, Raised pressure and protein. LP may help reduce CSF pressure.
  • Thrombophilia screen should be done where an alternative explanation is not forthcoming. Testing is usually done several weeks after stopping anticoagulation. If abnormal results are found in assays for lupus anticoagulant, anticardiolipin, or anti-β2 glycoprotein-I antibodies, then these should be repeated at least 3 months later, as the diagnosis of antiphospholipid syndrome is strengthened by two positive determinations of these biomarkers.
  • Malignancy in older patients it might be reasonable when there is no alternative cause to exclude an occult malignancy

Prognosis is worse with deep cerebral vein thrombosis. Males and those with right lateral sinus thrombosis also do worse

Aetiology of Venous thrombosis at a Glance

AetiologyCauses
Inherited Prothrombotic disorder
  • Hyperhomocystinaemia
  • Antiphospholipid syndrome
  • Factor V Leiden
  • Prothrombin G20210 mutation
  • Protein C/S deficiency
  • Antithrombin II deficiency
Acquired Prothrombotic disorder
  • Malignancy
  • Pregnancy and the post-partum
  • Polycythaemia
  • SLE
  • Dehydration
  • Oral Contraception
  • L-asparaginase
Localised Disease
  • Infection e.g inner ear causing transverse sinus thrombosis
  • Fibrosis
  • Inflammation

CT with contrast showing Superior Sagittal Sinus thrombus with Empty Delta Sign

Management

  • Management is as for DVT and involves immediate anticoagulation with Heparin (IV or LMWH S/C)
  • Patients may be monitored in neurology ITU with hyperventilation and sedation
  • Local IV thrombolysis has been given in selected cases
  • There is no indication for steroids having a benefit, even in patients with parenchymal lesions
  • Anticonvulsants for any seizures
  • LP may be used to reduce ICP especially where sight involved. First ensure no raised ICP from parenchymal lesions.
  • Warfarin is given for 3-6 months followed by lifelong anti-platelets. Prolonged warfarin course for 12 months or even lifelong may be considered if idiopathic cause or an ongoing procoagulant condition.
  • In those with large infarcts and raised ICP decompressive hemicraniectomy may be required

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