Pragmatic solutions to reduce the global burden of stroke: a World Stroke Organization-Lancet Neurology Commission

Stroke is the second leading cause of death worldwide. The burden of disability after a stroke is also large, and is increasing at a faster pace in low-income and middle-income countries than in high-income countries. Alarmingly, the incidence of stroke is increasing in young and middle-aged people (ie, age <55 years) globally. Should these trends continue, Sustainable Development Goal 3.4 (reducing the burden of stroke as part of the general target to reduce the burden of non-communicable diseases by a third by 2030) will not be met. In this Commission, we forecast the burden of stroke from 2020 to 2050. We project that stroke mortality will increase by 50%—from 6·6 million (95% uncertainty interval [UI] 6·0 million–7·1 million) in 2020, to 9·7 million (8·0 million–11·6 million) in 2050—with disability-adjusted life-years (DALYs) growing over the same period from 144·8 million (133·9 million–156·9 million) in 2020, to 189·3 million (161·8 million–224·9 million) in 2050. These projections prompted us to do a situational analysis across the four pillars of the stroke quadrangle: surveillance, prevention, acute care, and rehabilitation. We have also identified the barriers to, and facilitators for, the achievement of these four pillars. DISABILITY-ADJUSTED LIFE-YEARS (DALYS): The sum of the years of life lost as a result of premature mortality from a disease and the years lived with a disability associated with prevalent cases of the disease in a population. One DALY represents the loss of the equivalent of one year of full health On the basis of our assessment, we have identified and prioritised several recommendations. For each of the four pillars (surveillance, prevention, acute care, and rehabilitation), we propose pragmatic solutions for the implementation of evidence-based interventions to reduce the global burden of stroke. The estimated direct (ie, treatment and rehabilitation) and indirect (considering productivity loss) costs of stroke globally are in excess of US$891 billion annually. The pragmatic solutions we put forwards for urgent implementation should help to mitigate these losses, reduce the global burden of stroke, and contribute to achievement of Sustainable Development Goal 3.4, the WHO Intersectoral Global Action Plan on epilepsy and other neurological disorders (2022–2031), and the WHO Global Action Plan for prevention and control of non-communicable diseases. Reduction of the global burden of stroke, particularly in low-income and middle-income countries, by implementing primary and secondary stroke prevention strategies and evidence-based acute care and rehabilitation services is urgently required. Measures to facilitate this goal include: the establishment of a framework to monitor and assess the burden of stroke (and its risk factors) and stroke services at a national level; the implementation of integrated population-level and individual-level prevention strategies for people at any increased risk of cerebrovascular disease, with emphasis on early detection and control of hypertension; planning and delivery of acute stroke care services, including the establishment of stroke units with access to reperfusion therapies for ischaemic stroke and workforce training and capacity building (and monitoring of quality indicators for these services nationally, regionally, and globally); the promotion of interdisciplinary stroke care services, training for caregivers, and capacity building for community health workers and other health-care providers working in stroke rehabilitation; and the creation of a stroke advocacy and implementation ecosystem that includes all relevant communities, organisations, and stakeholders.

Anatomy and physiology of cisternostomy

Cisternostomy is defined as opening the basal cisterns to atmospheric pressure. This technique helps to reduce the intracranial pressure in severe head trauma as well as other conditions when the so-called sudden "brain swelling" troubles the surgeon. We elaborated the surgical anatomy of this procedure as well as the proposed physiology of how cisternostomy works. This novel technique may change the current trends in neurosurgery.

A comparative study between Marshall and Rotterdam CT scores in predicting early deaths in patients with traumatic brain injury in a major tertiary care hospital in Nepal

PURPOSE

CT plays a crucial role in the early assessment of patients with traumatic brain injury (TBI). Marshall and Rotterdam are the mostly used scoring systems, in which CT findings are grouped differently. We sought to determine the values of the scoring system and initial CT findings in predicting the death at hospital discharge (early death) in patients with TBI.

METHODS

There were consecutive 634 traumatic neurosurgical patients with mild-to-severe TBI admitted to the emergency department of College of Medical Sciences. Their initial CT and status at hospital discharge (dead or alive) were reviewed, and both CT scores were calculated. We examined whether each score is related to early death; compared the two scoring systems' performance in predicting early death, and identified the CT findings that are independent predictors for early death.

RESULTS

Both imaging score (Marshall) and clinical score (Rotterdam) can be used to reliably predict mortality in patients with acute traumatic brain injury with high prognostic accuracy. Other specific CT characteristics that can be used to predict early mortality are traumatic subarachnoid hemorrhage, midline shift and status of the peri-mesencephalic cisterns.

CONCLUSIONS

Marshall CT classification has strong predictive power, but greater discrimination can be obtained if the individual CT parameters underlying the CT classification are included in a prognostic model as in Rotterdam score. Consequently, for prognostic purposes, we recommend the use of individual characteristics rather than the CT classification. Performance of CT models for predicting outcome in TBI can be significantly improved by including more details of variables and by adding other variables to the models.

Effect of Helicopter Transportation of Acute Ischemic Stroke Patients on Mortality and Functional Outcomes: A Systematic Review and Meta-Analysis

OBJECTIVE

The "time is brain" concept denotes the importance of the expedited transfer of patients to stroke care centers. Helicopter emergency medical services (HEMS) can reduce the time to definitive care, which could improve neurologic prognosis and reduce mortality.

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, a search for randomized controlled trials, nonrandomized controlled trials, and prospective and retrospective cohort studies was performed through specific databases from inception to February 2020. Helicopter, acute stroke, and their synonyms (according to Medical Subject Headings) were included in this search. The Newcastle-Ottawa Scale was used to assess the quality of the included studies, and the Egger test was used to assess for publication bias.

RESULTS

A total of 8 studies matched the inclusion criteria and were included for meta-analysis. The overall number recruited for helicopter transportation was 1,372, and for emergency standard transportation, it was 8,587. The association among HEMS and mortality was not statistically significant (odds ratio [OR] = 0.7; 95% confidence interval [CI], 0.60-1.06; P = .12). There was a significant association between good outcomes and HEMS (OR = 2; 95% CI, 1.79-2.34; P ≤ .001), and the overall poor neurologic outcome was reduced (OR = 0.52; 95% CI, 0.46-0.60; P ≤ .001).

CONCLUSION

A good neurologic outcome was higher with HEMS compared with emergency standard transportation. The mortality rate was less in the emergency standard transportation group after pooled analysis but was not significant; the reduction in a poor outcome was statistically significant.

Traumatic Cervical Spondyloptosis in a Neurologically Stable Patient: A Therapeutic Challenge

This is a case report of a neurologically intact patient following posttraumatic cervical spondyloptosis. We discuss the disease, management protocol and some surgical nuances to prevent any damage to the cord during different stages of its treatment.

Role of bromocriptine in multi-spectral manifestations of traumatic brain injury

PURPOSE

Despite the prevalence and cost of traumatic brain injury related disabilities, there is paucity in the literature on modern approaches to pharmacotherapy. Medications may promote recovery by enhancing some neurological functions without impacting others. Herein we discussed the role of bromocriptine in neurorehabilitation for patients with traumatic brain injury.

METHODS

A cohort comprising of 36 selective nonsurgical cases of traumatic brain injury in minimally conscious state were enrolled in the study. After hemodynamic stability, bromocriptine was given at paediatric dose of 3.75 mg/d and adult dose of 7.5 mg/d. It was administered through a naso-gastric (NG) feeding tube in the patients with minimally conscious state, then changed to oral route after proper swallowing and good gag reflex were ensured in the patient. The drug was slowly reduced over three weeks after neurological improvement in the patients. Positive result was determined by improved GCS score of 2 and motor power by at least 1 British Medical Council (BMC) motor score. Improvement of deficits was evaluated in terms of fluency of speech for aphasia, task switching, digit span double tasking and trail-making test for cognition and attention, and functional independence measure score for motor functioning and self-independence.

RESULTS

Accelerated arousal was seen in 47.0% of cases (8/17) in 4-40 days. In 41.2% of cases (7/17), Glasgow outcome score (GOS) was improved to 4/5 in 90 days. Improvement in hemiparesis by at least 1 BMC score was seen in 55.6% of cases (5/9) in 40 days. Aphasia was improved in 80% of cases (4/5) in 7-30 days. Moderate improvement in cognitive impairment was seen in 66.7% of cases (2/3) in 14-20 days. Improvement in memory was observed in 50% of cases (1/2) in over 30 days. No cases were withdrawn from the study because of adverse reactions of the drug. There was no mortality in the study group.

CONCLUSION

Bromocriptine improves neurological sequelae of traumatic brain injury as well as the overall outcome in the patients. If medication is given to promote recovery and treat its associated disabilities, clinicians should thoroughly outline the goals and closely monitor adverse effects.

Role of computed tomography scores and findings to predict early death in patients with traumatic brain injury: A reappraisal in a major tertiary care hospital in Nepal

BACKGROUND

Glasgow Coma Scale has been a long sought model to classify patients with head injury. However, the major limitation of the score is its assessment in the patients who are either sedated or under the influence of drugs or intubated for airway protection. The rational approach for prognostication of such patients is the utility of scoring system based on the morphological criteria based on radiological imaging. Among the current armamentarium, a scoring system based on computed tomography (CT) imaging holds the greatest promise in conquering our conquest for the same.

METHODS

We included a total of 634 consecutive neurosurgical trauma patients in this series, who presented with mild-to-severe traumatic brain injury (TBI) from January 2013 to April 2014 at a tertiary care center in rural Nepal. All pertinent medical records (including all available imaging studies) were reviewed by the neurosurgical consultant and the radiologist on call. Patients' worst CT image scores and their outcome at 30 days were assessed and recorded. We then assessed their independent performance in predicting the mortality and also tried to seek the individual variables that had significant interplay for determining the same.

RESULTS

Both imaging score (Marshall) and clinical score (Rotterdam) can be used to reliably predict mortality in patients with acute TBI with high prognostic accuracy. Other specific CT characteristics that can be used to predict early mortality are traumatic subarachnoid hemorrhage, midline shift, and status of the peri-mesencephalic cisterns.

CONCLUSION

We demonstrated in this cohort that though the Marshall score has the high predictive power to determine the mortality, better discrimination could be sought through the application of the Rotterdam score that encompasses various individual CT parameters. We thereby recommend the use of such comprehensive prognostic model so as to augment our predictive power for properly dichotomizing the prognosis of the patients with TBI. In the future, it will therefore be important to develop prognostic models that are applicable for the majority of patients in the world they live in, and not just a privileged few who can use resources not necessarily representative of their societal environment.

Case Report: Sciatic nerve schwannoma - a rare cause of sciatica

Herein we report a rare case of a sciatic nerve schwannoma causing sciatica in a 69-year-old female. Sciatic nerve schwannoma is a rare entity. It should always be considered as a possible cause of sciatica in patients that present with symptoms of sciatica with no prolapsed disc in the lumbar spine and a negative crossed straight leg raise test. Timely diagnosis and complete excision of the lesion leads to complete resolution of the symptoms of such patients.

Anterior single odontoid screw placement for type II odontoid fractures: our modified surgical technique and initial results in a cohort study of 15 patients

Objective: Anterior odontoid screw fixation for type II odontoid fracture is the ideal management option. However in the context of unavailability of an O-arm or neuro-navigation and poor images from the available C-arm may be an obstacle to ideal trajectory and placement of the odontoid screw. We herein detail  our surgical technique so as to ensure a correct trajectory and subsequent good fusion in Type II odontoid fractures. This may be advantageous  in clinical set ups lacking state of the art facilities.  Methods and Results: In this cohort study we included 15 consecutive patients who underwent anterior odontoid screw placement. We routinely dissect the longus colli to completely visualize the entire width of C3 body. We then perform a median C2-C3 disectomy followed by creating a gutter in the superior end of C3 body. We then guide the Kirchsner (K) wire purchasing adequate anterior cortex of C2. Rest of the procedure follows the similar steps as described for odontoid screw placement. We achieved 100% correct trajectory and screw placement in our study. There were no instances of screw break out, pull out or nonunion. There was one patient mortality following myocardial infarction in our study. Conclusion: Preoperative imaging details, proper patient positioning, meticulous dissection, thorough anatomical knowledge and few added surgical nuances are the cornerstones in ideal odontoid screw placement. This may be pivotal in managing  patients in developing nations having rudimentary neurosurgical set up.

A pilot study comparing pattern of damage sustained among instruments from different surgical units in a tertiary care centre in Nepal - reappraising the role of instrument reprocessing in retaining their value

Background: The quality of instruments plays a pivotal role in governing safe operating room culture. The reprocessing system followed in the institution determines their durability thereby ensuring patient safety as well as minimizing health spending. Rigorous reprocessing in a centralized instrument reprocessing department by well trained staff following formulated guidelines helps to achieve the target of "safe surgery saves lives" as formulated by the World Health Organization. Methods: We sought to determine the patterns of wear and tear sustained among sets of surgical equipment from two surgical units that had been sent to the repair department within a year of their purchase. Analysis of similar changes in the joints of the instrument, as well as pattern of fractures sustained was performed. Results: All patterns of wear and tear were common in both the general surgical arm and neurosurgical counterpart, with the exception of fractures and mal-alignments. Similar study was performed examining changes in the joints. Stains were the most commonly observed change pattern in both sets of instruments. Fractures were most frequent in the working ends in both sets of instruments. Conclusion: There is an alarming incidence of wear and tear patterns in the instruments used in the surgical units, even within the first year of their use. This supports the strict implementation of reprocessing guidelines by well trained workers and their quality assessments via audit checks. The quality of the purchased instruments also plays a pivotal role.

Prospective observational research on the clinical profile and outcome analysis among a cohort of patients sustaining traumatic cervical spine and cord injury in a peripheral tertiary spine care centre in Nepal

Background: In developing nations like Nepal, spinal cord injury has multispectral consequences for both the patient and their family members. It has the tendency to cripple and handicap the patients, and burn out their caretakers, both physically and mentally. Furthermore, the centralization of health care with only a handful of dedicated rehabilitation centers throughout Nepal further places patients into disarray. This study was carried out as a pilot study to determine the modes of injury, age groups affected, clinical profiles and patterns of injury sustained, as well as the efficacy of managing a subset of patients, who have sustained cervical spine and cord injuries. Methods: This was a prospective cohort study comprising of 163 patients enrolled over a period of three years that were managed in the spine unit of College of Medical Sciences, Bharatpur, Nepal. Results: Road traffic accidents were implicated in 51% of these patients. 65% of them were in the age group of 30-39 years. Traumatic subluxation occurred in 73 patients with maximum involvement of the C4/5 region (28.76%). Good outcome was seen in patients with ASIA 'C' and 'D' with 55% of patients showed improvement from 'C' to 'D' and 95% of patients showed improvement from 'D' to 'E' at 1 year follow up. The overall mortality in the patients undergoing operative interventions was only 1.98%. Conclusions: The prevalence of cervical spine injuries in the outreach area is still significant. The outcome of managing these patients, even in the context of a resource limited setup in a spine unit outside the capital city of a developing nation, can be as equally as effective and efficient compared to the outcome from a well-equipped and dedicated spine unit elsewhere.

Case Report: Traumatic anterior cerebral artery aneurysm in a 4-year old child

Traumatic intracranial aneurysm in the proximal part of the anterior cerebral artery in the pediatric population has not been documented so far. Here we report the case of a 4 year-old child who developed a pseudo-aneurysm after minor head trauma and was managed successfully with trapping of the aneurysm. A ventriculo-peritoneal shunt was placed as the child became dependent on extraventricular drain during the post-operative period. The patient made excellent recovery in neurological status within 1 month of post-operative clinical follow up.

Case Report: Multiple hemorrhagic metastases to the brain from primary lung choriocarcinoma

Herein we report a very rare entity of multiple hemorrhagic metastases to the brain from a primary lung choriocarcinoma in a young woman. The patient presented with recent onset of progressive headache, decreased level of consciousness and multiple episodes of vomiting. CT of the head revealed multiple hemorrhagic lesions within the brain. The patient's serum B-human chorionic gonadotrophin was increased.  A chest X-ray revealed a right lung mass. The patient urgently underwent operative excision of the lesion in the posterior fossa, so as to prevent impending tonsillar herniation. The histology from the lesion provided the diagnosis of choriocarcinoma. After surgery, ultrasonography of the abdomen and pelvis was normal, and a chest CT revealed an enhanced and highly vascular right apical lung lesion, suggestive of lung primary choriocarcinoma, with regard to the clinical background. The patient was then started on chemotherapy, following which her serum B-HCG level decreased rapidly. This case highlights the importance of keeping this entity in the differential diagnosis of hemorrhagic lesions in any patients of a child bearing age. Early diagnosis and rapid initiation of multimodal therapy is prudent for ensuring a good outcome from an otherwise rapidly metastasizing and highly vascular lesion.

Case Report: Levetiracetam causing acute liver failure complicating post-operative management in a neurosurgical patient

Background: Herein we report a rare case of acute liver failure due to levetiracetam, which has been considered to have an excellent safety profile with minimal hepatic side effects.

Case presentation: A 55-year-old male patient presenting with sudden onset dizziness, slurring of speech and headache was operated for posterior fossa cerebellar hematoma. His post-surgical period was complicated by development of icterus with elevation of liver enzymes. After ruling out common inciting factors, it was decided to stop levetiracetam which was given prophylactically for preventing seizures owing to presence of external ventricular drain. From the next day patient had dramatic improvement in liver functions and sensorium.

Conclusions: We would like to highlight this side effect that is potentially life threatening, though rare, of levetiracetam, which is very commonly used in today’s practice and fast superseding all other time-tested antiepileptics.

Case Report: Case report on multiple extradural thoracic lesions with myelopathy as the clinical presentation in a systemic sarcoidosis- another tale of a lurking entity

Herein, we report a rare case study of a sarcoidosis presenting with the features of compressive myelopathy. There were multiple extra-dural lesions in the thoracic region. Computerized Tomography (CT) of the chest revealed fibrotic changes with a pleural based nodular lesion in the right lung. The patient underwent laminectomy and partial excision of both the lesions. The histology revealed presence of non-caseating granulomas. The patient made a good recovery following adjuvant medical management with steroid and Methotrexate. Repeat CT scan of the chest also confirmed good resolution in the size of the pleural based nodule.

A pilot study on assessing the role of intra-operative Flow 800 vascular map model in predicting onset of vasospasm following micro vascular clipping of ruptured intracranial aneurysms

Objective To ascertain the predictive value of intra-operative FLOW 800 vascular map model in predicting onset of post-operative clinical vasospasm and delayed cerebral ischemia among patients undergoing micro-vascular clipping of ruptured intracranial aneurysms.  Material and methods A total of 40 patients were enrolled in the study and their variables such as age, World Federation of Neurological Surgeons (WFNS) grade at presentation, Computerized Tomography (CT) Fisher grading, location of the aneurysms, and Indocyanine Green (ICG) flow status were compared and statistically analyzed along with differences in Absorption Intensities (AI) and difference in time lag values obtained from the FLOW 800 vascular map studies for predicting onset of vasospasm.  Results The Receiver Operating curve (ROC) of the model for predicting post-operative vasospasm was highest (.892) for difference in the AI followed by CT Fisher grading (.778), difference in time lag (.700) and WFNS grading (.699).Analysis of variance for different variables studied in our model for predicting vasospasm was significant for all except for age (.991) and the ICG flow through the parent vessel (.079).Multivariate analysis done for predicting the vasospasm was significant for all variables except for age (.869) and ICG main flow (.196) Conclusion Our study confirmed the role of FLOW 800 study model in predicting clinical vasospasm. Inclusion of this entity would therefore help in taking timely and correct therapeutics measures to ensure better patient outcomes.

Mini Craniotomy in the Management of Supratentorial Spontaneous Intracranial Hemorrhage: A Single-Center Outcome of the Minimally Invasive Treatment

Hemorrhagic stroke accounts for a significant proportion of mortality and confers a poor quality of life with high dependency among survivors. Surgical evacuation of hematoma has the advantage of rapidly controlling the increased intracranial pressure, halting the ongoing herniation syndrome, and mitigating the secondary cascades of events mediated by the inflammatory and blood degradation products. The advantage is hindered by the concurrent insult to the healthy brain tissue while passing through the normal brain tissue. Therefore, minimally invasive approaches to evacuate the hematoma are employed, but the need for an expensive surgical armamentarium and the expert multidisciplinary team is the bottleneck for their application, particularly in low-income nations. We herein performed a study upon the role of mini craniotomy open surgical method of evacuating hematoma in selected patients with supratentorial intracerebral hemorrhage. We found a significant reduction in the surgery length, minimized risk of post-surgery complications, shortened intensive care unit stay, and reduced mortality compared to the full-fledged craniotomy and endoscopy-guided surgery. There is a need for a large-scale randomized multicenter prospective study to verify the advantages of minimally invasive approaches in the management of symptomatic supratentorial intracerebral hemorrhages.

Case Report: Acute obstructive hydrocephalus associated with infratentorial extra-axial fluid collection following foramen magnum decompression and durotomy for Chiari malformation type I

Acute obstructive hydrocephalus due to infratentorial extra-axial fluid collection (EAFC) is an extremely rare complication of foramen magnum decompression (FMD) and durotomy for Chiari malformation type I. Presence of infratentorial  EAFC invariably causes obstruction at the level of the fourth ventricle or aqueduct of Silvius, thereby indicating its definitive role in hydrocephalus. Pathogenesis of EAFC is said to be a local arachnoid tear as a result of durotomy, as this complication is not described in FMD without durotomy. Controversy exists in management. Usually EAFC is said to resolve with conservative management; so hydrocephalus doesn't require treatment. However, in this case EAFC was progressive and ventriculo-peritoneal shunting (VPS) was needed for managing progressive and symptomatic hydrocephalus.

Case Report: A giant but silent adrenal pheochromocytoma - a rare entity

Herein we report a rare entity of a giant adrenal pheochromocytoma in a fifty-year-old male presenting with a vague abdominal pain. A computerised tomogram of the abdomen revealed a well-defined  left supraadrenal giant lesion with no evidence of invasion to surrounding structures.The patient underwent surgical excision without any untoward postoperative events. Histopathological study revealed a benign pheochromocytoma. This report highlights the importance of acknowledging the fact that sometimes a giant adrenal pheochromocytoma can present with paucity of clinical  signs and symptoms.Thorough investigations and a multidisciplinary team approach may lead  to a better outcome in these patients.

Reappraising Neurosurgical Residency in Nepal-Stepping Stone for Paradigm Shift from Its Current Perspectives

BACKGROUND

Nepal has a critical shortage of health workers for achieving its projected sustainable development goals pertaining to its health sector.

METHODS

To counteract this crisis and reduce the morbidity and mortality associated with untreated brain injuries secondary to inadequate access, it is pivotal to generate solutions through the establishment of improved educational and training objectives. Objectives must align themselves with achieving equitable access to neurologic health. To that end, the cadre of health professionals able to treat neurologic disease should be sharply skilled and increased in number. We outline potential sustainable solutions at the training level to address this public health problem.

RESULTS

Demanding and limitless working hours, burnout, social stressors, and minimal monthly stipend likely contribute to limited applications for neurosurgery residency programs. Measures should be taken to improve participation and access to extracurricular nonwork activities so as to improve resident well-being and avoid burnout. Moreover, gender inequality has also become a matter of concern as there were no females among 31 new specialist registrations in neurosurgery in 2017 and only 5 female neurosurgeons in practice to date in Nepal as per the NMC registration.

CONCLUSIONS

Every effort should be directed toward honing the "value of neurosurgeon" among residents and promoting and nurturing their capabilities thereby maximizing sustainability in our health care system.

Aggressive fibromatosis in the infratemporal fossa presenting as trismus: a case report

BACKGROUND

Here we report a very rare entity of an infratemporal region aggressive fibromatosis in a 23-year-old Tharu man who had presented with the symptoms of painless but progressive trismus.

CASE PRESENTATION

We describe a case of aggressive fibromatosis in a 23-year-old Tharu man. Radiological imaging as well as an immunohistochemistry panel from a biopsy indicated a diagnosis of an aggressive fibromatosis. Since there was no aggravation in his trismus following surgery and because of his poor socioeconomic status, he was advised to attend regular follow-up visits without any adjuvant therapy.

CONCLUSIONS

This case report adds to the notion of keeping the differential diagnosis of an aggressive fibromatosis in all patients presenting with progressive but painless trismus. The characteristic imaging findings as well an immunohistochemistry panel will help us clinch the correct diagnosis.

Case Report: A giant myopericytoma involving the occipital region of the scalp - a rare entity

Herein we report a rare case of a giant myopericytoma presenting in a 16-year-old girl as a slowly progressive swelling involving the scalp in the occipital region. It was managed by complete excision. Histological examination of the lesion revealed  spindle-shaped cells forming characteristic rosettes around the blood vessels, and positive staining with smooth muscle actin.