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1 Department of Radiology, Division of Neuroradiology, University of Washington,
1959 NE Pacific St., NW 011, Box 357115, Seattle, WA 98195-7115.
2 Department of Radiology, Harborview Medical Center, Seattle, WA.
Received September 7, 2007;
accepted after revision January 30, 2008.
Address correspondence to Y. Anzai
(anzai{at}u.washington.edu).
Abstract
 Top Abstract INTRODUCTIONEDUCATIONAL OBJECTIVESRECOMMENDED READINGINSTRUCTIONSReferences |
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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.
Keywords: brain imaging • case-based learning • emergency • neuroradiology • self-assessment
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TopAbstractINTRODUCTIONEDUCATIONAL OBJECTIVESRECOMMENDED READINGINSTRUCTIONSReferences |
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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).
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| QUESTION 1 Which of the following is the preferred diagnosis?
QUESTION 2 Which one of the following is NOT associated with vasculitis?
QUESTION 3 What is the most definitive test for diagnosing CNS vasculitis?
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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 medium-sized 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 sensitivity of 84% [2]. Therefore, the most definitive test is biopsy of the blood vessels. Option C is the best response.
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.
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.
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| QUESTION 4 What is your preferred diagnosis after the initial CT scans
(Figs. 2A and
2B)?
QUESTION 5 Which one of the following techniques is LEAST appropriate to confirm a diagnosis of venous sinus thrombosis?
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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 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?
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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-of-flight (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.
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.
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
volume-rendering (Fig. 3D)
images showed a lobulated saccular aneurysm arising from the anterior
communicating artery and measuring approximately 5 mm.
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| QUESTION 7 What is the most likely cause of the findings on unenhanced
CT?
QUESTION 8 What is the 30-day mortality rate of subarachnoid hemorrhage secondary to aneurysm?
QUESTION 9 Which of the following factors does NOT influence management decisions for a ruptured aneurysm?
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?
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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 Aneurysm 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 87–100% [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 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.
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.
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| QUESTION 11 Assuming the patient does not have any medical conditions,
what would be the most appropriate urgent therapy at this point?
QUESTION 12 What percentage of patients with acute ischemic stroke are treated with IV tPA?
QUESTION 13 Which of the following is NOT associated with poor neurologic outcomes in patients with acute ischemic infarction?
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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
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.
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.
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| QUESTION 14 What is your preferred diagnosis in this patient?
QUESTION 15 Which of the following in a patient's medical history is LEAST likely to be associated with septic emboli in the brain?
QUESTION 16 What are the characteristic MRI findings of disseminated cerebral aspergillosis in immunocompromised patients?
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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).
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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 lesionsare 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 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 anti-fungal therapy can
be initiated.
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,
6B,
6C,
6D).
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| QUESTION 17 What is the diagnosis given the imaging abnormality and
clinical presentations?
QUESTION 18 Which of the followings is LEAST likely to be a risk factor for Wernicke's encephalopathy?
QUESTION 19 Which one of the following is a characteristic clinical feature of Wernicke's encephalopathy?
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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 B1)
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.
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.
Leigh disease is a mitochondrial disorder caused by pyruvate carboxylase deficiencies. It leads to necrotizing encephalomyelopathy. Leigh disease often affects the putamina bilaterally, other deep gray matter structures, and the brain stem [21]. Option B is not the best response.
Maple syrup urine disease results from severe inherited defects in branched-chain amino acids. Patients are unable to catabolize branched-chain amino acids (leucine, isoleucine, and valine), which are increased in the blood and urine. The primary therapy is a protein-restricted diet. MRI findings are white matter involvement in the cerebellum, the periaqueductal gray matter along the dorsal midbrain, the cerebral peduncle, and the basal ganglia and thalami. Mamillary bodies are not involved. Patients with maple syrup urine disease present as newborns or in infancy. Option D is not the best response.
Wilson's disease is an autosomal recessive disorder. The Wilson's disease gene is mapped to chromosome 13. The main feature is accumulation of copper in the tissues, predominantly in the cornea, brain, and liver. A suppressed level of ceruloplasmin is observed in more than 80% of patients. Clinical symptoms include dysarthria, dystonia, rigidity, and ataxia. MRI findings in Wilson's disease are signal abnormality in the lentiform nucleus and the thalami as well as tegmentum of the midbrain, red nuclei, and substantia nigra. Periaqueductal gray matter involvement has been reported in Wilson's disease. Mamillary bodies are not normally abnormal in Wilson's disease. Option E is not the best response.
Solution to Question 18
Wernicke's encephalopathy is a neurologic disorder with acute onset. It is
caused by a thiamine deficiency due to poor oral intake in chronic alcoholics,
food refusal in anorexia nervosa, or recurrent vomiting in pregnant patients.
Approximately 50% of patients with Wernicke's encephalopathy are not
alcoholic. This patient presented with 2 weeks of nausea and vomiting. Other
causes include chronic infection and a febrile status, pancreatitis, cancer,
chronic dialysis, and prolonged parenteral hyperalimentation without a vitamin
supplement [22]. Options A, B,
C, and E are not the best responses.
Gastrectomy is often associated with vitamin B12 deficiencies. In order for vitamin B12 to be absorbed from the small bowel, it needs to be chemically linked to an intrinsic factor that is produced in the stomach. Gastrectomy leads to malabsorption of vitamin B12, which results in pernicious anemia. Gastrectomy is least likely to be associated with Wernicke's encephalopathy. Option D is the best response.
Solution to Question 19
The triad of encephalopathy, ataxic gait, and oculomotor dysfunction is
seen in only one third of patients with Wernicke's encephalopathy. Ocular
abnormalities are the hallmarks of Wernicke's encephalopathy. The oculomotor
signs are nystagmus, bilateral lateral rectus palsies, and conjugate gaze
palsies reflecting involvement of the oculomotor and abducens nerves.
Option D is the best response. Gait ataxia is believed to be due to
focal midline degeneration of the superior vermis, as opposed to global
ataxia, a sign of cerebellar dysfunction. Option E is not the best response.
Cerebellar testing with the finger-to-nose or heel-to-shin test may not elicit
any notable deficit. Vestibular dysfunction without hearing loss is also a
common finding.
Rigidity and tremor as well as bradykinesia and postural instability are common symptoms seen in patients with Parkinson's disease, not in patients with Wernicke's encephalopathy. Visual hallucination is associated with psychiatric disorders and drugs, particularly alcohol. Patients with schizo phrenia often have visual and, more often, auditory hallucinations. Learning disability refers to a group of disorders affecting academic and functional skills, including the abilities to listen, speak, write, read, and organize information. It is not specific for Wernicke's encephalopathy. Thus, options A, B, and C are not the correct responses.
Conclusion
Wernicke's encephalopathy is a severe medical emergency that is often
associated with malnutrition states. It is an underdiagnosed disease that can
be reversed or treated with IV thiamin. Wernicke's encephalopathy should be
considered in patients with chronic alcohol abuse and malnutrition or
prolonged vomiting along with acute confusion, ataxia, oculomotor
abnormalities, and memory disturbance. Brain MRI should be ordered to assess
changes in the patient's mental status. It is important for radiologists to
recognize this disease so that appropriate treatment is initiated
immediately.
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