The 'Light bulb sign' of liver hemangioma [MRI]

 Light bulb sign refers to the persistent T2 bright homogeneous signal intensity of a typical liver hemangioma, on increasing the TE  (T2 weightage) of the image. The bright signal is compared to that of a glowing light bulb. This may however also be seen in hypervascular metastases. 

MRI Liver of an young patient with multiple hemangiomas in both lobes. 

On increasing the TE, the signal intensity of hemangioma is well preserved, whereas the signals of other structures such as liver and spleen gets reduced.  

Hemangiomas are T2 homogenously hyperintense, with well defined margins with or without small lobulatations. They appear hypointense in T1WI, hyperintense in DWI. In post Gadolinium images they show peripheral nodular intense enhancement in the arterial phase, with gradual centripetal filling-in of the contrast. In the delayed hepatobiliary phase hemangiomas appear hypointense as they do not contain any hepatocytes. 

Isolated Area Postrema Syndrome (APS) presenting as intractable nausea and vomiting (NMOSD)

 Area Postrema (AP) is an emetic reflex center, one of the circum-ventricular organs that is outside the blood-brain barrier(BBB). It is located in the dorsal aspect of the medulla, at the caudal end of the fourth ventricle. AP along with Nucleus Tractus Solitarius (NTS) and dorsal motor nucleus of Vagus forms the dorsal vagal complex, where most of the vagal afferents terminate. AP by its location outside the BBB is exposed to the toxins in the blood. Activation of the AP brings nausea and vomiting, due to its projections into the NTS. 

AP through its hypothalamic,brainstem connections also regulate fluid balance, immunomodulation etc. It also chemo-sensitive neurons regulating hiccups. 

Neuro Myelitis Optic Spectrum of Disorders (NMOSD) are a group of autoimmune inflammatory demyelinating diseases of the CNS. Most of these show characteristic antibody to aquaporin-4 (AQP-4) water channel. 

 Attacks of intractable nausea, vomiting or hiccups (INVH) in the presence of a dorsal medullary lesion is called as the Area Postrema Syndrome (APS) and upto 30% of NMOSD patients will have APS during their disease course. 

NMOSD lesions in the Area Postrema shows loss of AQP-4 immunoreactivity and inflammation and characteristically lacks necrosis and demyelination which is seen in spinal cord and optic lesions, explaining reversibility of the symptoms. Patients have to tested for Serum and CSF AQP4-IgG antibodies. 

Isolated APS is easily mistaken clinically and is often attributed initially to other causes like gastritis including H.Pylori, GERD, Cholecystitis, Pancreatitis, food poisoning, gastroparesis etc. 

Immunotherapy usually results in rapid relief of symptoms usually within 2-3 days, responding to Methyl Prednisolone or Immunotherapy in most cases. Refractory cases may need drugs like Azathioprine, MMF, Rituximab.   

Below are the MRI images of a young female with intractable nausea and vomiting. 

T2 and T2 FLAIR hyperintensity noted in the region of the Area Postrema, called the Inverted-V sign.

Bilateral symmetrical normal optic nerves.

No restricted diffusion seen in the abnormal signal areas of Area Postrema.

Corresponding sagittal T2 FLAIR image showing the level of Area Postrema.
Abnormal signal intensity is also seen in the inferior colliculi of midbrain in the sagittal image. 

Diagram showing the location of AP, NTS in the dorsal medulla.

Hepatocellular Adenomas

Hepatic / Hepatocellular adenomas are uncommon benign tumor commonly seen in young to middle aged women, with history of oral contraceptive use. 

👉 Hepatic adenomatosis:  >10 adenomas. Adenomas in hepatic adenomatosis is not related to the hormonal or other risk factors. They tend to be multiple, progressive, symptomatic, more likely to lead to hepatic dysfunction and possible malignant transformation. 

HCAs are now classified based on the genetic and pathologic subtypes as :

1. Inflammatory hepatocellular adenoma.
2. Hepatocyte-nuclear-factor-1-alpha (HNF-1α-mutated) hepatocellular adenoma. 
3. β-catenin-mutated hepatocellular adenomas.
4. Unclassified subtype (includes HCAs without any genetic abnormalities).

Typical hepatic adenomas show moderate arterial phase enhancement with washout in portal venous and delayed, appears isointense to rest of liver. Chemical shift imaging can produce loss of signal of the adenoma in out of phase images due to the presence of fat within.


Name two hepatocyte specific contrast agents?

1. Gd-BOPTA / Gadobenate Dimeglumine
2. Gadoxetate Sodium.

What will happen in case of HCA with hepatocyte specific contrast agents?
Ans : Will appear darker than rest of liver, as the hepatocytes in HCA are non-functional.

Easy to remember Hepatic Adenoma better as ‘Hepatocyte’ Adenoma, as it lacks biliary epithelium, portal vein and even Kupffer cells.

Incidence Ratio in Female to Male is 9:1, Why 

Ans: OCP use. (Anabolic steroids also increase the risk, common with young men).

Surgery is recommended irrespective of size, why?

1. Risk of rupture and shock.
2. Transformation into HCC.

Below MRI images are of a 25yr old female patient who presented with pain related to cholecystolithiasis. Three incidental slightly echogenic lesions are seen in both lobes during USG, for which MRI was suggested.

T2 weighted images showing slightly T2 hyperintense lesion in the superior subcapular portion of the left lobe, lateral segment. 

Another similar signal intensity lesion in right lobe, segment VII/VIII

The main lesion showing the signal intensity loss in the Out-phase images, suggesting intralesional microscopic fat content. No restricted diffusion were seen in these lesions. 

Subtlest of three in the superior portion of segment VII of right lobe, again showing the loss of signal intensity. 

Increasing the TE of T2 WI reduces the signal intensity of the lesion in addition to that of rest of the structures. (c.f. hemangioma shows similar signal on increasing TE). See this article to see how a hemangioma looks like on increasing TE ('The Light Bulb Sign')

  Dynamic post contrast images shows prompt arterial phase enhancement of the lesion (yellow arrow), and appearing someehat isointense to rest of liver in the further images.

References:

1. Luigi Grazioli, Lucio Olivetti, Giancarlo Mazza, Maria Pia Bondioni, "MR Imaging of Hepatocellular Adenomas and Differential Diagnosis Dilemma", International Journal of 
   Hepatology, vol. 2013, Article ID 374170, 20 pages, 2013.
2. Hepatocellular Adenomas: Correlation of MR Imaging Findings with Pathologic Subtype Classification, Radiology.
3. Hepatic Adenomas: Imaging and Pathologic Findings. Luigi Grazioli, Michael P. Federle, Giuseppe Brancatelli, Tomoaki Ichikawa, Lucio Olivetti, Arye Blachar, Radiographics.

Persistent Trigeminal Artery (PTA), Tau sign

Persistent Primitive Trigeminal Artery is one of the persistent carotid-vertebro-basilar anastomoses. PTA arises from petrous-cavernous junction, runs posterolaterally along the trigeminal nerve, crosses over or through dorsum sella.  

Two types of PTA have been described. 

Saltzman Type I : PTA supplies the distal basilar artery. PComs are usually absent. The distal basilar artery is absent or hypoplastic. Distal vertebral arteries are also hypoplastic. 

Saltzman Type II : PTA supplies the Superior Cerebellar Arteries, with PCAs supplied by the PCom. 

TOF MRA images showed Saltzman type I PPTA, where the PTA is seen replacing the distal basilar artery. 

Sagittal MIP MRA image showing the distal basilar artery completely supplied by the PTA. 

The Tau sign, resembling a 'T' is classically described in the sagittal images. 

Perineural cysts (Tarlov cysts) of the cervical spine

Incisive Canal Cyst (Nasopalatine Duct Cyst, NPDC)

Incisive canal cyst also known as nasopalatine duct cysts (NPDC), is a developmental cyst arising from the epithelial remnants of nasopalatine duct, a duct connecting the nasal cavity with anterior maxilla in fetal life. It is considered the most common non-odontogenic cyst of jaw bone.

Often it presents in 4th to 6th decades, with slight male predilection. Patients may be asymptomatic, or can have pain, discharge and swelling often due to infection.

Incisive canal cyst is often >15mm in size, whereas the normal finding of incisive foramen is not expected to cross 6mm in diameter.  These cyst is seen superior to the roots of the maxillary incisors and usually doesn't result in any root resorption, but can sometimes result in displacement of the incisor roots.


Below are MRI images of incidentally detected Incisive canal cyst in a 50 year old male patient. MRI was done for evaluation of headache. T2 weighted sagittal, coronal and axial images shows a hyperintense cystic lesion in the anterior maxilla with mild displacement of the roots of maxillary incisors. Cyst measured 13.3mm in width.

Cyst was isointense to muscle in T1 WI (not shown), and hyperintense in T2 FLAIR images (not shown).

See another case of Incisive Canal Cyst : CT images HERE.

Septic arthritis of hip joint

 Young male patient with fever of ~5-6 weeks duration, right hip pain.

STIR Coronal : Green arrow - joint effusion, Orange arrow: asymmetric red marrow / marrow edema.
(See last MRI image also)

STIR Axial image, Grade 3 joint effusion

STIR Axial image, marked.

Thickening and enhancement of the joint capsule / synovial layers.

Ultrasound: Echogenic fluid with debris within the anterior synovial recess. Anterior peri-articular muscle edema+. Probe tenderness+.

Eventhough the T1 hypointense signals in the intertrochanteric region (left) can be explained by the presence of residual red marrow in this 20yr old patient, the signal intensity is markedly reduced on right side, suspicious of marrow edema.

Bilateral basal ganglia T1 hyperintensity

Left image shows normal T1 signal intensity of Globus Pallidus, where as
right T1 axial image in a 54yr old male with known chronic liver disease
 shows bilateral globus pallidus T1 hyperintensity.

 

Right image: Another CLD patient with bilateral T1 hyperintensity of Globus Pallidus.

Common causes of bilateral T1 hyperintense basal ganglia include:
1. Physiologic calcification.
2. NF-1
3. Hepatic Encephalopathy.
4. Hyperalimentation (Patients undergoing parenteral feeding).

Less common causes:
1.HIE (Term HIE, Hypoxic cerebral infarction).
2. CO poisoning.
3. Kernicterus.
4. Wilson's Disease.

Rarely thyroid / parathyroid hormonal imbalances, hypoglycemia, Fahr's disease, Hallervorden-Spatz syndrome, JE, Congenital HIV etc. also may cause T1 hyperintensity of the basal ganglia.

In chronic liver disease / cirrhotic patients there is symmetrical T1 hyperintensity in Globus Pallidus and Substantia Nigra.


References:
1. Expert-DDx Brain.

Hibernomas

A hibernoma is a rare benign fatty tumor arising from the vestiges (remnant / trace) of fetal brown fat. It is predominantly seen in 20-40 yrs age group with a slight female predilection. It is named so because of resemblance to brown fat in hibernating animals.

Most often the lesion is located in subcutaneous regions of the back (periscapular /interscapular region), neck, axilla, shoulder, thorax, thigh and retroperitoneum. Rarely these are also seen in scalp, breast, peri-ureteric region and scrotum.

Hibernoma usually manifest as slowly growing painless soft-tissue mass. Sometimes patient can be symptomatic due to compression of adjacent neuro-vascular structures, for example sciatica in a posterior thigh lesion.

In ultrasound these usually appear as hyperechoic lesions. Angiography will reveal lesional vascularity with arterio-venous shunting. These can mislead due to increased uptake in 18-FDG-PET.

In CT these lesions show low attenuating lesion, slightly higher attenuating than the subcutaneous fat. Enhancing septae may be seen, with lesion showing mild enhancement. MRI usually demonstrate lesion to be isointense to subcutaneous fat in most cases, with intervening enhancing sepatations. Reduced T1 and T2 signal intensity is also described in few cases. Contrast enhancement need not be present in all cases.

Additionally prominent lesional vessels may be seen in the ultrasound or as T2 flow voids in MRI, with can cause torrential hemorrhage during biopsy, especially in deep seated lesions.

Case courtesy of Dr Matt A. Morgan, Radiopaedia.org. From the case rID: 37589

Above image shows an intermuscular lesion between the gluteus medius and maximus muscles, with intermediate attenuation between fat and muscle. Prominent feeding vessel is seen along the lateral margin of the lesion.

Pre-operatively differentiating from liposarcomas is difficult. Four histological subtypes have been defined: Typical (~80%), Myxoid (8%), Lipoma-like and spindle cell variant. 'Typical' variant has predominantly brown fat. Myxoid variant is seen more often in men with higher water content (increased T2 signal). Lipoma-like lesion is seen more commonly in thigh, more resembling adult fat.


References:
Imaging Findings of a Hibernoma of the Neck
A.C.B.S. da Motta, D.E. Tunkel, W.H. Westra and D.M. Yousem
American Journal of Neuroradiology September 2006, 27 (8) 1658-1659;

CT and MR characteristics of hibernoma: six cases
Dursun, Memduh et al.
Clinical Imaging , Volume 32 , Issue 1 , 42 - 47

From the Archives of the AFIP
Benign Musculoskeletal Lipomatous Lesions
Mark D. Murphey, John F. Carroll, Donald J. Flemming, Thomas L. Pope, Francis H. Gannon, and Mark J. Kransdorf. RadioGraphics 2004 24:5, 1433-1466

Transient Synovitis of Hip Joint

Transient Synovitis (Coxitis fugax) is the most common cause of acute hip pain in children aged 3 to 10 years. It is a self-limiting acute inflammatory condition which is managed symptomatically. However it needs to be differentiated from Septic Arthritis, which will require antibiotics and surgical drainage.¹

Over 90% of hip joint effusions can be attributed to transient synovitis. ²
It has a male gender predilection and more frequently affects the right hip joint.

Etiology of transient synovitis remains unknown. Various theories include response to infection (URTIs), trauma, allergen / antigen etc. Clinical, laboratory and radiological findings help in differentiating Transient Synovitis from Septic Arthritis. The latter is usually associated with fever, elevated ESR & CRP.

X-Ray may reveal mild joint space widening due to effusion. Ultrasound is often the initial modality as it can reliably assess presence of joint effusion in the anterior recess.

MRI findings of Transient Synovitis include:
1. Joint effusion.
2. Synovial thickening & enhancement.
3. Adjacent soft tissue edema, with characteristic absent bone marrow edema.
4. Contralateral effusion (lesser volume usually).

Below MR images are of a 10yr old girl child with limping showing features of transient synovitis in right hip joint. No bone marrow edema or contra-lateral effusion is seen in this child. Grade 3 joint effusion is present in right hip joint.

Very rarely Transient Synovitis can cause osteonecrosis. But most often with analgesics and other symptomatic treatment, it resolves gradually, without any known long term sequelae. Eventhough it is most commonly seen in children, tranisent synovitis can also develop in adults.

Hip joint effusion is graded according to Mitchell Classification. 0 : None, 1 Minimal, 2 - Enough to surround the femoral neck and 3 distension of joint recesses.

References:

1. MR imaging of transient synovitis: Differentiation from septic arthritis. Pediatric Radiology, 2006.
2. Radiopedia.

What's 'GRE Susceptibility Vessel Sign' ?

(Above image showing the Susceptibility Vessel Sign : hypointense signal on SWI of right vertebral artery (V4 segment), more or less equivalent to hyperdense Vertebral Artery on CT).

Thrombi are mainly of three types based on their composition : platelet rich (white) thrombi, red thrombi containing rich fibrin network and RBCs and finally the mixed ones. White thrombi are formed mainly in atherosclerotic plaque ruptures, where as red thrombi are formed in low pressure systems like cardiac or venous systems.

The oxyhemoglobin which gets degraded into de-oxy hemoglobin, methemoglobin and hemosiderin, all have paramagnetic properties and produces susceptibility artifacts in GRE images. This concept is the main core of Susceptibility Vessel Sign.

Teaching Point : GRE SVS is associated with red thrombi and thereby favors a Cardio-Embolic Stroke in most cases. And it also signifies increased chance of subsequent spontaneous recanalization and also increased success rates with fibrinolytic therapy. 

 

Exceptions :

1.SVS –ve cardio-embolic thrombi : 

Can occur if MRI was taken before the degradation of Oxy-Hb to Deoxy-Hb (which usually occurs in few hours) OR due missing the section of small thrombus in GRE due to the interslice gap.

2.SVS +ve (Large Artery) Atherosclerotic thrombi :

due to the formation of white thrombus initially, can lead to stagnant or reduced flow velocity within the vessel, there by gradually causing increased fibrin and RBC content of thrombus.


References :
1. Significance of Susceptibility Vessel Sign on T2*-Weighted Gradient Echo Imaging for Identification of Stroke Subtypes. Kyung-Hee Cho, MD; Jong S. Kim, MD, PhD; Sun U. Kwon, MD, PhD; A-Hyun Cho, MD; Dong-Wha Kang, MD, PhD. Stroke, November 2005.

Vertebral Hemangiomas

.

T1 and T2 hyperintense lesions in D6, D7 and L1 vertebrae.

Acute Embolic Infarcts

Vascular loops in Internal Acoustic Canal (IAC)

(Above CISS image showing type II Vacular loop (AICA) entering < 50% of the IAC lumen)

Question 3 : Diagnosis?

Click on this image for answer !!!

Diagnosis Please Series : December 2016 : Q1

4 year old child with upper abdominal pain. Serum Amylase >2000.

Synovitis with Bone Infarcts in distal femur

Bone infarcts are seen in distal femur. Thickened synovium with thickening of plica is also noted.

Post contrast Axial, Sagittal and Coronal images of the knee joint showing intense enhancement and thickening of the Synovium, consistent with synovitis.

Frontal lobe abscess : follow up MRI

Patient 2 months back, presented with headache and fever. CT and MRI done were consistent with the clinical diagnosis of Brain Abscess in the frontal lobe, which measures ~5.1cm x 4.6cm x 3.1cm (~37mL as per 0.52 x ABC). Abscess was aspirated at that time.

Present MRI showed T2 hyperintense lesion with hypointense rim / capsule. Perilesional vasogenic oedema was seen in frontal-parietal and temporal white matter.

Lesion is showing a T1 iso to mildly hyperintense rim. 

SWI images showed peripheral blooming artefacts of the lesion, which are seen tracking towards the calvarium - indicating the possibility of post aspiration haemorrhage.

Track is also seen showing susceptibility artefacts.

The entire contents of the abscess cavity is showing restricted diffusion.

Smooth rim enhancement of the lesion in post contrast images are noted. 

The track is also noted enhancing. Surrounding parenchyma also showed intense enhancement. No other lesions were seen. No CVT / Oto-mastoiditis seen. Lesion in the current study measured only about ~8mL.