Chih-Chun Wu

Endovascular Management of Post-Irradiated Carotid Blowout Syndrome

Purpose To retrospectively evaluate the clinical and technical factors related to the outcomes of endovascular management in patients with head-and-neck cancers associated with post-irradiated carotid blowout syndrome (PCBS). Materials and Methods Between 2000 and 2013, 96 patients with PCBS underwent endovascular management. The 40 patients with the pathological lesions located in the external carotid artery were classified as group 1 and were treated with embolization. The other 56 patients with the pathological lesions located in the trunk of the carotid artery were divided into 2 groups as follows: group 2A comprised the 38 patients treated with embolization, and group 2B comprised the 18 patients treated with stent-graft placement. Fisher’s exact test was used to examine endovascular methods, clinical severities, and postprocedural clinical diseases as predictors of outcomes. Results Technical success and immediate hemostasis were achieved in all patients. The results according to endovascular methods (group 1 vs 2A vs 2B) were as follows: technical complication (1/40[2.5%] vs 9/38[23.7%] vs 9/18[50.0%], P = 0.0001); rebleeding (14/40[35.0%] vs 5/38[13.2%] vs 7/18[38.9%]), P = 0.0435). The results according to clinical severity (acute vs ongoing PCBS) were as follows: technical complication (15/47[31.9%] vs 4/49[8.2%], P = 0.0035); rebleeding (18/47[38.3%] vs 8/49[16.3%], P = 0.0155). The results according to post-procedural clinical disease (regressive vs progressive change) were as follows: alive (14/21[66.7%] vs 8/75[10.7%], P<0.0001); survival time (34.1±30.6[0.3–110] vs 3.6±4.0[0.07–22] months, P<0.0001). Conclusion The outcomes of endovascular management of PCBS can be improved by taking embolization as a prior way of treatment, performing endovascular intervention in slight clinical severity and aggressive management of the post-procedural clinical disease.

Artifact reduction of different metallic implants in flat detector C-arm CT.

BACKGROUND AND PURPOSE: Flat detector CT has been increasingly used as a follow-up examination after endovascular intervention. Metal artifact reduction has been successfully demonstrated in coil mass cases, but only in a small series. We attempted to objectively and subjectively evaluate the feasibility of metal artifact reduction with various metallic objects and coil lengths. MATERIALS AND METHODS: We retrospectively reprocessed the flat detector CT data of 28 patients (15 men, 13 women; mean age, 55.6 years) after they underwent endovascular treatment (20 coiling ± stent placement, 6 liquid embolizers) or shunt drainage (n = 2) between January 2009 and November 2011 by using a metal artifact reduction correction algorithm. We measured CT value ranges and noise by using region-of-interest methods, and 2 experienced neuroradiologists rated the degrees of improved imaging quality and artifact reduction by comparing uncorrected and corrected images. RESULTS: After we applied the metal artifact reduction algorithm, the CT value ranges and the noise were substantially reduced (1815.3 ± 793.7 versus 231.7 ± 95.9 and 319.9 ± 136.6 versus 45.9 ± 14.0; both P < .001) regardless of the types of metallic objects and various sizes of coil masses. The rater study achieved an overall improvement of imaging quality and artifact reduction (85.7% and 78.6% of cases by 2 raters, respectively), with the greatest improvement in the coiling group, moderate improvement in the liquid embolizers, and the smallest improvement in ventricular shunting (overall agreement, 0.857). CONCLUSIONS: The metal artifact reduction algorithm substantially reduced artifacts and improved the objective image quality in every studied case. It also allowed improved diagnostic confidence in most cases.

Direct measurement of the signal intensity of diffusion-weighted magnetic resonance imaging for preoperative grading and treatment guidance for brain gliomas

Background: Magnetic resonance diffusion‐weighted imaging (DWI) has been widely used clinically in imaging diagnosis of intracranial disorders. The purpose of current study was to present a quantitative method of direct measuring the DWI signal intensity of brain gliomas on the monitors of hospital picture archiving and communicating system (PACS) for grading gliomas. Methods: This study recruited 135 patients with treatment‐naïve brain gliomas. Direct measurement of the signal intensity of selected tumoral regions of interest (ROIs) by DWI on the monitors of the hospital PACS was performed for all patients. From the measurements, we obtained three values, defined as DWIT (tumor), DWIN (the homologous normal‐appearing area of the tumor ROI in the contralateral hemisphere), and DWIWM (normal‐appearing white matter) in the contralateral frontal lobe. Two ratios, DWIT/WM and DWIT/N, were obtained for each tumoral ROI. The same method was used for apparent diffusion coefficient (ADC) ratios of the tumoral ROI. Fractional polynomial regression and the Mann–Whitney U test were applied to determine the correlation between tumor grading, MIB‐1 labeling index, and DWI and ADC ratios. Logistic regression models and receiver operating characteristic curve analysis were used to establish diagnostic models. Measurements of intraobserver and interobserver agreement were also made at 1‐month interval. Results: The DWI ratios correlated positively with tumor grade and MIB‐1 value (p < 0.01). Cut‐off ratios of 1.62 for DWIT/WM and 1.47 for DWIT/N generated the optimal combination of sensitivity (0.82, 0.80), specificity (0.79, 0.86), and sound discriminating power, with an area under the curve of 0.87 and 0.84, respectively, to differentiate low‐grade from high‐grade gliomas. ADC ratios showed relatively worse sensitivity, specificity, and discriminating power than DWI ratios. Almost all intraobserver and interobserver measurements were within 95% agreement. Conclusion: The proposed method – direct measuring of tumor signal intensity of DWI on PACS monitors – is feasible for grading gliomas in clinical neuro‐oncology imaging services and has a high level of reliability and reproducibility.

Pretreatment Diagnosis of Suprasellar Papillary Craniopharyngioma and Germ Cell Tumors of Adult Patients

BACKGROUND AND PURPOSE: Suprasellar papillary craniopharyngiomas and germ cell tumors in adults share some clinical and imaging similarities but have different therapeutic strategies and outcomes. This study aimed to evaluate the pretreatment diagnosis of these 2 tumors to improve the therapeutic outcome. MATERIALS AND METHODS: We retrospectively enrolled 18 adults with papillary craniopharyngiomas and 17 with germ cell tumors. The MR imaging findings were evaluated, including signal change and anatomic extension. The medical records were reviewed to collect clinical findings, management, and outcomes. RESULTS: The clinical findings of papillary craniopharyngiomas versus germ cell tumors were as follows: age: 46 ± 13.9 years versus 23 ± 7.1 years (P < .0001); diabetes insipidus: 2/18 (11%) versus 11/17 (65%) (P = .001); recurrence 13/16 (81%) versus 4/17 (24%) (P = .0031). The MR imaging findings of papillary craniopharyngiomas versus germ cell tumors were as follows—pituitary stalk thickening: 1.6 ± 0.4 mm versus 5.4 ± 4.2 mm (P < .0001); vertical infundibular extension: 1/18 (6%) versus 16/17 (94%) (P < .0001); sagittal spheric shape: 17/18 (94%) versus 1/17 (6%) (P < .0001); diffusion restriction: 1/17 (6%) versus 8/12 (67%) (P = .0009). CONCLUSIONS: Younger age, diabetes insipidus, MR imaging characteristics of restricted diffusion, and vertical infundibular extension favor the diagnosis of germ cell tumors. Spheric shape without infundibular infiltration provides clues to papillary craniopharyngiomas, which originate from the pars tuberalis and are located outside the third ventricle. We suggest that suprasellar germ cell tumor is possibly an intraventricular lesion. Appropriate treatment planning can be initiated according to the diagnosis and anatomic location.

Thyroid transcription factor-1 distinguishes subependymal giant cell astrocytoma from its mimics and supports its cell origin from the progenitor cells in the medial ganglionic eminence

Subependymal giant cell astrocytoma is a benign brain tumor mostly associated with tuberous sclerosis complex. However, it may be misinterpreted as other high-grade brain tumors due to the presence of large tumor cells with conspicuous pleomorphism and occasional atypical features, such as tumor necrosis and endothelial proliferation. In this study, we first investigated thyroid transcription factor-1 (TTF-1) expression in a large series of subependymal giant cell astrocytomas and other histologic and locational mimics to validate the diagnostic utility of this marker. We then examined TTF-1 expression in non-neoplastic brain tissue to determine the cell origin of subependymal giant cell astrocytoma. Twenty-four subependymal giant cell astrocytoma specimens were subjected to tissue microarray construction. For comparison, a selection of tumors, including histologic mimics (21 gemistocytic astrocytomas and 24 gangliogliomas), tumors predominantly occurring at the ventricular system (50 ependymomas, 19 neurocytomas, and 7 subependymomas), and 134 astrocytomas (3 pleomorphic xanthoastrocytomas, 45 diffuse astrocytomas, 46 anaplastic astrocytomas, and 40 glioblastomas) were used. Immunohistochemical stain for TTF-1 was positive in all 24 subependymal giant cell astrocytomas, whereas negative in all astrocytomas, gangliogliomas, ependymomas, and subependymomas. Neurocytomas were positive for TTF-1 in 4/19 (21%) of cases using clone 8G7G3/1 and in 9/19 (47%) of cases using clone SPT24. In the three fetal brains that we examined, TTF-1 expression was seen in the medial ganglionic eminence, a transient fetal structure between the caudate nucleus and the thalami. There was no BRAFV600E mutation identified by direct sequencing in the 20 subependymal giant cell astrocytomas that we studied. In conclusion, TTF-1 is a useful marker in distinguishing subependymal giant cell astrocytoma from its mimics. Expression of TTF-1 in the fetal medial ganglionic eminence indicates that subependymal giant cell astrocytoma may originate from the progenitor cells in this region.

Venous hypertension and cerebral aneurysm rupture.

To investigate the correlation between the sinus asymmetry and aneurysm rupture. We retrospectively reviewed all diagnostic and therapeutic conventional angiograms of patients with cerebral aneurysms in our hospital from January 2000 to April 2008. Cases were categorized according to gender, presence or absence of aneurysm rupture, and presence or absence of symmetric dural sinuses. Exclusion criteria included patients with underlying fibromuscular dysplasia, dissecting aneurysms, pseudoaneurysms, and the presence of arteriovenous malformations or fistulas. The venous pressure was measured by MR phase contrast with standard fluid dynamics notation as Poiseuilles Law. A total of 193 cases (131 females and 62 males) were included for Chi-squared analysis, which showed significant difference (p < 0.05) between aneurysm rupture and venous asymmetry in the entire group as well as in females, but not in males. There was an association between side of rupture and side of asymmetry as well as between the size of hemorrhage. Ruptured aneurysm is more frequent at the same side of dominant dural sinus than the side of hypoplasia venous sinus. MRA phase contrast is able to show the venous pressure gradient of asymmetrical dural sinuses. With our preliminary data, we propose that dural sinus asymmetry is associated with aneurysm rupture.

Angioarchitecture and Posttreatment Magnetic Resonance Imaging Characteristics of Brain Arteriovenous Malformations and Long-Term Seizure Control After Radiosurgery.

OBJECTIVE To corroborate which pretreatment angioarchitectural characteristics and posttreatment magnetic resonance imaging (MRI) features were associated with better seizure and antiepileptic drug outcomes in patients with brain arteriovenous malformations (AVMs) treated by Gamma Knife radiosurgery. METHODS During the period 2007-2010, 220 patients with intracranial AVMs undergoing radiosurgery at our hospital were evaluated. Imaging features on digital subtraction angiography and follow-up MRI, medical records, and direct patient interview were retrospectively assessed. Seizure outcome was assessed using the Engel classification and the status of antiepileptic drug use. RESULTS At the last follow-up, 21 of 31 patients (68%) who met the recruitment criteria had AVM obliteration on digital subtraction angiography or MRI. Seizure-free status (Engel class 1) was achieved in 20 patients (65%), and 13 of 20 (65%) seizure-free patients were medication-free. The presence of total obliteration at last imaging follow-up (P = 0.013), absent retrograde cortical veins on digital subtraction angiography before GKRS (P = 0.013), nidus <3.7 cm (P = 0.006), and lower modified radiosurgery-based AVM score (P = 0.026) were significant predictors of seizure-free outcome. The strongest independent predictor of seizure-free status was absence of retrograde veins (odds ratio = 9.9). No angioarchitectural feature, postradiosurgery imaging finding on MRI, or radiosurgical treatment parameter was a significant predictor of seizure control or cessation of medication in seizure-free patients. CONCLUSIONS This study suggests that radiosurgery provides favorable outcomes in patients with AVM-related epilepsy. Patients with intracranial AVMs can benefit from seizure control after GKRS before undergoing AVM obliteration. Absence of retrograde veins is associated with better seizure-free outcomes, regardless of the parenchymal changes after radiosurgery.

Tumor pseudoprogression and true progression following gamma knife radiosurgery for recurrent ependymoma

Background Gamma knife radiosurgery (GKRS) has become an effective salvage therapeutic option for recurrent ependymomas. However, its effectiveness can be assessed only by neuroimaging before clinical deterioration occurs. We analyzed the evolution of post‐GKRS magnetic resonance imaging (MRI) features and sought to establish the feasibility of timely appropriate clinical management of the recurrent tumors. Methods We retrospectively investigated 19 recurrent ependymomas of 11 patients treated with GKRS in our hospital from 1994 to 2013. All included tumors had sequential MRI at 3–6‐month intervals, and tumor response was volumetrically calculated on consecutive MRI. Results Post‐GKRS tumors might show an increased enhancement or loss of enhancement associated with tumor enlargement or straight shrinkage. Seven of 19 tumors (37%) had continuously regressed or remained stable up to the last follow‐up. Twelve of 19 tumors (63%) showed enlargement of enhancing lesions through examination of the post‐GKRS follow‐up MRI within the first 18 months. Five of 12 tumors (42%) showed continuous enlargement, which was interpreted as true progression; seven of 12 (58%) exhibited transient increasing enhanced volume that resolved within 6 months, and which was interpreted as pseudoprogression. There was no significant association between the presence of pseudoprogression and the pathological grades or locations of the tumors, and the concomitant chemotherapy or previous radiotherapy. Statistically significant differences were found for mean apparent diffusion coefficient (ADC) values and ADC ratio (prior to and after GKRS) of enhancing lesions between pseudoprogression and true progression. Conclusion The MRI patterns of post‐GKRS recurrent ependymomas are heterogeneous. Transient increased tumor volume may represent pseudoprogression, whose final tumor control rate was not significantly different from those cases with straight tumor shrinkage. ADC values, ADC ratio, and sequential follow‐up MRI scans are beneficial to differentiate between pseudoprogression and true progression, and help guide clinical management.

Prolonged cerebral circulation time is more associated with symptomatic carotid stenosis than stenosis degree or collateral circulation

Background and purpose Current practice of revascularization for carotid stenosis (CS) primarily relies on symptoms and degree of stenosis. Other parameters, such as collateral circulation and cerebral circulation time (CCT), might influence the stroke risk in CS. This study was conducted to (1) investigate whether CCT is more associated with symptomatic CS than degree of stenosis and (2) elucidate the associations among the degree of stenosis, collateral status, and CCT. Methods From 2010 to 2016, 82 patients with unilateral CS were enrolled for DSA and divided into symptomatic and asymptomatic groups based on clinical presentation. CCT was defined as the difference between the time taken by the cavernous internal carotid artery and parietal vein to reach the maximal contrast medium intensities on lateral DSA. The degree of stenosis, collateral status, and CCT of the two groups were compared. Logistic regression analysis was performed to estimate the OR for symptomatic CS with the imaging variables. Results The symptomatic group had a significantly higher degree of stenosis and longer CCT. CCT (OR 1.95, p=0.013) was more associated with symptomatic CS than the degree of stenosis (OR 1.03, p=0.229), after adjustment for potential confounders—namely, age, sex, antithrombotic use, and collateral status. Symptomatic high grade CS with collaterals had a non-significantly shorter CCT than those without collaterals. Conclusions DSA derived CCT is more reflective of the hemodynamic differences between symptomatic and asymptomatic CS than degree of stenosis. Collaterals may not effectively reduce CCT in symptomatic high grade CS.

Lateral Sinus Dural Arteriovenous Fistulas: Sinovenous Outflow Restriction Outweighs Cortical Venous Reflux as a Parameter Associated with Hemorrhage

Purpose To investigate whether sinovenous outflow restriction (SOR) is more strongly associated with hemorrhage than cortical venous reflux (CVR) in patients with lateral sinus dural arteriovenous fistulas (DAVFs). Materials and Methods An institutional review board approved this retrospective study and waiver of informed consent was obtained. From 1995 to 2016, 163 cases of lateral sinus DAVFs were included and divided into hemorrhagic and nonhemorrhagic groups based on initial presentation. Their angiograms and magnetic resonance images were evaluated, with two evaluators independently grading CVR and SOR. The SOR was scored as the combined conduit score (CCS), ranging from zero (total occlusion) to 8 (fully patent). The CVR and CCS of the hemorrhagic and nonhemorrhagic groups were compared. Logistic regression models were established for both the CVR and CCS to compare their performances in discriminating DAVF hemorrhage. Results Sinovenous outflow was significantly more restrictive (lower median CCS) in the hemorrhagic group than in the nonhemorrhagic group (1 vs 6.5; P < .001). A CCS of less than or equal to 2 best discriminated between the groups with a sensitivity of 90.0% and a specificity of 88.1%. The CCS model had a higher discriminative performance than did the CVR model (area under the curve, 0.933 vs 0.843; P = .018). Conclusion The CCS grading system semiquantifies SOR. SOR may represent a stronger risk factor associated with hemorrhage in patients with lateral sinus DAVFs than does CVR, and thus may offer guidance in therapeutic decision making.