Accuracy of Noncontrast CT Brain in Detection of Cerebral Venous Sinus Thrombosis

Background and Purpose: Increasing concern of cerebral venous thrombosis due to treatable and curable causes of stroke. The diagnosis of cerebral venous sinus thrombosis is challenged due to nonspecific clinical symptomatology. Patients may present at an emergency room with a variety of neurological conditions such as severe headache, weakness, seizure, etc. Neuroimaging, particularly noncontrast cranial computed tomography (NCCT), is an investigation of choice in differentiation and triage the patients for further treatment. CT is sensitive in the detection of acute thrombosis or blood clots in all regions of the body. We hypothesize that NCCT might be sensitive to diagnose cerebral venous thrombosis immediately. Materials and Methods: Retrospectively review the electronic database of our patients, there are 27 patients with cerebral sinus venous thrombosis (SVT) and 4 patients with cerebral deep venous thrombosis (DVT). Other 79 patients present with clinically diagnosed cerebral venous thrombosis but the final result can exclude cerebral venous thrombosis. We use MR imaging and CT venography as the gold standard. Independently reviewed by two neuroradiologists for CT direct sign and CT indirect signs that suggest SVT or DVT. CT direct signs for SVT and DVT are the presence of hyperdensity in the sinus venous or deep venous system (cord sign, attenuated vein sign) and CT indirect signs are the changes in brain parenchyma (brain edema, hemorrhagic infarction). Results: Sensitivity and specificity of NCCT in detection attenuated vein sign and diagnosis DVT are 75% and 100% whereas the sensitivity and specificity of NCCT in detection cord sign and diagnosis SVT are 43.8% and 99.7% as respectively. Conclusions: NCCT might not sensitive in detection of SVT without CT direct sign which needs further investigation. However, NCCT might beneficial for emergency conditions such as DVT patients, cortical vein thrombosis and also in SVT patients with the positive CT direct sign.


Introduction
Cerebral venous thrombosis (CVT) is one of the causes of stroke even though less common comparable to stroke from arterial thrombosis. It still represents the common cause of stroke in young adults. Nowadays, CVT is increasingly encountered in daily practice.
Early diagnosis of cerebral venous thrombosis is important for the early treatment which can improve morbidity and mortality of the patients. Clinical symptoms of CVT are nonspecific [1] [2] with a wide range of severity such as headache, nausea, vomiting, dizziness up to neurological deficits and epilepsy [3] [4].
In contrast to the patients with stroke from arterial thrombosis, the symptoms of CVT patients are not present in the acute stage but slow progression [5] [6] [7]. Severe headache is the most common symptom which is counts as 74% -90% of CVT patients and nonspecific [3] [8]. Early diagnosis of CVT should be in the lists of differential diagnoses whenever encountered in the young patients with unusual severe headache, with clinical arterial stroke and absence of risk factors, with intracranial hypertension or patients with hemorrhagic infarction on NCCT. The most common locations of intracranial dural venous sinuses are superior sagittal sinus followed by transverse sinus and sigmoid sinus as respectively [3] [4] [9].
Although CVT is not common, altogether with this condition awareness and new model of imaging CT scanner with rapid scan time, thin slices section, high resolution, the incidence of CVT is increase. Shorter time from onset of symptoms to diagnosis is with average of 7 days [3] [8].
The disadvantages of MRI are such as time consuming imaging technique, need patient cooperation particularly in the emergency condition [2] [6] [11]. So, multidetector computed tomography with venography (MDCTV) is of increased utility as the imaging modality in diagnosis CVT after inconclusive by NCCT.
NCCT can be performed faster and is suitable in the neuroemegency condition, still use as the first line of imaging modality in most centers. The radiologic patterns of NCCT in diagnosis of CVT (both SVT and DVT) are divided into direct signs and indirect signs. "Direct sign" refers to the visualization of the acute intraluminal blood clot or acute thrombosis that developed in the cranial venous system. If the thrombus formed within a week (acute stage), the attenuation value or CT density is higher than brain density and locates along course  [6]. After one to two weeks (subacute stage), the thrombus is getting decreased density to the same level of brain (isodensity) or lower than the brain (hypodensity) which might not be easily diagnosed by NCCT. "Indirect sign" refers to the brain parenchyma density changes resulting from cerebral venous thrombosis which could be brain edema or hemorrhagic infarction, etc. [6].
Previous study reports that the sensitivity and specificity of NCCT in detection direct sign in cerebral venous thrombosis for SVT is poor [7] which is contrary to our experiences in daily practice. The purpose of this study is to reevaluation the usefulness of NCCT in diagnosis CVT.

Material and Method
This study was approved by institutional review board committee and performed in Siriraj hospital.

Definitions
We defined the patients with cerebral venous thrombosis into two subgroups such as sinus venous thrombosis (SVT) which represents thrombosis in course dural sinus such as superior sagittal sinus, inferior sagittal sinus, transverse sinus, sigmoid sinus and deep venous thrombosis (DVT) which thrombosis is detected in those following veins as thalamostriate vein (TSV), internal cerebral veins (ICV), basal vein of Rosenthal (BVR), great vein of Galen (VG).

Imaging
All patients included in our study had undergone NCCT (n = 110). CT Venography were performed in 90 patients and MR venography were performed in 20 patients.

Procedure Parameters
All imaging procedures are undergone by the following machines and protocols: All NCCT were undergone by one of the two 64-slices multidetector CT International Journal of Clinical Medicine All CT Venography were undergone by the same 64-slices multidetector CT scanners. CTV protocol parameters as 120 kV, 120 -140 mAs; collimation, 4 -10 mm., 80 -100 mL contrast medium, injection rate 3 -5 mL/s and delay 35 s.
All MR Venography were undergone by one of the two 3.0T MR scanner and 1.5 T MR scanner (Inter Achieva, Philips) with protocol parameters as follows: T1-weighted SE-sequence (TR, 9.5 ms; TE, 8 ms; section thickness, 5 mm; FOV, 230 mm; matrix size, 256).

Image Review
All of patients' imaging modalities study were interpreted by two neuroradiologists independently without available patients' clinical information and final diagnosis. Reading on PACS workstation in department of Radiology and recorded imaging informations in case record forms.
Recorded imaging data of the NCCT scan are the presence or absence of hyperdense sign (cord sign) in all sinus venous and cortical vein, hyperdense sign (attenuated vein sign) in deep vein. Presence or absence of brain edema, hemorrhagic infarct were also recorded. Then, the readers had to make conclusion for the diagnosis of SVT or DVT. After completing all NCCT interpreta-International Journal of Clinical Medicine tions, the disconcordance cases are in consensus reading of the two readers with obtaining other imaging modalities such as CTV or MRV as well as clinical data of those cases.

Statistical Analysis
The statistical analysis of our recorded images data was performed by using of standard software (Excel and Access; Microsoft, STATA). The sensitivity and specificity of NCCT in the diagnosis of SVT and DVT as well as 95% confidence intervals were analyzed. Interobserver agreement of the hyperdense sign in sinuses or deep veins were analyzed with multirater values were calculated as de-   Table 2.   number, albeit the sensitivity for overall DVT was about 75% (Table 5 and Ta Table 3 and Table 4. The sensitivity and specificity of attenuated vein sign in patients with DVT were 75% and 100% whereas the sensitivity and specificity of cord sign in patients with SVT were 43.8% and 99.7% as respectively. The interobserver agreement of attenuated vein sign was 0.59 (range 0.47 -0.79; Table 3) International Journal of Clinical Medicine

Discussion
Early treatments for the patients with CVT have been proved to obtain an excel- 70.8% and 75% whereas cord sign is only 43.8%. Even though, the sensitivity of cord sign by NCCT in diagnosis sinus venous thrombosis is too low in the present study, however, is similar to previous studies sensitivity 25% -56% [10] [15]. We suggest that the negative case by NCCT in the patients suspected cerebral venous thrombosis might not exclude sinus venous thrombosis (SVT). One main reason of low sensitivity NCCT in SVT found in our study is due to intrasinus thrombosis clot density, if it was isodensity to the brain, it is not possible to diagnosis by means of NCCT ( Figure 6 and Figure 7). The density of thrombus is directly related to age of thrombus, the isodensity thrombus is not in acute stage but to subacute or chronic stage which might reflect to variety of clinical symptoms and nonspecific, delayed imaging can occur. Our findings are different from previous study by Alsafi A. et al. [18] that those cases are in acute stage hyperattenuated (HU > 67) greater than density of the brain, we found some of cases that isodensity blood clot in the sinuses ( Figure 6 and

Conclusion
NCCT has an impact on the diagnosis of deep cerebral vein thrombosis (DVT) as well as cortical vein thrombosis with high sensitivity and specificity. Absence of hyperattenuating vein signs and parenchymatous changes are less suspicious of deep cerebral vein thrombosis. On contrary, NCCT has poor sensitivity in detection of sinus venous thrombosis (SVT), negative detection suggests to be further investigated by CTV or MRV.