Patients and characteristics
This retrospective study was performed on 91 patients who were diagnosed with CVST at a hospital from May 2016 to Dec 2020. The study was approved by the Scientific Research and Clinical Trial Ethics Committee of the First Affiliated Hospital of Zhengzhou University and was exempt from informed consent due to the purely retrospective analysis. Inclusion criteria included: confirmation of CVST, the interval from the first clinical symptom onset to MR examination and endovascular therapy within 30 days; Exclusion criteria included general contraindications to MR examination and medical history of CVST or other synchronous brain diseases. Recurrent CVST patients were also excluded because residual thrombi may exist [17, 18].
Patients’ information, including age, gender, duration of the clinical symptom onset, MR imaging results, DSA images, risk factors, and therapy methods, were collected for analysis. Based on the interval from the clinical symptom onset to MR examination, the patients were divided into three groups: acute stage (≤ 7 days), subacute stage (8 to 15 days), and chronic stage (16 to 30 days) . The patients’ characteristics were listed in Table 1.
All CVST patients were conducted by T1-SPACE on a 3.0-T MR scanner (MAGNETOM Prisma, Siemens Healthcare, Erlangen, Germany) with a 64-channel head/neck coil. The scan parameters included: repetition time = 650 ms, echo time = 13 ms, parallel acceleration factor = 2, turbo factor = 40, bandwidth = 539 Hz/pixel, field of view = 260×208 mm2, voxel size = 0.8×0.8×0.8 mm3, acquisition time = 5 min 27 s.
The MR examination was performed before endovascular therapy for the patients within three days. One patient received anticoagulation initially and transferred to endovascular therapy later because the symptoms unrelieved and suddenly deteriorated. Thus, the patient was conducted by T1-SPACE three times: 1. before anticoagulation; 2. after the anticoagulation 2 days but before endovascular therapy; 3. follow-up study after endovascular therapy.
Treatments of CVST
Conventional anticoagulation with low molecular weight heparin (LMWH) was the initial treatment in all the patients after MR examination confirming the CVST. Patients who satisfied the following criteria would receive endovascular thrombectomy and thrombolysis: 1. Glasgow Coma Score (GCS) was low than 10 points at admission or during treatment; 2. symptoms were rapidly deteriorated after anticoagulation treatment (GCS < 10 points); 3. straight sinus thrombosis; 4. large area cerebral infarction or intracranial hematoma. The exclusion criteria were as follows: 1. anticoagulant therapy was effective and the symptoms significantly relieved; 2. significant cardiac, liver, or renal dysfunction; 3. patients with a cerebral hernia; 4. CVST secondary to malignancy such as leukemia; 5. patients refused interventional thrombolysis.
LMWH (85IU/Kg, SANOFI, CHINA) was given twice per day for 14 days for patients who received conventional anticoagulant treatment. Partial thromboplastin time (PTT) monitoring was performed. Oral anticoagulation combined before the discontinuation of LMWH.
Twenty-nine of 91 patients received endovascular therapy. The procedures were initially performed under local anesthesia or monitored awake sedation. Femoral arterial and venous access were chosen, and a bolus dose of 3000 to 5000 units of heparin was given at the beginning. A cerebral arterial angiogram diagnosed CVST firstly, and an 8 F guide sheath or guiding-catheter was then advanced into the carotid vein. Machine thrombectomy was performed as the first-line endovascular therapy with either stent-retriever (Solitaire stent, Medtronic, USA) or direct contact aspiration technique by an aspiration catheter (Naive catheter, Medtronic, USA). After several attempts to retrieve the intra-sinus thrombus, a microcatheter was placed in the superior sagittal sinus or the straight sinus. Urokinase (15000U/Kg, iv, qd) was administered by microcatheter. The microcatheter was remained until significant clinical improvement or partial recanalization of the sinus confirmed by DSA.
MR image analysis
The acquired MR images were loaded onto a workstation (Leonardo, Siemens AG, Germany) for image review and analysis. The cerebral venous system was divided into 13 segments for analysis, i.e., superior sagittal sinus, inferior sagittal sinus, right transverse sinus, right sigmoid sinus, left transverse sinus, left sigmoid sinus, straight sinus, confluences of sinus, veins of Galen, internal cerebral veins, Rosenthal veins, veins of Labbé, and cortical veins.
To determine which venous segment occurs thrombosis, the presence of thrombus in each segment as detected by T1-SPACE was recorded and reviewed by two experienced radiologists, both blinded to the patients’ clinical information, each with > 5 years MR experience. Discrepancies were resolved by two readers using consensus with the auxiliary DSA and/or other MR images.
To quantitatively analyze the thrombus signal characteristics on T1-SPACE images, the thrombus was semi-automatically segmented, and then the volume and signal intensities of the thrombus were measured from T1-SPACE images using an open software (ITK-SNAP, www.itksnap.org/pmwiki/pmwiki.php). Due to the use of parallel imaging in T1-SPACE, the contrast ratio (CR), instead of contrast to noise ratio, was calculated to quantify the contrast between two tissues . Specifically, the CRtg was the ratio of signal intensities between the thrombus and gray matter and CRtl was the ratio of signal intensities between the thrombus and venous lumen.
Outcome of the endovascular therapy
To investigate if the thrombus signal characteristics on T1-SPACE images can be used to predict the endovascular therapy outcome, we collected all DSA images before and after the endovascular therapy. The recanalization status was then evaluated on patient and segment levels, respectively. The evaluation was finished by two interventional neurologists with blinded to the randomization assignments. Both neurologists have more than 5 years of interventional experience. Any discrepancies between the neurologists were resolved by consensus.
Similar to the method introduced by Porter and Moneta , thrombolytic ratio was used to evaluate the recanalization status on the patient level. The thrombolytic ratio was calculated using ([total thrombus scores pre-lysis] – [total thrombus scores post-lysis]) / [total thrombus scores pre-lysis] × 100%, where a thrombus score of each segment was calculated based on a 4-point scale: 0 = patent and completely free of thrombus; 1 = partial occlusion (< 50%); 2 = partial occlusion (> 50%); 3 = complete occlusion, and thus the total thrombus scores before and after lysis were calculated by adding the scores of the thromboembolic segments.
According to the method introduced by Aguiar et al , the following standard was used to assess the recanalization status on the segment level. The standard includes complete recanalization, partial recanalization, and absent recanalization. 1. complete recanalization defined as blood flow without any interruption; 2. partial recanalization defined as small interruptions of continuous blood flow and narrowing of the venous lumen; 3. absent recanalization defined as interrupted blood flow. After all the thromboembolic segments were assessed, the recanalization rate was then calculated as the number of recanalization segments divided by the total number of all thromboembolic segments.
Statistical analysis was performed using SPSS 21.0 (IBM, USA). Continuous variables following a normal distribution and equal variances were presented as means±SD and analyzed using the one-way ANOVA; otherwise, they were presented as median (interquartile range) and analyzed using Kruskal-Wallis H test. LSD-t test was used for further comparison between groups of the continuous variables after the one-way ANOVA analysis. Mann-Whitney U test was used for further comparison between groups for abnormal distribution variables. Chi-squared test was used to compare categorized variables at different stages. The interobserver agreements in thrombus presence of all patients, thrombus scores, and recanalization status were evaluated by Cohen’s kappa coefficient. A value of p < 0.05 was considered significant.