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Cerebral Venous Sinus Thrombosis

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Overview

Also known as cerebral venous thrombosis, cerebral venous sinus thrombosis (CVST) describes the formation of a thrombus (blood clot) in the venous system of the brain. It is a neurological emergency that may be missed due to its vague presentation. CVST is an umbrella term for specific syndromes affecting different sites:

  • Sagittal sinus thrombosis – the most common type
  • Transverse sinus thrombosis – the second most common type
  • Cavernous sinus thrombosis – often due to the spread of an infection such as sinusitis
  • Straight sinus thrombosis
  • Cerebral vein thrombosis
  • Jugular vein thrombosis

Causes

CVST can be divided into:

  • Aseptic CVST – a thrombus forming due to non-infective causes (e.g. hypercoagulable states, combined oral contraceptives/oestrogen-containing hormone replacement therapy):
    • Most common form of CVST
    • Most commonly affects the superior sagittal sinus
  • Septic CVST – a thrombus arising from infection (e.g. sinusitis, otitis media, osteomyelitis)
    • Much less common
    • Most commonly affects the cavernous sinus

Risk Factors

  • History of facial infection or sinusitis
  • History of periorbital infection
  • Any prothrombotic state such as:
    • Haematological disorders
    • Cancers
    • Pregnancy
    • Antiphospholipid antibodies
    • Oral contraceptive use
    • Hereditary thrombophilias

Presentation

Overview

CVST should be suspected in young and middle-aged patients, especially if they have risk factors for hypercoagulability. Features include:

  • Headache – due to increased intracranial pressure:
    • This may be sudden and severe, similar to that of a subarachnoid haemorrhage
    • This may be positional – worse with positional or postural changes (e.g. leaning forward)
  • Papilloedema and visual abnormalities – due to increased intracranial pressure
  • Nausea and vomiting – due to increased intracranial pressure
  • Focal neurological deficits (e.g. hemiparesis, aphasia, sensory/visual field deficits, cranial nerve palsies)
  • Encephalopathy – reduced consciousness (reduced GCS), confusion, or delirium

Features of specific syndromes

  • Sagittal sinus thrombosis – most common type:
  • Transverse sinus thrombosis – second most common type:
    • Headache
    • Papilloedema (increased intracranial pressure)
  • Cavernous sinus thrombosis:
    • Most likely to be due to an infection spreading from the sinuses, nose, and middle ear – a history of sinusitis may be present
    • Chemosis – swelling of the conjunctiva
    • Proptosis
    • CN III, CN IV, CN V, CN VI cranial nerve palsies
  • Straight sinus thrombosis:
    • Altered mental state
    • Bilateral motor deficits
    • Reduced consciousness (Glasgow Coma Scale, GCS)
  • Cerebral vein thrombosis:
    • Motor and sensory deficits +/- seizures
  • Jugular vein thrombosis:
    • Neck pain, pulsatile tinnitus, and cranial nerve palsy

Differential Diagnoses

Brain abscess

  • May also be due to infectious spread from sinuses etc.
  • Features of raised ICP + fever are suggestive of a brain abscess
  • ESR, CRP, and white cell count are usually raised

Idiopathic intracranial hypertension (IIH)

  • In IIH, the headache is more gradual and not as acute
  • Headaches, blurred vision, and papilloedema are the main features
  • Consciousness is not impaired
  • Incidence is higher in female patients who are obese

Encephalitis

  • The main features are altered mental state and reduced GCS
  • Psychiatric symptoms (e.g. personality changes or memory problems) may be present

Investigations

  • Full blood count:
    • May show leukocytosis suggesting septic CVST
  • Blood culture:
    • May show underlying pathogen in septic CVST
  • Screening for hypercoagulable states:
    • Factor V Leiden
    • Antiphospholipid and anticardiolipin antibodies – antiphospholipid syndrome
    • Protein C and protein S – to screen for deficiency
    • Antithrombin III – to screen for deficiency
  • MRI venography:
    • The gold-standard
    • CT venography may be considered as an alternative if this is not available
    • Shows abnormal filling defects according to the regions the sinuses correlate with

Management

Initial management

  • 1st-line: anticoagulation:
  • In some cases, fibrinolysis or surgical thrombectomy may be necessary

Co-existing complications

  • Raised intracranial pressure:
    • Head elevated to 30º
    • IV mannitol or hypertonic saline – draws water out of brain cells
    • Hyperventilation – reduces pCO2 leading to vasoconstriction of the cerebral arteries and reduces intracranial pressure
  • Seizures:
    • Treated with anticonvulsants
  • Infection:
    • Empirical IV broad-spectrum antibiotics
  • Inflammation causing cerebral oedema:
    • Dexamethasone

Complications

  • Acute complications:
  • Chronic complications:
    • Epilepsy
    • Depression
    • Visual impairment
    • Neurological deficits

Prognosis

  • Early diagnosis and intervention are associated with a better prognosis
  • In general, the prognosis is good but there can be residual neurological deficits

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