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Cerebral Venous Thrombosis


Learning objectives

  • Causes of Cerebral Venous Thrombosis
  • Symptoms and signs of Cerebral Venous Thrombosis
  • Investigations of Cerebral Venous Thrombosis
  • Management of Cerebral Venous Thrombosis

Introduction

  • Cerebral venous thrombosis (CVT) refers to occlusion of venous channels in the cranial cavity.
  • Classically the patients are young, female and procoagulant - pregnancy, puerperium, inherited thrombophilia,on OCP
  • The presentation can be subtle. You need to consider it to get an CTV or MRV to diagnose it.
  • Where there is a venous prothrombotic state and new central neurology one should always ask - could this be venous thrombosis
  • If it enters the diagnostic differential then imaging should be seriously considered

Classification

  • Dural venous thrombosis: affecting Superior sagittal sinus, Lateral sinuses, Straight sinus, Cavernous sinus
  • Cortical vein thrombosis: affecting smaller veins on cortical surface
  • Deep cerebral vein thrombosis : prognosis often poor due to bilateral thalamic infarction

Pathophysiology

  • 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.
  • Cerebral venous thrombosis usually progresses to venous infarction
  • Increasing access to improved imaging has led to increased diagnosis of this condition.
  • There are superficial veins which lie in the subarachnoid space and drain the cerebral cortex and empty into the venous sinuses.

Anatomy

  • Cerebral veins and sinuses lack valves and tunica muscularis. Absence of valves permits blood flow in various directions while absence of tunica muscularis permits veins to remain dilated.
  • Venous sinuses are located between two rigid layers of duramater. This prevents their compression when intracranial pressure rises.
  • Communication between various venous sinuses either via communicating veins or through merger into each other especially at torcular Herophili, explains lack of correlation between the severity of underlying pathology and infrequent clinical symptomatology.
  • 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.
  • Emissary veins from scalp, face, paranasal sinuses and ears, etc., diploic veins, and meningeal veins drain into cerebral venous sinuses either directly or via venous lacunae.
  • Therefore CVT can occur as a complication of infective pathologies in the catchment areas, e.g., cavernous sinus thrombosis in the facial infections.

Aetiology

  • 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.
  • Venous thrombosis of the cerebral vessels may be due to localised infection e.g. mastoiditis or a systemic procoagulant condition.
  • 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.
Risk Factors
  1. Inherited Thrombophilia
    • Hyperhomocystinaemia
    • Antiphospholipid syndrome
    • Factor V Leiden
    • Prothrombin G20210 mutation
    • Protein C/S deficiency
    • Antithrombin II deficiency
  2. Oral Contraception
  3. Hyperviscosity/Polycythaemia
  4. Pregnancy / early post partum 6 weeks
  5. Nephrotic syndrome
  6. Meningitis / sinus infections
  7. Dehydration / Ecstacy
  8. Behcet's disease, SLE
  9. Localised mastoid, ear or sinus infections
  10. Underlying malignancy
  11. Idiopathic, L-asparaginase

Location

SiteFrequency
Superior sagittal sinus72%
Lateral sinus (combined)70%
Straight sinus13%
Cavernous sinus<10%

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. However CVT may also be the cause of the thunderclap headache for which you are doing the LP !

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

  • FBC, U&E, LFTs, CRP: look for evidence of malignancy or infection/inflammatory disorders
  • 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 a typical arterial territory. Thrombus can appear as hyperdense vein within the sinus for the first 1-2 weeks and this is a useful sign and may be called the cord sign on non contrast CT due to fresh clot along falx. Subarachnoid blood may be seen. Clot may be seen in the superior sagittal sinus, Lateral sinuses, Straight sinus and Cavernous sinus but usually CTV/MRV is needed to confirm the diagnosis. Haemorrhage or infarction may be seen with a disproportionate amount of surrounding oedema.
  • CT with contrast: may show a Empty delta sign is a CT sign of dural venous sinus thrombosis involving the superior sagittal sinus. Contrast outlines a triangular filling defect (thrombus). It is only seen when contrast is given with CT or MRI.
  • MRI with Gradient echo and MRV: Can show extent of infarcts, oedema, haemorrhage and evidence of venous thrombosis
  • CSF:: Not usually done but may be done as CVT may present as a thunderclap headache. Shows Raised pressure and protein. LP may help reduce CSF pressure. With raised CSF pressure the clinician should now exclude CVT as the cause of the headache.
  • 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
Complications
  • Infarction and Haemorrhage
  • Raised ICP and coma
  • Acquired Dural AV fistula link

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)
  • Prognosis is worse with deep cerebral vein thrombosis as there is often bilateral thalamic venous infarction.
  • Males and those with right lateral sinus thrombosis also do worse
  • Patients may be monitored in neurology ITU with hyperventilation and sedation
  • Direct IV thrombolysis has been given in selected cases whereby Interventional neuroradiologists can infuse catheter directed thrombolysis into the affected sinuses.
  • 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 incipient coning due to 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

References and further reading

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