Overview of the utility of noncontrast CT brain in the diagnosis of cerebral vein thrombosis

Abstract

Cerebral venous thrombosis (CVT) accounts for approximately 1% of all stroke presentations and due to variable clinical presentation, it can present a diagnostic difficulty. The purpose of this review is to re-iterate the usefulness of noncontrast CT brain (CTB) in detecting CVT. In this pictorial essay, we highlight our experience in multiple cases where unenhanced CTB demonstrated imaging features of CVT allowing early diagnosis and ensuing prompt management of CVT. This reduces reliance on additional imaging modalities which may prove beneficial in departments where modalities such as magnetic resonance venogram which is considered gold standard imaging for CVT, are not readily available. This in turn may prove crucial in provision of earlier diagnosis and more favorable prognostic outcomes.

Introduction

Cerebral venous thrombosis (CVT) refers to thrombotic occlusion of the deep or superficial intracranial venous vasculature accounting for approximately 1% of all stroke presentations [1]. Presenting symptoms may be nonspecific and demonstrate great variability from asymptomatic to comatose patients. Annual incidence of CVT ranges from 1 to 2 per 100,000 and is more common in females due to increased risk associated with pregnancy and oral hormonal contraceptives [2]. Other risk factors include prothrombotic haematological conditions, systemic illness or local factors such as trauma. Vague presenting symptoms often result in diagnostic challenge and ultimately delay initiation of pertinent investigations and treatment.

Knowledge of the intracranial cerebral venous system is important for accurate diagnosis which includes a superficial system of cortical based venous drainage composed of Dural sinuses, cortical veins and a deep venous system. The internal jugular veins are the final drainage point (Fig. 1).

Fig. 1.

Illustration of the major cerebral venous sinuses and their tributaries [3].

Historically digital subtraction angiography was the gold standard diagnostic test, however its use has dramatically declined and now only used alongside planned therapeutic endovascular procedures or rarely to clarify equivocal imaging findings [4]. Computed tomography (CT) and magnetic resonance imaging (MRI) have become the mainstream diagnostic tests for CVT. Combined MRI and magnetic resonance venogram (MRV) is considered now to be gold standard of diagnostic imaging for CVT [5]. Nevertheless, both modalities offer diagnostic pitfalls and limitations. Recent guidelines offered by the European Stroke association have suggested that CT venography can be a valid alternative to MRV for patients with suspected CVT [6] and subsequent studies have validated this [7,8].

A noncontrast CT brain (CTB) is the most commonly performed first line imaging in patients presenting to the emergency department with nonspecific neurological symptoms such as headache, seizures or asymmetric focal neurology. The role of the unenhanced CT brain in suspected CVT is often underplayed. In this review, we present a case series where noncontrast CTB demonstrated considerable usefulness in the acute context enabling prompt and appropriate guidance to second line imaging such as CT venogram or MRV.

Clinical and imaging prospective

CTB may be normal or demonstrate nonspecific features in up to 30% of CVT cases [1]. However, when findings are present, they range from subtle to markedly abnormal. Indirect signs may be apparent such as cerebral oedema, intracranial mass effect or varying degrees of intracranial haemorrhage. The direct feature of CVT is hyperdensity of the affected vein or sinus relative to surrounding parenchyma or contralateral vasculature, referred to as the dense clot sign. The hyperdense vein or sinus can persist for 7-14 days [9].

Case 1

A middle aged female presented with a 4 day history of throbbing headache, vomiting, visual disturbance and unsteady gait. Her past medical history consisted of intraductal carcinoma of the breast which was treated with radiotherapy and chemotherapy, she had started tamoxifen some months earlier. No other regular medications were prescribed and was an ex-smoker. Her clinical examination and inflammatory markers were normal.

Imaging findings: Axial and sagittal images of noncontrast CT brain (Fig. 2, Fig. 3) demonstrates hyperattenuation in the internal cerebral veins, vein of Galen and straight sinus extending into the confluence of sinuses (torcula herophili). A difference of 10 Hounsfield units (HU) is observed between the CVT in the straight sinus when compared to normal density superior sagittal sinus (Fig. 3)

Fig. 2.

Axial noncontrast CT brain demonstrating hyperattenuation of the proximal straight sinus (black arrow) at the confluence of the vein of Galen and inferior sagittal sinus internal cerebral veins. No brain parenchymal abnormality identified.

Fig. 3.

Sagittal (A) and coronal (B) of noncontrast CT Brain demonstrating hyperattenuation in the internal cerebral veins, vein of Galen (white arrow) and straight sinus (black arrow) extending into the confluence of sinuses, the mean HU of the hyperdense straight sinus is 78HU vs. 68HU in the superficial sagittal sinus (B).

Diagnosis: Diagnosis of deep and superficial venous thrombosis was confirmed on subsequent MR venography (Fig. 4, Fig. 5).

Fig. 4.

Precontrast T1 Fat suppressed (FS) sagittal image sequence demonstrating T1 hyperintense signal within the deep cerebral veins, vein of Galen and straight sinus (black arrow).

Fig. 5.

Postcontrast T1 FS sagittal image depicts a filling defect in the vein of Galen confirming cerebral venous sinus thrombosis.

Tamoxifen was discontinued as the most likely precipitant. She was started on therapeutic low molecular weight heparin (LMWH) and had a short inpatient stay. On discharge the patient had a full recovery and LMWH was switched to direct oral anticoagulant.

Case 2

A young female presented to the emergency department with a 5 day history of throbbing migratory headache which was followed by 1 day of nausea, vomiting and extreme fatigue. She had no past medical history and was prescribed the oral contraceptive pill. On examination there was no objective neurological findings. Her blood count showed lymphocytosis, otherwise her bloods were normal and a normal CRP of 5mg/L.

Imaging findings: Initial non contrast CTB demonstrated subtle asymmetric hyperattenuation along the course of the right transverse sinus (Fig. 6) with mild dilatation of the straight sinus. The possibility of CVT was raised and the patient proceeded to contrast enhanced imaging.

Fig. 6.

Axial noncontrast CTB shows asymmetrically hyperattenuating right transverse sinus (black arrow) representing cerebral venous thrombosis.

Diagnosis: CVT was later confirmed on CT venogram (Fig. 7) which showed thrombus extension to the right internal jugular foremen.

Fig. 7.

Axial CT venogram shows a filling defect with the right transverse sinus (Black arrow) correlating with CTB findings and confirming cerebral venous thrombosis.

The patient was initially prescribed LMWH following diagnosis and had a short term hospital stay. At time of discharge she was asymptomatic and changed to direct oral anticoagulant.

Case 3

A young female presented to our institution in status epilepticus which was preceded by multiple seizures that night and a 4 day history of headache. On admission to the emergency department she had a prolonged low level of consciousness (GCS 8). She had a noncontributory past medical history and was taking no regular medications. There was no family history of venous thromboembolic disorder. ON examination she generalized diminished reflexes and right upper limb weakness. Her blood count showed neutrophilia and a slightly elevated CRP at 5mg/L. Venous blood gas showed lactic acidosis presumably secondary to status epilepticus.

Imaging findings: CTB showed low attenuation in the right frontal and temporal lobes with multiple punctate hyperattenuating foci superiorly in the left frontal lobe. A hyperdense cortical vein is seen overlying the right frontal lobe (Fig. 8). Findings were concerning for acute CVT and associated right cerebral venous ischemia with petechial haemorrhage.

Fig. 8.

Axial (A), coronal (B) and sagittal CTB demonstrates hyperdense superficial cortical vein overlying the right frontal lobe (black arrow) suggestive of a cortical venous thrombosis.

Diagnosis: The diagnosis was confirmed on subsequent CT venogram (Fig. 9) demonstrating a correlating filling defect in the superficial cortical vein extending to the superior sagittal sinus.

Fig. 9.

Coronal (A), axial (B) and sagittal (C) CT venogram shows a filling defect within a right cortical vein (white arrows A and B) overlying the right front lobe confirming a superficial cerebral vein thrombosis with extension to the superior sagittal sinus (C).

Upon admission the patient was commenced on LMWH and antiepileptic medication. During her in hospital stay, the coagulation team advised changing anticoagulation to warfarin. Prior to discharge following a relatively short inpatient stay, she was consulted on avoiding oestrogen based contraceptive for life and advised progesterone only pill or intrauterine contraceptive device as suitable alternatives. She was asymptomatic with no residual focal neurological abnormality on discharge home.

Case 4

A young female in early first trimester pregnancy presented with nonspecific back pain, left lower limb weakness and fatigue. As per collateral history she had demonstrated acute behavioral changes and confusion for 2 days prior to her presentation. She had presented 2 days earlier to the local maternity hospital with nausea and vomiting which settled following anti-emetics. On examination there was no notable focal neurological abnormality. Apart from an elevated CRP 15mg/L, her bloods were all within normal limits.

Imaging findings: Non contrast CTB showed hyperdense right transverse, sigmoid sinus and superior sagittal sinus highly suggestive of extensive CVT (Fig. 10).

Fig. 10.

Axial (A), sagittal (B) and coronal (C) CTB shows asymmetric hyperdense right transverse (black arrow), sigmoid sinus and superior sagittal sinus in keeping with extensive CVT.

Diagnosis: Findings of extensive venous thrombosis and multifocal venous infarction (Fig. 11) in the bilateral frontal and parietal lobes were confirmed on CT venogram (Fig. 12) and later MR venogram.

Fig. 11.

Axial FLAIR (A), DWI (B) and ADC (C) MRI brain shows multifocal bilateral acute venous infracts in the frontal and parietal lobes with associated gyral swelling and sulcal effacement.

Fig. 12.

Sagittal (A), axial (B) and coronal (C) CTV shows filling defects seen primarily in the superior sagittal sinus (white arrows) extending from right transverse and sigmoid sinus providing confirmation of CVT suggested by CTB in Fig. 10.

Following diagnosis, LMWH was immediately commenced. The patient was then transferred to interventional neuroradiology for a successful percutaneous venous thrombectomy. The patient had significant neurological deficits and a protracted hospital stay. After a number of months, LMWH was discontinued as per advice of the stroke team and the patient was transferred to a rehabilitation centre.

Discussion

Unenhanced CT brains are a widely available first line imaging technique in the majority of clinical settings from smaller resource limited departments to larger tertiary care centers. In those presenting with acute neurological symptoms, the role of the noncontrast CT brain has primarily been of 1 of exclusion of parenchymal intracranial abnormalities such as haemorrhage, ischaemia and focal mass effect.

CVT may be a rare cause of stroke presentation but under diagnosis because of nonspecific presentation is common and can result in fatal outcomes [1]. The examples provided in this pictorial review highlight the undervalued role of noncontrast CT brain in CVT diagnosis. Each of the cases detailed occurred in an out of hours setting, occasionally with CT venogram occurring in tandem with CTB. MR venogram was unavailable until normal working hours. Therefore, early diagnosis with noncontrast CTB and escalation to CT venogram allowed therapy commencement at an early stage in all cases.

In studies, comparison is normally made between the diagnostic accuracy of CT venography and MR. Of the few studies assessing the diagnostic efficacy of noncontrast CT imaging markers in CVT, it has shown to be of a high sensitivity and moderate specificity adding value as a first line investigation in the acute setting [10,11].

Conclusion

The aim of this review is to help re-focus assessment to the venous vasculature and to act as reminder to radiologists to consider including the venous sinuses and cortical veins as review areas when assessing noncontrast CT Brain imaging. An early diagnosis of cerebral venous thrombosis on initial CT can prove crucial to initiating further investigation and subsequent treatment ultimately resulting in improved patient outcomes. This is particularly important in the out-of-hours setting or resource-limited departments where access to advanced imaging such as CT venogram or MRI is not readily available.

Ethics statement

All ethical standards were followed. Abiding by national and local guidelines, formal ethical approval was not required due to retrospective case series design type (SJH/TUH Joint Research Ethics Committee).

Patient consent

Appropriate consent has been obtained regarding submission and potential publication of this manuscript.