¹Assistant Professor, Department of Radio-Diagnosis, Karnataka Institute of Medical Sciences, Hubballi, Karnataka-580022

Email: vinamaradi@gmail.com

 

 

 

 

Table 1: Comparison of baseline parameters and HU

Most common locations for CVST in present study were superior sagittal sinus (68%), transverse sinus (59%), sigmoid sinus (53%) and cortical veins (32%). Others were straight sinus (21%), internal jugular veins (12%), vein of Galen (12%), internal cerebral vein (9%) and cavernous sinus (6%)

 

Table 2: Distribution of CVST.

All patients underwent CVST followed by MR venography. Interpreters were kept blind for other diagnosis. On plain CT, CVST was diagnosed in 30 cases, while failed to diagnose 4 cases, which were positive on MR venography.

 

Table 3: CVST diagnosis

 

t HU levels 62, specificity and sensitivity of plain CT for diagnosing CVST was 88 % and 95 % respectively. Accuracy of plain CT at 62 HU was 93% for diagnosing CVST.

 

Table 4: Statistical analysis

 

 

 

 

CASE 1-

Figure 1: 50Years old male patient presented with headache, loss of memory and irrelevant speech since 2days

A: Axial plain CT shows hyperdense superior sagittal sinus with left temporo-parietal hemorrhagic infarct; B: Axial contrast enhanced CT shows empty delta sign with non opacification of left transverse sinus; C: MR Venography confirms thrombosis of distal segment of superior sagittal sinus and left transverse sinus. Hounsfield unit (HU)-68 ; Haematocrit (HCT)-42.2% ; HU: HCT=1.61

 

CASE 2-

Figure 2: 26years old female patient presented with altered sensorium and 1 episode of seizure

A: Axial plain CT shows bilateral thalami infarct with hyperdense straight sinus; B:Axial contrast CT image shows non opacification of straight sinus confirming thrombosis, C:MR Venography shows occlusion of straight sinus

Hounsfield unit (HU)-63 ; Haematocrit (HCT)-42% ; HU: HCT=1.5 HU: HCT=1.61

 

CASE 3-

Figure 3: 40years             male patient presented with altered sensorium and left hemiparesis A: Axial plain

CT shows hemorrhagic infarct in right temporo-parietal region with midline shift to left; B: Axial contrast CT shows non opacification of right cortical veins and empty delta sign of superior sagittal sinus; C and D: MR Venography shows occlusion of superior sagittal sinus, right transverse and sigmoid sinus and right superficial cerebral veins

Hounsfield unit (HU)-61 ; Haematocrit (HCT)-41% ; HU: HCT=1.5

 

Figure 4: 26 year old patient presented with altered sensorium and 1 episode of seizure and 1 episode of seizure

A: Axial plain CT shows bilateral thalami infarct with hyperdense straight sinus; B: Axia contrast CT image shows non opacification of straight sinus confirming thrombosis C: MR venography shows occlusion of straight sinus

Hounsfield unit(HU)-63; Haematocrit(HCT)-42%; HU;HCT=1.5

 

DISCUSSION

The imaging modality of choice for CVST is magnetic resonance venography as it allows direct visualisation of the dural venous sinuses and the large cerebral veins.⁶ It is an invasive procedure with catheterisation of the jugular vein and therefore has associated risks. Acute thrombosis within the vessel lumen is usually seen as hyperattenuating material in NCCT performed in the acute phase of the disease. The increased attenuation, usually attributed to the decreased amount of water in the retracted clot and increased concentration of red blood cells and hemoglobin.⁹ In the study by Narayan et al..,¹⁰ they noted that mean age of the patients in this study being 31.3 years and had a larger proportion of males than females. Another study which recruited 612 consecutive patients of CVT from various hospitals of Mumbai had a male to female ratio of 3:2. Narayan et al.. and Pai et al..¹¹, have reported only 9.8% and 8% patients in the postpartum or pregnant state, respectively. Thrombus is visible on nonenhanced CT as a high-attenuation lesion in the venous channel, producing dense triangle or cord sign represents an intravascular acute blood clot.¹² With passage of time, the thrombus gets rechannelled as well as RBC and haemoglobin are degraded. The hyper attenuating signs can serve as unique findings indicating an acute stage, this is the stage when treatment is most effective and if identified early can have a great outcome on patient management.^13,14 In literature this sign has been referred to as the hyperattenuated dural sinus CVST. In a recent study by Ali Alsafi et al.., 768 venous sinuses were analyzed; 46 with CVST and 720 without. The average HU of vessels containing a thrombus was 68 ± 1.56, which was significantly higher than that of normal vessels 52 ± 0.28.¹⁵ Similar findings were noted in present study. Appreciating moderate increases in attenuation by the attenuation measurement with in the dural sinus can be helpful in the detection of acute CVST.¹⁶ Goldstein et al.. found a mean attenuation of 73.9 HU in thrombosed venous sinus.¹⁷ At HU levels 62, specificity and sensitivity of plain CT for diagnosing CVST was 88 % and 95 % respectively. Accuracy of plain CT at 62 HU was 93% for diagnosing CVST. Tayyebi S et al..,¹⁸ at cutoff value of 61 HU noted a sensitivity of 82% and specificity of 100%. Avsenik J et al..,¹⁹ noted sensitivity and specificity of NCCT for overall presence of CVST were 100% and 83%, respectively. The ROC analysis noted a sensitivity of 85% and specificity of 87%. Quantitative measurement of attenuation is believed to be more accurate than subjective evaluation, as it can appreciate moderate increases in mean sinus density.²⁰ With new advancement and with thinner CT sections, this sign is detected much more frequently. Hyperdense sign of venous sinuses on NCT scan has a sensitivity of 84% and 95% and specificity of 96% and 95% with a HU (Hounsfield unit) cut‑off value of 65 and 62, respectively, as shown by some recent studies.^21,22 Shayganfar et al..²³ noted that the attenuation value of > 60.4 Hounsfield unit (HU) with 71.4% sensitivity and Hounsfield-hematocrit (H: H) ratio of > 1.42 with 94.3% sensitivity calculated based on unenhanced CT could strongly detect CVT in the emergency setting. Diagnosis of cerebral sinus thrombosis on plain CT has a sensitivity of 50–100% and a specificity of 83–100%.²⁴ A meta-analysis summarizing the diagnostic accuracy of CT (non-contrast- and contrast-enhanced) for CVT noted that, the pooled sensitivity and specificity of CT were 81% (95%CI 78–84%) and 89% (95%CI 88–91%), respectively.²⁵ An explanation for these wide ranges may be the different scan technologies and acquisition measures used, with a generally lower sensitivity in older studies.²⁶ The indirect signs for CVST diagnosis on plain CT includes differential appearance of the involved cerebral parenchyma, loss of gray-white matter differentiation, focal hemorrhaging areas, white matter edema, sulcal effacement, etc.²⁷ Increase in parenchymal volume without attenuation or signal intensity alterations can be found, possibly as a reflection of the capillary venous congestion, with effacement of sulci, decrease in the width of the cisterns as well as in the size of the ventricular system.²⁷ Plain CT is imaging technique of choice for evaluation of patients with suspected CVST. Present study was a small sample size, institution based study. Large sample, multicentric studies are much needed to confirm our findings. Digge et al..⁹ proposed that plain CT is specific enough for the diagnosis of acute CVT, and no confirmatory imaging, such as venography, is needed. However, they concluded that parallel to age clot progression, the sensitivity of CT attenuation would decrease. According to the Indian guidelines for stroke management, patients suspected to be having a stroke due to CVT should be investigated by MRI/MRV/CTV only if the CVT is not diagnosed by a CT scan.²⁸

 

CONCLUSION

Plain CT is affordable, widely available and gives reports quickly. Prompt diagnosis and treatment of CVST has a better outcome, so early diagnosis is essential. Plain CT is imaging technique of choice for evaluation of patients with suspected acute CVST.

 

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