Tag Archive | advanced

Puff of smoke sign – describes the characteristic angiographic…

Puff of smoke sign – describes the characteristic angiographic appearance of tiny abnormal intracranial collateral vessel networks in moya moya disease. Progressive narrowing of the supraclinoid internal carotid arteries and circle of Willis vessels results in extensive small collateral arterial networks evolving from the lenticulostriate and choroidal arteries. When viewed angiographically, the abnormal collaterals simulate smoke emanating away from the major arteries. 

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CLASSIC CASE: Post contrast MRI demonstrating an enhancing mass…

CLASSIC CASE: Post contrast MRI demonstrating an enhancing mass within the left lobe of liver with a central “scar”. Try out the BRAND NEW RADIOPAEDIA.ORG QUIZ MODE to work through this case and learn about the diagnosis. Click to enter QUIZ MODE

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Puff of smoke sign – describes the characteristic angiographic…

Puff of smoke sign – describes the characteristic angiographic appearance of tiny abnormal intracranial collateral vessel networks in moyamoya disease. Progressive narrowing of the supraclinoid internal carotid arteries and circle of Willis vessels results in extensive small collateral arterial networks evolving from the lenticulostriate and choroidal arteries. When viewed angiographically, the abnormal collaterals simulate smoke emanating away from the major arteries.    

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Shepherd’s crook deformity – refers to a distinctive…

Shepherd’s crook deformity – refers to a distinctive abnormal contour of the proximal femur in the setting of fibrous dysplasia.  As the bone deforms the angle made between the neck of the femur and the femoral shaft decreases (coxa vara) and the bone becomes rounded simulating the appearance of a shepherd’s crook, a stick with a C-shaped end carried by shepherd’s particularly common in biblical times.

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Haemosiderin cap sign – a spinal tumour appearance where a cap…

Haemosiderin cap sign – a spinal tumour appearance where a cap of hypointense haemosiderin is seen on T2 weighed imaging above and / or below the tumour due to previous haemorrhage. It is most often associated with spinal ependymomas, being seen in 20-33% of these cases.  The sign however may also be seen in hemangioblastomas and paragangliomas and therefore while it is highly suggestive of ependymoma it is not pathognomonic. 

See our YouTube video tutorial on ‘Spinal Ependymoma’ here.

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Inferior rib notching – refers to a remodeling deformity of the…

Inferior rib notching – refers to a remodeling deformity of the lower aspect of the ribs, usually induced by dilated intercostal vessels. Arterial dilatation most commonly occurs when there is obstruction of the aorta such as in coarctation, while venous dilatation may occur in the setting of SVC obstruction. In both settings the intercostal vessels act as collaterals to bypass the primary vascular obstruction with the rib notching being a secondary effect. Nerve sheath tumours are the major non-vascular cause of inferior rib notching. 

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Acoustic neuroma – a relatively common type…

Acoustic neuroma – a relatively common type of schwannoma arising from the vestibulocochlear nerve (CN VIII). It typically presents with sensorineural hearing loss or tinnitus and accounts for 75 – 90% of cerebellopontine angle masses. Extension into the internal acoustic canal is a major differentiating feature and results in a trumpeted appearance of the canal and a classic ice-cream cone appearance with the portion outside the canal representing the ice-cream. When seen bilaterally, acoustic neuromas are strongly suggestive of neurofibromatosis type 2.   

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Insular ribbon sign – refers to loss of the normal insular…

Insular ribbon sign – refers to loss of the normal insular cortex grey-white differentiation and is one of the earliest imaging sign of middle cerebral artery territory infarction. The insular cortex is located along the Sylvian fissure overlying the external capsule where a ‘ribbon’ of normal cortex should be appreciable (red arrows). In the setting of MCA infarction, cytotoxic oedema leads to hypoattenuation such that the normal insular ribbon is no longer visible (blue arrows).

Case on the left shows a very early infarct (within the first few hours) while the case on the right shows a more established infarct (greater than 4 hours old).

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Bear’s paw sign -refers to a distinctive cross-sectional…

Bear’s paw sign -refers to a distinctive cross-sectional imaging appearance of the kidney in xanthogranulomatous pyelonephritis.  In this chronic granulomatous disease the kidney is progressively replaced by a mass of reactive tissue appearing like the pads of a bear’s paw. The disease is almost always incited by staghorn calculi as was the case for this patient.

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Black turbinate sign – an important MRI sign of mucormycosis; a…

Black turbinate sign – an important MRI sign of mucormycosis; a deadly form of acute invasive fungal sinusitis seen in diabetic and immunocompromised patients. Fungal spores germinate to produce angioinvasive hyphae that cause infarction as they invade the nasal mucosa. This results in a ‘black’ area of non-enhancing mucosa which stands out against the normal enhancing mucosa. The sign may be critical to early detection and treatment of mucormycosis which when untreated can result in blindness and death within 2 weeks.

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