Friday, September 28, 2012

Intracranial Hypotension and Diffuse Dural Enhancement

Intracranial hypotension refers to decreased CSF pressure leading to a headache (usually orthostatic). The four main imaging findings are:
  1. downward displacement of the midbrain
  2. diffuse, smooth dural enhancement
  3. distended dural sinuses
  4. subdural hematoma or hygroma
Absence of one of these signs does not preclude the diagnosis.

The dural enhancement in intracranial hypotension is pachymeningeal (dura-arachnoid) and is seen along the inner table of the skull, as opposed to leptomeningeal enhancement (arachnoid-pia) which is seen on the surface of the brain.

The differential for dural enhancement includes:
  1. meningitis - leptomeningeal enhancement
  2. dural metastases - scattered, "bumpy" enhancement
  3. granulomatous disease (sarcoid, TB) - nodular enhancement
  4. meningioma with focal enhancement of the dural tail
  5. postoperative changes - transient

Smirniotopoulous JG, Murphy FM, Rushing EJ, et al. Patterns of contrast enhancement in the brain and meninges. Radiographics 2007;27:525-51.

Thursday, September 27, 2012


Tonsilloliths are stones that form in the crypts of the palatal tonsils. Most patients with tonsilloliths are asymptomatic and the finding is made incidentally, as in the patient above (multiple coarse calcifications in the bilateral tonsils). However, large tonsilloliths may cause obstruction leading to infection with possible abscess formation. Thus, the presence of tonsilloliths, even if incidental, should be reported.

Mody RN and Srivastava S. Bilateral multiple tonsilloliths. Oral Radiology 2009;25(1):67-70.

Wednesday, September 26, 2012

Tumors Identified via Selective Catheterization of the External Carotid Artery

1. Juvenile nasopharyngeal angiofibroma:
  • young boys presenting with epistaxis 
  • vascular hamartoma
  • embolization is therapeutic
2. Carotid body paraganglioma:
  • found at the bifurcation of the carotid artery where they splay its internal and external branches
  • prolonged, intense tumor blush
  • resectability depends on angle between ICA and ECA
  • patients often left with hoarseness due to proximity of vagus nerve
  • preoperative embolization may be considered
3. Meningioma:
  • highly vascular extra-axial neoplasm 
  • core is supplied by branches of the ECA while periphery is supplied by the ICA
  • "spoke wheel" appearance on angiogram
  • resection is usually curative
  • large tumors may be embolized prior to resection

Pribram HFW. Selective catheterization of the external carotid artery. Radiology 1966;87:315-20.
Roberson GH, Price AC, Davis JM, et al. Therapeutic embolization of juvenile angiofibroma. AJR Am J Roentgenol 1979;133:657-63.
Wieneke JA, Smith A. Paraganglioma: carotid body tumor. Head Neck Pathol 2009;3(4)303-6.
Wilson G, Weidner W, Hanafee W. The demonstration and diagnosis of meningiomas by selective catheter angiography. AJR Am J Roentgenol 1965;95(4):868-73.

Tuesday, September 25, 2012

Blunt Diaphragmatic Rupture

Traumatic blunt diaphragmatic rupture (BDR) is most commonly due to motor vehicle accidents (as was the case in the above patient). The left hemidiaphragm is more commonly injured than the right due to protective effects of the liver. Prompt diagnosis of BDR is important due to potentially life threatening complications if this injury is missed. Common signs indicating BDR on plain films and CT are as follows:

Radiographic signs:
  • loss of diaphragmatic continuity
  • intrathoracic herniation of a hollow viscus (stomach, bowel) or solid organ (liver, spleen)
  • visualization of nasogastric tube tip in thorax
  • collar sign - focal constriction of a herniating viscus at the site of diaphragmatic tear
CT signs:
  • discontinuity of diaphragm
  • collar sign (as above)
  • dependent viscera sign - herniated viscera is no longer freely suspended in the abdominal cavity and falls dependently (along the posterior ribs)

Desir A and Ghaye B. CT of blunt diaphragmatic rupture. Radiographics 2012;32:477-98.
Iochum S, Ludig T, Walter F, et al. Imaging of diaphragmatic injury: a diagnostic challenge?. Radiographics 2002;22:S103-16.

Monday, September 24, 2012

Maffucci Syndrome

Maffucci Syndrome
  • nonhereditary 
  • enchondromatosis combined with hemangiomas
  • enchondromas in Maffucci syndrome carry a relatively high risk of malignant transformation 
    • chondrosarcoma is the most common musculoskeletal malignancy 
  • high risk of developing non musculoskeletal malignancies
    • ovarian, pancreatic, gastrointestinal adenocarcinoma, glioma
Imaging Findings
  • expansile metaphyseal lesions 
  • sclerotic margins
  • chondroid mineralization with "ring and arc" pattern that is typical of cartilage containing lesions
  • increased signal intensity on T2W MR due to high water content of hyaline cartilage

Flach HZ, Ginai AZ, Oosterhuis JW. Maffucci syndrome: radiologic and pathologic findings. Radiographics 2001;21:1311-16.

Friday, September 21, 2012

Emphysematous Pancreatitis

Acute pancreatitis can progress to emphysematous pancreatitis when superinfection with a gas forming organism occurs. Other causes for intraductal or parenchymal pancreatic gas include end organ infection, enteric fistula, iatrogenic (post endoscopic instrumentation), and reflux from the duodenum after sphincterotomy. The diagnosis carries a poor prognosis and requires aggressive treatment with antibiotics with possible debridement or drainage.

CT is the best modality to detect emphysematous pancreatitis. In addition to retroperitoneal air within and surrounding the pancreas (as on the above images), complications such as abscess formation and necrosis may seen.

The liver findings on the above images are discussed here.

Grayson DE, Abbott RM, Levy AD, et al. Emphysematous infections of the abdomen and pelvis: a pictorial review. Radiographics 2002;22:543-61.

Thursday, September 20, 2012

Caroli's Disease and Syndrome

Caroli's Disease
  • autosomal recessive abnormality in ductal plate development
  • communicating cavernous biliary ectasia 
  • US will show:
    • dilated intrahepatic bile ducts that are saccular or fusiform
    • outpouchings may contain sludge/calculi due to biliary stasis 
    • central dot sign - color Doppler shows flow in the portal triads surrounded by the dilated ducts
  • ERCP/MRCP will show dilated ducts that communicate with the central biliary tree
Caroli's syndrome is Caroli's disease + congenital hepatic fibrosis.

Levy AD, Rohrmann CA, Murakata LA, et al. Caroli's disease: radiologic spectrum with pathologic correlation. AJR Am J Roentgenol 2002;179:1053-7.

Wednesday, September 19, 2012

The Basion-Dens Interval

Injuries at the craniocervical junction are important to recognize due to their critical clinical implications. The basion-dens interval (BDI) is a parameter used to define the normal articulation between the occiput and the cervical spine. Measured on a midline sagittal image, the distance between the inferior tip of the basion and the tip of the dens is less than 12 mm in 95% of adults. A value greater than 12 mm is concerning for atlanto-occipital dislocation.  

The above image is from a patient with bilateral atlanto-occipital dislocation with anterior translation of the occiput relative to the cervical spine.

Deliganis AV, Baxter AB, Hanson JA, et al. Radiologic spectrum of craniocervical distraction injuries. Radiographics 2000;20:S237-50.

Tuesday, September 18, 2012

Segmental Testicular Infarction

The presentation of an acute scrotum in the emergency setting typically leads to a work up for testicular torsion with ultrasound imaging. Accurate diagnosis of acute testicular torsion is important because the risk of global testicular infarction increases with time from onset of symptoms. 

Segmental testicular infarction is a rarer entity that is not well described in the literature. Ultrasound will demonstrate wedge shaped, hypoechoic regions in the testes with absence of vascular flow. The differential diagnosis for this finding is:

  • polycythemia vera
  • intimal hyperplasia of the spermatic artery
  • sickle cell anemia
  • vasculitis
    • systemic lupus erythematosus
    • polyarteritis nodosa
  • venous thromboses (in hypercoagulable states)
  • severe epididymo-orchitis that is unresponsive to treatment
  • trauma

Differentiation between these entities and testicular torsion is important because treatment of the underlying condition (i.e. with steroids for polyarteritis nodosa) can prevent an unnecessary orchidectomy.

Fernandez-Perez GC, Tardaguila FM, Velasco M, et al. Radiologic findings of segmental testicular infarction. AJR Am J Roentgenol 2005;1587-93.
Sriprasad S, Kooiman GG, Muir GH, et al. Acute segmental testicular infarction: differentiation from tumor using high frequency colour Doppler ultrasound. BJR 2001;74:965-7.

Monday, September 17, 2012

Mucocele of the Appendix

The above images are from a patient who presented to the emergency room with right lower quadrant pain and nausea. Acute appendicitis was suspected. CECT demonstrated a dilated, tubular, fluid filled structure arising from the cecal base. Its maximal diameter was 3 cm. No pericecal inflammatory changes were seen. The patient was taken to the operating room and found to have an appendiceal mucocele.

Mucocele of the appendix refers to a dilated, mucus-filled appendix. CECT findings depend on the histologic type of mucocele. Mucosal hyperplasia (simple mucocele) and mucinous cystadenoma (benign tumor) will appear as a well circumscribed cystic structure with water attenuation of its lumen. Peripheral calcifications are seen in approximately 50% of cases. Mucinous cystadenocarcinoma (malignant tumor with higher risk of perforation) appears as a large, irregular mass with nodular mural thickening, solid and cystic components, and calcifications.

Clinically, the presentation of appendiceal mucocele is identical to that of acute appendicitis. However, pre-operative diagnosis of the former is important since it changes the surgical management - rupture of a mucocele can cause free spillage of mucus into the peritoneal cavity resulting in pseudomyxoma peritonei. Discovery of a neoplastic cause for appendiceal mucocele usually warrants a right hemicolectomy.

Bennett GL, Tanpitukpongse TP, Macari M, et al. CT diagnosis of mucocele of the appendix in patients with acute appendicitis. AJR Am J Roentgenol 2009;192(3):W103-10.
Pickhardt PJ, Levy AD, Rohrmann CA, et al. Primary neoplasms of the appendix manifesting as acute appendicitis: CT findings with pathologic comparison. Radiology 2002;224:775-81.

Friday, September 14, 2012

Cystic and Solid Lesions of the Cardiophrenic Space

The cardiophrenic space is located at the base of the mediastinum and is defined by the base of the heart, the diaphragm, and the chest wall. Normally, this space is occupied by fat although both benign and malignant lesions can be found in this location.

Cystic Lesions
  1. Pericardial cysts
    • benign
    • usually in the right cardiophrenic space
    • CT: well defined, smooth-walled cyst filled with simple fluid
    • MR: high signal intensity on T2WI
  2. Hydatid cyst
    • rare
    • may be a herniated hepatic hydatid cyst
    • CT: uni- or multilocular cyst with peripheral mural calcifications
    • MR: mother cyst (the matrix) is usually intermediate signal intensity on T1WI; daughter cysts are high signal intensity on T2WI
  3. Thymic tumors with cystic components
Solid Lesions
  1. Lymphadenopathy
    • > 8mm in short axis diameter is considered pathologic
    • lymphoma is most common cause
  2. Thymoma

Pineda V, Andreu J, Caceres J, et al. Lesions of the cardiophrenic space: findings at cross-sectional imaging. Radiographics 2007;27:19-32.

Thursday, September 13, 2012

Extracapsular Rupture of Breast Implants

The above images are from a woman who presented with left chest wall pain after a motor vehicle accident. CECT demonstrates bilateral prepectoral breast implants with asymmetry in size, retraction of the left implant, thickening of its capsule and surrounding hematoma. Findings are suspicious for extracapsular rupture.

While most centers use CECT for the initial evaluation of trauma patients, MRI with dedicated breast coil is the most sensitive for detecting implant rupture. Findings on various imaging modalities include:

  • wrinkled contour of implant
  • dense, globular masses due to extracapsular silicone
  • stepladder sign - linear echogenic layers of the collapsed implant shell
  • "snowstorm" appearance - increased echogenicity due to extracapsular spread of silicone
  • T2WI may show extracapsular high signal
  • use of water suppressed STIR images will render bright signal for silicone

Brown SL, Middleton MS, Berg WA, et al. Prevalence of rupture of silicone gel breast implants revealed on MR imaging in a population of women in Birmingham, Alabama. Am J Roentgenol 2000;175:1057-64.
Scaranelo AM, Marques AF, Smialowski EB, et al. Evaluation of the rupture of silicone breast implants by mammography, ultrasonography and magnetic resonance imaging in asymptomatic patients: correlation with surgical findings. Sao Paulo Med J 2004;122(2):41-7.

Wednesday, September 12, 2012

Pepper Pot Skull

Pepper pot skull (or salt and pepper skull) refers to a granular, mottled appearance of the calvarium with tiny hyperlucent areas. Other descriptive terms for this finding include ground glass texture and loss of differentiation between the inner and outer tables of the skull. This appearance is attributed to the resorption of trabecular bone and is seen in hyperparathyroidism. While some may use the term pepper pot skull to describe the lytic skull lesions seen in multiple myeloma, these lesions typically produce larger hyperlucent areas in the calvarium and are often referred to as "punched out" lucencies.

I recommend taking a look at the reference below - a cute reminder of all of the "food signs" in radiology.

Roche CJ, O'Keeffe DP, Lee WK, et al. Selections from the buffet of food signs in radiology. Radiographics 2002;22:1369-84.

Tuesday, September 11, 2012

Pericardial Effusions in HIV Infection

The above image is from a patient with a history of HIV and lymphoma. CECT demonstrates a thickened, enhancing pericardium with a complex pericardial effusion. Bilateral pleural effusions, right greater than left, are also noted. 

Pericardial effusions are the most common cardiovascular complication of HIV infection and usually carry a poor prognosis. The majority of cases are due to an idiopathic cause. Other causes that must be considered in this population are tuberculosis, bacterial infection (S. aureus is the most common), malignancy (lymphoma and Kaposi's sarcoma), viral, and fungal.

Chen Y, Brennessel D, Walters J, et al. Human immunodeficiency virus-associated pericardial effusion: report of 40 cases and review of the literature. Am Heart J 1999;137(3):516-21.
Restrepo CD, Diethelm L, Lemos JA, et al. Cardiovascular complications of human immunodeficiency virus. Radiographics 2006;26:213-31.
Wang ZJ, Reddy GP, Gotway MB, et al. CT and MR imaging of pericardial disease. Radiographics 2003;23:S167-80.

Monday, September 10, 2012

Cystic Lesions of the Renal Sinus

Peripelvic Cysts
  • multiple benign cysts arising in the renal sinus (extraparenchymal)
  • likely originate from sinus lymphatics
  • usually bilateral
  • may mimic hydronephrosis on US and NCECT but cannot be traced to the ureter
  • indistinguishable from renal sinus lipomatosis on excretory urography

Parapelvic Cysts
  • simple cysts originating from the medial renal parenchyma
  • same imaging features as simple renal cysts (Bosniak I)
  • usually asymptomatic but a large parapelvic cyst that compresses the renal vasculature/collecting system may cause hypertension, hematuria, and hydronephrosis

Rha SE, Byun JY, Jung SE, et al. The renal sinus: pathologic spectrum and multimodality imaging approach. Radiographics 2004;24:S117-31.

Friday, September 7, 2012

The Air Crescent Sign

The air crescent sign refers to a radiolucent rim around a soft tissue density and is characteristic of invasive pulmonary aspergillosis (or other angioinvasive fungal infections) in immunocompromised patients. It results when Aspergillus invades the pulmonary vasculature and causes hemorrhage with subsequent infarction of pulmonary tissue. Over time, the infarcted tissue retracts and is absorbed along its periphery by leukocytes which is what gives rise to the air crescent appearance. The visualization of the air crescent sign indicates a favorable outcome because patients without leukocyte function cannot form this consolidation.

The image above is from a patient with prior history of tuberculosis who presented with a cough. The air crescent sign is seen in the left upper lobe.

Abramson S. The air crescent sign. Radiology 2001;18:230-2.

Thursday, September 6, 2012

The Molar Tooth Sign - Joubert Syndrome

Joubert syndrome is an autosomal recessive disorder characterized by cerebellar vermian hypoplasia with a midline cleft and lack of decussation of the superior cerebellar peduncles, the latter causing an enlargement of the peduncles. Other decussation defects of the central pontine and corticospinal tracts as well as dysplasia of the olivary nuclei may also be present. Associated renal, retinal, and hepatic abnormalities are often seen. 

The molar tooth sign refers to the characteristic appearance of the midbrain seen on axial imaging (CT or MR) in patients with Joubert syndrome. Thickened superior cerebellar peduncles surrounding an elongated fourth ventricle give this appearance. A vermian cleft may also be recognized.

McGraw P. The molar tooth sign. Radiology 2003;29:671-2.

Wednesday, September 5, 2012

Discitis/Vertebral Body Osteomyelitis

Vertebral body osteomyelitis (and associated discitis) is an infection involving the vertebral body endplates that extends to the intervening disc space. While vertebral body endplate destruction may be visible on plain films or bone CT studies, MR is the preferred imaging modality to assess for spread of infection to the disc space and paraspinal tissues, or for development of an epidural abscess. T1W images (A, D) will show endplate destruction and thickening of the paraspinal tissues with ill-defined fat places. T2W images (B) will demonstrate high signal in the intervertebral disc. Gadolinium enhanced images (C) will demonstrate enhancement of the infected vertebral bodies and paraspinal tissues. In the presence of an epidural abscess fluid sensitive sequences will show a collection in the epidural space that demonstrates peripheral enhancement upon gadolinium administration. 

Dagirmanjian A, Schils J, McHenry M, et al. MR imaging of vertebral osteomyelitis revisited. Am J Roentgenol 1996;167(6):1539-43.
Kowalski TJ, Layton KF, Berbari EF, et al. Follow-up MR imaging in patients with pyogenic spine infections: lack of correlation with clinical features. Am J Roentgenol 2007;28:693-99.

Tuesday, September 4, 2012

Pulmonary Pseudotumors

Nodular Pulmonary Amyloid (Amyloidoma)
  • one of the three presentations of amyloidosis in the chest (the other two are tracheobronchial and nodular septal)
  • solitary or multiple nodules with smooth contours
  • lower lobe, subpleural/peripheral location 
  • may calcify or undergo osseous metaplasia
  • larger nodules may cavitate or become hemorrhagic
  • resection is diagnostic and curative
  • differential - primary or metastatic neoplasms
Exogenous Lipoid Pneumonia
  • caused by aspiration of mineral, vegetable, or animal oil present in food, radiologic contrast media, or oil based medications
  • NECT will show low attenuation, mass-like consolidation, with regions of fat density
  • crazy paving

Gimenez A, Franquet T, Prats R, et al. Unusual primary lung tumors: a radiologic-pathologic overview. Radiographics 2002;22:601-19.

Monday, September 3, 2012

Happy (Non) Labor Day