Central Vein Thrombosis; Idiopathic intracranial hypertension (IIH) Flashcards
Define central venous thrombosis [1]
Cerebral venous thrombosis (CVT) is caused by partial or total occlusion of the cerebral veins and sinuses by a thrombus.
Describe the risk factors for CVT [5]
Prothrombotic condition: Most common risk factor seen in over 40% of CVT cases
* Genetic thrombophilias including antiphospholipid syndrome; antithrombin III deficiency; protein C deficiency; protein S deficiency; Factor V Leiden mutation and Hyperhomocysteinemia
* Acquired thrombophilias such as pregnancy and the puerperium, oral contraceptive pill use and malignancy
Infection: most commonly Staphylococcus aureus spread from infections of the sinuses. May also be caused by meningitis or a subdural empyema
Trauma & Surgery
Chronic inflammatory diseases
- SLE
- Behcet
- GPA
- Sarcoidosis
Haematological disorders:
- such as paroxysmal nocturnal haemoglobinuria; thrombotic thrombocytopenic purpura, sickle cell disease and polycythemia
Describet the primary and secondary mechanisms of injury in CVT
Primary mechanism of injury:
- cerebral vein or sinus becomes partially or totally occluded by a venous thrombus, deoxygenated blood will begin to pool within the brain parenchyma
- Causes an increase in cerebral venous pressure which has 3 effects: decreased cerebral perfusion & therefore parenchymal injury and cytotoxic oedema; disruption of BBB, causing vasogenic oedma (blood plasma into interstitial space); cerebral vein and capillary rupture
Secondary mechanism of injury:
- Obstruction of the superior sagittal, jugular or lateral venous sinuses causes decreased cerebrospinal fluid reabsorption.
- This will ultimately result in raised intracranial pressure
NB: In most cases of cerebral venous thrombosis (CVT), both the cerebral veins and the sinuses are involved.
Describe the clinical features of CVT [+]
Isolated intracranial hypertension (90%):
- Headache is the most frequent symptom experienced by CVT patients. It is typically subacute in onset and can be generalised or focal, and is often worse with positional or postural changes
- Papilloedema and visual disturbances are also commonly seen in this syndrome
Focal neurological abnormalities (45%):
- May include motor weakness (e.g. hemiparesis), fluent aphasia; and sensory/visual field defects
Seizures (35%):
- Focal and generalised seizures may occur, as may status epilepticus.
Encephalopathy:
- Typically seen in severe cases of CVT or with straight sinus thrombosis. Causes reduced GCS, cognitive dysfunction and delirium/confusion
Which sinuses are most commonly affected in CVT? [3]
Superior saggital sinus
Transverse sinus
sigmoid sinus
(most patients have multiple sinus involvement_
All patients presenting under the age of 50 with one or more of the following features should be urgently investigated for cerebral venous thrombosis (CVT): [4]
Isolated intracranial hypertension
Focal neurological deficits
Seizures
Encephalopathy
Ix for CVT?
MRI with venography is the preferred imaging modality, but if this is not available cranial CT or CT venography can also be used.
- MRI (T2 weighted) in combination with MR venography is the most sensitive neuroimaging method for diagnosis of CVT. In T2 weighted sequences the thrombus will be seen as a hypo-intense area within the occluded vein or sinus
Describe the acute treatment for CVT [3]
Acute antithrombotic therapy:
- low molecular weight heparin or unfractionated heparin in the majority of cases to recanalise the venous / sinous occlusion. Most recover with this
- Some need fibrinolysis (but big risk of intracranial haemorrhage so needs further discussion)
- Patients who still deteriorate despite optimal anticoagulation may require surgical thrombectomy, although this is rare.
Tx of complications:
Raised intracranial pressure:
- due to the high risk of herniation and subsequent patient death, raised intracranial pressure must be treated urgently.
- Patients should have the bed elevated, have osmotic therapy (mannitol or hypertonic saline) administered and be hyperventilated in an intensive care setting. Brain herniation may need emergency decompressive surgery
Seizures:
- anticonvulsants can be used both to treat seizures, and also as prophylaxis against seizures in patients deemed at high risk on neuroimaging review (large areas of cerebral oedema or infarction)
infection/inflammation:
- antibiotic treatment for infection and glucocorticoid therapy for those with inflammatory disorders is often used
Describe the long term treatment for CVT - How does it differ for provoked vs unprovoked CVT? [2]
All patients with confirmed CVT require long-term anticoagulation with warfarin with an INR target of 2.5.
- This is for 3-6 months in provoked CVT and 6-12 months in those with an unprovoked CVT.
- Women who previously were taking the oral contraceptive pill will need advice regarding non-oestrogen methods of contraception such as the progesterone-only pill
During the acute phase (first 30-days) there is a 5% mortality rate amongst patients. Death occurs as a result us: [4]
Transtentorial herniation from large venous haemorrhage (most common cause)
Diffuse cerebral oedema
Status epilepticus
Pulmonary embolism
The cause of idiopathic intracranial hypertension is unknown.
Significant risk factors include: [3]
Female gender (90% of those affected are female)
Obesity (often associated with recent weight gain)
Pregnancy
Symptoms of IIH are usually gradual and progressive, including: [+]
Headache - 90%
- w N&V
Transient visual obscurations - 70%
- These last seconds at a time and can be bilateral or unilateral.
Photopsia - 50%
- Bright flashes of light that may occur following changes in position, Valsalva, bright light or eye movement.
Pulsatile tinnitus - 55%
- This symptom in association with a headache is very suggestive of IIH.
Physical signs:
* Papilloedema - 95% - Typically bilateral and symmetric, but may also be asymmetric/unilateral.
* Visual field loss - 95% - Typically peripheral , but central visual field can be involved late in the course of disease or earlier if there is concurrent macular disease.
* 6th nerve palsy
* Relative afferent pupillary defect
Mx for IIH?
Conservative
- Weight loss x low Na diet
- Potentially causative medications such as tetracyclines, retinoids and thyroid replacement therapies, should be stopped.
- Regular opthalmolic follow up w visual field testing
Medical:
- Acetazolamide is first-line for all patients with visual loss on presentation
- Topiramate may be used as an alternative and has the added benefit of causing weight loss in most patients
- Refractory cases: loop diuretics may be used; repeated lumbar punctures may be used as a ‘holding’ measure in refractory cases but are not used longer-term
* Analgesia: Paracetamol/NSAIDs are recommended first-line for head or back pain.
Surgical
* If patients lose vision in spite of maximal medical therapy, surgical treatment by optic nerve sheath fenestration or CSF shunting can be done.
* + Ventriculoperitoneal Shunt: Reserved for patients with refractory IIH or those with rapidly progressive visual loss. The procedure diverts excess CSF from the brain to the peritoneal cavity.
The principal concern in patients with IIH regards the possibility of [1]
The principal concern in patients with IIH regards the possibility of irreversible vision loss.
The principal concern in patients with IIH regards the possibility of irreversible vision loss.
- What is this specifically from? [1]
- Describe the course of the vision loss [1]
The visual field loss is due to post-papilloedema optic atrophy.
- The peripheries of vision are typically affected first with predominantly nerve fibre bundle type defects.
How do you manage IIH x symptomatic patients with extensive field loss and severe papilloedema ? [1]
Symptomatic patients with extensive field loss and severe papilloedema should be considered for a surgical procedure emergently.
An overweight teenage girl presents with a headache and blurred vision. On examination she is noted to have papilloedema - idiopathic intracranial hypertension
