Monday, 9 October 2017

Cerebral Venous Thrombosis

In a lot of places I work, headaches either go home for GP review, or get admitted as a ?SAH. And if they're a possible SAHs, they get a normal CT in six hours (maybe) and many go home without an LP. This really worries me, as there's loads of other serious causes of headache I don't think we exclude thoroughly. In the "old" days, a second doctor generally reviewed the ?SAH to do (or get the results of) a lumbar puncture. So one of the diagnoses we could be missing that worries me is a cerebral  venous thrombosis - this is dangerous to miss.

 Is there a difference between cerebral venous thrombosis and cavernous venous sinus thrombosis?
CVT and CVST have common underlying etiologies including thrombosis, and terms are occasionally used synonomously. CVST is specifically thrombosis in the cavernous sinus, normally with infection, so cerebral venous thrombosis is a safer term.

If you can't remember your venous sinus anatomy, check out Andy's posts on emergency medicine ireland. I can not think of a better way to learn anatomy.
At a very basic level, what happens is you get a clot in one of the veins in the head, which causes problems. At its worst, this can cause death and coma. Middling effects present as a stroke, especially now anyone slightly lopsided seems to get a stroke call. At the "mild" end, a headache may be the only presenting symptom.

There are lots of theories about what is happening to cause these symptoms. It is thought that venous occlusion leads to the development of collateral veins, which combined with altered arachnoid absorption of CSF causes cerebral oedema - which can cause the headache. They can also cause cerebral venous infarction (in 50% of cases) and even haemorrhage.

Risk Factors
Excess Oestrogen: 
oral contraceptive pill: very common cause in female patients <50 years of age 2
pregnancy, IVF
puerperium - more common then than in the pregnancy

prothrombotic haematological conditions: 35% 2
e.g. prothrombin 20210 (factor II) mutation 7
infection: especially mastoid sinus (dural sinus occlusive disease - DSOD)
systemic illness
dehydration: e.g. gastroenteritis
connective tissue disorders

Local Factors
skull abnormalities/trauma
compressing mass: e.g. meningioma

idiopathic: ~12% - this is worrying. If you're going to get a rare disease, being in the rarest bit of rare is unlucky!

Presenting Features
Headache (70-90% of cases)
    There is no particular "type" of headache, but it is normally persistent. Onset may be sudden, like in sub-arachnoid, or gradual. Most patients present with symptoms that have evolved over days or weeks.
Headache is the most frequently (80–90%) occurring symptom in cerebral venous thrombosis and often the first symptom reported by patients. The International Classification of Headache Disorders describes the headache as having no specific characteristics[2] but one study found the headache was usually acute or subacute in onset, localised, continuous and moderate to severe.[23] Cases have been reported where headache is the only neurological symptom or sign but this is very rare.

  Stroke without any typical risk factors, especially in young people may be due to CVT. Up to 75% of cases have focal deficit and headache.
Diplopia here (CN VI palsy) is a focal sign here, and should stimulate you to look for papiloedema...and really think hard about CVT.

Symptoms are not always classic, but they can be associated with the thrombus location.3,4
– Cortical vein thrombosis presents with motor and sensory deficits, as well as seizure.
– Sagittal sinus thrombosis may present with motor deficits, bilateral deficits, and seizures.
– Patients with thrombus in the lateral sinus may present with intracranial hypertension and headache alone.
– Thrombosis of the left transverse sinus can present as aphasia.
– Thrombosis of the deep venous sinus can cause behavioral symptoms due to lesions in the thalamus.

Cavernous sinus thrombosis is associated with ocular pain, chemosis, proptosis, and oculomotor palsies.3,4

 Seizures occur in 30- 50% of presentations, and they are often followed by a Todd's paresis. Superior sagittal sinus thrombosis (4%) can present with bilateral or alternating neurological deficits.

 Coma or encephalopathy
This isn't common, but you can get a rapidly progressive illness with deepening coma, headache, nausea and pyramidal signs, due to extensive involvement of the deep cerebral veins.
More often other clinical manifestations present at onset or develop during the course of the disease. These include papilloedema, focal deficits, altered consciousness, seizures and cranial nerve signs, in particular diplopia caused by sixth nerve palsy. Psychosis, in conjunction with focal neurological signs, has also been reported.[25] The development of symptoms may occur over hours, days or even weeks.

Examination Features
 Altered vision
 Neurological symptoms

Examination of the cerebrospinal fluid (CSF) does not necessarily help in establishing the diagnosis as there are no pathognomonic features. Abnormalities are found in up to 84% of cases and include raised CSF pressure, increased protein content, the presence of red blood cells and pleocytosis.
D-dimers probably not useful

CT -             Often normal, but there may be subtle hyperdensity of the affected sinus or vein for the first 7 - 14 days. May have associated venous haemorrhage or infarction. Haemorrhagic infarcts may be multiple, in no particular location.

String Sign
Seen in 25% of patients with a cavernous sinus thrombosis. It looks like elongated hyperdense image relating to the brain parenchyma.

Dense Triangle
This can be seen in the first two weeks in up to 60% of patients. Fresh, coagulated blood causes a superior sagittal sinus opacification. The opposite of this is the empty delta sign, where contrast is administered highlighting an intraluminal filling deficit. It is not a specific sign.

Anticoagulation - In the last Confidential Enquiries into Maternal Deaths in the United Kingdom report there were four deaths from CVT compared with eight in 2003–05.[22] The previous report expressed the hope that increasing application of thromboprophylaxis among at-risk women will reduce deaths from both pulmonary embolism and CVT but figures are as yet too small to draw a conclusion.[1]

General measures like proper headboard inclination, adequate oxygenation, and protection of airway due to risk of bronchoaspiration are recommended (although now this has been disproved in stroke, I wonder if its accurate).
Anti-convulsant treatment after even a single seizure is reasonable

Lumbar puncture not recommended by LITFL

Full References

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