An Evidence-Based Approach to Imaging of Acute Neurological
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December 2007 An Evidence-Based Approach Volume 9, Number 12 Authors To Imaging Of Acute Joshua Broder, MD, FACEP Assistant Professor, Associate Residency Director, Division of Emergency Medicine, Duke University Neurological Conditions Medical Center, Durham, NC Robert Preston, MD Division of Emergency Medicine, Duke University It’s Monday afternoon, the ED is full, and neuroimaging seems to be the Medical Center, Durham, NC “theme” for the day. You realize how your clinical skills are merged with Peer Reviewers Yu-Feng Yvonne Chan, MD, FACEP technology and how dependent your clinical decision-making is on Assistant Professor, Department of Emergency Medicine, radiology. Mount Sinai School of Medicine, New York, NY A 75-year-old male presents with two hours of right-sided hemiplegia. Andrew Perron, MD Residency Program Director, Department of Emergency The on-call neurologist recommends TPA if the head CT does not show Medicine, Maine Medical Center, Portland, ME hemorrhage. The radiologist tells you there is no blood but there are early CME Objectives ischemic changes…. Upon completion of this article, you should be able to: A 55-year-old male presents after a syncopal episode. He has a normal 1. Describe indications for neuroimaging for a variety of neurological exam and no evidence of head trauma. His wife asks if a head clinical presentations. 2. Describe a systematic approach to the interpretation CT should be done to rule out stroke…. of non-contrast head CT. A 19-year-old female presents with four days of severe headache. She 3. Select the most appropriate imaging modality for a describes a thunderclap onset, with some improvement over the past several variety of acute neurological complaints. 4. Compare and contrast CT and MR in terms of sensi- days. You initially suspect subarachnoid hemorrhage; however, her non- tivity and specificity for the evaluation of neurological contrast head CT is normal. After prochlorpromazine and fluids, she is pathology. 5. Identify areas of overuse or misuse of imaging tech- eager to leave…. niques in the assessment of neurological complaints. A 20-year-old male presents with a new onset tonic clonic seizure wit- 6. Select a diagnostic algorithm that improves patient nessed by his roommate. He has no past medical history and takes no medi- care by facilitating rapid and accurate diagnosis while minimizing radiation exposure and cost. cations or drugs. He is back to his baseline and his neurological exam is Date of original release: December 1, 2007 completely normal. The CT scanner is backed up for at least two hours and Date of most recent review: November 8, 2007 you wonder if it would be OK to send him home for an outpatient workup… Termination date: December 1, 2010 A 52-year-old male is involved in a motor vehicle collision. He does not Time to complete activity: 4 hours Medium: Print & online recall the moment of impact and appears to have had a brief loss of con- Method of participation: Print or online answer form sciousness. He is now neurologically intact with no other complaints and a and evaluation Prior to beginning this activity, please see “Physician CME normal exam. You wonder whether CT is necessary… Information” on the back page. A lot of patients, a lot of decisions; not enough CT scanners! Editor-in-Chief LSU Health Science Center, New Gregory L. Henry, MD, FACEP, EM/IM Program, University of Beth Wicklund, MD, Regions Orleans, LA. CEO, Medical Practice Risk Maryland, Baltimore, MD. Hospital Emergency Medicine Andy Jagoda, MD, FACEP, Assessment, Inc; Clinical Residency, EMRA Representative. Wyatt W. Decker, MD, Alfred Sacchetti, MD, FACEP, Professor and Vice-Chair of Chair and Professor of Emergency Academic Affairs, Department of Associate Professor of Medicine, University of Michigan, Assistant Clinical Professor, International Editors Emergency Medicine; Mount Sinai Emergency Medicine, Mayo Clinic Ann Arbor. Department of Emergency School of Medicine; Medical College of Medicine, Rochester, Medicine, Thomas Jefferson Valerio Gai, MD, Senior Editor, Director, Mount Sinai Hospital, MN. Keith A. Marill, MD, Instructor, University, Philadelphia, PA. Professor and Chair, Dept of EM, Department of Emergency New York, NY. Francis M. Fesmire, MD, FACEP, Corey M. Slovis, MD, FACP, University of Turin, Italy. Medicine, Massachusetts General Director, Heart-Stroke Center, FACEP, Professor and Chair, Associate Editor Hospital, Harvard Medical School, Peter Cameron, MD, Chair, Erlanger Medical Center; Boston, MA. Department of Emergency Emergency Medicine, Monash Assistant Professor, UT College of Medicine, Vanderbilt University John M. Howell, MD, FACEP, University; Alfred Hospital, Medicine, Chattanooga, TN. Charles V. Pollack, Jr, MA, MD, Medical Center, Nashville, TN. Clinical Professor of Emergency Melbourne, Australia. FACEP, Professor and Chair, Medicine, George Washington Michael J. Gerardi, MD, FAAP, Jenny Walker, MD, MPH, MSW, Department of Emergency Amin Antoine Kazzi, MD, FAAEM, University, Washington, DC; FACEP, Director, Pediatric Medicine, Pennsylvania Hospital, Assistant Professor; Division Associate Professor and Vice Director of Academic Affairs, Best Emergency Medicine, Children’s University of Pennsylvania Health Chief, Family Medicine, Chair, Department of Emergency Practices, Inc, Inova Fairfax Medical Center, Atlantic Health System, Philadelphia, PA. Department of Community and Medicine, University of California, Hospital, Falls Church, VA. System; Department of Preventive Medicine, Mount Sinai Irvine; American University, Beirut, Emergency Medicine, Morristown Michael S. Radeos, MD, MPH, Medical Center, New York, NY. Lebanon. Editorial Board Memorial Hospital, NJ. Research Director, Department of Ron M. Walls, MD, Emergency Medicine, New York Professor and Hugo Peralta, MD, Chair of Michael A. Gibbs, MD, FACEP, William J. Brady, MD, Associate Hospital Queens, Flushing, NY; Chair, Department of Emergency Emergency Services, Hospital Professor and Vice Chair, Chief, Department of Emergency Assistant Professor of Emergency Medicine, Brigham & Women’s Italiano, Buenos Aires, Argentina. Department of Emergency Medicine, Maine Medical Center, Hospital, Boston, MA. Medicine, Weill Medical College Maarten Simons, MD, PhD, Medicine, University of Virginia, Portland, ME. of Cornell University, New York, Charlottesville, VA. Research Editors Emergency Medicine Residency Steven A. Godwin, MD, FACEP, NY. Director, OLVG Hospital, Peter DeBlieux, MD Assistant Professor and Robert L. Rogers, MD, FAAEM, Nicholas Genes, MD, PhD, Mount Amsterdam, The Netherlands. Professor of Clinical Medicine, Emergency Medicine Residency Assistant Professor and Sinai Emergency Medicine Director, University of Florida Residency Director, Combined Residency. HSC/Jacksonville, FL. Accreditation: This activity has been planned and implemented in accordance with the Essentials and Standards of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of Mount Sinai School of Medicine and Emergency Medicine Practice. The Mount Sinai School of Medicine is accredited by the ACCME to provide continuing medical education for physicians. Faculty Disclosure: Dr. Broder, Dr. Preston, Dr. Chan, and Dr. Perron report no significant financial interest or other relationship with the manufacturer(s) of any commercial product(s) discussed in this educational presentation. Commercial Support: Emergency Medicine Practice does not accept any commercial support. mergency physicians are frequently confronted however, strong evidence is lacking for many of the Ewith patients with neurological complaints clinical questions addressed. requiring emergent imaging for diagnosis and treat- Principles Of Evidence-Based Medicine ment. The diversity and variations of imaging modalities may appear confusing, resulting in physi- Imaging studies for neurological emergencies share a cian uncertainty about the most appropriate modality common problem in that the gold-standard for to evaluate the presenting complaint. An evidence- diagnosis is often another imaging study, and there is based approach, with the modality and technique no clear, independent means of settling discrepancies. selected based on patient characteristics and differen- It is unclear what strategy should be used when two tial diagnosis, is essential. In this review, the evidence imaging studies yield divergent results. For example, supporting the use of computed tomography (CT) and if CT is compared to MR for evaluation of acute magnetic resonance imaging (MRI) for the diagnosis intracranial hemorrhage, which test should serve as and treatment of emergency brain disorders will be the gold standard? Given a negative CT in the context reviewed. Adjunctive imaging techniques will also be of a positive MR, is the CT a false negative or the MR considered, including conventional angiography, plain a false positive? Alternative gold standards may films, and ultrasound. Clinical decision rules include clinical follow-up for mortality, readmission, intended to target imaging utilization to high-risk neurosurgical intervention, or neurological outcome. patients will also be discussed. When evaluating a study’s relevance to clinical practice, the strength of the gold standard must be Abbreviations Used In This Article considered. Another important concept when interpreting the CASL: Continuous Arterial Spin Labeling (an MRI results of a study is “point estimate” versus “95% technique for magnetic labeling of blood) confidence