CEREBRAL VENOUS SINUS THROMBOSIS

ANATOMY OF DURAL VENOUS SINUSES

Dural venous sinuses -

These are endothelial lined spaces between the outer peri-osteal and the inner meningeal layers of the dura mater that eventually lead to the internal jugular veins.

All the cerebral , cerebellar ,brainstem veins along with diploic & emissary veins drain into dural venous sinuses.

Dural venous sinuses

Unpaired sinuses

Sup.sagittal sinus

Inf. Sagittal sinus

Straight sinus

Occipital sinus

Basilar sinus

Confluence of sinuses

Paired sinuses

Transverse sinuses (rt. and Lf )

Sigmoid sinuses (rt and Lf )

Cavernous

Sphenoparietal

Sup .petrosal

Inf . Pertrosal

Superior sagittal sinus -

It is present in the superior border of the falx cerebri and receives cerebral veins from the superior surface of cerebral hemisphere ,diploic and emissary veins & veins from falx cerebri . It ends at the confluence of sinuses and drains into the right transverse sinus.

Inferior sagittal sinus –

It is present in the inferior border of falx cerebri and few cerebral veins & veins from falx cerebri .It ends posteriorly near the tentorium cerebelli and forms the straight sinus after joining with the great cerebral vein(of galen).

The straight sinus runs along falx cerebri and tentorium cerebelli and drains at the confluence of sinuses into the left transverse sinus.

Confluence of sinuses, transverse and sigmoid sinuses -

The superior sagittal , occipital and straight sinus drain into the confluence of sinuses which is present at the internal occipital protruberance and drains into right and left transverse sinuses .

The transverse sinuses run along the occipital bone and receives blood from superior petrosal sinus ,veins of inferior part of cerebral hemispheres and ends as the sigmoid sinus which inturn drains into the internal jugular vein.

Superior and inferior petrosal sinuses –

Superior petrosal sinus originates from the cavernous sinus and drains into the transverse sinus and runs along the superior margin of the petrous part of temporal bone .

Inf .petrosal sinus drains the cavernous sinus into the internal jugular vein.

Cavernous sinuses –

These are paired sinuses lying against the lateral aspect of the sphenoid bone on either side of the sella turcica . It receives blood not only from the cerebral veins but also from the opthalmic vein . Inter-cavernous sinuses connect the two cavernous sinuses .

Many important structures pass through the sinus –

• Internal carotid artery

• Abducent nerve (vi)

Structures present in the lateral wall of the sinus include –

• Occulomotor nerve(iii)

• Trochlear nerve (iv)

• Opthalmic nerve (v 1)

• Maxillary nerve (v 2)

Cerebral veno-sinus thrombosis

It is the thrombosis of the draining venous sinuses of the cerebral cortex and the least common of all other types of cerebro vascular accidents .

• This condition frequently affects young adults and children . More commonly effecting women than men with a f:m ratio of 3:1 most probably due to the presence of gender specific risk factors like pregnancy , puerperium and OC pills & HRT .

• It is one of the leading causes of maternal mortality and morbidity with cases of puerperal CVT occuring 10 -12 times more frequently in India than the west .

• In ISCVT it was found that the mean age of patients with CVT was 39yrs with only 8% of subjects being >65 yrs .

Aetiology-

The exact etiology in most of the cases is unclear but many possible risk factors have been identified . These may either be transien tor permanent .

Prothrombotic conditions either genetic or acquired

OC pills especially 3 generation pills with desogestrel

Pregnancy and puerperium

Malignancy

Infections –head,face &ear (cavernous ,transverse and sigmoid ) and meningitis .

Head injuries and mechanical precipitants(surgical procedures )

In more than 85% pts one of the risk factors has been identified most often prothrombotic states .where as infections were present only in 6-12% of the patients.

Pathogenesis –

Two basic mechanisms for the development of symptoms have been identified to be responsible for the clinical features in CVT –

Thrombosis of cerebral veins or sinuses leading to cerebral parenchymallesions or dysfunctios .

Occlusion of dural venous sinus resulting in decreased CSF absorption and elevated intracranial pressure .

Obstruction of venous structures > increased venous pressure >decreased capillary perfusion >increased cerebral blood vol. >disruption of blood brain barrier >plasma leakage into interstitial space>cerebral edema,parenchymal changes ,venous haemorrhage .

Clinical features -

The clinical presentation of CVT is highly variable with acute /subacute/chronic presentation .

• The symptoms and signs of CVT depends on the sinuses involved, the pace of occlusion, involvement of cortical veins and presence of collaterals ,paranchymal changes and the patients age .

• Symptoms of CVT have been grouped under three major clinical syndromes-

Isolated intracranial hypertension syndrome( headache with or without vomiting ,papilledema ,and visual problems )

Focal syndrome (focal deficits or seizures or both)

Encephalopathy ( multifocal signs ,mental status changes ,stupor or coma )

Headache –

This is the most common and least specific of all symptoms of CVT .in the ISCVT study 89% of pts presented with headache .Headdache is usually the first symptome is CVT .

• headache is gradual in onset , increase over a period of days to weeks , severe in intensity.

• It is more often localised than diffuse .

• In some patients it may be severe thunderclap type of headache mimicing subarachnoid haemorrhage .

• In patients with raised ICP it is severe, diffuse ,generalized pain which worsens on valsalva manouver and recumbence. Visual obscurations may occur coinciding with these bouts .

• It may resemble migrane with aura .

Focal signs and symptoms –

Motor weakness with monoparesis or hemiparesis is the most common focal deficit associated with CVT .

Aphasia is especially associated with left lateral sinus thrombosis .

Seizures –

focal or generalised seizures including status epilepticus are more common

in CVT than in any other type of stroke .

Encephlopathy –

disturbances of consiousness and cognitive dysfunctions such as delirium

,apathy , frontal lobe syndrome ,multifocal deficits can be present .

Presentation of isolated sinus and vein thrombosis -

Cavernous sinus thrombosis –ocular signs predominate :ocular pain,chemosis,proptosis and ocular palsies .

Sagittal sinus occlusion –motor deficits ,bilateral deficits ,seizures .

Lateral sinus occlusion –isolated intracranial hypertension . If left lateral sinus thrombus is present aphasia is seen .

Jugular vein obstruction –isolated pulsating tinnitus .

Deep venous system occlusion – severe signs &symptoms with coma ,mental problems and motor deficits which are often bilateral .But if limited thrombosis is present then the symptoms are mild .

Lateral sinus and jugular vein thrombosis –multiple cranial nerve palsies .

I . NEUROIMAGING

II .LABORATORY TESTS

INVSTIGATIONS

NEUROIMAGING-

Neuroimaging features include findings that suggest primary underlying pathology of venous thrombosis and associated paranchymal lesions( focal areas of edema, haemorrhagic venous infarction , diffuse brain edema)

MRI –

MRI using gradiend echo t2 susceptiblity weighted sequences in combination with MR venography is most sensitive for demonstrating thrombus and occluded dural sinus and vein.thecharecteristics of MRI deend on the age of the thrombus-

• First 5 days thrombus appears isointense (t1) and hypointense (t2)

• Beyond 5 days thrombus becomes more apparent in both t1 and t2 weighted images .

Paranchymal brain lesions secondary to venous thrombus including brain swelling,edema,venous infarctions appear hypo or isointense on t1 weighted images and hyperintense on t2 weighted images .

Haemorrhagic infarcts appear hyperintense in both MRI sequences .

MR venography –

This is useful in demonstrating absence of flow in cerebral venous sinuses .

Head CT-

CT is often the first investigation to be performed in clinical practice and is used to rule out other acute or subacute cerebral disorders.

The following are direct signs of CVT demonstrated in CT –

Dense triangle sign –seen as hyperdensity with triangular shape at the posterior end of superior saggital sinus caused by venous thrombus .

Empty delta sign – seen in head CT with contrast as a triangular patter of contrast enhancement surrounding a central region lacking contrast enhancement .

Cord sign – as linear or curvilinear hyperdensity over the cerebral cortex caused by thrombosed cerebral veins .

Indirect signs of CVT on CT include demonstration of contrast enhancement of falx and tentorium ,dilated trans cerebral veins ,paranchymal abnormalities .

Non-haeemorrhagic lesions including focal areas of hypodensity caused by edema or venous infarction .

Dense clot sign

Empty delta sign

Laboratory tests-

Current guidelines from AHA/ASA recommend routine blood studies consisting of –

Complete blood picture

Prothrombin time

Activated partial thromboplastin time

Other investigations –

D-dimer testing ( elevated levels support the diagnosis of CVT however normal levels do not exclude the diagnosis )

Lumbar puncture –to exclude meningitis in pts with CVT . More therapeutic advantage than diagnostic .

Treatment is to be started as soon as the diagnosis is confirmed and consists of –

1. Treating the underlying cause when known

2. Control of seizures and intracranial hypertension

3. Antithrombotic therapy

TREATMENT OF CVT

Cerebral venous thrombosis can result in death or permanent disability but usually has a favorable outcome .

Predictors of mortality at 30 days include –

• Depressed consciousness

• Altered mental status

• Thrombosis of deep venous system

• Right hemisphere haemorrhage

• Posterior fossa lesions

Transtentorial herniation secondary to haemorrhage is the main cause of acute death in CVT.

Otherr causes include –status epilepticus ,diffuse brain edema ,pulmonary embolism and other medical complications .

Predictors of poor prognosis includes –

Central nervous system infection

Malignancy

Thrombosis of deep venous system

Haemorrhage on head CT or MRI

Glasgow coma score <9 at admission

Mental status abnormalities

Age >37 yrs

Male gender

TREATMENT PLAN –

1. ACUTE ANTITHROMBOTIC TREATMENT –

the goals of this are-

• To recanalize the occluded veins

• To prevent the propagation of the thrombus

• To treat underlying prothrombotic state

The main treatment option to achieve these goals is anticoagulation using heparin or LMWH (i.v/s.c)

Anticoagulants appear to be safe in adults who have intracranial haemorrhages .

AHA/ASA guidelines for CVT management conclude that initial treatment with weight adjusted LMWH /dose adjusted unfractioned heparin in full anticoagulant dose followed by vit.k antagonists is reasonable regardless of presence of ICH.with recommended target INR is 2-3 .

2.ACUTE SYMPTOMATIC TREATMENT –

i.Elevated ICP and herniation –

• Elevating the head end

• Administration of mannitol

• Hyperventilation to a target paCO2 of 30-35 mm hg

• Impending herniation of unilateral hemispheric lesions hemicraniotomy can be life saving .

• Therapeutic lumbar puncture to decrease csf pressure and offer headache relief .

ii.Seizures –

• Recurrent seizures are likely to develop in those who present with seizures or with supra tentorial lesions therefore anti epileptic drugs profhylaxis are recommended for these patients .Valproate is preferred to phenetoin due to fewer drug interactions with oral anticoagulants .

2. Management after acute phase -

The aim of continuing anticoagulants after the acute phase is to prevent recurrence.

It is recommended that anticoagulant therapy with warfarin should be given for a minimum of 3 months after acute CVT aiming at an INR target of 2.5(2-3).

European guidelines recommend –

• 3 mnts treatment with oral anticoagulants for a patient with initial CVT secondary to a transient risk factor.

• 6-12 mnts of ral anticoagulants for patients with idiopathic CVT and those with mild thrombophilia .

• Indefinite therapy for patients with recurrent CVT and one episode of CVT and severe thrombophilia