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Northwestern University Feinberg School of Medicine
Department of Radiology
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Case of the Week

Case of the week is a resident-run investigation into the nuts-and-bolts of daily diagnostic work, with a focus on challenging cases, specialized discoveries, and quality patient care by the medical team in all divisions.

Week of August 28, 2020: Imaging Sign for Acute Infarct

A patient presented at the hospital after experiencing a few hours of left-sided weakness following trauma. 

The initial non-contrast CT was mostly unremarkable without any bleed or big infarct visible on CT. What can be seen adjacent to the suprasellar cistern is a hyperdense curvilinear structure in the region where one would normally expect the M1 segment of the right MCA. Typically, these vessels can be visualized on a few slices on noncontrast CT but the appearance here is far more dense. 

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This finding should raise suspicions for an obstructing thrombus in the vessel - the so-called "hyperdense MCA sign." Oftentimes, clinicians reviewing imaging will think they see a dense MCA but it's usually just an artifact. If the appearance is for hyperdense MCA - if the clinical picture fits and if the patient is within the window for treatment - vascular imaging is a must. 

Here, we got a CTA which shows complete occlusion of the distal M1 segment of the right MCA in the same region as the hyperdense MCA. This finding confirms our suspicion that the patient was taken for mechanical thrombectomy. 

Also shown was complete occlusion of the internal carotid artery on the same side due to a bad acute dissection. 

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The following MRI shows a large right MCA territory infarct with increased signal on DWI and corresponding low ADC signal (diffusion-restriction). A tiny infarct in the left frontal lobe suggests this is all related to showering emboli from the ICA dissection. 

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Follow-up vascular imaging post-thrombectomy shows reconstitution of the right ICA AND MCA. 

The hyperdense MCA sign is the earliest visible sign of MCA infarction - seen within 90 minutes after the event. The sensitivity is very low, however, at 30%, the absence of this sign doesn't rule out pathology. 

The finding is, as it sounds, just hyperdensity of the MCA relative to the other side and basilar artery. Be careful not to overcall this on just thick axial slices as there can be asymmetry. Use thin-section CT and multiplanar reformats to confirm in addition to vascular imaging. 

References:

Chayhan GB, Shroff MM. Twenty classic signs in neuroradiology: A pictoral essay. Indian J Radiol Imaging. 19 (2): 135-45. doi: 10.4103/0971-3026.50835

Tomsick T, Brott W, Broderick J, Haley EC, Spilker J, Khoury J. Prognostic value of the hyperdense middle cerebral artery sign and stroke scale score before ultraearly thrombolytic therapy. (1996) AJNR. American journal of neuroradiology. 17 (1): 79-85. 

 

 

 

 

 

 

 

 

 

 

Previous Cases

 April 14, 2020: COVID-19 in Lung Screening

An older male with multiple comorbidities presented with nonspecific shortness of breath, found to be in florid heart failure. COVID-19 testing returned positive. Here’s what we are seeing on imaging throughout the admission.

Prior comparison CXR: clear, without significant evidence of underlying lung disease on radiographs. 

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Admission CXR: Patchy bilateral airspace opacities with mild consolidation in the right lower lobe. 

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CXR 2 days later: florid progression of disease with extensive patchy airspace opacities throughout both lungs. Denser areas of consolidation are also seen more pronounced in the lower lobes. 

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CT Chest (same day as above): Progressive ground-glass opacities with dense consolidation in the bilateral lower lobes, suspicious for pneumonia including atypical etiologies such as coronavirus. No pleural effusions.

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Follow-up CT Chest (almost 2 weeks after above exam): Progression of extensive ground-glass opacities throughout the lungs with a slight peripheral predominance, as well as progressive dense consolidation of the lower lobes. No pleural effusions.

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Clinical Bullet Points

  •  Nonspecific clinical presentation delays or precludes diagnosis in many cases.
  •  Clinical diagnosis is by RT-PCR, with a known significant false negative rate. New rapid testing is being developed with goals of higher sensitivity.
  •  Complications include ARDS, acute cardiac injury, secondary infection (bacterial pneumonia), sepsis, AKI, multiorgan failure.

Imaging Bullet Points:

  •  Here’s a summary of what the Fleischner Society consensus published 7 April 2020:
    •  Imaging is not indicated in patients with suspected COVID-19 and mild clinical symptoms
    •  Imaging is indicated in a COVID-19 patient with worsening respiratory symptoms
    •  In the setting of resource limitations, imaging is indicated for medical triage of patients with suspected COVID-19 presenting with moderate-severe clinical features and high pretest probability.
  •  Key Imaging features: findings of atypical pneumonia or organizing pneumonia in the setting of clinical suspicion for COVID-19:
    •  Plain Radiograph: airspace opacities (consolidation or ground-glass opacities); bilateral, peripheral, lower lung predominant; pleural effusion is rare.
      •  May be normal in early disease
      •  Findings are most extensive 10-12 days after symptom onset
    •  Chest CT: 
      •  Ground-glass opacities (GGOs) - bilateral, peripheral/subpleural
      •  Crazy paving (GGOs with interlobular septal thickening)
      •  Air space consolidation
      •  Bronchovascular thickening
      •  Traction bronchiectasis
    •  Many asymptomatic patients may have CT abnormalities.

Take home point: Peripheral distribution, predominantly ground-glass opacities without pleural effusions should raise suspicion for COVID-19 in the appropriate clinical setting

 April 20, 2020: Identifying an Abnormal Enhancement Pattern

This week, we have a younger gentleman with multiple comorbidities. On the supplied image we see hyperenhancement of the liver - specifically in segment IV as well as multiple abnormal collateral vessels throughout the abdominal wall.

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Hot quadrate sign refers to a focal area of increased enhancement in the medial segment of the left hepatic lobe (segment IV). This finding is classically due to obstruction of the superior vena cava with portosystemic venous shunting between the SVC and left portal vein (via the internal thoracic and paraumbilical veins). This is contrasted with the Budd-Chiari syndrome which causes hypervascularity of the caudate lobe due to differential venous outflow. 

Key point: Identifying the abnormal enhancement in this specific location as well as the collaterals suggests pathology elsewhere (in the SVC). 

 

 April 25, 2020: Hand Joint Swelling Without Joint Space Destruction

A middle-aged man came in with hand pain and swelling.

 

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There is nodular soft tissue swelling of several fingers and mild osteoarthritis (joint space narrowing and osteophytosis) of several joins in a distal distribution, favoring DIPs. There are few erosions which are characterized as juxtaarticular erosions, meaning the lucencies are not actually along the join but outside of the synovial covering of the joint space. (See the small arrows.) A few areas of mineralization are seen in the soft tissues as well.

A notable negative is that the MCPs are essentially unaffected. 

Diagnosis: Gouty arthritis. 

Key takeaways: This case is an example of a bunch of gouty tophi around the joints. The swelling around the joins is classic due to the urate crystal deposits around the joint. These can calcify (see the mineralization around the radial side of the second MCP on the left hand). The urate deposits cause an inflammatory reaction that can result in bone resorption and lytic foci in the juxtaarticular bone. This is not within the synovial joint, hence why we're not seeing joint space destruction.  

 May 4, 2020: Diagnosing Inflammatory Breast Cancer

A middle-aged woman with a palpable abnormality. She noted her skin has been red and tender on her left breast. 

Findings: The first image shows the initial evaluation demonstrating a mass in the outer left breast with mild skin thickening. Remaining images are a follow-up diagnostic mammogram workup months after.

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This case shows a large irregular mass in the upper-outer left breast (2 o'clock position), with remarkable skin thickening throughout the left breast. There's a trabecular thickening and slightly increased density of the left breast overall. 

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If you look closely, there's a small calcification associated with the mass as well as a biopsy clip -- a finding that should should raise the radiologist's suspcions for cancer. Other findings include multiple enlarged left axiliar nodes in the LMO projection. US shows a large irregular hypoechoic mass without shadowing. 

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Diagnosis: Inflammatory breast cancer - a clear case for BIRADS 5.

Inflammatory breast cancer is a diagnosis that requires both tissue biopsy and clinical evidence of inflammatory disease. It is a common occurrence for a middle-aged woman to come in having developed a hot, swollen breast very rapidly, sometimes showing the peau d'orange appearance clinically. This appearance is due to tumor invasion of the skin lymphatics so tissue sparing surgeries are generally not performed. Up to 30% of these cancers are metastatic at presentation. Inflammatory breast cancer itself is considered stage IIIb at presentation due to skin invasion so immediate action is required. 

An important distinction: DDX is mastitis clinically. Mastitis is usually related to breast feeding so the patient can be younger. This should be resolved with therapy. Inflammatory breast cancer can also be associated with pregnancy, which is something to look out for.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 June 1, 2020: Left Lower Lobe Atelectasis On Chest X-ray

A 50 year-old female presented to the hospital with shortness of breath. She had a history of breast cancer. A chest X-ray was ordered. 

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A PA view of the chest demonstrates the classic findings of left lower lobe atelectasis. The retrocardiac sail sign describes a triangular opacity in the posteromedial aspect of the left lung (shown with the yellow arrow). The flat waist sign describes flattening of the left heart border as is also shown in this example. There is also slight inferior displacement of the left hilum. On this example, the hila are approximately level with eachother whereas the left hilum is normally slightly superior to the right hilum. 

A repeat chest radiograph the following day demonstrates persistent left lower lobe atelectasis with suggestion of an abnormal density within the left mainstem bronchus. CT was recommended for further evaluation. 

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The CT showed a 2.6m mass in the left hilar region that completely obstructs the left lower lobe bronchus and results in complete collapse of the left lower lobe. Bronchoscopic biopsy was recommended for further evaluation. 

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Diagnosis: The left hilar mass resulting in obstruction of the left lower lobe bronchus. Differential includes primary lung or bronchogenic malignancy, as well as metastasis. Bronchoscopic biopsy in this case confirmed a primary squamous cell carcinoma. 

This case shows typical findings for left lower lobe atelectasis on chest X-ray. It is important to be aware of the radiographic appearance of all types of lobar atelectasis. 

It is also a good example of the satisfaction of search phenomenon. On the second X-ray, it would be easy to call this persistent left lower lobe atelectasis. However, you should always look further for the cause of the lobar collapse as seen in this instance. 

The differential for an endobronchial lesion is broad. In children, central obstruction is most often due to a mucus plug or foreign body. In young adults, a low-grade endobronchial tumor such as carcinoid or adenoma enters the differential. After age 40, bronchogenic carcinoma is a common cause. 

 June 15, 2020: Ultrasound Diagnosis of Median Arcuate Ligament Syndrome

A 30 year-old female presented with epigastric pain and nausea after eating. An epigastric bruit was noted on the physical exam. Ultrasound was ordered to look for abdominal aortic aneurysm.

Findings show, during expiration there is narrowing of the origin of the celiac artery with a fish-hook configuration. 

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With inspiration, the celiac artery assumes a more vertical orientation with decreased narrowing at its origin. 

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A side-by-sie view demonstrates the difference in orientation of the celiac artery during expiration and inspiration. 

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During expiration, there is elevation of the peak systolic velocity of the celiac artery to 297 cm/ sec. There is also focal aliasing at the origin of the celiac artery, indicative of turublent high-velocity flow. 

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During inspiration, there is normalization of the peak systolic velocity to 171 cm/ sec and resolution of the focal aliasing at the origin of the celiac artery.

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Diagnosis: Median arcuate ligament syndrome

Median arcuate ligament syndrome, also known as celiac artery compression syndrome, is a condition in which the proximal part of the celiac trunk is compressed by the median arcuate ligament of the diaphragm during expiration. This ligament is a fibrous arch that connects the diaphragmatic crura on either side of the aortic hiatus. 

During inspiration, the celiac artery descends in the abdomen and the artery assumes a more vertical orientation, relieving the compression. For this reason, the symptoms associated with MALS are also relieved during standing as the celiac artery descends further in the abdominal cavity on standing. 

On ultrasound, this can be diagnosed when there is narrowing at the origin of the celiac artery (often with a fish-hook orientation) and a peak systolic velocity in the compressed segment of the celiac artery >200 cm/ sec during expiration. There should also be a >3:1 ratio of peak systolic velocity in the celiac artery during expiration compared to the peak systolic velocity in the abdominal aorta immediately below the diaphragm. Normalization of the velocity on inspiration and standing is classic. 

CT is the more common method to diagnose this condition. On CT, you will see proximal celiac stenosis with the classic fish-hook configuration. You may also see post-stenoic dilation and prominent collaterals as seen int he example below obtained from Dr. Mahmoud Yacout Alabd on Radiopaedia.org

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This is often treated surgically with laparoscopic division of the median arcuate ligment. 

 June 22, 2020: Dysphagia lusoria

A 70 year-old male reported dysphagia and sensation of food getting stuck at the level of the suprasternal notch. A fluoroscopic esophagram was ordered for further evaluation. 

Frontal and lateral views show a mild posterior and lateral impression on the upper thoracic esophagus at the level of the aortic arch. Note that there is also laryngeal penetration and a small amount of tracheal aspiration in the second picture due to the patient's difficulty swallowing. 

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There is also a cricopharyngeal bar at the C5-C6 level causing greater than 50% impression on the posterior cervical esophagus. 

 

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Subsequent CT of the chest demonstrates an aberrant right subclavian artery which courses posterior to the esophagus and causes posterior compression on the esophagus. Note the calcific atherosclerosis at the origin of the aberrant right subclavian artery. 

 

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Diagnosis: Dysphagia lusoria and cricopharyngeal bar

Dysphagia lusoria is impairment in swallowing due to an aberrant right subclavian artery. Fluoroscopy will show an indentation in the posterior wall of the esophagus at the level of the aortic arch. Cross-sectional imaging is necessary to confirm the presence of the aberrant vessel. It is important to note that most patients with an aberrant right subclavian artery do not have symptoms. As in this case, the presence of atherosclerosis or aneurysm in the aberrant artery will often lead to worse symptoms. 

A cricopharyngeal bar will appear on lateral fluoroscopic images as a smooth posterior indentation of the cervical esophagus at the C5-C6 level - which is the level of the cricopharyngeus muscle. It can be idiopathic or related to cricopharyngeus muscle spasm or hypertrophy. It is usually an incidental finding. However, some patients complain of dysphagia. It can result in a Zenker diverticulum so be sure to look for that as well. 

 July 13, 2020: Golden S-Sign

This week, an older gentleman reported progressive shortness of breath. 

What we are seeing in the CXR is the Golden S-sign or S-sign of Golden. Here, the right upper lobe collapse is related to a mass in the hilum. As the right upper lobe collapses, it pulls the minor fissure upwards and the hilar mass impresses on the fissure downwards resulting in the S-shape. 

 

 

This is one of the signs residents learn about but don't often see. This, like many radiologic signs, were really important in the days before CT. Radiologists at that time were amazing at plain film interpretation. 

In this case, we have an image of a quick scan through the CT showing the mass and the right upper lung bronchus that's almost collapsed. The presenting X-ray a few months after the CT shows a complete collapse. The other image is the prior X-ray before the right upper lung collapse. 

 

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 July 27, 2020: Testicular Torsion

A man in his 60s with a history of right inguinal hernia repair within the past year is now presenting with several weeks of right testicular pain. 

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The echotexture of the right testicle is heterogeneous when compared to the normal homogenous echotexture of the left testicle. The hypoechoic (dark) regions within the testicle represent areas of necrosis. Note also the large complex hydrocele surrounding the necrotic right testicle with multiple septations, which is reactive in the setting of testicular torsion.

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Doppler images of the right testicle demonstrate no evidence of arterial or venous blood flow. Absence of blood flow within the testicle is a sign of complete torsion. 

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Compare the absent arterial and venous waveforms of the right testicle shown above to this normal arterial waveform in the left testicle. Note the arterial waveforms with sharp systolic upstrokes -- a normal finding.

 

The cine clip shown above shows the classic "whirlpool sign" of twisting of the right spermatic cord including the vascular pedicle. 

Diagnosis: Testicular Torsion with Necrosis

This is a classic case of complete testicular torsion with necrosis. This occurs when the spermatic cord and vascular pedicle twist and cut off blood supply to the testicle. Initially, the twisting is less than 360 degrees and only obstructs the venous outflow (incomplete torsion). Over time, as the twisting becomes greater than 360 degrees, the arterial inflow is also obstructed (complete torsion) and the testicular necrosis occurs. 

These patients usually present with acute testicular pain. Early diagnosis is important so that the testicle can be salvaged before testicular necrosis or infarction occurs. The time between onset of pain and detorsion is directly related to testicular salvage with nearly 100% salvage if the detorsion occurs within six hours. Only 20% salvage is expected if there is a delay of 12-24 hours. Treatment involves orchiectomy in order to prevent subsequent infection of the necrosed testicle. 

A review of the typical ultrasound findings, many of which are shown above: 

  • Twisting of the spermatic cord or "whirlpool sign" (the most sensitive and specific finding)
  • Absence of blood flow in complete torsion; elevated resistive indices or to-and-fro flow in incomplete torsion
  • Homogenous texture early on before necrosis occurs; heterogeneous echotexture with areas of necrosis in late presentations
  • Reactive hydrocele
  • Reactive thickening of scrotal skin

 August 3, 2020: Subdural Hematoma

A male in his 60s presents to the Emergency Department with acute onset of slurred speech. Stroke code was activated.

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Findings show a large, mixed attenuation subdural hematoma overlying the left frontoparietal cerebral convexity with hyperdense (bright) components with acute blood products. 

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The large subdural collection results in significant effect with effacement/ flattening of the underlying cerebral gyri and 1.4 cm of left-to-right midline shift at the level of the septum pellucidum. The coronal image above nicely demonstrates subfalcine herniation and the axial image demonstrates mild effacement of the left aspect of the suprasellar cistern, indicative of developing uncal herniation. 

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There is also effacement of the atrium of the left lateral ventricle (shown on the left) and asymmetric dilatation of the temporal horn of the left lateral ventricle (shown on the right). These findings are related to ventricular trapping from mass effect by the large subdural collection. 

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Due to the significant mass effect and developing herniation, the patient underwent emergent craniotomy for decompression. On the left, you can see the postsurgical changes including a subdural drain that was left in place for drainage of the large hematoma. On the right, you can see the significantly decreased mass effect after surgery including decreased midline shift and decreased effacement of the atrium of the left lateral ventricle. 

Diagnosis: Subdural hematoma requiring emergent decompressive craniotomy

Subdural hematomas are collections of blood located between the dura and arachnoid mater. They occur from tearing of the bridging cortical veins as they cross the subdural space before draining into a dural venous sinus. They are often crescent-shaped and are not limited by cranial sutures, which is why the subdural collection in this case extends across nearly the entirety of the left cerebral convexity. 

This is in opposition to epidural hematomas, which are often secondary to tearing of the middle meningal artery in the presence of a skull fracture. They appear lens-shaped and are limited by cranial sutures. 

On CT, the appearance of the subdural hematoma changes with time. In the first hour (hyperacute stage), the collection often has a swirling appearance due to mixing of clot and ongoing unclotted blood. In the acute stage, they key imaging feature is hyperdense (bright) blood as seen in our case here. In rare cases, acute SDH can appear isodense to the brain due to anticoagulation/ coagulopathy or severe anemia. In the subacute phase (3-21 days), the collection becomes isodense to the underlying cortex. In the chronic phase (beyond 3 weeks), the collection becomes hypodense (dark) relative to the cortex. An acute-on-chronic SDH will often appear with a hematocrit level, with a hyperdense component layering posteriorly. 

Treatment depends on the degree of mass effect. Small subdural collections are often managed with serial CT scans to exclude enlargement. Symptomatic cases with a large amount of mass effect, as seen in our case, require surgery to evacuate the collection. 

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