Revisiting the Kittel's model of antiferroelectricity: phase diagrams, hysteresis loops and electrocaloric effect.

We revisit the Kittel's model of antiferroelectricity by extending the model to study the phase transitions, hysteresis loop behaviors and electrocaloric effect (ECE) of antiferroelectrics (AFEs). By considering both the first- and second-order AFEs, explicit expressions for the physical and staggered polarizations of AFEs in the stable states are derived. We also obtain the analytical solutions for describing the dielectric susceptibilities of AFEs in the AFE and paraelectric (PE) phases. Coercive fields in AFE are also derived and studied. To verify the usefulness of the Kittel's model of antiferroelectricity, we apply the model to systematically investigate the phase transitions, hysteresis loops and ECEs of PbZrO3(PZO). By adopting appropriate values of the Kittel's parameters for first-order transition, analytical and numerical results are obtained and discussed. Our results show that PZO exhibits a complex temperature (T)-electric field (E) phase diagram, consisting of the AFE, ferroelectrics, ferrielectric, PE and mixed phases. TheT-Ephase diagram is qualitatively agreed with the new AFE model that was derived based on symmetry by Tolédano and Khalyavin (2019Phys. Rev.B99024105). We found that the calculated zero-field dielectric susceptibility is qualitatively and quantitatively agreed with experimental results. We show that the polarizations and dielectric susceptibilities of PZO in heating and cooling deviate from each other, as expected for the first-order materials. Our calculated results also reveal that the ECE in PZO has an electro-heating of ΔT≈ +6.5 °C and an electro-cooling of ΔT≈ -4.0 °C, respectively, which are comparable to the experimental results.

Hong Kong College of Physicians Position Statement and Recommendations on the 2017 American College of Cardiology/American Heart Association and 2018 European Society of Cardiology/European Society of Hypertension Guidelines for the Management of Arterial Hypertension.

The American College of Cardiology/American Heart Association released guidelines for the prevention, detection, evaluation, and management of high blood pressure (BP) in adults in 2017. In 2018, the European Society of Cardiology (ESC)/European Society of Hypertension (ESH) published new guidelines for the management of arterial hypertension. Despite the many similarities between these two guidelines, there are also major differences in the guidelines in terms of diagnosis and treatment of hypertension. A working group of the Hong Kong College of Physicians (HKCP) convened and conducted a focused discussion on important issues of public interest, including classification of BP, BP measurement, thresholds for initiation of antihypertensive medications, BP treatment targets, and treatment strategies. The HKCP concurs with the 2018 ESC/ESH guideline on BP classification, which defines hypertension as office systolic BP ≥140 mm Hg and/or diastolic BP ≥90 mm Hg. The HKCP also acknowledges the growing evidence of home BP monitoring and ambulatory BP monitoring in the diagnosis and monitoring of hypertension and endorses the wider use of both methods. The HKCP also supports the direction of a risk-based approach for initiation of antihypertensive medications and the specification of a treatment target range for both systolic and diastolic BP with consideration of different age-groups and specific disease subgroups. Non-pharmacological interventions are crucial, both at the societal and individual patient levels. The recent guideline publications provide good opportunities to increase public awareness of hypertension and encourage lifestyle modifications among the local population.

Rich antiferroelectric phase diagram of antiferroelectric-ferroelectric superlattices: internal electric field- and interface induced phase transitions.

We propose a thermodynamic model to the study the antiferroelectric (AFE) phase transitions in antiferroelectric-ferroelectric (AFE-FE) superlattices in which the coupling at the interface between two layers is mediated by local polarizations. Phase diagram of the AFE layer in term of the degree of interfacial effect λ and temperature T involving ferrielectric (FI) and ferroelectric (FE) phases is investigated. These two phases are stabilized by the interfacial effect and internal electric field. AFE thickness L AFE versus T phase diagram is also constructed. Intermediate regions of two-phase coexistence (IM) emerge in the λ-T and L AFE-T phase diagrams, if certain interface properties λ and layer thickness L AFE criteria are met. These IM regions are metastable states, which exist as a transition state between two phases. A tricritical point locates at the boundaries across the FI, IM and FE phases is found in the L AFE-T phase diagram. Competition among the internal electric field due to the electrostatic coupling, the FE ordering arises from the interfacial effect and the antiferroelectric ordering within the AFE layer giving rises to the rich AFE phase diagram.

A comparison of health expectancies over 10 years: implications for elderly service needs in Hong Kong.

OBJECTIVES: We aimed to estimate health expectancies at age 65 based on physical and cognitive function in 2001-2002 and 2011-2012 and project future needs for carers from 2021 to 2041. METHODS: Data from the Elderly Health Centres (EHCs) of the Department of Health of the Government of Hong Kong comprising of people aged 65 years or older who enrolled between 2001 and 2002 (EHC 2001-2002) and between 2011 and 2012 (EHC 2011-2012) provided proportion estimates for physical impairment (assessed by independence in activities of daily living) and cognitive impairment (assessed by Abbreviated Mental Test/Mini-Mental Status Examination and self-reported doctor diagnosis of dementia). Health expectancies (years lived with/without physical and/or cognitive impairment) were calculated by Sullivan's method. The proportions of physical and/or cognitive impairment were used to project future needs for carers. RESULTS: Between 2001-2002 and 2011-2012, years lived without physical/cognitive impairment decreased for men but increased for women, both of which were less than the increases in total life expectancy. Men assessed in 2011-2012 (classified as EHC 2011-2012) lived more years with physical and/or cognitive impairment than those assessed in 2001-2002 (classified as EHC 2001-2002), and women in EHC 2011-2012 lived more years with physical impairment, but fewer years with cognitive impairment than those in EHC 2001-2002, and women enrolled in EHC 2011-2012 lived more years with physical impairment, but fewer years with cognitive impairment than those in EHC 2001-2002. As populations age, the number of carers needed is expected to increase from 344,000 in 2021 to 629,000 by 2041, or an increase of 82.9%. Sensitivity analyses excluding the participants who had been assessed in 2011-2012 from EHC 2001-2002 gave similar estimations. CONCLUSIONS: Increased life expectancy was not accompanied by an increase in years lived without physical/cognitive impairment. These findings suggest that people will live longer but could be more dependent, which would have considerable implications for elderly service needs in Hong Kong.

Canadian Stroke Best Practice Recommendations for Acute Stroke Management: Prehospital, Emergency Department, and Acute Inpatient Stroke Care, 6th Edition, Update 2018.

The 2018 update of the Canadian Stroke Best Practice Recommendations for Acute Stroke Management, 6th edition, is a comprehensive summary of current evidence-based recommendations, appropriate for use by healthcare providers and system planners caring for persons with very recent symptoms of acute stroke or transient ischemic attack. The recommendations are intended for use by a interdisciplinary team of clinicians across a wide range of settings and highlight key elements involved in prehospital and Emergency Department care, acute treatments for ischemic stroke, and acute inpatient care. The most notable changes included in this 6th edition are the renaming of the module and its integration of the formerly separate modules on prehospital and emergency care and acute inpatient stroke care. The new module, Acute Stroke Management: Prehospital, Emergency Department, and Acute Inpatient Stroke Care is now a single, comprehensive module addressing the most important aspects of acute stroke care delivery. Other notable changes include the removal of two sections related to the emergency management of intracerebral hemorrhage and subarachnoid hemorrhage. These topics are covered in a new, dedicated module, to be released later this year. The most significant recommendation updates are for neuroimaging; the extension of the time window for endovascular thrombectomy treatment out to 24 h; considerations for treating a highly selected group of people with stroke of unknown time of onset; and recommendations for dual antiplatelet therapy for a limited duration after acute minor ischemic stroke and transient ischemic attack. This module also emphasizes the need for increased public and healthcare provider's recognition of the signs of stroke and immediate actions to take; the important expanding role of paramedics and all emergency medical services personnel; arriving at a stroke-enabled Emergency Department without delay; and launching local healthcare institution code stroke protocols. Revisions have also been made to the recommendations for the triage and assessment of risk of recurrent stroke after transient ischemic attack/minor stroke and suggested urgency levels for investigations and initiation of management strategies. The goal of this updated guideline is to optimize stroke care across Canada, by reducing practice variations and reducing the gap between current knowledge and clinical practice.

Trajectories of frailty among Chinese older people in Hong Kong between 2001 and 2012: an age-period-cohort analysis.

Background: there is little evidence to suggest that older people today are living in better health than their predecessors did at the same age. Only a few studies have evaluated whether there are birth cohort effects on frailty, an indicator of health in older people, encompassing physical, functional and mental health dimensions. Objectives: this study examined longitudinal trajectories of frailty among Chinese older people in Hong Kong. Methods: this study utilised data from the 18 Elderly Health Centres of the Department of Health comprising a total of 417,949 observations from 94,550 community-dwelling Chinese people aged ≥65 years in one early birth cohort (1901-23) and four later birth cohorts (1924-29, 1930-35, 1936-41, 1942-47) collected between 2001 and 2012, to examine trajectories of the frailty index and how birth cohorts may have contributed to the trends using an age-period-cohort analysis. Results: more recent cohorts had higher levels of frailty than did earlier cohorts at the same age, controlling for period, gender, marital status, educational levels, socioeconomic status, lifestyle and social factors. Older age, being female, widowhood, lower education and smoking were associated with higher levels of frailty. Conclusion: more recent cohorts had higher levels of frailty than did earlier cohorts. Frailty interventions, coupled with early detection, should be developed to combat the increasing rates of frailty in Hong Kong Chinese.

Trends in activities of daily living disability in a large sample of community-dwelling Chinese older adults in Hong Kong: an age-period-cohort analysis.

BACKGROUND: To examine the trends in activities of daily living (ADL) disability in older Chinese adults in Hong Kong between 2001 and 2012. METHODS: Using data from the Elderly Health Centres (EHCs) of the Department of Health comprising a total of 54 808 community-dwelling Chinese adults aged ≥65 years in 1 early cohort (1904-1917) and 10 3-year birth cohorts (1918-1920, 1921-1923, 1924-1926, 1927-1929, 1930-1932, 1933-1935, 1936-1938, 1939-1941, 1942-1944, 1945-1947), we examined trends in ADL disability by using age-period-cohort (APC) models. ADL disability was defined as being unable to perform at least 1 of 7 ADL activities (bathing, dressing, toileting, transferring, feeding, grooming, walking) independently. Cross-classified random-effects logistic regressions were performed for each of the APC trends with adjustment for age, period, cohort, sociodemographic, lifestyle, comorbidity and self-rated health. RESULTS: The mean age of the cohort was 70.9±4.7 (range 65-99) years. The prevalence rate of ADL disability was 1.6%. ADL disability increased with age (p<0.001) and the gradient of the increase was steeper in the older age groups. At the same age, women (1.7%) were more likely to report ADL disability than men (1.4%, p=0.001). For both genders, there was an increase in ADL disability between 2003 and 2012; adjustment for age, cohort and other covariates has diminished the trends observed among men. There was no cohort effect in ADL disability. CONCLUSIONS: ADL disability in older adults has increased over the last decade. Further study is required to identify possible causes behind the disability trends.

Aneurysmal SubArachnoid Hemorrhage-Red Blood Cell Transfusion And Outcome (SAHaRA): a pilot randomised controlled trial protocol.

INTRODUCTION: Anaemia is common in aneurysmal subarachnoid haemorrhage (aSAH) and is a potential critical modifiable factor affecting secondary injury. Despite physiological evidence and management guidelines that support maintaining a higher haemoglobin level in patients with aSAH, current practice is one of a more restrictive approach to transfusion. The goal of this multicentre pilot trial is to determine the feasibility of successfully conducting a red blood cell (RBC) transfusion trial in adult patients with acute aSAH and anaemia (Hb ≤100 g/L), comparing a liberal transfusion strategy (Hb ≤100 g/L) with a restrictive strategy (Hb ≤80 g/L) on the combined rate of death and severe disability at 12 months. METHODS: Design This is a multicentre open-label randomised controlled pilot trial at 5 academic tertiary care centres. Population We are targeting adult aSAH patients within 14 days of their initial bleed and with anaemia (Hb ≤110 g/L). Randomisation Central computer-generated randomisation, stratified by centre, will be undertaken from the host centre. Randomisation into 1 of the 2 treatment arms will occur when the haemoglobin levels of eligible patients fall to ≤100 g/L. Intervention Patients will be randomly assigned to either a liberal (threshold: Hb ≤100 g/L) or a restrictive transfusion strategy (threshold: Hb ≤80 g/L). Outcome Primary: Centre randomisation rate over the study period. Secondary: (1) transfusion threshold adherence; (2) study RBC transfusion protocol adherence; and (3) outcome assessment including vital status at hospital discharge, modified Rankin Score at 6 and 12 months and Functional Independence Measure and EuroQOL Quality of Life Scale scores at 12 months. Outcome measures will be reported in aggregate. ETHICS AND DISSEMINATION: The study protocol has been approved by the host centre (OHSN-REB 20150433-01H). This study will determine the feasibility of conducting the large pragmatic RCT comparing 2 RBC transfusion strategies examining the effect of a liberal strategy on 12-month outcome following aSAH. TRIAL REGISTRATION NUMBER: NCT02483351; Pre-results.

AML multi-gene panel testing: A review and comparison of two gene panels.

BACKGROUND/OBJECTIVE: Risk adapted therapy is standard practice in Acute Myeloid Leukemia (AML). A common diagnostic approach involves focusing on a three gene panel (CEPBA, FLT3, and NPM1). However, a complete representation of prognostic and predictive factors in AML necessitates an expanded series of genes, due to the dynamic interactions present between concurrent mutations. Hence, the current study aims to describe the benefits of an expanded risk profile in an unselected cohort of AML cases. METHODS: The genomes of 11 randomly selected patients with AML were sequenced using next generation sequencing. A narrow three gene panel and broader 50 gene panel were contrasted. RESULTS: The expanded gene panel detected one additional pathogenic mutation in five patients and two pathogenic mutations in two patients, resulting in a change in their risk profile. Only 5/11 (45%) of AML patients demonstrated a pathogenic mutation on the 3 gene profile, however all patients had at least one detectable pathogenic mutation on the broader gene panel. The detection of a concurrent mutation by the expanded gene panel reversed the favorable risk profile for three patients. CONCLUSIONS: Detection of concurrent mutations enables rejection or validation of prognoses associated with NPM1 or CEBPA mutations. DNMT3a and TP53 mutations in AML have a pertinent prognostic and therapeutic value for patients and their addition enhances the current three gene panel. In our small study, the three gene panel changed the prognosis for three patients (3/11, 27%) with the detection of commonly occurring AML mutations.

Multimodal Diagnostic Imaging for Hyperacute Stroke.

In April 2015, the American Roentgen Ray Society and the American Society of Neuroradiology cosponsored a unique program designed to evaluate the state of the art in the imaging work-up of acute stroke. This topic has grown in importance because of the recent randomized controlled trials demonstrating the clear efficacy of endovascular stroke treatment. The authors, who were participants in that symposium, will highlight the points of emphasis in this article.

Management experience of subglottic stenosis by endoscopic bougie dilatation with mitomycin C and review of literature: case series.

The aim of the study was to examine and analyze the epidemiology and outcome of treatment for paediatric acquired subglottic stenosis treated with endoscopic bougie dilatation and topical mitomycin C. There were 15 patients identified from 2008 until 2013. All of them had acquired subglottic stenosis due to history of intubation. Majority of the patients had grade III stenosis, with the total of seven. Three patients had grade IV; three were grade II and two were grade I. All of the patients with severe stenosis (grade III and IV) needed tracheostomy while only one in mild stenosis group (grade I and II) required it for prolonged ventilation rather than obstruction due to subglottic stenosis. All of them underwent direct laryngoscopy under general anesthesia followed by endoscopic dilatation with bougie and topical mitomycin C 0.4 mg/ml for 5 min. Aim of success in our study was decannulation of tracheostomy or absence of symptoms at exertion. We achieved 6 (60 %) successful decannulation out of 10 patients with tracheostomy (excluded the patient with tracheostomy in grade I stenosis due to prolonged ventilation). As for those without tracheostomy, 3 (75 %) out of 4 patients were asymptomatic even at exertion. Average number of dilatation was 3.1 times, with mean duration of 28 min. No complications were reported in our series. One patient with grade I stenosis passed away due to severe pneumonia unrelated to the stenosis or dilatation, and she did not have any dilatation before she passed away. Multiple related risk factors were identified such as intubation, prematurity, movement of endotracheal tube, respiratory infection, traumatic intubation and gastroesophageal reflux disease. Experience of open surgical method was very limited in our centre in Sabah in East Malaysia. Endoscopic technique plays an important role in treatment of subglottic stenosis with adjunct like mitomycin C possibly booster the successful rate.

A versatile RNA vector for delivery of coding and noncoding RNAs.

The discovery that RNA viruses, lacking any DNA intermediate, can be engineered to express both coding and noncoding RNAs suggests that this platform may have therapeutic value as a delivery vehicle. Here we illustrate that a self-replicating, noninfectious RNA, modeled on influenza virus, provides one such example of a versatile in vivo delivery system for silencing and/or expressing a desired RNA for therapeutic purposes.

Computed tomography angiography intraluminal filling defect is predictive of internal carotid artery free-floating thrombus.

INTRODUCTION: Filling defects at the internal carotid artery (ICA) origin in the work-up of stroke or transient ischemic attack may be an ulcerated plaque or free-floating thrombus (FFT). This may be challenging to distinguish, as they can appear morphologically similar. This is an important distinction as FFT can potentially embolize distally, and its management differs. We describe a series of patients with suspected FFT and evaluate its imaging appearance, clinical features, and evolution with therapy. METHODS: Between 2008 and 2013, we prospectively collected consecutive patients with proximal ICA filling defects in the axial plane surrounded by contrast on CT/MR angiography. We defined FFT as a filling defect that resolved on follow-up imaging. We assessed the cranial-caudal dimension of the filling defect and receiver operating characteristics to identify clinical and radiological variables that distinguished FFT from complex ulcerated plaque. RESULTS: Intraluminal filling defects were identified in 32 patients. Filling defects and resolved or decreased in 25 patients (78 %) and felt to be FFT; there was no change in 7 (22 %). Resolved defects and those that decreased in size extended more cranially than those that remained unchanged: 7.3 mm (4.2-15.9) versus 3.1 mm (2.7-3.7; p = 0.0038). Receiver operating characteristic analysis established a threshold of 3.8 mm (filling defect length), sensitivity of 88 %, specificity of 86 %, and area under the curve of 0.86 (p < 0.0001) for distinguishing FFT from plaque. CONCLUSION: Filling defects in the proximal ICA extending cranially >3.8 mm were more likely to be FFT than complex ulcerated plaque. Further studies evaluating filling defect length as a predictor for FFT are warranted.

Use of nutritional health supplements and associated factors among parents with children at kindergartens in Hong Kong.

OBJECTIVES. To estimate the prevalence of so-called nutritional health supplement consumption among kindergarten children; secondarily to explore potential factors associated with such consumption. DESIGN. Cross-sectional, self-administered questionnaire survey. SETTING. One kindergarten each in Hong Kong island, Kowloon, and the New Territories region. SUBJECTS. Parents who had a child studying at the three sampled kindergartens in April 2010. RESULTS. Of 951 sets of parents, 730 (77%) responded. Approximately 52% (95% confidence interval, 47-58%) of the respondents gave regular health supplements to their child. The commonest type of supplement given was cod fish oil (69%). Approximately 36% of the respondents did not know the upper limit dosage of their supplement. Parents of only 66% of regular health supplements consumers, compared to 75% of non-regular users, knew that there was an inherent risk from over-consumption (P=0.018). Parental beliefs that "It is useful/important for normal child development" (adjusted odds ratio=1.93; 95% confidence interval, 1.18-3.16; P=0.009), "It is useful/important for immune function" (1.79; 1.05-3.05; P=0.032) were associated with consumption of health such supplements. CONCLUSION. There is high rate of health supplement consumption among healthy kindergarten children in Hong Kong. There are wrong beliefs from parents that health supplements are important for normal-growing children for their normal growth and body immunity. About one-third of parents has limited knowledge on potential side-effects of overdose and do not know the limit of consumption. Education on "Less (health supplement) is more (health)" is recommended.

Evaluation of a continuous quality improvement initiative for end-of-life care for older noncancer patients.

OBJECTIVES: The burden of suffering among patients with end-stage chronic diseases may be greater than those of cancer patients, as a result of longer duration of illness trajectory and high prevalence of symptoms, yet they may be less likely to receive palliative care services. To improve the quality of care of these patients, we carried out a continuous quality improvement initiative among medical and nursing staff of a convalescent facility. DESIGN: Evaluation of a quality improvement initiative. SETTING: Nonacute institution in Hong Kong SAR, China. PARTICIPANTS: The participants were patients with advanced chronic diseases not opting for active treatment. INTERVENTION: The intervention was a continuous quality improvement process carried out over a 3-month period, consisting of service reengineering, provision of guidelines and educational material, and interactive sessions to achieve culture change among staff. Evaluation before and after the intervention included patient symptoms checklist and quality-of-life measures for patients; quality-of-life and cost-of-care index for family members; quality-of-life and carer burden for staff; and use of various health care services. RESULTS: There were 80 and 89 participants in the pre- and post-intervention phase. The initiative resulted in shorter duration of stay, fewer investigations, fewer transfers back to the affiliated acute care hospital, and more follow-up by the outreach team, with no significant difference in mortality after adjusting for age and comorbidity. Symptoms of pain and cough were reduced, while there was a trend toward more constipation but less dizziness. Family members' satisfaction improved. CONCLUSIONS: It is possible to improve quality-of-life care for elderly patients with end-stage chronic diseases by staff education, and culture and system change, not only without additional resources, but likely savings were achieved in terms of reduced use of health care resources.

Dynamic nature of the CT angiographic "spot sign".

The "spot sign", first described in 2007, has shown that a focal area of contrast extravasation within an intracerebral haematoma (ICH) can be correlated with haematoma expansion. We describe a case where time-resolved dynamic CT angiography (dCTA) shows the appearance of the "spot sign" only in later images. This finding highlights the importance of timing of the static CT angiogram which, if performed too early, might result in a false-negative diagnosis.

Psychosocial condition of family caregivers of patients with chronic obstructive pulmonary disease in Hong Kong.

OBJECTIVES. Chronic obstructive pulmonary disease is associated with physical and psychological burdens. Although there is research about health-related quality of life (HRQOL) of such patients, less is known about the psychosocial condition of their family caregivers. The objectives of this study were to examine the HRQOL and the burden of chronic obstructive pulmonary disease patient caregivers, and to identify associated relevant factors. METHODS. A total of 81 eligible caregivers completed a caregiver survey on HRQOL (Short Form-36 Questionnaire), caregiving burden (Cumulative Illness Rating Scale, CIRS) and other biopsychosocial factors. Descriptive statistics, correlations, and multiple linear regression models were used to analyse data. RESULTS. The caregiver's Mental Component Summary measure of the Short Form-36 was associated with each caregiver's total CIRS scores, the anxiety subscale of the Hospital Anxiety and Depression Scale, and the Lubben Social Network Scale. The caregiver's Physical Component Summary measure was associated with the patient's disability allowance, the caregiver's total CIRS score, and the Barthel Index score. Caregivers' Caregiving Burden Scale scores were associated with their Geriatric Depression Scale total score and the need to take care of other family members. CONCLUSIONS. This study demonstrates that depressive and anxiety symptoms are associated with caregivers' burden and HRQOL. Further studies on evaluating interventions on caregivers' HRQOL and burden should take mood symptoms into consideration.

A pilot study to examine the feasibility and acceptability of a community model for exercise prescription for patients with chronic disease.

1. A model of community care for chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) that incorporates exercise prescription is lacking, although the benefits of exercise for these diseases are established. 2. Group programmes incorporating exercise, disease education, and social support consisting of weekly sessions for 12 weeks were designed for COPD and CHF patients, in groups of 8 to 10. A home exercise programme was also prescribed. 3. This model was feasible, enjoyed good compliance, improved symptoms and measures of psychosocial outcome for both disease and improved exercise tolerance in the CHF group. 4. This model could be further developed as an integral part of community management for patients with chronic diseases.

Vertebral artery dissection with a normal-appearing lumen at multisection CT angiography: the importance of identifying wall hematoma.

BACKGROUND AND PURPOSE: CT angiography (CTA) is widely used and may be the only vascular imaging technique ordered for emergent evaluation of neurovascular disease. With thin-section multisection CTA, the resolution of vessel wall imaging has improved. We describe cases of acute vertebral artery dissection (VAD) in which the only abnormality on CTA was a characteristic thickening of the wall of the V3 portion of the vertebral artery (VA). The arterial lumen at the dissection site was normal in caliber. This type of dissection is easily overlooked if only lumen-opacifying studies such as contrast MR angiography (MRA) or conventional angiography are performed. We highlight the importance of recognizing this finding, the "suboccipital rind" sign, in the V3 portion, a segment commonly affected in VAD. The purpose of our study was to review the CTA imaging characteristics of patients with VAD in the V3 portion compared with normal controls. MATERIALS AND METHODS: Our imaging data base was reviewed for cases of acute VAD and the presence of a "suboccipital rind" sign. A control group of 50 patients was randomly recruited from a group of patients undergoing CTA. The VA luminal diameter, the wall thickness (total diameter-luminal diameter), and the ratio of luminal diameter/total diameter were measured along 5 adjacent V3 segments and were compared between the 2 groups. RESULTS: There was no evidence of luminal tapering or narrowing in the dissected VAs compared with controls (P = .1). The average wall thickness of the dissection group was 2.96 mm greater than that for the control group (P < .001; 95% confidence interval, 2.6-3.3). There was a significant difference in the ratio of lumen diameter/lumen+wall diameter in dissected segments compared with controls (P < .001). CONCLUSIONS: Cross-sectional vascular imaging is often performed with multisection helical CTA for a variety of concerns, some without neurologic symptoms. Our study confirms that in cases of the "suboccipital rind" sign, the lumen appears normal in caliber, with wall thickening as the only imaging sign of VAD. In our center, this clinically occult VAD would influence management, with patients usually treated with antiplatelet agents. We caution against using only luminal-opacifying techniques such as contrast-enhanced MRA or conventional angiography to exclude VAD because they are limited in the evaluation of mural hematoma.