窥知

Neuroradiology_Essentials.pdf R A D I O L O G I C C L I N I C S O F N O R T H A M E R I C A Radiol Clin N Am 44 (2006) xi xiPreface Neuroradiology EssentialsRonald L. Wolf, MD, PhD Guest Editor Department of Neuroradiology University of Pennsylvania Medical Center 3400 Spruce Street Philadelphia, PA 19104, USA E-mail address: ronald.wolf@uphs.upenn.eduWhen asked to serve as the Guest Editor for an issue of Radiologic Clinics of North America includ- ing essential neuroradiology topics, I decided to focus on some of the most common conditions in which imaging plays a key role. Although common—or rather, because they are common—advances in treatment and management strategies as well as imaging strategies make it necessary to constantly reassess our understanding and approach to these problems. The goal of this issue was to provide a practical approach to each problem, incorporating relevant clinical and radiologic advances. Trauma is unfortunately all too common, and this is the topic of the first two articles. Over the last several years, cross-sectional imaging requests from our trauma services have been increasing quite steeply, at least partially due to the prolifera- tion of multidetector CT scanners and the wealth of information available with this technique. In the first article, traumatic injury to the spinal column is discussed. This is followed by an article discuss- ing the imaging of neurovascular traumatic injury. Screening for such injuries has become much more aggressive, and yet, widely accepted guide- lines for screening are not fully established. In the next two articles, the focus is on the most common0033-8389/06/$ – see front matter © 2005 Elsevier Inc. All rights radiologic.theclinics.commechanisms of nontraumatic brain injury in the adult and pediatric populations: ischemic injury in adults and hypoxic injury with or without hypo- perfusion for children. These types of injury can certainly occur in both populations, but the etiolo- gies and resulting patterns and mechanisms of injury are quite different. The next two articles thus focus on adult and pediatric populations sepa- rately. In the outpatient setting, two of the most common imaging requests are for cervical node evaluation and multiple sclerosis. These are the topics for the next two articles. Finally, for the benefit of the reader, two additional articles rele- vant to essential neuroradiology and previously published in Neuroimaging Clinics of North America have been included: one providing an overview of epilepsy and a discussion of MR imaging interpre- tation in this setting, and the other reviewing im- aging of orbital pathology. I am of course indebted to the authors for taking time out of their busy schedules to provide com- prehensive and practical discussions of these topics. I would also like to express my gratitude to the series editor, Mr. Barton Dudlick, for his guidance and remarkable patience in the preparation of this issue.reserved. doi:10.1016/j.rcl.2005.10.005 R A D I O L O G I C C L I N I C S O F N O R T H A M E R I C A Radiol Clin N Am 44 (2006) 1–12 1 Imaging of Spinal Trauma Linda J. Bagley, MD* & Indications for imaging Whiplash & Cervical spine imaging & Thoracic and lumbar imaging & Concerns about radiation dosing & Screening of pediatric patients & MR imaging & Clinical issues InstabilityDepartment of Radiology, University of Pennsylvania Sch Center, Philadelphia, PA, USA * Department of Radiology, University of Pennsylvania Sc Center, 3400 Spruce Street, Philadelphia, PA 19104. E-mail address: linda.bagley@uphs.upenn.edu 0033-8389/06/$ – see front matter © 2005 Elsevier Inc. All rights radiologic.theclinics.comVascular injury Subacute and chronic injuries & Summary & ReferencesApproximately 30,000 injuries to the spinal col- umn occur in the United States each year. Most injuries are secondary to blunt trauma (motor vehi- cle accidents, falls, sports injuries), although pene- trating trauma accounts for approximately 10% to 20% of the cases. Roughly 2% to 3% of blunt trauma victims are affected, with the incidence of cervical spinal trauma being increased in those with significant craniofacial trauma. Approximately 40% to 50% of spinal injuries produce a neurologic deficit, often severe and sometimes fatal [1]. Sur- vival is inversely correlated with patient age, and mortality during initial hospitalization approaches 10% [2]. Because most patients affected are young, the costs of lifetime care and rehabilitation are extremely high, often exceeding $1,000,000 per individual [3]. Plain radiography, CT, andMR imag- ing may all be used in the evaluation of the spinal column and are often complementary.Indications for imaging Pain, neurologic deficit, distracting injuries, altered consciousness (caused by head injury, intoxication,or pharmaceutical intervention), and high-risk mechanism of injury have been shown to be appro- priate, highly sensitive clinical indications for spinal imaging. In the multicenter National Emer- gency X-Radiography Use Study led by Hoffman and coworkers [4], 34,069 blunt trauma patients underwent cervical spine imaging, 4309 (12.6%) of whom did not meet the clinical criteria for imaging discussed previously. A total of 818 injuries were reported in this study, eight occurring in the group that would not otherwise have been imaged. Two of those injuries were clinically significant. Overall sensitivity for clinical evaluation was approximately 99.6%. Similarly, the Canadian C-Spine Rule study identified patients judged to be ‘‘low risk’’ (ambu- latory, without midline tenderness or immediate onset of pain, able to attain a sitting position, vic- tims of simple rear-end motor vehicle crashes). Such low-risk patients who could actively turn their heads 45 degrees in both directions were deemed not to require imaging. Overall sensitivity of clinical criteria in this study was 100% [5]. Similar clinical criteria have been evaluated in the thoracic and lumbar spine. Frankel and coworkersool of Medicine, University of Pennsylvania Medical hool of Medicine, University of Pennsylvania Medical reserved. doi:10.1016/j.rcl.2005.08.004 2 Bagley[6] reported 100% sensitivity when the clinical criteria of back pain, the presence of a neurologic deficit, a Glasgow Coma Scale score of 8 or less, a fall from a height of 10 feet or more, ejection from a motorcycle, or involvement in a motor vehicle accident with speeds greater than 50 miles per hour were applied.Fig. 1. (A) Lateral plain film is quite limited, imaging only t of C2. (B) Sagittal reformatted view reveals a fracture odontoid view demonstrates lateral displacement of the la reformatted view reveal a markedly comminuted fracture eral mass.Cervical spine imaging In the setting of acute spinal trauma, CT scanning has been shown to be more time efficient [7,8] and significantly more sensitive for fracture detection than plain films [9–16]. Multidetector CT provides superior evaluation of bony anatomy and pathol-o C2, demonstrating irregularity and possible fractures through the base of the odontoid. (C) Open mouth teral masses of C1. (D and E) Axial CT scan and coronal of the atlas with lateral displacement of the left lat- 3Spinal Trauma Imagingogy. Images may be rapidly acquired and re- constructed at narrow intervals (eg, 1 mm) with edge-enhancing algorithms. Multiplanar and three- dimensional images can subsequently be created [Fig. 1]. In a number of studies, the sensitivity of CT scanning for cervical spinal fracture detection has been reported to be between 90% and 99% with specificities of 72% to 89%. In contrast, the reported sensitivity of plain films has ranged from 39% to 94% with variable specificity. Sensitivity of plain films has inversely correlated with severity of trauma sustained [9–16]. Multiple studies have demonstrated the limitations of plain radiography in the cervical spine, particularly at the craniocervi- cal and cervicothoracic junctions. In a 1995 study by Link and coworkers [17], patients with sub- stantial head trauma (Glasgow Coma Scale 3–6) un- derwent axial CT scanning of the craniocervical junction. Eighteen percent of patients had fractures of C1, C2, or occipital condyles. Eight of nine oc- cipital condyle fractures and 13 of 33 fractures of C1 or C2 were not seen on plain films. Although most condylar fractures are stable, these injuries may be a cause of persistent pain, produce cranial nerve deficits, or lead to vertebrobasilar vascular injury or compromise [Fig. 2]. Furthermore, 6 of 13 fractures of C1 or C2 seen on CT only were un- stable. Similarly, Nunez and coworkers [18] com- pared lateral plain films with helical CT of the cervical spine performed with 5-mm collimation and sagittal and coronal reformatted images. Thirty-two of 88 fractures detected by CT were not seen on limited plain film evaluation, and one third of those fractures were clinically significant or unstable. In addition, a number of centers have reported CT scanning in moderate- to high-risk trauma patients to be a more cost-effective screening mo-Fig. 2. (A and B) Axial and coronal reformatted CT scans occipital condyle.dality than plain radiography when the costs of missed injuries and preventable paralysis (includ- ing the costs of prolonged hospitalizations, rehabili- tation, lost productivity, and malpractice suits) are taken into account [10,11]. Delays in diagnoses of clinically significant cervical spine injuries have been reported in approximately 5% to 23% of patients in various series, most of which used plain radiography as the initial screening modal- ity. Neurologic deterioration (possibly secondary to mismanagement) occurred in 10% to 50% of these patients [19]. In contrast, development of a second- ary neurologic deficit occurred in only 1.4% of patients whose injuries were detected on initial screening in Reid and coworkers’ cohort [20]. CT is rapidly becoming the initial screening modality for osseous spinal pathology in adults, particularly those judged to be at moderate to high risk for spinal fracture based on mechanism of injury and clinical data.Thoracic and lumbar imaging Thoracic and lumbar spinal injuries also affect approximately 2% to 3% of blunt trauma victims and are associated with an approximately 40% to 50% incidence of neurologic deficit. CT scanning has been shown to be superior to plain films for detection and characterization of fractures. In a 1995 study by Campbell and coworkers [21], 20% of unstable burst fractures (involving the posterior vertebral body cortex) of the thoracic and lumbar spine were misdiagnosed as stable wedge compres- sion fractures (single-column injuries) by plain films. CT better detected fractures of the posterior elements, malalignment, and intracanalicular frag- ments. Given the frequency with which many vic-demonstrate a mildly displaced fracture of the right Fig. 3. (A) Axial reconstructed CT image reveals a comminuted burst fracture of L1 with retropulsed posterior cortex and a large prevertebral hematoma. (B) Sagittal reformatted view demonstrates marked loss of height of the vertebral body with retropulsed cortex and canal compromise. 4 Bagleytims of blunt trauma undergo multidetector CT scanning of the chest, abdomen, and pelvis, the use of reformatted images from visceral protocol CT scans to evaluate the spine has dramatically increased [Fig. 3] [22–25]. When compared with plain radiography in the study by Sheridan and coworkers [22], visceral CT scans reformatted at 2.5-mm intervals with sagittal and coronal recon- structed views were shown to improve sensitivity for detection of lumbar fractures from 95% to 97% and of thoracic fractures from 62% to 86%. Detail and likely sensitivity can be further improved with reformatting performed at 1-mm intervals.Concerns about radiation dosing Although CT scanning has been shown to be more time efficient and in certain circumstances more cost effective than plain radiography, there is a significant increase in radiation exposure associated with CT screening [26,27]. Adelgeis and coworkers [28] reported an approximately 50% increase in mean radiation dose to the cervical spine in pediat- ric patients for helical CT compared with conven- tional radiography. When organ-specific doses were examined, the results were even more concerning. Rybicki and coworkers [29] found an approxi- mately 10-fold increase in radiation dose to the skin (28 versus 2.89 mGy) and an approximately 14-fold increase in dose to the thyroid (26 versus 1.80 mGy) with CT examination of the entire cer- vical spine (using 3-mm collimation, pitch of 1.5:1, 120 kV [peak], and 240 mA and single lateral ra- diograph) rather than a four- to five-view radio- graphic series.Screening of pediatric patients Spinal injuries in children occur somewhat less commonly than in adults, with pediatric spinal injuries accounting for approximately 2% to 5% of all such injuries. The types of injuries sustained in children, particularly younger children (under age 8), also differ from those sustained in adults. Mechanisms of injury often differ with age. The up- per cervical spine is most often affected in children, and dislocations and cord injuries without asso- ciated fractures occur more often in children than in adults [30,31]. Furthermore, the tissues and organs of children, particularly those under age 5, are more prone to development of radiation-induced malignancies, because of increased radiosensitiv- ity of certain organs; a longer expected lifetime in which to develop a cancer; and frequent failure of adjustment of scanning parameters (eg, tube current) based on patient size [26]. Multiple series have demonstrated little improvement in detec- tion of fractures and malalignment with CT com- pared with plain films in the pediatric population [28,32], with substantial increases in radiation ex- posure reported with CT. Many normal anatomic variants in children, however, may mimic fractures and warrant additional evaluation with CT or MR imaging [33]. Because children often require sedation for CT scanning, the improvements in time efficiency and length of emergency depart- ment stay observed in adults undergoing CT screen- ing are often not appreciated in children [32]. Given these differences between children and adults, spinal trauma screening protocols must be modi- fied for the pediatric population. Plains films may be used as the initial screening modality with CT ...