Edi Catheter (NOT MRI SAFE)

Edi (Electrical activity of the diaphragm) catheters are nasogastric or orogastric catheters that estimate the neural respiratory drive and send that information to the mechanical ventilator. The ventilator uses that information to control respiration, guided by the patient's own neural control of breathing. This concept is called Neurally Adjusted Ventilatory Assist or NAVA).

The sensor part of the Edi Catheter is positioned in the esophagus at the level of the diaphragm (video on placement of the catheter). The Edi catheter from Maquete can also act as a normal nasogastric feeding tube and has a barium sulfate strip for identification on x-rays, but you wouldn't recognize it as anything other than a normal NG or OG tube unless you recognize that it looks different from the rest of the catheters used in your institution.

The above is kind of important because the catheter is NOT CONSIDERED SAFE FOR MRI.

References

Stein H, Hall R, Davis K, White DB. Electrical activity of the diaphragm (Edi) values and Edi catheter placement in non-ventilated preterm neonates. J Perinatol. 2013 Sep;33(9):707-11.

False Perpetuations: Ovarian Torsion, Doppler Ultrasound, and CT

Contrast-enhanced CT (top) and gray-scale US (bottom) in the same patient, both modalities demonstrating right ovarian torsion. Note the enlarged and heterogenous right ovary, peripheral follicles, and ascites

• False Perpetuation: After a normal CT for lower abdominal or pelvic pain, an ultrasound with color Doppler is necessary to "rule out ovarian torsion"

• Ovarian/adnexal torsion is caused by complete or partial rotation of the ovarian pedicle on its long axis. This results in lymphatic and venous congestion, inturn limiting arterial inflow
• Torsion of both the ovary and fallopian tube occurs more often than that of either structure alone
• Occurs more frequently on the right

• Findings on Ultrasound
• Enlarged ovary
• Eccentric mass (usually a cyst) serving as a lead point
• Round/'full' ovary with a central 'ground glass' appeaerance
• Peripheral follicles
• The presence of (or decrease in) arterial/venous flow predicts a better outcome
• The absense of ovarian flow suggests necrosis
• Even if there is ovarian flow on Doppler imaging, there can still be torsion
• One study (J Ultrasound Med 2001; 20:1083-1089) evaulated the use of Doppler in pathologic proven cases of ovarian/adnexal torsion and found:
• No arterial or venous flow in 40% of cases
• No venous flow, decreased arterial flow in 7% cases
• No arterial flow, decreased venous flow in 33% cases
• Decreased arterial and venous flow in 13% cases
• Normal arterial and venous flow in 7% cases
• A meta-analysis (Eur J Pediatr Surg 2015; 25:82-86) looked at different modalities in diagnosing ovarian torsion in pediatric patients. Regarding morphologic and Doppler criteria on ultrasound for the diagnosis of ovarian torsion, this study found:
• Morphologic features: 92% sensitive and 96% specific
• Some of the morphologic features reviewed:
• Enlarged heterogenous ovary (compared to contralateral normal ovary)
• Ovarian volume 12x larger than contralateral volume, or 75 mL absolute ovarian volume
• Ovarian diameter 2.3x larger than contralteral diameter
• Multiple peripheral cortical follicles with transudative fluid
• Whirlpool-sign
• Cystic mass, particularly > 5cm in diameter
• Doppler: 55% sensitive and 87% specific
• Thus, the diagnosis of ovarian torsion is made or excluded based on grayscale appearance, not the Doppler findings

• Regarding CT and ovarian torsion
• One study (Abdom Imaging 2015; 40:3206-3213) retrospectively evaluated the utility of Doppler ultrasound in the assessment of ovarian torsion following a negative contrast-enhanced CT (the ultrasound and CT were performed within a 24 hour period) found:
• Of the 48 cases with ovarian enlargement (defined as greater than 5 cm), 11 had torsion
• Of the 235 cases without ovarian enlargment, 0 had torsion
• Other CT findings assessed:
• Presense of free fluid
• Uterine deviation
• Fallopian tube thickening
• Smooth wall thickening of a cystic mass
• Ovarian fat stranding
• Twisted Pedicle
• Abnormal ovarian enhancement
• The most common ultrasound finding associated with ovarian torsion was ovarian enlargement (either due to the enlarged ovary itself or a mass functioning as a lead point)
• A completely negative CT was never associated with a Doppler ultrasound suspicious for ovarian torsion (negative predictive value of 100%)
• There is no utility in the addition of a Doppler Ultrasound (specifically for the evaluation of ovarian torsion) following a negative contrast-enhanced CT of the abdomen and pelvis
• Ovarian size should be used as a dominant feature in the exclusion of ovarian torsion on both CT and US

*This blog was inspired by and based on a workshop given at the Society of Abdominal Radiology 2018 annual meeting by Dr. Maitray D. Patel of Mayo Clinic Arizona

Cowpers duct syringocele

Axial contrast-enhanced CT (top), axial T2W MRI (middle), and sag T2W with fat-saturation MRI (bottom)
demonstrate an ovoid cystic structure associated with the midline posterior aspect of the bulbous urethra

• The Cowper glands (bulbourethral glands) are paired pea-sized accessory exocrine glands analogous to the Bartholin glands in females
• The main glands lie within the urogenital diaphragm
• The ducts insert into the bulbous urethra  
• Provide lubrication of the urethra and protection of the sperm
• Obstruction of the ducts may result in formation of retention cysts, also referred to as syringoceles
• May be congenital or acquired 
• Most often asymptomatic although when large, may result in urinary obstruction and hematuria
• Categorized as either open or closed 
• Open cysts communicate with the lumen of the urethra and may mimic a urethral diverticulum or even an ectopic ureter
• More likely to cause symptoms of postvoid dribbling, purulent discharge and hematuria
• Closed or imperforate cysts become dilated due to duct obstruction resulting in cyst dilatation and extrinsic mass effect on the bulbar urethra
• More likely to result in obstructive symptoms
• Imaging typically detects a Cowper duct cyst as a unilocular cystic lesion at the posterior or posterolateral aspect of the posterior urethra 
• Open cysts may be opacified during urethrography 
• Closed cysts may appear as a smooth extrinsic filling defect on the ventral wall of the bulbous urethra 
• MRI is useful to exclude solid neoplasms and to detect complications such as hemorrhage or infection
• Symptomatic cases are treated surgically with cyst unroofing. Transperineal ligation of the Cowper gland ducts may be performed in refractory cases

References

1. Shebel HM, Farg HM, Kolokythas O, El-Diasty T. Cysts of the lower male genitourinary tract: embryologic and anatomic considerations and differential diagnosis. Radiographics. 2013 Jul-Aug;33(4):1125-43.
2. Surana S, Elshazly M, Allam A, Jayappa S, AlRefai D. A Case of Giant Cowper's Gland Syringocele in an Adult Male Patient. Case Rep Urol. 2015; 2015:682042.
3. Melquist J, Sharma V, Sciullo D, McCaffrey H, Khan SA. Current diagnosis and management of syringocele: a review. Int Braz J Urol. 2010 Jan-Feb;36(1):3-9.
4. Moskowitz PS, Newton NA, Lebowitz RL. Retention cysts of Cowper's duct. Radiology. 1976 Aug;120(2):377-80.
5. Kickuth R, Laufer U, Pannek J, Kirchner TH, Herbe E, Kirchner J. Cowper's syringocele: diagnosis based on MRI findings. Pediatr Radiol. 2002 Jan;32(1):56-8

Persistent Sciatic Artery

Axial and coronal CT images with intravenous contrast demonstrate a left persistent sciatic artery (long arrows) coursing through the greater sciatic notch and deep to the gluteus maximus muscle. Note the asymmetrically diminutive left external iliac artery (short arrows)

• A persistent sciatic artery (PSA) is a rare vascular anomaly in which the internal iliac artery courses through the greater sciatic notch and in to the thigh
• During embryonic development, the sciatic artery usually involutes as the femoral artery develops
• Recognition of an unusually enlarged internal iliac artery and a diminutive external iliac artery are some clues in diagnosing a PSA
• The PSA course runs close to the sciatic nerve, and can run within the nerve sheath in some cases
• Distally, the PSA runs deep to the gluteus maximus muscle, coursing along the adductor magnus muscle
• Reported in up to 0.03-0.06% of the population and can be bilateral in 20% of cases
• PSA is considered complete when it is the dominant blood supply to the popliteal artery and incomplete with the femoral artery is the dominant blood supply to the popliteal artery
• 5 types have been described:
• type 1 is a complete PSA with a normal femoral artery
• type 2 is a complete PSA with a incompletely developed femoral artery
• type 3 is a incomplete PSA (only the cephalic portion is present) and normal femoral artery
• type 4 is a incomplete PSA (only the caudal portion is present) and normal femoral artery
• type 5 is when the PSA arises from the median sacral artery
• Majority (80%) become symptomatic at some point presenting with intermittent claudication, ischemia, pulsatile mass or neurologic symptoms
• Susceptible to repetitive trauma from sitting and hip flexion/extension
• Results in premature atherosclerosis and aneurysm formation
• Aneurysm found in 48%, and stenosis and occlusion of the PSA in 7% and 9%, respectively

References:

1. Mcquaid M, Gavant ML. Posttraumatic pseudoaneurysm of a persistent sciatic artery. AJR Am J Roentgenol. 1995;164 (6): 1514-5. 
2. Pillet J, Albaret P, Toulemonde JL, Cronier P, Raimbeau G, Chevalier JM. Tronc arteriel ischiopoplite, persistance de l’artere axiale. Bull Assoc Anat 1980;64:109e22.
3. Pillet J, Cronier P, Mercier Ph, Chevalier JM. The ischio popliteal arterial trunk: a report of two cases. Anat Clin 1982; 3:329e31. 
4. Gauffre S, Lasjaunias P, Zerah M. Sciatic artery: a case, review of literature and attempt of systematization. Surg Radiol Anat 1994;16(1):105e9.
5. Bower EB, Smullens SN, Parke WW. Clinical aspect of persis- tent sciatic artery: report of two cases and review of the literature. Surgery 1977;81(5):588e95.

Dilated Cisterna Chyli: A Potential Mimicker of Lymphadenopathy

  

Axial (top) and coronal (bottom) contrast-enhanced CT images
demonstrate a retrocrural fluid-filled tubular structure with imperceptible walls
 (black arrows), the classic imaging features of a cisterna chyli

Coronal T2-weighted MRI shows the tubular cystic structure of the cisterna chili
and it's continuity with the thoracic duct (white arrow)

• The cistern chyli is a dilated lymphatic sac ommonly located in the right retrocrural region, at the level of L1-L2, extending 5-7 cm in CC dimension. It classically receives draining lymph from two lumbar trunks and an intestinal trunk, and continues cephalad as the thoracic duct

• Can enhance on delayed MRI >5 min

• Has an average size of 7.4 mm in the AP dimension, although some authors consider it dilated when ≥6 mm

• Dilatation can be secondary to lymphatic damage from prior gastroesophageal or retroperitoneal surgery, uncompensated cirrhosis, hypoalbuminemia, lymphangioleiomyomatosis, elevated central venous pressure, and biliary obstruction

• Size changes can vary depending on phase of respiration, hydration, and lower thoracic duct peristalsis

• Important to know of this entity because it can mimic retrocrural lymphadenopathy in the oncologic setting

• Mulitplanar reformations and MRI can help demontrsate the tubular cystic nature of the cistern chyli and its continuity with the thoracic duct 

References 

1. Rosenberger A, Abrams HL (1971) Radiology of the thoracic duct.Am J Roentgenol Radium Ther Nucl Med 111:807–820
2. Pinto PS, Sirlin CB, Andrade-Barreto OA, et al. (2004) Cisternachyli at routine abdominal MR imaging: a normal anatomicstructure in the retrocrural space. Radiographics 24(3):809–817 
3. Smith TR, Grigoropoulos J (2002) The cisterna chili: incidence and characteristics on CT. Clin Imaging 26:18–22
4. Arrive ́ L, Azizi L, Lewin M, et al. (2007) MR lymphography ofabdominal and retroperitoneal lymphatic vessels. AJR189(5):1051–1058
5. Gollub MJ, Castellino RA (1996) The cisterna chyli: a potentialmimic of retrocrural lymphadenopathy on CT scans. Radiology199(2):477–480 

Re

Gout of the extensor mechanism of the knee

Patient with leukemia (note abnormal marrow signal) who presented with acute knee pain and pre-patellar soft tissue swelling. Imaging shows gouty tophi involving the extensor tendons of the knee, with nodules in the distal quadriceps and proximal patellar tendons (yellow arrows). Lateral conventional radiograph does not show any calcifications. Patients with cancer are pre-disposed to gout due to hyperuricemia in the setting of high cell turnover or treatment-related tumor lysis.

Tophaceous masses of gout at the knee are most commonly located on the medial aspect of the infrapatellar fat pad and anterior joint recess (~90% of cases), at the lateral femoral condyle at the attachment site of the popliteus tendon (~80%), and the intercondylar fossae (~70%). Involvement of the extensor mechanism (distal quadirceps tendon and the patellar tendon) is less common, but characteristic.

Gouty tophi present as lobulated or amorphous masses. On MRI, they are isointense on T1-WI and heterogeneously intermediate-to-hypointense on T2-WI, with variable enhancement. Well-defined erosions of the patella can be seen with large tophi. Large erosions can mimick malignancy. Calcifications, when present can help narrow the differential diagnosis; however, as in the case above, they may not always be present.

Differential considerations include:

• Post-traumatic or reactive enthesopathy, hydroxyapatite deposition: Will have calcifications.
• Tenosynovial giant cell tumor: Can have low signal due to hemorrhage. No calcifications.
• Amyloid deposition: Typically low signal. Can have calcifications.
• Sarcoma: Gouty tophi can get very aggressive and erode into the patella, mimicking a soft tissue sarcoma.

References

• Kester C, Wallace MT, Jelinek J, Aboulafia A. Gouty involvement of the patella and extensor mechanism of the knee mimicking aggressive neoplasm. A case series. Skeletal Radiol. 2018 Jan 14. [Epub ahead of print]
• Ko KH, Hsu YC, Lee HS, Lee CH, Huang GS. Tophaceous gout of the knee: revisiting MRI patterns in 30 patients. J Clin Rheumatol. 2010 Aug;16(5):209-14.
• Wadhwa V, Cho G, Moore D, Pezeshk P, Coyner K, Chhabra A. T2 black lesions on routine knee MRI: differential considerations. Eur Radiol. 2016 Jul;26(7):2387-99.

Myxofibrosarcoma Recurrence

Serial contrast-enhanced axial images of the forearm in a patient with recurrent myxofibrosarcoma (MFS). Arrows indicate slowly enlarging, tail-like recurrence along the superficial fascia in the resection bed.

Myxofibrosarcoma (MFS, previously myxoid malignant fibrous histiocytoma) is an intermediate-grade soft-tissue sarcoma with fibroblastic and myxoid components. Patients are typically in the sixth to eighth decades of life.

These lesions can range from round and well-defined (like most soft tissue sarcomas) to predominantly infiltrating, with tails extending along fascial planes. They have high T2 signal intensity related to their myxoid content and heterogeneous enhancement that can be feather-like (typically seen with myxoid neoplasms).

Despite best efforts at acquiring negative margins (made difficult by infiltrating tails), MFS has a propensity for repeated local recurrence, with rates of up to 79%. Recurrence can be tricky to detect. As seen in the image above, tail-like recurrence can be easily dismissed as being related to inflammation or trauma. Our group has found no association between the appearance of MFS at presentation (well-defined vs. tail-like) and the pattern of recurrence, so it's important to watch out for tails regardless of the initial tumor presentation.

In summary, the key to early detection of recurrent MFS is

1. Know that you're dealing with MFS (look at the path report, and know that some pathologists may still call these "myxoid MFH").
2. Be aware of propensity for tail-like recurrence.
3. Make sure to compare to multiple studies dating back to post-operative baseline to increase sensitivity for detection of these slowly growing lesions.

References

Daniels C , Wang WL , Madewell JE, Wei W, Amini B. Pattern of Recurrence of Myxofibrosarcoma is not Associated with Pattern at Presentation or Rate of Delayed Diagnosis. Iran J Radiol. 2017 ;14(1):e13469.

Pleomorphic adenoma

Pleomorphic adenoma (also known as benign mixed tumor) is the most common tumor of the major salivary glands, and the most common benign tumor of the parotid glands (~75% of all benign salivary gland tumors). Prior head and neck irradiation is a risk factor. They are typically solitary, slowly growing, and asymptomatic. They are typically diagnosed after palpation by the patient or incidentally on imaging studies. Surgical resection is advised due to risk of malignant transformation.

On MRI, pleomorphic adenomas, have polylobulated margins a rim of low T2 signal corresponding to a fibrous capsule. They have heterogeneous low-to-intermediate signal intensity on T1-weighted images. High T2 signal and avid, solid enhancement are considered relatively specific features, especially when present in a younger patient (< 57 years). Dynamic contrast-enhanced (DCE) MRI shows gradual enhancement. On diffusion-weighted imaging (DWI), pleomorphic adenomas tend to have very high ADC values; however, DWI is not able to differentiate between benign and malignant parotid gland tumors.

On ultrasound, pleomorphic adenomas are typically hypoechogenic. They can have mild to moderate uptake on FDG PET.

Differential considerations include:

• Warthin tumor: 10–15% are bilateral. Can have proteinaceous cystic components with high T1 signal ranging from a few millimeters to 1–2 cm. Solid components have rapid enhancement and washout.
• Adenoid cystic carcinoma: Small, low-grade lesions can be mistaken for pleomorphic adenomas. Variable signal intensity on T2-weighted depending on type. Low-grade tumors have high T2 signal in the solid parts. Large tumors can have cystic areas of hemorrhagic necrosis.
• Myoepithelial adenoma: Also tend to have very high ADC values
• Basal cell adenoma: More commonly in the superficial lobe of the parotid gland. Tend to be round and well-circumscribed tumors. Have heterogeneous enhancement on CT.
• Carcinoma in pre-existing pleomorphic adenoma (carcinoma ex pleomorphic adenoma): Typically less well-circumscribed than benign pleomorphic adenoma. Tends to occur after 10–15 years of an existing pleomorphic adenoma, with sudden rapid growth (3–6 months) in patients in the sixth-to-eighth decades of life.
• Lymphoma: Tend to be multiple. Can have well-defined and lobulated margins. Tend to have low T2 signal and slight enhancement.
• Sarcoid: Can be placed in any differential, including this one.

References

• Christe A, Waldherr C, Hallett R, Zbaeren P, Thoeny H. MR imaging of parotid tumors: typical lesion characteristics in MR imaging improve discrimination between benign and malignant disease. AJNR Am J Neuroradiol. 2011 Aug;32(7):1202-7.
• Habermann CR, Arndt C, Graessner J, Diestel L, Petersen KU, Reitmeier F, Ussmueller JO, Adam G, Jaehne M. Diffusion-weighted echo-planar MR imaging of primary parotid gland tumors: is a prediction of different histologic subtypes possible? AJNR Am J Neuroradiol. 2009 Mar;30(3):591-6.
• Heaton CM, Chazen JL, van Zante A, Glastonbury CM, Kezirian EJ, Eisele DW. Pleomorphic adenoma of the major salivary glands: diagnostic utility of FNAB and MRI. Laryngoscope. 2013 Dec;123(12):3056-60.
• Kato H, Kanematsu M, Watanabe H, Kajita K, Mizuta K, Aoki M, Okuaki T. Perfusion imaging of parotid gland tumours: usefulness of arterial spin labeling for differentiating Warthin's tumours. Eur Radiol. 2015 Nov;25(11):3247-54.
• Kato H, Kanematsu M, Mizuta K, Ito Y, Hirose Y. Carcinoma ex pleomorphic adenoma of the parotid gland: radiologic-pathologic correlation with MR imaging including diffusion-weighted imaging. AJNR Am J Neuroradiol. 2008 May;29(5):865-7.
• Okahara M, Kiyosue H, Hori Y, Matsumoto A, Mori H, Yokoyama S. Parotid tumors: MR imaging with pathological correlation. Eur Radiol. 2003 Dec;13 Suppl 4:L25-33.

Osseous Pseudoprogression after Spine Stereotactic Radiosurgery

One of the issues we run into when assessing response to radiation therapy is pseudoprogression: Enlargement of the area of abnormality that is not truly progression. This phenomenon is best known in brain lesions following gamma knife therapy, but has also been seen in lung lesions after stereotactic body radiotherapy (SBRT).

In the spine, we can see pseudoprogression after spine stereotactic radiosurgery (SSRS) in bone lesions (osseous pseudoprogression, or OPP), as well as in the epidural soft-tissue components of bone lesions.

The take-away messages are:

• We have so far only seen OPP after single-fraction SSRS. This is likely due to the higher biological dose of single-fraction therapy.
• If you see an enlarging bone lesion on MRI performed within 3-6 months after single-fraction SSRS, you can't be confident that it represents true progression, because about 1/3 of these enlarging bone lesions will represent OPP.
• The only finding on conventional MRI that has been shown to be associated with OPP is tumor growth confined to the 80% iso-dose line and the slope of enlargement (earlier time to tumor enlargement).

References

• Amini B, Beaman CB, Madewell JE, Allen PK, Rhines LD, Tatsui CE, Tannir NM, Li J, Brown PD, Ghia AJ. Osseous Pseudoprogression in Vertebral Bodies Treated with Stereotactic Radiosurgery: A Secondary Analysis of Prospective Phase I/II Clinical Trials. AJNR Am J Neuroradiol. 2016 Feb;37(2):387-92.
• Bahig H, Simard D, Létourneau L, Wong P, Roberge D, Filion E, Donath D, Sahgal A, Masucci L. A Study of Pseudoprogression After Spine Stereotactic Body Radiation Therapy. Int J Radiat Oncol Biol Phys. 2016 Nov 15;96(4):848-856.

Hemochromatosis: Hand Manifestations

50-year-old man with subtle manifestations of hemochromatosis arthropathy. Note narrowing of the metacarpophalangeal (MCP) joints, more advanced at the index and middle fingers. Other features of hemochromatosis arthropathy are not present, specifically, there is no subchondral cyst formation, hook-like osteophytes, osteoporosis, or chondrocalcinosis and the radiocarpal articulation is unaffected.

Hemochromatosis: General

• Autosomal recessive disorder
• Several genes implicated
• Body has mechanism for dealing with low Fe (increased intestinal absorption), but no effective way of dealing with excess Fe
• Fe accumulates in organs
• Damage via Fe²⁺ -> Fe³⁺ -> Oxidation -> Free radicals

Arthropathy

• Present in 50% of patients when rigorous criteria are used to define arthritis
• Males affected earlier and more severely
• Associated with use of joint
• Typically a chronic process
• Acute episodes of inflammatory arthritis may occur: May be associated with recovery of CPPD crystals from joint fluid aspiration.
• Rare syndrome of septicemia accompanied by monoarticular or oligoarticular septic arthritis caused by Yersinia species described: Prosthetic joints seem especially susceptible to this infection.

Pathophysiology

• Hemosiderin found in superficial synovial lining cells and macrophages (phagocytosis of iron loaded synoviocytes)
• Very little iron detected in deeper synovial layers, and only occasionally in macrophages.
• Arthropathy generally non-inflammatory. Chronic inflammatory cell infiltrate rarely seen.
• Minimal to no iron deposition in cartilage.
• Chondrocalcinosis a frequent finding
• No close spatial relationship between iron and CPPD crystals, and crystals can be found even in the absence of iron deposits.

Imaging Features

• Overlap with those of idiopathic OA and CPPD
• Joint space narrowing
• Subchondral sclerosis
• Subchondral cysts
• Osteophyte formation (hook-like osteophytes can be seen)
• Chondrocalcinosis in articular and non-articular cartilage
• Osteoporosis

The deal with chondrocalcinosis

• Fe2+ (but not Fe3+) inhibits pyrophosphatase
• Leads to diminished hydrolyzation of inorganic pyrophosphate
• Contributes to precipitation of inorganic pyrophosphate with calcium.

References

• Dallos T, Sahinbegovic E, Aigner E, Axmann R, Schöniger-Hekele M, Karonitsch T, Stamm T, Farkas M, Karger T, Cavallaro A, Stölzel U, Keysser G, Datz C, Schett G, Manger B, Zwerina J. Validation of a radiographic scoring system for haemochromatosis arthropathy. Ann Rheum Dis. 2010 Dec;69(12):2145-51.
• Frenzen K, Schäfer C, Keyßer G. Asymmetrical hemochromatosis arthropathy in a patient with a history of poliomyelitis. Rheumatol Int. 2012 Apr;32(4):1045-7.
• van Vulpen LF, Roosendaal G, van Asbeck BS, Mastbergen SC, Lafeber FP, Schutgens RE. The detrimental effects of iron on the joint: a comparison between haemochromatosis and haemophilia. J Clin Pathol. 2015 Aug;68(8):592-600.

Chordoma Drop Metastases

Chordoma drop metastases are extremely rare, with ~11 reported cases. Of these, 1 was present at the time of initial presentation and 3 were only seen at autopsy. The naturally slow growth of chordomas, lack of symptoms in several cases, and late age of onset may mask true incidence of intradural drop metastases.

The imaging features are nonspecific and tend to mirror those of the primary neoplasm.

References

Martin MP, Olson S. Intradural drop metastasis of a clival chordoma. J Clin Neurosci. 2009 Aug;16(8):1105-7.

Radiation-Associated Sarcomas

Patient with history of radiation therapy for head and neck cancer. Radiation field extended into the supraclavicular nodal stations. CT shows an osteoid producing soft tissue mass to the right of midline. Bone scan and PET show uptake in the lesion, as well as contralateral lymph nodes. PET shows an FDG-avid lung nodule. T1-WI post-contrast MRI with FS shows a peripherally enhancing soft tissue mass.

The incidence of radiation-associated sarcomas of bone and soft tissue is about 0.1%. They are more commonly seen in patients with breast cancer, lymphoma, head and neck malignancies, and gynecologic cancers. The distribution of primary cancers is likely related to the larger numbers of patients with these cancers and the high survival rates for these tumors.

The majority of radiation-associated tumors are soft tissue sarcomas, with bone sarcomas making up about 20-30% of cases. The majority are high grade and aggressive. The most common soft tissue sarcomas are unclassified pleomorphic sarcoma (UPS, formerly MFH), followed by angiosarcoma (particularly in breast cancer), fibrosarcoma and leiomyosarcoma (particularly in retinoblastoma). The most common bone sarcomas are osteosarcomas.

The latency between radiation and sarcoma ranges from as little as a few months to 54 years. The average is 7 to 16 years. In breast cancer, the average is 10 to 11 years (4-8 years for angiosarcomas). In childhood cancers, the average latency is between 12 to 13 years.

Risk factors include, dose (Rarely seen with low doses: <40 Gy), age at exposure, concomittant chemo exposure (particularly alkylating agents) and genetic tendency (e.g., Li-Fraumeni syndrome).

References

Maki, R. et al. Radiation-Associated Sarcomas. UpToDate

Keloids and Hypertrophic Scars

T1 axial post-contrast MRI of a keloid or hypertrophic scar formation along the margins of a myocutaneous flap. The enhancement can fool you into thinking that there is recurrent tumor, but the linear pattern along the flap margin is the clue that this is related to the scar.

Keloids and hypertrophic scars are fibroblastic proliferations of the dermis. Their morphologic and pathologic features overlap. They are associated with trauma, infection, and connective tissue diseases. They do not spontaneously regress and tend to recur after surgical excision, so surgery is often combined with topical corticosteroid injection or, less commonly, radiation therapy.

In contrast to hypertrophic scars, keloids tend to grow beyond the margins of the injury site, have keloid collagen, and are less likely to stain for smooth muscle actin. Keloids have a higher recurrence rate than hypertrophic scars.

Keloids are hypocellular and are composed of dense collagen. The abundance of type I collagen results in low T2 signal. Keloids occur most frequently in patients aged 15–45 years. People of African and Chinese origin have a higher predilection for keloids. The face, shoulders, forearms, and hands are most commonly affected. They tend to occur where there is increased skin tension

References

Dinauer PA, Brixey CJ, Moncur JT, Fanburg-Smith JC, Murphey MD. Pathologic and MR imaging features of benign fibrous soft-tissue tumors in adults. Radiographics. 2007 Jan-Feb;27(1):173-87.

The axillary nerve and adhesive capsulitis

The axillary nerve (yellow arrow) and the posterior humeral circumflex artery (red arrow) in the region of the quadrilateral space. Note proximity to the inferior capsule.

The axillary nerve is closely related to the inferior capsule of the shoulder. It passes inferior to the subscapularis muscle and travels adjacent to the capsule before entering the quadrilateral space.

The axillary nerve is associated with adhesive capsulitis in at least 2 ways.

First, the axillary nerve can be irritated in the setting of inflammation and thickening of the inferior capsule. The evidence for this is somewhat anecdotal, but makes anatomic sense. The image below is from a patient with adhesive capsulitis. Note the teres minor atrophy (green arrow) in the setting of thickening of the inferior capsule (blue arrow), and constrained fluid in the joint (orange arrow) being forced into the superior subscapularis recess (orange*). The bone lesions are from myeloma, in case you were wondering.



Second, the close proximity of the nerve to the joint capsule predisposes it to injury during arthroscopic capsule release for treatment of adhesive capsulitis. Risk of injury is decreased by placing the incision of the glenohumeral joint capsule at the glenoid insertion with the arm in the abducted and externally rotated position.

We can appreciate the extent of inflammation on other imaging modalities too. On FDG PET/CT, for example, patients with adhesive capsulitis tend to have uptake at the inferior capsule that extends into the adjacent tissues.

References

• Sridharan R, Engle MP, Garg N, Wei W, Amini B. Focal uptake at the rotator interval or inferior capsule of shoulder on ¹⁸F-FDG PET/CT is associated with adhesive capsulitis. Skeletal Radiol. 2017 Apr;46(4):533-538.
• Salem U, Zhang L, Jorgensen JL, Kumar R, Amini B. Adhesive capsulitis mimicking metastasis on 18F-FDG-PET/CT.Clin Nucl Med. 2015 Feb;40(2):e145-7.
• Jerosch J, Filler TJ, Peuker ET. Which joint position puts the axillary nerve at lowest risk when performing arthroscopic capsular release in patients with adhesive capsulitis of the shoulder? Knee Surg Sports Traumatol Arthrosc. 2002 Mar;10(2):126-9.
• E. B. G. D. Santos, P. M. E. Souza (pdf). Teres minor beyond quadrilateral space syndrome: a pictorial review. ECR 2014 conference.

Sacrum

I was reading an article on the role of religion in the secular Turkish state and came across this statement:

It is possible -- such is the argument of Carter Findley in his Turks in World History -- that in doing so it drew on a long Turkish cultural tradition, born in Central Asia and predating conversion to Islam, that figured a sacralisation of the state, which has vested its modern signifier, devlet, with an aura of unusual potency.

You may be wondering what the heck a congenital variant of spinal segmentation has to do with religion. From the always-excellent Online Etymology Dictionary:

Bone at the base of the spine, 1753, from Late Latin os sacrum "sacred bone," from Latin os "bone" + sacrum, neuter of sacer "sacred" (see sacred). Said to be so called because the bone was the part of animals that was offered in sacrifices. Translation of Greek hieron osteon. Greek hieros also can mean "strong," and some sources suggest the Latin is a mistranslation of Galen, who was calling it "the strong bone."

Rind-like Perirenal Soft-Tissue Masses

Rind-like perirenal soft tissue masses: Retroperitoneal fibrosis

Differential diagnosis for rind-like perirenal soft-tissue masses:

• Lymphoma (and Waldenstrom Macroglobulinemia)
  • Usually due to contiguous spread from retroperitoneal or renal lymphoma: Distinct imaging patterns: multiple masses, solitary mass, diffuse infiltrating mass, rindlike soft-tissue thickening, and direct invasion from adjacent retroperitoneal lymphadenopathy
  • Isolated perirenal lymphoma very unusual (<10% of cases): Uniformly attenuating rindlike soft-tissue mass.
  • Does not necessarily affect renal function.
• Erdheim-Chester disease
  • Rindlike soft-tissue lesions surrounding the kidneys and ureters
  • Severe compression of renal parenchyma and ureters leads to progressive renal failure
  • Percutaneous nephrostomy made difficult because due to fibrous perinephritis.
• Retroperitoneal Fibrosis (shown above)
  • Typically localized to infrarenal aorta and common iliac arteries
  • Isolated or related to multifocal fibrosclerosis (may include autoimmune pancreatitis, sclerosing cholangitis, scleroderma, Riedel thyroiditis, fibrotic pseudotumor of the orbit, and fibrosis involving multiple organ systems).
  • Perirenal involvement can be from extension from retroperitoneal fibrosis, without associated retroperitoneal fibrosis, or one of manifestations of multifocal fibrosclerosis
  • Perirenal involvement: Soft-tissue mass enveloping kidneys without displacing them.

References

Surabhi VR, Menias C, Prasad SR, Patel AH, Nagar A, Dalrymple NC. Neoplastic and non-neoplastic proliferative disorders of the perirenal space: cross-sectional imaging findings. Radiographics. 2008 Jul-Aug;28(4):1005-17.

Toxic Osteoblastoma

Toxic osteoblastoma is an extremely rare variant of osteoblastoma that is associated with systemic symptoms, such as fever, anorexia, weight loss. There is also marked systemic periostitis, not only of the involved bone, but also at other skeletal sites.

Patients tend to be young children (5-7 years of age). On physical examination, there is massive swelling, warmth, and induration of the overlying skin and prominent superficial vessels overlying the lesion. Patients can also have hyperdynamic circulation and even high-output cardiac failure. Regional adenopathy can also be present.

The systemic response is thought to be due to an exaggerated immune response to the tumor. Interleukins can lead to fever and the diffuse periostitis, as well as anemia and massive limb swelling and vascular proliferation. Another possibility is toxic substances released by the tumor itself.

The lesions are highly vascular, and arteriovenous shunting within the lesion can lead to finger clubbing and diffuse periostitis and can account for hyperdynamic circulation.

Differential considerations include osteomyelitis and osteosarcoma.

References

• Dale S, Breidahl WH, Baker D, Robbins PD, Sundaram M. Severe toxic osteoblastoma of the humerus associated with diffuse periostitis of multiple bones. Skeletal Radiol. 2001 Aug;30(8):464-8.
• Mirra JM, Cove K, Theros E, Paladugu R, Smasson J. A case of osteoblastoma associated with severe systemic toxicity. Am J Surg Pathol. 1979 Oct;3(5):463-71.
• Theologis T, Ostlere S, Gibbons CL, Athanasou NA. Toxic osteoblastoma of the scapula. Skeletal Radiol. 2007 Mar;36(3):253-7.

Nerve Root(s)

In season 3, episode 18 of Star Trek: Deep Space Nine Dr. Bashir has to deal with some deep-seated personal issues. One of these is the fact that he graduated second in his medical school class because he mistook a "pre-ganglionic fiber for a post-ganglionic nerve." Spoiler alert: He did it on purpose because he didn't want to deal with the pressure of being first.

Dr. Bashir is not alone. I see this lead to 2 errors every day in our trainees. The clinical implication is zero, because the referring physicians also don't make this distinction (two wrongs do make a right, apparently).

First, take a look at the image below:



Note that there are 2 nerve roots (dorsal and ventral) on each side (left and right). When you say a lumbar disc compresses a nerve root in the central spinal canal, you need to add an "s," because these dorsal and ventral nerve roots travels down together in the cauda equina. Next time you look at an axial T2-WI of the lumbar spine, see if you can see two distinct nerve roots on either side.

Second, note that once we're post-ganglionic, we're dealing with a nerve, not a root. So, if you're talking about a nerve root outside the foramen, you're about as anatomically correct as a Ken doll.


The same goes for the "nerve roots" of the brachial plexus and the famous Randy Travis Drinks Cold Beer mnemonic for the brachial plexus anatomy (sorry, Randy). All is not lost. Just replace Randy Travis with Nikola Tesla.

Reference

• Basic anatomy that everyone ignores.

Ventriculus Terminalis

The ventriculus terminalis (also known as the terminal ventricle and the fifth ventricle) is a rarely identified cerebrospinal fluid cavity within the conus medullaris. The ventriculus terminalis does not communicate with the subarachnoid space or the central canal of the spinal cord, and may actually be an embryonal remnant of the primitive central canal, leading some to refer to it a sinus terminalis instead.

They are occasionally associated with caudal regression of the spinal cord, Chiari type I malformation, lipomyelomeningoceles, and lumbosacral "lipomas." Some authors believe that all of us have some sort of cystic CSF space at the conus medullaris, but that it's simply larger [and detectable on imaging] in some people and tends to regress (but not completely resolve) over time.

The characteristic imaging features are more commonly seen in children: Cystic lesion of the conus medullaris without spinal cord signal abnormality. In adults, ventriculus terminalis is more likely to have septations and be associated with spinal cord edema, kyphotic deformity and spinal arteriovenous malformations.

Rarely, ventriculus terminalis can enlarge in the presence of meningeal hemorrhage or deformities of the vertebral canal. An enlarged or symptomatic ventriculus terminalis can be treated by cyst fenestration with or without shunting to the subarachnoid space, pleural cavity, or peritoneal cavity.

References

• Kernohan JW. The ventriculus terminalis: its growth and development. J Comp Neurol 1924;38:107–125.
• Suh SH, Chung TS, Lee SK, Cho YE, Kim KS. Ventriculus terminalis in adults: unusual magnetic resonance imaging features and review of the literature. Korean J Radiol. 2012 Sep-Oct;13(5):557-63.
• Woodley-Cook J, Konieczny M, Spears J. The Slowly Enlarging Ventriculus Terminalis. Pol J Radiol. 2016 Nov 7;81:529-531.

False Perpetuations: Main Portal Vein Size and Portal Hypertension

Perpetuation: A main portal vein (MPV) diameter >13 mm is "consistent with portal hypertension" (pHTN)

This cutoff of 13 mm is based on weak literature (mainly from the 1980's), some of which did not include comparison values of normal patients

• One comparative study using ultrasound found (Radiology 1982; 142: 167-172):
• In 79 patients with pHTN
• 36 had a MPV diameter of <13 mm 
• 33 had a MPV diameter >/= 13 mm
• The MPV was not visualized in 10 patients
• In the 45 control patients
• The MPV diameter was < 13 mm in 41 cases
• The MPV was not visualized in 4 patients. 

More recent studies have found that there is no significant difference in MPV diameters when comparing patients without cirrhosis to patients with cirrhosis, and the normal MPV diameter is significantly larger than the 13 mm cutoff

• A study (Eur J Gastroenterol Hepatol 2004; 16:147-155) from King's College using ultrasound (49 controls and 14 cirrhotics) found: 
• the average MPV diameters were 9.6 cm and 10.8 cm in patients without and with cirrhosis, respectively.
• A second study (JCAT 2008; 32: 198-203) from UCSF using CT (59 controls and 67 cirrhotics) found:
• The average MPV diameters were 14.5 cm and 14.8 cm in patients without and with cirrhosis, respectively.
• Using CT, the MPVs in healthy renal donor patients were measured before and after the administration of intravenous contrast, and in the axial and coronal planes (Abdom Radiol 2016; 41:1931-1936). This study found:
• The average MPV diameter was 15.5 +/- 1.9 mm
• This value was significantly different than 13 mm
• Post-contrast MPVs were 0.56 mm larger compared to non-contrast
• A positive correlation between BMI and height versus MPV diameter

In fact, the MPV size can be reduced in portal hypertension and has been described as a sign of hepatofugal MPV flow (AJR 2003; 181: 1629-1633). This study found:

• A MPV diameter of less than 1 cm is a highly sensitive (but not very specific) for MPV flow reversal in patients with cirrhosis