Nontraumatic Emergent Neuroradiology: Review and Self-Assessment Module

Transcription

1 1.5 CME 1.0 SAM AJR Integrative Imaging LIFELONG LEARNING FOR RADIOLOGY Nontraumatic Emergent Neuroradiology: Review and Self-Assessment Module Yoshimi Anzai 1 and Basavaraj Ghodke 2 Abstract Objective The educational objectives for this case-based self-assessment module on imaging of nontraumatic emergent neuroradiology are to use case examples to teach the imaging features of CT and MRI of emergent neuroradiologic diagnoses and to improve the reader s understanding of the pathophysiology and clinical management of each clinical scenario. Imaging plays a critical role in assessing patients with acute neurologic symptoms. CT is quick and easy to perform in an emergency setting and is often the technique of choice for any neurologic emergency situations. Clinical correlation is crucial for accurate diagnosis and triaging patients for further evaluation. Persistent or progressive neurologic symptoms despite negative CT should prompt other imaging studies. Conclusion At the end of this self-assessment module, readers will be able to generate a concise list of differential diagnoses for imaging findings that often are encountered in patients with nontraumatic neurologic emergency. INTRODUCTION This self-assessment module on nontraumatic emergent neuroradiology diagnoses has an educational component and a self-assessment component. The educational component consists of six case scenarios that the participant should work through and four recommended articles that may provide additional information and perspective. The self-assessment component consists of 19 multiple-choice questions with solutions. All of these materials are available on the ARRS Website ( To claim CME and SAM credit, each participant must enter his or her responses to the questions online. EDUCATIONAL OBJECTIVES By completing this educational activity, the participant will: A. Exercise, self-assess, and improve his or her understanding of the imaging features of nontraumatic emergent neuroradiology diagnoses. B. Exercise, self-assess, and improve his or her understanding of the clinical features of nontraumatic emergent neuroradiology diagnoses. RECOMMENDED READING 1. Provenzale JM. Centennial dissertation. Honoring Arthur W. Goodspeed, MD and James B. Bullitt, MD. CT and MR imaging and nontraumatic neurologic emergencies. AJR 2000; 174: Wintermark M, Albers GW, Alexandrov AV, et al. Acute stroke imaging research roadmap. Stroke 2008; 39: Beauchamp NJ Jr, Bryan RN. Acute cerebral ishemic infarction: a pathophysiologic review and radiologic perspective. AJR 1998; 171: Zuccoli G, Gallucci M, Capellades J, et al. Wernicke encephalopathy: MR findings at clinical presentation in twenty-six alcoholic and nonalcoholic patients. AJNR 2007; 28: INSTRUCTIONS 1. Complete the educational and self-assessment components. 2. Visit and select Publications/Journals/ SAM Articles from the left-hand menu bar. 3. Using your member login, order the online SAM as directed. 4. Follow the online instructions for entering your responses to the self-assessment questions and complete the test by answering the questions online. Keywords: brain imaging, case-based learning, emergency, neuroradiology, self-assessment DOI: /AJR Received September 7, 2007; accepted after revision January 30, Department of Radiology, Division of Neuroradiology, University of Washington, 1959 NE Pacific St., NW 011, Box , Seattle, WA Address correspondence to Y. Anzai (anzai@u.washington.edu). 2 Department of Radiology, Harborview Medical Center, Seattle, WA. AJR 2008;191:S1 S X/08/1913 S1 American Roentgen Ray Society S1

2 Anzai and Ghodke Scenario 1 Clinical History A 32-year-old man presented to the emergency department complaining of headache and general fatigue. He was diagnosed with a viral syndrome and discharged with symptomatic treatment. Two weeks later he presented to the emergency department with severe headache and confusion. He was afebrile but his mental status had changed since his previous emergency department visit. A working diagnosis of bacterial meningitis was considered. The patient denied any focal weakness or sensory or visual changes. Unenhanced CT (Fig. 1A) and CT angiography (Fig. 1B) of the head were performed. The patient also underwent cerebral angiography (Figs. 1C and 1D). Description of Images Unenhanced CT of the head showed a large right frontal intraparenchymal hematoma with surrounding edema, likely representing a subacute intracranial hematoma. CT QUESTION 1 Which of the following is the preferred diagnosis? A. Arteriovenous malformation. B. Hypertensive hemorrhage. C. Hemorrhagic tumor or metastasis. D. Vasculitis. E. Amyloid angiopathy. A angiography did not reveal any cerebral aneurysms, arteriovenous malformation, or enhancing focus as possible causes of a hematoma. Cerebral angiography showed irregularity of small- to medium-sized vessels and a beaded appearance, consistent with vasculitis. The patient admitted that he smoked marijuana almost daily and had a long history of amphetamine use. QUESTION 2 Which one of the following is NOT associated with vasculitis? A. Polyarteritis nodosa. B. Tuberculosis. C. Systemic lupus erythematosus. D. Drugs (amphetamine, cocaine). E. Marfan syndrome. QUESTION 3 What is the most definitive test for diagnosing CNS vasculitis? A. CT angiography with 3D volume rendering. B. Cerebral angiography. C. Biopsy. D. MR angiography. E. Transcranial Doppler sonography. Fig year-old man with headache and general fatigue who was diagnosed with viral syndrome and discharged but returned with severe headache and confusion. A and B, Unenhanced CT (A) and CT angiography (B) of head were performed. Unenhanced CT shows large right frontal intraparenchymal hematoma and surrounding edema (arrow, A), likely representing subacute intracranial hematoma. CT angiography does not reveal any cerebral aneurysms, arteriovenous malformation, or enhancing focus as possible cause of hematoma. C and D, Cerebral angiography shows irregularity of small- to medium-sized vessels (arrows, D) and beaded appearance, consistent with vasculitis. Patient admitted that he smokes marijuana almost daily and has long history of amphetamine use. B C D S2

3 Nontraumatic Emergent Neuroradiology Solution to Question 1 Arteriovenous malformation (AVM) is not an unusual cause of intracranial hematoma for the young patient in this case. Patients with AVM often present with acute intracranial hemorrhage or ischemic symptoms due to steal phenomenon. CT angiography often reveals a tangle of markedly dilated arteries and veins with a nidus of AVM. If the AVM is small, it may not be visualized or diagnosed correctly with CT angiography. In this setting, cerebral angio graphy is the most definitive test. However, cerebral angio graphy in this patient did not show early venous filling or an abnormal tangle of blood vessels to indicate AVM. Therefore, option A is not the best response. Acute intracranial hematoma can have a number of causes. The most common cause is hypertensive hemorrhage. Hypertensive hemorrhages, which originate from terminal small vessels, are often centered at the basal ganglia, particularly the putamen and the external capsule; the thalamus; the pons; and occasionally, the cerebellum. Lobar hemorrhage can be seen in a setting of hypertension ( 1 2%), but it is rare. Hypertensive hemorrhage is much more common in older patients. Option B is not the correct response. Certain types of brain tumors are often associated with intracranial hemorrhage. These are often aggressive tumors, such as glioblastoma multiforme, or vascular tumors, such as metastases from renal cell carcinoma or melanoma, but rarely papillary thyroid cancer and choriocarcinoma. Lung cancer and breast cancer are not considered vascular; however, the incidence of brain metastasis from lung and breast cancers is exceedingly higher than that of other vascular cancers. Thus, when all hemorrhagic brain metastases are reviewed, lung and breast remain the two top primary choices. Intracranial hemorrhage associated with brain tumor often has a focal area of enhancement and significant mass effect or vasogenic edema. Option C is not the best response. Vasculitis is one of the causes of intracranial hemorrhage and is more frequently seen in young patients. Vasculitis can present with acute hemorrhage or ischemic symptoms. Many causes of vasculitis affect small- to medium-sized vessels; therefore, CT angiography may not show an irregularity of the blood vessels as definitively as cerebral angiography. Cerebral angiography in Figures 1C and 1D shows a classic appearance of segmental narrowing and poststenotic dilatation involving multiple small- to medium-sized blood vessels, consistent with vasculitis. Option D is the best response. Amyloid angiopathy often causes a lobar intracranial hemorrhage centered at the deep white matter in the frontal or parietal lobes. Amyloid angiopathy is much more common in elderly patients and is rare in young patients. Cerebral angiography may not show any irregularity or narrowing. Amyloid angiopathy is often diagnosed after excluding other causes in elderly patients. Option E is not the best response. Solution to Question 2 The causes of vasculitis are often divided into infectious and noninfectious. Infectious causes include tuberculosis, fungal infection, bacterial vasculitis, and HIV vasculitis. The frequent causes of noninfectious vasculitis are immune-mediated vasculitis such as rheumatoid arthritis and systemic lupus erythematosus, and granulomatous disease, such as Wegener s granulomatosis and sarcoid, as well as giant cell arteritis (also called temporal arteritis). Drugs, particularly amphetamines and cocaine, are frequent causes of noninfectious vasculitis. An amphetamine causes inflammatory vasculitis with vascular wall necrosis and subsequent hemorrhage. The pathologic features of amphetamine-related vasculitis are similar to those of polyarteritis nodosa. This patient had taken amphetamines for several years. Cocaine, on the other hand, induces cerebral infarction or ischemia as well as hemorrhage by vasoconstrictive effect and increased platelet aggregation, rather than a vasculitis-type inflammation of the vessels [1]. Options A, B, C, and D are not the best responses. Marfan syndrome is an autosomal dominant disorder of the connective tissue characterized by disproportionally long limbs and tall stature. It affects the heart and aorta and causes aortic root dilatation, aortic regurgitation, and dissection. However, involvement of CNS vessels is unusual. Option E is the best response. Solution to Question 3 Because many cases of vasculitis affect small to mediumsized blood vessels, MR angiography is relatively insensitive for the diagnosis of CNS vasculitis. CT angiography is less accurate than cerebral angiography. Cerebral angiography is used as the gold standard for diagnosis at many institutions. When characteristic angiographic findings such as alternating areas of stenosis and dilatation or a beading appearance are observed in multiple vessels and multiple vascular beds, cerebral angiography is diagnostic. However, angiography can be normal in up to 40% of biopsy-proven cases. Thus, negative cerebral angiography does not completely exclude the diagnosis. Moreover, its specificity is not perfect. Intracranial atherosclerotic disease may show irregularity of multiple vessels, mimicking CNS vasculitis. Transcranial Doppler sonography is used to characterize the morphology of the superficial temporal artery as a screening tool for temporal arteritis. However, transcranial Doppler sonography is not suitable to evaluate arteries fully to diagnose CNS vasculitis. Options A, B, D, and E are not the best responses. Biopsy of CNS tissue would logically be considered the ultimate gold standard of diagnosis, but clearly the procedure is limited by several factors. It is highly invasive and carries certain risks. Successful biopsy requires a willing and experienced neurosurgeon, who may not be readily available. Sampling error could result in limited sensitivity. The site of biopsy should be tailored to the individual patient [2]. The biopsy of the superficial temporal artery is often performed in patients suspected of having giant cell vasculitis. The false-negative rate of biopsy for a diagnosis of vasculitis has been reported to be 16%, yielding a sensi- S3

4 Anzai and Ghodke tivity of 84% [2]. Therefore, the most definitive test is biopsy of the blood vessels. Option C is the best response. Scenario 2 Clinical History A 19-year-old woman presented to an outside hospital with severe headache, nausea, vomiting, and photophobia. She had no significant medical history. Laboratory examinations were unremarkable. Her initial head CT scans (unenhanced and contrast-enhanced) are shown in Figures 2A and 2B. Description of Images Unenhanced CT of the head showed a focal area of low attenuation in the left temporal lobe and mild regional mass effect. The ventricles were normal in size with no shift of midline structures. No parenchymal hemorrhage was evident. The contrast-enhanced image showed the empty delta QUESTION 4 What is your preferred diagnosis after the initial CT scans (Figs. 2A and 2B)? A. Acute infarction of the left middle cerebral artery (MCA). B. Herpes encephalitis. C. Underlying tumor. D. Sinus thrombosis. A Conclusion Vasculitis involving the CNS presents diagnostic challenges to clinicians as well as radiologists. There are many causes, including infection, autoimmune disease, drug exposure, radiation, and malignancies. Cerebral angiography is more sensitive than noninvasive vascular imaging (CT angiography or MR angiography), but it is invasive and has limited sensitivity and specificity. Treatment of noninfectious vasculitis is long-term, high-dose immunosuppression, which causes profound morbidity as a result of opportunistic infection or organ failures. sign (Fig. 2B). Brain MRI, including sagittal T1-weighted imaging (Fig. 2C), diffusion-weighted imaging (Fig. 2D), and apparent diffusion coefficient (ADC) mapping (Fig. 2E) were also performed at the outside hospital. The sagittal T1-weighted image showed an isointense clot along the superior sagittal sinus that was of concern for superior sagittal sinus thrombosis. The diffusion-weighted image showed no areas of restricted diffusion or ADC map abnormality. The patient s mental status deteriorated at the outside hospital and she was transferred to the emergency department of our hospital, at which time she was unresponsive and obtunded, and her pupils were dilated. CT of the head was QUESTION 5 Which one of the following techniques is LEAST appropriate to confirm a diagnosis of venous sinus thrombosis? A. Rapid contrast-enhanced gradient-echo MRI with contrast-enhanced multiplanar imaging. B. MDCT angiography or venography. C. Brain MRI and phase-contrast MR venography. D. Cerebral angiography. E. Brain MRI with time-of-flight MR venography. B Fig year-old woman who presented to another hospital with severe headache, nausea, vomiting, and photophobia. A, Unenhanced CT scan of head obtained at outside hospital shows focal area of low attenuation in left temporal lobe and mild regional mass effect. Ventricles are normal in size with no shift of midline structures. No parenchymal hemorrhage is evident. B, Contrast-enhanced image from other hospital shows empty delta sign (arrows). (Fig. 2 continues on next page) S4

5 Nontraumatic Emergent Neuroradiology obtained immediately after her admission (Figs. 2F and 2G) and showed marked worsening of the cerebral edema and diffuse effacement of the cortical sulci and basilar cistern. In addition, a new focus of venous infarction and parenchymal hemorrhage was present in the left frontal lobe. Solution to Question 4 In the inferior aspect of the superior sagittal sinus on initial head CT was an area of high attenuation with a convex border that was of concern for superior sagittal sinus thrombosis. Contrast-enhanced head CT showed lack of contrast enhancement in the superior sagittal sinus, the empty delta sign. Findings were consistent with venous sinus thrombosis and venous infarction involving the left temporal lobe. The patient had been taking oral contraceptives for the previous 3 months. CT findings of middle cerebral artery (MCA) infarction are loss of gray and white matter differentiation or presence Fig. 2 (continued) 19-year-old woman who presented to another hospital with severe headache, nausea, vomiting, and photophobia. C E, Brain MR images, including sagittal T1-weighted (C), diffusion-weighted (D), and apparent diffusion coefficient (ADC) map (E) images obtained at outside hospital. T1-weighted image shows hyperintense clot along superior sagittal sinus (arrows), causing concern for superior sagittal sinus thrombosis. Diffusion-weighted images show no areas of restricted diffusion or ADC map abnormality. F and G, CT scans of head obtained immediately after admission to our hospital show marked worsening of cerebral edema and diffuse effacement of cortical sulci and basilar cistern. In addition, new focus of venous infarction and parenchymal hemorrhage (arrow, F) is present in left frontal lobe. C of an acute clot in the expected location of the proximal MCA (dense MCA sign). In this case, an area of low attenuation predominantly involved the white matter and spared the gray matter. In addition, diffusion-weighted imaging and the ADC map showed no area of restricted diffusion. Option A is not the best response. QUESTION 6 Which one of the following is NOT associated with venous sinus thrombosis? A. Sickle cell disease. B. Oral contraceptives. C. Cancer. D. Disseminated intravascular coagulation. E. Dehydration. D F E G S5

6 Anzai and Ghodke Herpes encephalitis typically involves the medial temporal lobe and is often associated with parenchymal hemorrhage. This was the diagnosis made at the outside hospital, and the patient was treated with acyclovir. However, herpes encephalitis does not explain the presence of a clot in the superior sagittal sinus. Option B is not the best response. The presence of tumor with vasogenic edema is also a possibility based on the area of low attenuation in the left temporal lobe. However, this does not explain the presence of a clot in the superior sagittal sinus. Option C is not the best response. The correct diagnosis is venous sinus thrombosis and venous infarction involving the left temporal lobe. Option D is the best response. The venous sinus can show slightly high attenuation, particularly among athletes, smokers, or neonates. The lateral border of the venous sinus, in these normal settings, should be concave, not convex toward the brain parenchyma. After the administration of contrast material, the dura may enhance but the venous sinus does not, giving the empty delta sign. Venous sinus thrombosis can be a challenging diagnosis to make unless one has a high clinical suspicion. Patients present with nonspecific headache or confusion, and a clinical history of oral contraceptive use is often not available to radiologists at the time of interpretation. Sagittal T1-weighted MR images at the outside hospital showed lack of flow void along the superior sagittal sinus, highly suggestive of the diagnosis. Please note that diffusion-weighted images and the ADC map did not necessarily show an area of restrictive diffusion in the setting of venous infarction because increased venous pressure initially causes vasogenic edema. This is distinctly different from arterial infarction, when the arterial supply to an area of the brain is abruptly terminated, resulting in cytotoxic edema. Lack of diffusion signal change should not exclude venous infarction. However, venous infarction does progress to cytotoxic edema with restricted diffusion if the disease remains untreated. Solution to Question 5 The next diagnostic test to confirm venous sinus thrombosis is brain MRI with MR venography. On conventional MRI, venous sinus thrombosis may be suspected from lack of a flow void or high-signal thrombus in the dural sinuses. Lack of flow void is best appreciated on FLAIR or T2- weighted spin-echo images. Parenchymal changes, such as venous infarction or hemorrhage, along with lack of a flow void on conventional MRI raises the suspicion of venous sinus thrombosis. Superacute thrombus is relatively isointense on T1- and hypointense on T2-weighted images because of deoxyhemoglobin potentially mimicking slow venous flow on conventional MR images and thus requiring MR venography to confirm the diagnosis of venous sinus thrombosis [3]. A subacute blood clot in the venous sinus is often seen as hyperintense on T1-weighted images as a result of methemoglobin mimicking flowing blood on time-offlight (TOF) MR venography. Phase-contrast MR venography is a fairly reliable test for the diagnosis of subacute venous sinus thrombosis. Recently, rapid contrast-enhanced gradient-echo imaging has been reported to yield a higher diagnostic accuracy than 2D TOF MR venography [4, 5]. With advances in MDCT technology, CT angiography and venography have been increasingly used to diagnose venous sinus thrombosis and are considered a quick and reliable alternative to MR venography. Options A, B, C, and E, the appropriate next tests to confirm venous sinus thrombosis, are not the best responses. Cerebral angiography also shows lack of flow in the dural venous sinuses. However, cerebral angiography is an invasive test that is associated with complication rates of 1 2%. Noninvasive imaging should be considered first to confirm the diagnosis of venous sinus thrombosis. Option D, which is the least appropriate technique, is the best response. Solution to Question 6 Common medical conditions associated with venous sinus thrombosis are pregnancy, a postpartum state, and hypercoagulable states such as sickle cell disease, oral contraceptives use, and cancer. Dehydration often seen in neonates and elderly patients is associated with venous sinus thrombosis as a result of low-flow circulatory states. Extrinsic compression (tumor) or adjacent infection (mastoiditis) is also a risk factor. Options A, B, C, and E are not the best responses. Disseminated intravascular coagulation, however, is a hypocoagulable state and is not associated with venous sinus thrombosis. Option D is the best response. Venous sinus thrombosis is an underdiagnosed condition and can be a life-threatening disease if left untreated. Delay in diagnosis often leads to rapid deterioration and poor clinical outcomes. Intracranial hemorrhage is associated with 20 50% of cases of venous sinus thrombosis. Treatment for venous sinus thrombosis is immediate IV anticoagulation with low-molecular-weight heparin, despite the risk of hemorrhagic complications [6]. Conclusion Venous sinus thrombosis is an underdiagnosed condition that can potentially lead to adverse clinical sequelae. Findings on contrast-enhanced CT or conventional T1-weighted sagittal images should make one suspicious in the appropriate clinical setting. Understanding the risk factors and medical history of patients will help to guide further diagnostic testing and immediate treatment. S6

7 Nontraumatic Emergent Neuroradiology Scenario 3 Clinical History A 48-year-old woman presented to the emergency department with the worst headache of my life and a declining level of consciousness. No known medical history or medication use was noted. Unenhanced CT of head was first performed. Fig year-old woman with the worst headache of my life and declining level of consciousness. A and B, Unenhanced CT scans show diffuse subarachnoid hemorrhage in basilar cistern and sylvian fissures bilaterally and along anterior falx, associated with intraventricular hemorrhage. Temporal horns of lateral ventricle are mildly dilated, suggestive of developing hydrocephalus. Focal hematoma (arrow) in medial frontal region is also evident. C and D, Thin-slice maximum-intensity-projection (C) and 3D volume-rendering (D) images show lobulated saccular aneurysm (arrow) arising from anterior communicating artery and measuring approximately 5 mm. Proximal A2 segments (arrowhead, D) of anterior cerebral arteries are displaced laterally, likely due to surrounding aneurysm. E, Three-dimensional rotational angiography shows detailed anatomy and morphology of anterior communicating aneurysm, adjacent ophthalmic artery, and perforating arteries (arrow), which are not easily visualized on CT angiography. A Description of Images Unenhanced head CT (Figs. 3A and 3B) showed diffuse subarachnoid hemorrhage in the basilar cistern and sylvian fissures bilaterally and along the anterior falx, associated with intraventricular hemorrhage. The temporal horns of the lateral ventricle were mildly dilated, suggestive of developing hydrocephalus. Focal hematoma in the medial frontal region was also evident. The patient underwent CT angiography of head for further evaluation. Thin-slice maximum-intensity-projection (Fig. 3C) and 3D volumerendering (Fig. 3D) images showed a lobulated saccular aneurysm arising from the anterior communicating artery and measuring approximately 5 mm. The proximal A2 segments of the anterior cerebral arteries were displaced laterally, likely due to the presence of hematoma surrounding the aneurysm. Three-dimensional rotational angiography (Fig. 3E) showed detailed anatomy and morphology of the anterior communicating aneurysm and the adjacent ophthalmic artery and perforating arteries, which are not easily visualized on CT angiography. B D C E S7

8 Anzai and Ghodke QUESTION 7 What is the most likely cause of the findings on unenhanced CT? A. Arteriovenous malformation rupture. B. Venous sinus thrombosis. C. Cerebral aneurysm rupture. D. Amyloid angiopathy. E. Hypertensive hemorrhage. QUESTION 8 What is the 30-day mortality rate of subarachnoid hemorrhage secondary to aneurysm? A. 15%. B. 30%. C. 45%. D. 65%. E. 80%. QUESTION 9 Which of the following factors does NOT influence management decisions for a ruptured aneurysm? A. Age. B. Sex. C. Aneurysm size. D. Aneurysm location. E. History of hypertension. QUESTION 10 Despite CT angiography showing an aneurysm causing subarachnoid hemorrhage, cerebral angiography is still performed at some institutions. Which one of the following is NOT a rationale for performing cerebral angiography in this setting? A. Searching for an additional incidental aneurysm that could be treated at the same time. B. Better assessing the degree of incorporation of the aneurysm wall into the parent vessel. C. Assessing flow dynamics that is, the side of the internal carotid artery feeding anterior communicating aneurysm. D. Measuring the aneurysm neck dome ratio. E. Suspecting mycotic aneurysm in patients with IV drug use. Solution to Question 7 Arteriovenous malformation (AVM) is a congenital anomaly of blood vessels with one or more large feeding arteries and drainage veins. AVM often presents not only with subarachnoid hemorrhage but also with parenchymal hemorrhage or symptoms of ischemia due to steal phenomenon. Blood flow preferentially goes to AVMs with low resistance, leaving the adjacent normal brain relatively hypoperfused. CT may show a hyperdense mass or curvilinear or speckled calcification adjacent to a parenchymal hematoma. MRI may show numerous foci of flow voids and venous aneurysmal dilatation. Option A is not the best response. Venous sinus thrombosis could present with subarachnoid hemorrhage; however, it tends to be focal to the area of venous infarction or hypertension. Venous sinus thrombosis does not normally present diffuse subarachnoid hemorrhage. Option B is not the best response. Unenhanced CT of the head shows diffuse subarachnoid hemorrhage as well as a focal hematoma along the anterior falx, a typical location for a ruptured anterior communicating artery aneurysm. Option C is the best response. Approximately 50 70% of subarachnoid hemorrhages are due to aneurysm rupture. Of patients with subarachnoid hemorrhage, 10 15% have no aneurysm found even on cerebral angiography. Amyloid angiopathy commonly affects elderly patients and presents with a lobar rather than a subarachnoid hemorrhage. Option D is not the best response. Hypertensive hemorrhage often affects the small perforating vessels along the lenticulostriate or thalamoperforating vessels and thus is often present with parenchymal hemorrhage in the basal ganglia, thalamus, and pons. Option E is not the best response. Solution to Question 8 Aneurysmal subarachnoid hemorrhage (SAH) has a 30-day mortality rate of 45%, with approximately half of the survivors sustaining irreversible brain damage [7]. Option C is the best response. The annual incidence of aneurysmal SAH is six per 100,000 in the United States. Approximately 5 10% of stroke cases are secondary to ruptured saccular aneurysms [8]. Recurrent hemorrhage remains a serious consequence, with a 70% fatality rate in patients who rebleed. Solution to Question 9 Treatment options for a ruptured aneurysm are surgical resection or endovascular coil embolization. Endovascular occlusion of aneurysms using electrolytically detachable Guglielmi detachable coil system (GDC, Target Therapeutics [now Boston Scientific]) has been used to treat ruptured or unruptured aneurysms in a large number of patients worldwide. Published reports suggest that the endovascular technique is associated with fewer treatment-related complications than open surgery [7]. However, the long-term efficacy in the prevention of rupture or recurrence of aneurysm remains indeterminate. The recent International Subarachnoid Aneu- S8

9 Nontraumatic Emergent Neuroradiology rysm Trial (ISAT) showed that retreatment was performed in 17.4% of patients treated with endovascular coiling and in 3.8% of patients after surgical clipping [9]. Younger age and larger aneurysm size were risk factors for retreatment. A higher rate of recurrence is seen in posterior communicating artery aneurysms after endovascular coiling and anterior communicating artery aneurysms after surgical clipping, which might reflect the technical difficulty. Hyper tension is also associated with an increasing rate of rupture in patients with an unruptured aneurysm. Thus age, medical history such as hypertension, aneurysm location, and size are all relevant factors in treatment decisions and, therefore, options A, C, D, and E, all relevant factors in treatment decisions, are not the best responses. Although aneurysms are more common in women than in men, sex is not a factor affecting management decisions or predicting outcomes. Option B is the best response. Solution to Question 10 CT angiography is a noninvasive vascular imaging technique that has replaced catheter angiography in some institutions. CT angiography may show aneurysms larger than 3 mm with a sensitivity of 77 97% and specificity of % [10]. CT angiography also has been used as a screening tool in populations at high risk for cerebral aneurysms. Cerebral angiography, however, still remains the gold standard in the diagnostic evaluation of cerebral aneurysms. In particular, 3D rotational angiography shows the most information about Scenario 4 Clinical History A 65-year-old woman presented to the emergency department 4 hours after the onset of right-sided weakness and dysarthria. Unenhanced CT of the head was obtained. Description of Images Unenhanced CT of the head (Figs. 4A and 4B) showed loss of gray white matter differentiation in the left insular cortex and the temporal lobe. The left middle cerebral artery was hyperdense compared with the basilar artery. The patient underwent cerebral angiography for potential endovascular intervention. A left internal carotid artery injection image (Fig. 4C) showed the presence of a clot in the right internal carotid bifurcation and no flow visible in the anterior and middle cerebral arteries. The microcatheter was placed proximal to the clot before advancing the Merci retrieval device (Merci Retrieval System, Concentric Medical, Inc.) (Fig. 4D). Subsequent angiography showed persistent occlusion of the MCA branches (Fig. 4E). Intraarterial tissue plasminogen activator (tpa) was infused through the left MCA; after tpa infusion, angiography (Fig. 4F) showed opening of the anterior division of the left MCA and occlusion of the posterior division of the left MCA. small perforating vessels, the relationship of the aneurysm to the parent vessels (how much of the aneurysm wall is incorporated into the parent vessel), and the flow dynamics of aneurysms that affect surgical planning. Multiple aneurysms can be seen in patients with subarachnoid hemorrhage. These incidental aneurysms are often smaller than 3 mm, which CT angiography has a limited ability to detect. Small unruptured aneurysms are associated with a risk of future SAHs. If they are in a surgically or endovascularly accessible location, these incidental aneurysms can be treated at the same time as the ruptured primary aneurysm. Mycotic aneurysms often involve peripheral vessels and may present with subarachnoid or parenchymal hemorrhage or septic emboli. Because mycotic aneurysms involve distal vessels, cerebral angiography is a more definitive test than CT angiography. Options A, B, C, and E are not the best responses. The aneurysm neck dome ratio can be calculated on the basis of CT angiography. Option D is the best response. Conclusion SAH associated with aneurysm rupture has high rates of mortality and morbidity. Accurate detection and assessment of cerebral aneurysm lead to proper treatment decisions by either surgical clipping or endovascular coiling. Although CT angiography has rapidly replaced cerebral angiography in some institutions, 3D rotational angiography provides the most information regarding characterization of aneurysms in relation to parent or adjacent vessels. QUESTION 11 Assuming the patient does not have any medical conditions, what would be the most appropriate urgent therapy at this point? A. IV recombinant tissue plasminogen activator (tpa). B. IV streptokinase. C. IV heparin. D. Antiplatelet therapy and aspirin. E. Intraarterial tpa and mechanical clot removal. QUESTION 12 What percentage of patients with acute ischemic stroke are treated with IV tpa? A. Less than 6%. B. 8 15%. C %. D %. E %. S9

10 Anzai and Ghodke QUESTION 13 Which of the following is NOT associated with poor neurologic outcomes in patients with acute ischemic infarction? A. Hypoventilation. B. Extensive area of low attenuation and mass effect on initial head CT. C. Hyperglycemia. D. Hypothermia. E. Arrhythmia. A D Solution to Question 11 Current therapy for acute stroke is limited to IV recombinant tpa administered within 3 hours of symptom onset. The results of the National Institute of Neurologic Disorders and Stroke (NINDS) tpa trial showed that the use of tpa within 3 hours of ischemic stroke onset substantially improved functional outcomes compared with a placebo group at 3 months [11]. Based on this trial, for every 100 patients given tpa, 12 more experienced complete neurologic recovery than patients given a placebo. The European Corporative Acute Stroke (ECASS) randomized trial of tpa using a 6-hour therapeutic window did not show an overall benefit, primarily because of a high rate of cerebral hemorrhage [12]. The current strict Fig year-old woman 4 hours after onset of right-sided weakness and dysarthria who underwent cerebral angiography for potential endovascular intervention. A and B, Unenhanced CT scans show loss of gray matter white matter differentiation (arrowheads) in left insular cortex and temporal lobe. Left middle cerebral artery (MCA) is hyperdense compared with basilar artery (arrow, A). C, Left internal carotid artery injection image shows presence of clot (arrow) in internal carotid bifurcation and no flow visible in anterior and middle cerebral arteries. D, Unsubtracted angiography shows microcatheter placed proximal to clot (arrow) before retrieval device was advanced. E, Subsequent angiography shows persistent occlusion of MCA branches (arrow). Intraarterial tissue plasminogen activator (tpa) was infused through left MCA. F, After infusion, tpa angiography shows opening of anterior division of left MCA and occlusion (arrow) of posterior division of left MCA. B E C F S10

11 Nontraumatic Emergent Neuroradiology guideline is that IV tpa must be given within 3 hours of stroke onset. Option A is not the best response. Although administration of tpa after the 3-hour window may benefit some patients, the interval between onset of symptoms and initiation of thrombolysis remains the most critical factor in treatment, because therapeutic efficacy decreases even within the 3-hour window [12]. Clearly, time is brain. Whether diffusion perfusion mismatch can be used to better triage patients who benefit from endovascular treatment beyond the 6-hour window is yet to be determined in a large clinical trial. Streptokinase, used to treat acute ischemic stroke, is no longer used because of unacceptably high rates of hemorrhage. It should not be used. Option B is not the best response. Another thrombolytic agent, urokinase, has been occasionally used intraarterially to treat vertebral and basilar thrombosis in some institutions up to 24 hours after symptom onset. A randomized controlled trial from the International Stroke Trial showed that fewer recurrent ischemic strokes occur in patients given heparin, but this improvement was offset by an increase in hemorrhagic stroke [13]. Recent evidence does not support the routine use of heparin in patients with acute stroke. Option C is not the best response. The study evaluating the value of aspirin enrolled a large number of subjects. Aspirin was started between 12 and 24 hours after stroke onset. The results showed that aspirin significantly improved outcomes at 6 months, but the magnitude of the reduction was small. The early use of aspirin offers only modest benefit [14]. Option D is not the best response. Intraarterial tpa and mechanical clot removal can be performed up to 6 hours after the onset of symptoms to an area of blood clot via a microcatheter to an area of blood clot. The presence of intracranial hemorrhage, severely elevated blood pressure, low platelet count, anticoagulation therapy, and end-stage liver or kidney disease excludes the use of tpa. Option E is the best response. Solution to Question 12 Neurons die within a few minutes of oxygen deprivation. Neuronal death occurs in areas of no blood flow within a few minutes of stroke onset. Adjacent to such areas of neuronal death is a region of hypoperfused, electronically silent tissues that receive barely enough blood flow to keep neurons alive. This tissue is called the ischemic penumbra. A major goal of acute stroke management is resuscitation of the ischemic penumbra. Because neuronal death is time-dependent, it is critical to intervene as early as possible. Treatment of acute ischemic stroke with IV tpa has proven to be efficacious in clinical trials by reducing functional disability. However, only a fraction of patients with ischemic stroke receive IV tpa. In a community-based observational study of 13,440 patients, approximately 3% of all ischemic stroke patients, and 10.4% of patients admitted within 3 hours of stroke onset were treated with tpa [15]. Multicenter studies also report the rate of tpa use outside clinical trials ranges from 1.6% to 6%. Option A is the best response. Solution to Question 13 Maintaining adequate tissue oxygenation is critical in the setting of acute stroke to prevent hypoxia and potential worsening of brain damage. Patients with decreased consciousness or brain stem dysfunction have the greatest risk of airway compromise. The prognosis of a patient who requires endotracheal intubation is generally poor; approximately 50% of these patients die within 30 days of their stroke. Option A is not best response. An extensive area of low attenuation on initial head CT indicates widespread damage to the brain tissue. An early infarct sign on unenhanced CT involving more than one third of the territory of the middle cerebral infarction indicates a poor outcome. The presence of mass effect or edema is also associated with an eightfold increase in the risk of symptomatic hemorrhage [11]. Option B is not the best response. Hyperglycemia is associated with poor clinical outcomes, presumably due to increased tissue acidosis secondary to anaerobic glycolysis and lactic acidosis. Hyperglycemia may affect the blood brain barrier and lead to brain edema. Hypoglycemia may cause focal neurologic signs and symptoms that mimic acute ischemic stroke. Hypoglycemia itself may aggravate neuronal ischemia. The prompt assessment of the serum glucose level and correction of the glucose level are important. Option C is not the best response. Fever in the setting of acute ischemic stroke is associated with a poor neurologic outcome secondary to increased metabolic demands and enhanced release of neurotransmitters. Hypothermia is not associated with poor clinical outcomes. In fact, hypothermia has been reported to be neuroprotective in experimental models and small clinical trials. Hypothermia may delay depletion of the energy reserve, slow tissue acidosis, and slow calcium iron influx into cells. Option D is the best response. Patients with acute ischemic stroke have an increased risk of developing myocardial infarction and cardiac arrhythmia. Patients with infarctions of the right hemisphere, particularly those involving the insula, may have an increased risk of cardiac complications, presumably secondary to disturbances in autonomic nervous system function. The most common arrhythmia associated with acute stroke is atrial fibrillation, which may be either the cause of stroke or a complication. Life-threatening arrhythmia is relatively uncommon, but sudden death may occur. Cardiac monitoring is often required for at least first 24 hours after the onset of stroke symptoms. Option E is not the best response. Conclusion Stroke continues to have a devastating impact on public health and is the third leading cause of death in the United States. At least 700,000 new stroke cases occur every year. Approximately 85% of all strokes are ischemic in nature. Because of the narrow therapeutic windows for treatment of acute ischemic stroke, timely evaluation, diagnosis, and treatment are of paramount importance. S11

12 Anzai and Ghodke Scenario 5 Clinical History A 38-year-old woman presented to the emergency department with severe headache, nausea, and vomiting. Unenhanced CT of the head was ordered. The patient had a declining level of consciousness and was admitted on that day. MRI of the brain was performed 2 days later. The patient also had a history of a heart transplantation. Description of Images Unenhanced CT of the head showed a vague area of low attenuation in the right cerebellar hemisphere and mild mass effect on the right aspect of the fourth ventricle (Figs. 5A and 5B). Otherwise, no hemorrhage, hydrocephalus, or midline shift was present. Contrast-enhanced MRI was recommended for further imaging workup. QUESTION 14 What is your preferred diagnosis in this patient? A. Brain metastases. B. Multiple sclerosis. C. Tuberculosis. D. Septic emboli. E. CNS lymphoma. QUESTION 15 Which of the following in a patient s medical history is LEAST likely to be associated with septic emboli in the brain? A. Organ transplantation with pulmonary infection. B. Cancer and presently receiving systemic chemotherapy. C. IV drug abuse. D. Recent travel to Southeast Asia. E. Aortic valve replacement and endocarditis. QUESTION 16 What are the characteristic MRI findings of disseminated cerebral aspergillosis in immunocompromised patients? A. Numerous foci of restricted diffusion in the corticomedullary junction, basal ganglia, and thalami, with minimum or no enhancement. B. Markedly bright signal on diffusion-weighted images. C. Involvement of the middle cerebellar peduncle. D. Leptomeningeal invasion. E. Infection in the paranasal sinuses. FLAIR images (Figs. 5C and 5D) showed numerous foci of hyperintensity throughout the cerebral and cerebellar hemispheres, predominantly at the corticomedullary junction. Some lesions were seen in the basal ganglia as well as the thalamus. The extent of disease on MRI was much more than expected from head CT performed 2 days earlier, indicating rapid progression of the disease process. These numerous foci were markedly hyperintense on diffusion-weighted images (Figs. 5E and 5F). Contrast-enhanced images showed no area of abnormal enhancement on any of the lesions (Fig. 5G). Solution to Question 14 In this patient, the combination of rapid progression of disease, numerous small foci of restricted diffusion, and lack of enhancement makes septic emboli the most likely diagnosis. Option D is the best response. Brain metastasis and CNS lymphoma usually do enhance, making options A and E incorrect responses. Tuberculosis can have numerous small foci of parenchymal lesions, or could be miliary tuberculosis less than 2 mm in size. However, CNS tuberculous lesions are typically associated with a rim of enhancement or the target sign on gadolinium-enhanced images. Restricted diffusion is not typical for CNS tuberculosis. Option C is not the best response. The lesions involve both gray matter and white matter, and the rapid progression of disease is highly unusual for multiple sclerosis. Option B is not the best response. Solution to Question 15 Septic emboli are often seen in immunocompromised patients such as those who have undergone organ transplantation, those who have AIDS, and patients who have undergone chemotherapy. In these cases, organisms may include tuberculosis or fungal infections. Among immunocompetent patients, infection with Staphylococcus organisms is most often seen in IV drug abusers or in patients with endocarditis. Options A, B, C, and E are not the best responses. A history of recent travel to Southeast Asia can be seen in other infections such as tuberculosis, brucellosis, West Nile virus, hepatitis, and malaria. This is not the expected history in this patient. Option D is the best response. This patient had a history of heart transplantation and pulmonary aspergillosis. Pulmonary aspergillosis in severely immunocompromised patients is highly invasive and has a dismal prognosis (near 100% mortality). It quickly gains access to the systemic circulation and is disseminated throughout the body, including the brain. This patient died 4 days after MRI was performed. Solution to Question 16 Disseminated cerebral aspergillosis infection in immunocompromised patients is most often caused by hematogenous spread from pulmonary infection. Hematogenous, or angioinvasive, Aspergillus organisms characteristically S12

13 Nontraumatic Emergent Neuroradiology A D Fig year-old woman with severe headache, nausea, and vomiting. Patient had history of heart transplantation. A and B, Unenhanced CT scans of head shows vague area of low attenuation in right cerebellar hemisphere and mild mass effect on right aspect of fourth ventricle (arrow, A). No hemorrhage, hydrocephalus, or midline shift is present. C G, MR images of brain obtained 2 days after A and B. FLAIR images (C and D) show numerous foci of hyperintensity throughout cerebral and cerebellar hemispheres, predominantly at corticomedullary junction. Some lesions are seen in basal ganglia as well as thalamus. Extent of disease is more than expected from CT, indicating rapid progression of disease process. These numerous foci are markedly hyperintense on diffusion-weighted images (E and F). Contrast-enhanced T1-weighted image (G) shows no area of abnormal enhancement on any lesions. B E C F G S13

14 Anzai and Ghodke Scenario 6 Clinical History A 27-year-old woman with a 2-week history of nausea and vomiting after a recent cholecystectomy presented to the emergency department with abdominal pain and nausea. Abdominal CT and pelvic sonography were negative. The patient later developed slurred speech and confusion. Brain MRI was performed (Figs. 6A 6D). QUESTION 17 What is the diagnosis given the imaging abnormality and clinical presentations? A. Creutzfeldt-Jakob disease. B. Leigh disease. C. Wernicke s encephalopathy. D. Maple syrup urine disease. E. Wilson s disease. lodge inside medium-sized blood vessels, resulting in multifocal infarction, and then invade through the vascular walls, causing hemorrhagic transformation or direct extension into the parenchyma. This vasculopathy-mediated septic infarction has regional vulnerability to basal ganglia or thalami, in addition to the corticomedullary junction. The predilection to basal ganglia and thalami indicates involvement of the lenticulostriate and thalamoperforating arteries. Aspergillosis often destroys the internal elastic lamina of the cerebral arteries. Perforating vessels are the first ones to lose their patency because of their narrow diameter. MRI characteristics of disseminated aspergillosis involvement of the brain in 18 patients was reported by De- Lone et al. [16] and others [17, 18]. Those authors reported that the typical MRI appearance is a predilection to basal ganglia or thalami. Enhancement was minimal or absent. Lack of enhancement is most likely related to the host s immune capacity. Severely immunocompromised patients have no or little immune capacity to react to an infectious organism to form capsule or inflammatory response; thus, lack of enhancement may indicate poor prognosis and rapid dissemination of angioinvasive aspergillosis. Option A is the best response. Marked bright signal on diffusion-weighted images in this patient likely reflects infarction and cytotoxic edema. Numerous foci of restricted diffusion can be seen in patients with embolic infarction, brain abscesses, and metastases from highly cellular tumors [19]. Option B is not the best response. Neither involvement of the middle cerebellar peduncle nor leptomeningeal involvement is a typical finding for disseminated aspergillosis. Options C and D are not the best responses. Involvement of the paranasal sinuses is often seen in diabetic patients who have angioinvasive mucormycosis. Mucormycosis is a rare opportunistic infection caused by ubiquitous fungi typically found in soil or dust. The route of infection is usually rhinocerebral and is commonly seen in patients with uncontrolled diabetes, which is often associated with metabolic acidosis or ketoacidosis [20]. Mucormycosis can spread from the paranasal sinuses to the brain in a few days. Treatment should include aggressive débridement and IV amphotericin B. Option E is not the best response. Conclusion Rapid progression, early ischemic manifestation, and predilection for the perforating arteries are characteristic features of disseminated aspergillosis infection in severely immunocompromised patients. Diagnosis should be made when clinical suspicion is high so that aggressive IV antifungal therapy can be initiated. Description of Images FLAIR images showed bilateral symmetric hyperintensity involving the mamillary bodies, the medial thalami along the third ventricle, and the periaqueductal gray matter. Diffusion-weighted images also showed an area of hyperintensity in the medial thalami. QUESTION 18 Which of the followings is LEAST likely to be a risk factor for Wernicke s encephalopathy? A. Chronic alcoholism. B. Prolonged parenteral nutrition without a vitamin supplement. C. Hyperemesis gravidarum. D. Gastrectomy. E. Anorexia nervosa. QUESTION 19 Which one of the following is a characteristic clinical feature of Wernicke s encephalopathy? A. Learning disability. B. Rigidity and tremor. C. Visual hallucination. D. Nystagmus and bilateral lateral rectus paralysis. E. Global ataxia. S14

15 Nontraumatic Emergent Neuroradiology Fig year-old woman with 2-week history of nausea and vomiting after recent cholecystectomy. Patient presented with abdominal pain and nausea. A D, FLAIR images show bilateral symmetric hyperintensity involving mamillary bodies, medial thalami along third ventricle, and periaqueductal gray matter (arrows, A C). Diffusion-weighted image (D) also shows area of hyperintensity in medial thalami. Solution to Question 17 Brain MRI shows T2 hyperintensity predominantly involving the medial thalami, periaqueductal gray matter, and mamillary bodies. The distribution of signal abnormalities on MRI and a history of prolonged emesis make Wernicke s encephalopathy the most likely diagnosis. Wernicke s encephalopathy is a severe neurologic disorder caused by thiamine (vitamin B 1 ) deficiency. It is a disabling and potentially lethal condition that can be prevented or reversed if treated early. It is often unrecognized and is likely more prevalent than reported. Wernicke s encephalopathy can progress to a state of chronic amnesia called Korsakoff s syndrome. Patients suffering from Wernicke s encephalopathy show degeneration of the diencephalic regions, specifically the mamillary bodies and the medial thalamic nuclei along the mammillothalamic tract. Option C is the best response. A C Creutzfeldt-Jakob disease (CJD) is a rare neurodegenerative disorder that is currently thought to be caused by an abnormal protein called prion. Pathologically, CJD leads to spongiform encephalopathy. Patients with CJD often present with progressive dementia. CJD is divided into three types: sporadic CJD, with no known risk factors, the most common type in the United States; hereditary CJD, associated with genetic mutation; and acquired CJD, which is acquired by medical procedures such as corneal transplantation, human growth hormone injection, and so forth. Bovine spongiform encephalopathy (BSE) or mad cow disease, is called variant CJD, and is believed to be due to the ingestion of infected beef. The signal abnormality on FLAIR and diffusion images is seen in the cerebral cortex, striatum, and posterior thalami. Mamillary bodies are not usually involved in CJD. Option A is not the best response. B D S15