Secondary Chondrosarcoma from Osteochondroma in proximal humerus.

Radiograph of humerus 3 years before the present MRI showing sessile osteochondroma (arrow)

The present radiograph showing development of secondary chondrosarcoma.

The present CT scan axial section of the proximal humerus showing large exophytic mass with calcification seen in the posterior aspect. The mass is continuous with the cortex of the humerus (arrows).

T1 weighted image showing mixed signal intensity of the mass with multiple areas of calcification.

STIR coronal image showing the large mass predominantly hyperintense signals.

Axial T2 image showing the cortical continuity with the mass lesion.

Discussion:

Malignant Transformation of solitary osteochondroma <1% and for multiple exostosis is ~13%.

The cartilaginous cap deserves the most attention when differentiating a benign osteochondroma from a secondary chondrosarcoma that arose from a pre-existing osteochondroma.

In adults, the cartilaginous cap regresses and becomes thin due to enchondral ossification of the majority of the cap.

Malignant transformation is suggested by: 

• Cartilaginous cap thickness greater than 2cm 
• Cortical destruction 
• Back growth of the cartilaginous cap into the stalk or medullary canal
• Lysis of calcifications in cap

Imaging:

Radiograph:

• Chondroid Calcification in cap
• Increasing destruction or change in appearance is worrisome for malignancy

Ultrasound - Good for cap and bursae

Bone Scan - Increased uptake in the cap

MRI: Best test for evaluating thickness of cap and surrounding bursa

• Intermediate T1W Images
• High Intensity T2W Images because of fluid content

CT:

• The cap will appear as soft tissue with calcification
• Can be difficult to distinguish from muscle

Cap thickness:

• Benign < 1.5cm (0.1 - 3.0cm; Avg. 0.6 - 0.9 cm).
• Malignant > 1.5 cm (1.5 - 12cm; Ave. 6cm).

Hot cross bun sign - Multiple system atrophy

Transverse and sagittal T2-weighted MRimage of the brain of a patient with multiple system atrophy (MSA) of the cerebellar-predominant subtype (MSA-c) shows the hot cross bun sign as a cruciform hyperintensity

in an atrophied pons. Cerebellum and middle cerebellar peduncles are also atrophied.

Discussion:

Multiple system atrophy is a rare neurological disorder characterized by a combination of parkinsonism, cerebellar and pyramidal signs, and autonomic dysfunction. The term "Multiple System Atrophy" is synonymous with striatonigral degeneration (SND) when Parkinsonism predominates, olivopontocerebellar atrophy (OPCA) when cerebellar signs predominate, and Shy-Drager syndrome when autonomic failure is dominant. The incidence (new case per 100,000 person years) for ages 50 to 99 years is 3.0 (Bower et al, 1997), or about half as frequent as it's close relative, progressive supranuclear palsy (PSP). The mean age of onset is 54.

Pathophysiology: There is neuronal loss and gliosis in the inferior olives, pons, cerebellum, substantia nigra, locus ceruleus, striatum and the intermediolateral column of the spinal cord.

Similar pattern of neuronal loss is seen in a patient with parkinsonism, the neuronal loss being secondary to presumed vasculitis, and proposed that the sign may reflect wallerian degeneration of transverse pontocerebellar fibers secondary to vasculitic infarction.\

MRI - On T2-weighted MR images, a hyperintense rim at the putaminal edge, putaminal atrophy, and intrinsic signal intensity change are seen. In MSA-c, the changes predominantly affect the infratentorial structures. On T2-weighted MR images, atrophy and increased signal intensity within the pons, cerebellum, and middle cerebellar peduncles are seen.

References

1. Schrag A, Kingsley D, Phatouros C, et al. Clinical usefulness of magnetic resonance imaging in multiple system atrophy. J Neurol Neurosurg Psychiatry 1998;65:65–71.

2. Muqit MM, Mort D, Miskiel KA, Shakir RA. “Hot cross bun” sign in a patient with parkinsonism secondary to presumed vasculitis. J Neurol Neurosurg Psychiatry 2001;71:565–566.

Achilles tendon rupture - MRI

The STIR and T1 weighted sagittal images of the lower leg and ankle of a 52 year old female presented with trauma showing ruptured Achilles tendon (arrow) with proximal retraction of the tendon evidenced by wavy pattern of the hypointense tendon (arrow heads).

Achilles tendon tears may be grouped into 4 types ( according to severity of the tear and degree of retraction).

• type I : partial ruptures <= 50%
  • typically treated with conservative management
• type II : complete rupture with tendinous gap <= 3 cm
  • typically treated with end-end anastomosis
• type III : complete rupture with tendinous gap 3 to 6 cm
  • often requires tendon / synthetic graft
• type IV : complete rupture with defect of > 6 cm (neglected ruptures)
  • often requires tendon / synthetic graft and gastrocnemius recession.
  Reference: MAFFULLI NICOLA. “Current Concepts Review - Rupture of the Achilles Tendon.” J Bone Joint Surg Am 81, no. 7 (July 1, 1999): 1019-36.

Aberrant right subclavian artery

Coronal curved CT reformatted image of the 62 year old male patient presented with cough showing incidentally detected aberrant right subclavian artery arising from the left sided aortic arch (arrow).

Axial curved CT reformatted image of the 62 year old male patient presented with cough showing incidentally detected aberrant right subclavian artery arising from the left sided aortic arch (arrow) causing compression on the esophagus.

Sagittal oblique curved reformatted image better depicts the aberrant artery.

Discussion:

The aberrant artery usually arises just distal to the left subclavian artery and crosses in the posterior part of the mediastinum usually behind the esophagus on its way to the right upper extremity. Such course of this aberrant vessel may cause a vascular ring around the trachea and esophaugus. Dysphagia due to an aberrant right subclavian artery is termed dysphagia lusoria. Palsy of the recurrent laryngeal nerve is termed Ortner's syndrome.

The aberrant right subclavian artery frequently arises from a dilated segment of the proximal descending aorta, the so-called Diverticulum of Kommerell.

Carcinoma lung with intra-spinal metastases - PET/CT.

PET/CT fused image of a 65 year old smoker showing large intensely FDG avid mass lesion in the left upper lobe with areas of necrosis and mediastinal FDG avid lymphadenopathy.

Sagittal PET/CT fused whole spine image showing intraspinal intense FDG avid focal lesions at C7-D1 and L1 levels suggestive of metastases.

Sagittal PET/CT fused cervical spine image showing intraspinal intense FDG avid focal lesion.

Axial PET/CT fused cervical spine image at C7 level showing intraspinal intense FDG avid focal lesion.

Axial PET/CT fused cervical spine image at L1 level showing intraspinal intense FDG avid focal lesion

Discussion:

The intraspinal metastases may spread through several routes, such as arterial dissemination; venous spread through the network of communicating venous channels in the spinal cord and the cauda equina; spread via the perineural lymphatic vessels or the subarachnoid space; invasion of a dorsal root; or direct extension of the primary tumor.

Lung carcinoma commonly metastasize by arterial dissemination.

Renal angiomyolipoma-CT

Axial CT of kidneys in a 29 year old male showing small exophytic fat attenuation lesion in the left kidney (arrow) suggestive of angiomyolipoma.

Zoomed picture of the above showed image better shows the lesion.

Discussion:

Angiomyolipoma (AML) is the most common benign tumour of the kidney and is composed of blood vessels, smooth muscle cells and fat cells. It is strongly associated with tuberous sclerosis.

Imaging features:

Ultrasonography (USG) - Well defined hyper echoic lesion in the kidney. Hyperechogenecity is due to fat content of the lesion.

CT Scan: Well defined fat attenuation lesion as shown in our case. CT angiography may be helpful to identify the aneurysms which predict the fatal hemorrhage.

MRI - Hyperintense on both T1 and T2 weighted images due to its fat content and appears hypointense on fat suppressed T1 images. 

If the fatty tissue is scanty in-phase and out-phase images T1 weighted sequence is very helpful in identifying the fat component in the lesion, which is seen as loss of signal on out-phase images.

People with tuberous sclerosis needs yearly follow up  renal scans.

Treatment:

• If the lesion is < 4 cm - follow up imaging to look for the progression of the lesion.
• If it is > 4 cm or presence of aneurysm, needs to be treated with trans arterial embolisation or surgical excision. Embolising agents used are PVA (Polyvinyl alcohol) and absolute alcohol mixed with lipiodol. 

Renal cell carcinoma with Hiatus hernia-CT

Axial CT of kidneys in a 42 year old male showing large heterogeneously enhancing lesion in the left kidney with perinephric extension.

Axial section at the level of diaphragm of the same patient showing hiatus hernia (arrow) 

Duplex collecting system with ureterocele- CT Urography.

3D volume rendering maximum intensity projection image of CT urography in 29 year old male showing duplication of collecting system, upper and mid ureter on the left side (arrow head) with orthotopic ureterocele (arrow)

Duplex collecting system-CT Urography.

3D volume rendering maximum intensity projection image of CT Urography in 27 year old male showing duplication of collecting system, upper and mid ureter (arrow). Both the ureters are joining in their lower thirds (arrow head).

Papillary necrosis - CT Urography

Maximum intensity projection image of CT Urography in 32 year old male showing papillary necrosis in the right kidney with calyx cut off (arrow) due to old Koch’s

Renal parenchymal scarring-CT Urography

Coronal reformatted CT Urography images in a 32 year old male showing cortical scarring in bilateral kidneys due previous tuberculosis

Renal calculus-NCCT KUB (Stone protocol)

Axial and coronal reformatted non contrast CT images in a 32 year old female showing left renal calculus (arrows).

Renal cyst - CT

Axial and coronal reformatted CT images in a 36 year old male showing simple cortical cyst in the right kidney (Bosniak category I cyst).

Ureteric calculus-NCCT KUB (Stone protocol)

Axial and coronal reformatted non contrast CT images in a 41 year old showing right ureterovesical junction calculus (arrows).

Non contrast CT in multi slice CT (stone protocol) is the modality of choice for the diagnosis of ureteric calculus.

Fibromuscular dysplasia-CT Renal Angiography.

Volume rendered CT angiography image in 25 year old male scheduled for donor nephrectomy showing irregularity (string of beads) in the bilateral renal arteries (arrows) more so on the right side with aneurysm (arrow head) in one of the distal lobar renal artery branch.