Hui Ling Hsu

Working Memory in Patients with Mild Traumatic Brain Injury: Functional MR Imaging Analysis

PURPOSE To analyze brain activation patterns in response to tests of working memory after a mild traumatic brain injury (MTBI). MATERIALS AND METHODS Research ethics committee approval and patient written informed consent were obtained. Brain activation patterns in response to n-back working memory tasks (n = 1, 2, 3) were assessed with functional magnetic resonance (MR) imaging in 20 patients with MTBI within 1 month after their injury and in 18 healthy control subjects. In n-back working memory tasks, participants monitored a series of number stimuli and were to indicate when the presented number was the same as that presented n back previously. Nine (45%) MTBI patients underwent follow-up functional MR imaging studies 6 weeks later. Digit span, a memory test for how many numbers a person can remember in sequence, and continuous performance test (CPT), a test that measures a persons sustained and selective attention and impulsivity, were also performed before functional MR imaging studies and outside the imager for each participant. Clinical data were analyzed by using t and χ(2) tests. Within-group, between-group, and initial and follow-up differences of functional MR imaging data were analyzed by using one-sample, two-sample, and paired t tests, respectively. RESULTS Groups were similar for sex (P = .75), years of education (P = .069), digit span (P = .37 for total score), CPT (P = .31, .27, and .43 for omission error, commission error, and hit reaction time, respectively), and accuracy of n-back working memory performance (P = .90, .11, and .39 for one-, two-, and three-back tasks, respectively). Brain activation patterns differed between MTBI patients and controls in response to increasing working memory loads (P < .01, uncorrected). Control subjects maintained their ability to increase activation in the working memory circuitry with each increase in working memory load. In contrast, MTBI patients were impaired in their ability to increase activation in working memory circuitry under both moderate and high working memory load conditions. However, MTBI patients did show cerebral plasticity, as evidenced by more activation in some areas outside and inside the working memory circuitry as compared with control subjects (P < .01, uncorrected). In the 6-week follow-up study, compared with baseline, MTBI patients showed an improvement of activation in response to increasing working memory loads (P < .05, uncorrected). CONCLUSION MTBI-induced differences in working memory functional activity were observed even though differences in behavioral performance between MTBI patients and controls were absent, which suggests that this approach may increase sensitivity to MTBI compared with neuropsychological evaluation alone.

Prediction of cerebral hyperperfusion syndrome after carotid stenting: A cerebral perfusion computed tomography study

Purpose: The objective of this study was to evaluate the role of cerebral perfusion computed tomography (CT) in predicting cerebral hyperperfusion syndrome (CHS) after carotid stenting. Materials and Methods: This study was approved by the institutional review board, and written informed consent was obtained from all patients. Fifty-five consecutive symptomatic patients with greater than or equal to 70% of cervical carotid artery stenosis who underwent carotid stenting from March 2001 to December 2003 were recruited. Age, sex, stenting side, and degree of cervical carotid stenosis at the stenting and contralateral sides were recorded. Cerebral perfusion CT was performed 1 day before stenting. Absolute values of the cerebral blood volume, mean transit time, and cerebral blood flow were calculated. Relative values based on the comparison between ipsilateral and contralateral hemispheres, that is, relative cerebral blood volume (ipsilateral-to-contralateral ratio), relative cerebral blood flow (ipsilateral-to-contralateral ratio), and absolute difference in mean transit time (dMTT), were derived. The association between occurrence of CHS and parameters of cerebral perfusion CT was investigated by the Mann-Whitney U test. Results: Three (5%) of 55 patients had CHS after carotid stenting. The only significant factor related to the occurrence of CHS was dMTT (P = 0.003). A dMTT value of 3 seconds was considered as a cutoff value to distinguish between the occurrence and absence of CHS. The other clinical or cerebral perfusion CT parameters had no significant correlation with the occurrence of CHS. Conclusion: Our findings suggest that patients with a prolonged dMTT of more than 3 seconds should be closely monitored for evidence of hyperperfusion after undergoing carotid stenting.

Spinal dural arteriovenous fistula: Imaging features and its mimics

Spinal dural arteriovenous fistula (SDAVF) is the most common spinal vascular malformation, however it is still rare and underdiagnosed. Magnetic resonance imaging findings such as spinal cord edema and dilated and tortuous perimedullary veins play a pivotal role in the confirmation of the diagnosis. However, spinal angiography remains the gold standard in the diagnosis of SDAVF. Classic angiographic findings of SDAVF are early filling of radicular veins, delayed venous return, and an extensive network of dilated perimedullary venous plexus. A series of angiograms of SDAVF at different locations along the spinal column, and mimics of serpentine perimedullary venous plexus on MR images, are demonstrated. Thorough knowledge of SDAVF aids correct diagnosis and prevents irreversible complications.

Sex differences in working memory after mild traumatic brain injury: A functional MR imaging study

PURPOSE To evaluate sex differences in mild traumatic brain injury (MTBI) with working memory functional magnetic resonance (MR) imaging. MATERIALS AND METHODS Research ethics committee approval and patient written informed consent were obtained. Working memory brain activation patterns were assessed with functional MR imaging in 30 patients (15 consecutive men and 15 consecutive women) with MTBI and 30 control subjects (15 consecutive men and 15 consecutive women). Two imaging studies were performed in patients: the initial study, which was performed within 1 month after the injury, and a follow-up study, which was performed 6 weeks after the first study. For each participant, digit span and continuous performance testing were performed before functional MR imaging. Clinical data were analyzed by using Kruskal-Wallis, Mann-Whitney U, Wilcoxon signed rank, and Fisher exact tests. Within- and between-group differences of functional MR imaging data were analyzed with one- and two-sample t tests, respectively. RESULTS Among female participants, the total digit span score was lower in the MTBI group than in the control group (P = .044). In initial working memory functional MR imaging studies, hyperactivation was found in the male MTBI group and hypoactivation was found in the female MTBI group compared with control male and female groups, respectively. At the 6-week follow-up study, the female MTBI group showed persistent hypoactivation, whereas the male MTBI group showed a regression of hyperactivation at visual comparison of activation maps. The male MTBI group was also found to have a higher initial ß value than the male control group (P = .040), and there was no significant difference between the male MTBI group and the male control group (P = .221) at follow-up evaluation, which was comparable to findings on activation maps. In the female MTBI group, average ß values at both initial and follow-up studies were lower compared with those in the female control group but were not statistically significant (P = .663 and P = .191, respectively). CONCLUSION Female patients with MTBI had lower digit span scores than did female control subjects, and functional MR imaging depicted sex differences in working memory functional activation; hypoactivation with nonrecovery of activation change at follow-up studies may suggest a worse working memory outcome in female patients with MTBI.

Arterial Spin Labeling Perfusion Study in the Patients with Subacute Mild Traumatic Brain Injury

Background This study uses a MRI technique, three-dimension pulse continuous arterial spin labeling (3D-PCASL), to measure the patient’s cerebral blood flow (CBF) at the subacute stage of mild traumatic brain injury (MTBI) in order to analyze the relationship between cerebral blood flow and neurocognitive deficits. Objective To provide the relationship between cortical CBF and neuropsychological dysfunction for the subacute MTBI patients. Methods After MTBI, perfusion MR imaging technique (3D-PCASL) measures the CBF of MTBI patients (n = 23) within 1 month and that of normal controls (n = 22) to determine the quantity and location of perfusion defect. The correlation between CBF abnormalities and cognitive deficits was elucidated by combining the results of the neuropsychological tests of the patients. Result We observed a substantial reduction in CBF in the bilateral frontal and left occipital cortex as compared with the normal persons. In addition, there were correlation between post concussive symptoms (including dizziness and simulator sickness) and CBF in the hypoperfused areas. The more severe symptom was correlated with higher CBF in bilateral frontal and left occipital lobes. Conclusion First, this study determined that despite no significant abnormality detected on conventional CT and MRI studies, hypoperfusion was observed in MTBI group using 3D-PCASL technique in subacute stage, which suggested that this approach may increase sensitivity to MTBI. Second, the correlation between CBF and the severity of post concussive symptoms suggested that changes in cerebral hemodynamics may play a role in pathophysiology underlies the symptoms.

Undersized angioplasty and stenting of symptomatic intracranial tight stenosis with Enterprise: Evaluation of clinical and vascular outcome.

Background Severe intracranial arterial stenosis results in more than 10% incidence of stroke and transient ischemic attack. Using undersized angioplasty with off-label closed-cell Enterprise stent may be a feasible alternative option for treating patients with intracranial atherosclerotic disease who fail dual-antiplatelet medical therapy. The results of the authors’ study are presented in this paper. Materials and methods Between January 2013 and July 2014, 24 symptomatic patients with a total of 30 intracranial arterial stenotic lesions refractory to medical therapy, who underwent undersized angioplasty and Enterprise stenting, were retrospectively reviewed in the authors’ institution. The results evaluated include technical success rate, clinical outcome measured as modified Rankin Scale at presentation and follow-up, peri-procedural morbidity within 30 days and 1 year, and follow-up vessel patency. Results Stent deployment was successfully achieved in all stenotic lesions (30/30). Mean pre-stent and post-stent diameter residual stenosis was 81% and 18%, respectively. The peri-procedural complication rate during 30 days after stenting was 10% per lesion (3/30), including intracranial hemorrhage, in-stent thrombosis and ischemic stroke. No further thromboembolic event or complication occurred in any patient more than 30 days after stenting. Modified Rankin scale ≤ 2 was observed in 64% and 83% of patients at initial presentation and follow-up (mean 15.8 months), respectively. Imaging follow-up was available in 17 of 24 patients (70.8%) and 20 of 30 treated lesions (66.6%) with a mean follow-up period of 15.4 months. Only one asymptomatic in-stent restenosis occurred in 20 available lesions (5.0%). Conclusion This preliminary study suggests that using undersized angioplasty and Enterprise stenting may effectively treat high-degree symptomatic intracranial arterial stenosis with favorable clinical and angiographic outcome.

Bilateral persistent trigeminal arteries with unilateral trigeminal artery to cavernous sinus fistula: A case report

A 59-year-old man who denied a history of trauma presented with left pulsatile tinnitus and left orbital swelling for six months. Digital subtraction angiography showed a left persistent trigeminal artery (PTA) with a trigeminal artery to cavernous sinus (trigeminal-cavernous sinus) fistula and a right PTA. Transarterial detachable coil embolization of the left trigeminal-cavernous sinus fistula was performed, and the symptoms subsided. There has been no report of bilateral PTAs with a spontaneous fistula connected from one PTA to the ipsilateral cavernous sinus. This paper reports such a rare circumstance.

Effect of Age on Working Memory Performance and Cerebral Activation after Mild Traumatic Brain Injury: A Functional MR Imaging Study

PURPOSE To evaluate the age effect on working memory (WM) performance and functional activation after mild traumatic brain injury (MTBI). MATERIALS AND METHODS This study was approved by the local research ethics committee. All participants provided written informed consent. N-back WM cerebral activation was assessed with functional magnetic resonance (MR) imaging in 13 younger (mean age, 26.2 years ± 2.9; range, 21-30 years) and 13 older (mean age, 57.8 years ± 6.6; range, 51-68 years) patients with MTBI and 26 age- and sex-matched control subjects. Two functional MR images were obtained within 1 month after injury and 6 weeks after the initial study. Group comparison and regression analysis were performed among postconcussion symptoms, neuropsychologic tests, and WM activity in both groups. RESULTS In younger patients, initial hyperactivation was seen in the right precuneus and right inferior parietal gyrus (P = .047 and P = .025, respectively) in two-back greater than one-back conditions compared with younger control subjects, whereas in older patients, hypoactivation was seen in the right precuneus and right inferior frontal gyrus (P = .013 and P =.019, respectively) compared with older control subjects. Increased WM activity was associated with increased postconcussion symptoms in the right precuneus (r = 0.57; P = .026) and right inferior frontal gyrus (r = 0.60; P = .019) and poor WM performance in the right precuneus (r = -0.55; P = .027) in younger patients at initial studies but not in older patients. At follow-up examinations, partial recovery of activation pattern and decreased postconcussion symptoms (P = .04) were observed in younger patients but not in older patients. CONCLUSION The different manifestations of postconcussion symptoms at functional MR imaging between younger and older patients confirmed the important role of age in the activation, modulation, and allocation of WM processing resources after MTBI. These findings also supported that younger patients have better neural plasticity and clinical recovery than do older patients.

Teaching NeuroImages: Central variant of posterior reversible encephalopathy syndrome

A 55-year-old man with chronic hypertension presented with acute headache and dizziness. Physical examination showed severe hypertension (210/140 mm Hg) without any neurologic sign. Brain MRI showed diffuse brain edema over the brainstem, bilateral thalami, and cerebellar hemispheres with multiple microbleeds at bilateral basal ganglia (figure 1). His symptoms improved dramatically after antihypertensive therapy. Brain MRI 1 month later showed resolution of the edema (figure 2). “Central variant” of posterior reversible encephalopathy syndrome predominantly involving the brainstem and basal ganglia and relatively sparing the parieto-occipital lobe is rare.1 Paucity of brainstem signs and symptoms despite extensive neuroimaging abnormalities supports the diagnosis.2

May-Thurner syndrome: correlation between digital subtraction and computed tomography venography.

BACKGROUND/PURPOSE Digital subtraction venography (DSV) and computed tomography venography (CTV) are both recommended for diagnosing May-Thurner syndrome. The literature contains little information on the correlation between these imaging tools. We performed a retrospective case-series study to investigate this correlation. METHODS From August 2009 to August 2010, 42 patients with May-Thurner syndrome (34 women, 8 men; mean age: 52.8 ± 13.5 years) received DSV followed by CTV. The DSV was used to evaluate the degree of venous reflux, reflux start-up time, and flow time. By CTV, the ratio of cross-sectional area and the ratio of diameter between the narrowest region to that of the caudal part of the left common iliac vein were calculated. The correlation between these variables for DSV versus CTV was calculated using Spearmans rank correlation coefficients. RESULTS In DSV evaluation of the extent of reflux, 19.0% of cases were classified as Grade 0, 11.9% as Grade I, 28.6% as Grade II, and 40.5% as Grade III. The mean ± standard deviation flow times for these groups were 2.00 ± 0.38 seconds, 1.75 ± 0.29 seconds, 1.67 ± 0.72 seconds, and 1.81 ± 0.68 seconds, the mean time for total patients was 1.76 ± 0.78 seconds. The reflux start-up times for Grades I-III were 2.00 ± 1.00 seconds, 1.80 ± 1.23 seconds, and 1.40 ± 0.49 seconds, and the mean time was 1.6 ± 0.8 seconds. In CTV, the mean area ratio and diameter ratio were 0.78 ± 0.22 (range, 0.22-1.27) and 0.75 ± 0.24 (range, 0.33-1.25). The reflux start-up time showed a positive correlation with the cross-sectional area ratio (r = 0.518; p = 0.002) and diameter ratio (r = 0.413; p = 0.019). CONCLUSION The cross-sectional area ratio and diameter ratio in CTV correlate with the reflux start-up time in DSV. For May-Thurner syndrome, both CTV and DSV provide essential information for diagnosis and evaluation of the disease. The positive correlation between anatomical and hemodynamic properties corresponds with the underlying pathophysiology.