Frontoethmoidal Encephalocele

13 Year old female with hard swelling in the fore head. Volume rendering colour coded image of the face showing fromtoethmoidal encephalocele.

Volume rending image with bone algorithm showing bony prominence in the frontoethmoidal region. 

Cropped volume rendered image to show the defect in the frontoethmoid region

Oblique coronal reformatted bone window image showing the defect. 

Sagittal reformatted bone window image showing the defect clearly.

Coronal T2 fat saturated MR image showing herniation of the meninges through the above showed defect.

Discussion:

Encephalocele can be a congenital or an acquired abnormality of the brain in which intracranial contents including meninges, CSF, and brain tissue herniate through a skull defect. Congenital encephaloceles occur when the mesodermal layer between the neural tube and the ectoderm fails to develop and the anterior neuropore remains open. Anterior encephaloceles can also occur after trauma or surgery. Brain pulsations are presumed to push brain tissue through the defect. Patients are prone to recurrent episodes of meningitis. In addition, visual acuity and hypothalamic function may be affected. Clinical presentation includes a nasopharyngeal mass, which may enlarge with Valsalva's maneuver.

Differential considerations include a tumor traversing the cribriform plate, granuloma or esthesioneuroblastoma.

Tibialis posterior tenosynovitis - Ultrasonography

48 year old male came with history of redness and swelling in the posteromedial aspect of the right ankle. Ultrasonography showed mildly thickened tibialis posterior tendon with significant amount of fluid collection around the tendon. No effusion in the ankle joint/ No DVT / No varicose veins. Features are consistent with tibialis posterior tenosynovitis.

Discussion:

Tenosynovitis is inflammation of tendon sheath. It can be caused by trauma, pyogenic infection, tuberculosis, seronegative spondylarthropathies or rheumatoid arthritis.

USG features are:

• Thickened tendon.
• Fluid collection around the tendon.
• Mildly increased vascularity within the tendon.

MRI features: Usually acute presentation. 

• Fluid collection around the tendon in its proximal aspect.
• Signal change within the tendon is usually not seen in the acute stage and will be seen in chronic stage.

We need to differentiate the tenosynovitis with the paratendonitis which occur more in the distal aspect of the tendon. paratendonitis seen on MR as partially circumferential high signal intensity located distally around the posterior tibialis tendon.  This signal intensity is usually slightly hypointense to fluid.

Neurocysticercosis - MRI

MRI Brain of 26 year old male presented with seizures, T1 image showing well defined small hypointense lesion in the right frontal cortical region, which is showing hyperintense on T2 image. CISS 3D - heavily weighted T2 images (bottom row) showing fluid intensity lesion with small hypointense focus. The findings are consistent with neurocysticercosis.

Syrinx - MRI

Cervical spine MRI in a 54 year old male patient showing focal dilatation of the central spinal canal with no enhancing focal lesion within the cord. The features are consistent with the focal syrinx.

Discussion:

Hydromyelia: An accumulation of cerebrospinal fluid (CSF) may lead to simple distention of the central canal of the spinal cord lined by ependymal cells.

Syringomyelia: an accumulation of CSF may dissect into the surrounding white matter to form a paracentral cavity, which is not lined by ependyma.

syringohydromyelia: Combination of both which is seen in most of the cases.

I - In 1973, Barnett et al classified syringohydromyelic cavities into 5 types:

1. Communicating (with the subarachnoid space, usually at the level of the obex at the inferior aspect of the fourth ventricle)
2. Posttraumatic
3. Tumor-related
4. Arachnoiditis-related
5. Idiopathic.

II - Milhorat et al, the intramedullary cavities were classified into communicating, noncommunicating, and atrophic types.

III -  Noncommunicating syringes are subdivided into 6 types:

1. Chiari II malformation with hydrocephalus
2. Chiari I malformation without hydrocephalus
3. Extramedullary compressive lesions at the craniocervical junction or along the length of the spinal canal
4. Spinal cord trauma
5. Intramedullary tumors and intraperimedullary infections
6. Multiple sclerosis

Endometrioma - MRI

32 year old female underwent MRI for pain in the lower abdomen a) T2 weighted fat saturated axial image showing bilateral ovarian cysts and one of the cyst in the right ovary (arrow) shows hemosiderin fluid levels (T2 shading). b) The same cyst in the T1 WI showing hyperintese fluid with hypointense hemosiderin. The features are consistent with endometrioma.

Discussion:

Endometriosis is defined as the presence of endometrial glandular tissue outside of the uterus. Endometriomas are frequently present in the premenopausal stage. It is present in 32% of women with infertility and/or pelvic pain between the ages of 20 and 45 years. Incidence is 29 - 54%.

USG:

The spectrum of findings on transabdominal sonography (TAS) is wide due to difficulty in accurately characterising the lesion. On TVS, the endometrioma is seen as a round homogeneous hypoechoic 'tissue', of low-level echoes, with a clear demarcation from the parenchyma and without papillary proliferation is present in at least 80% of cases of endometriomas.

Endometrioma do not shows acoustic streaming where as other cysts shows the same. 'Acoustic streaming' is a useful tool for differentiating endometriomas from other benign cystic lesions. 'Acoustic streaming' is defined as the bulk movement of fluid due to a sound field caused by energy transfer from an US wave to a fluid. The presence of hyperechoic wall foci (punctate peripheral echogenic foci) on ultrasonographic examination is very specific to endometriomas.

The diagnostic points described for endometrioma by different authors as follows:

• A round-shaped homogeneous hypoechoic 'tissue' of low-level echoes without papillary proliferations associated with 'poor' vascularization (defined by Aleem et al. in 1995);
• A round-shaped homogeneous hypoechoic 'tissue' of low-level echoes with an echogenic portion in which no flow is detected (atypical findings).

MRI:

MRI demonstrates these endometriomas as cystic masses with very high signal intensity on T1-weighted images and very low signal intensity on T2-weighted images with layering of blood products termed as "T2 shading". Another common finding is a very dark peripheral rim (arrowhead), due to hemosiderin deposition, which is also the result of blood degradation.

Recently susceptibility-weighted imaging (SWI) has shown to contribute to the diagnosis of endometrioma by depicting hemosiderin deposition in the cyst wall.

HIV Encephalopathy - MRI

MRI axial fluid attenuation inversion recovery (FLAIR) images in 48 year old male with HIV showing generalised cerebral atrophy with diffuse white matter hyperintenisty signal change seen in the bilateral periventricular frontal and paroeto-occipital regions consistent with HIV encephalopathy.

Discussion:

Clinically it is usually presents with progressive dementia, initially cognitive impairment and later accompanied by motor symptoms like gait disturbance and tremor. Collectively this is called as AIDS dementia complex.

Histopathology may reveal subacute encephalitis, cerebral atrophy and demyelination.

CT - The sole finding in most of the patients may be cerebral atrophy. In progressive advanced patient may see periventricular confluent white matter hypodensities. 

MRI- Cerebral atrophy, classical appearance of confluent, bilateral and symmetrical white matter lesions seen as diffuse white matter change in the periventricular regions and centrum semiovale, with relativesparing of the subcortical white matter and posterior fossa structures. These lesions shows hyperintense on T1 and iso to hypointense on T1 images. There will be no contrast enhancement or mass effect.

MR Spectroscopy shows decreased N Acetyl Aspartate and increased choline peaks and changes in the glutamate and glutamine levels. 

Choledocholithiasis - MRCP

45 year old female with pain abdomen and jaundice underwent MRI and MRCP revealed calculus in the distal common bile duct obstructing the lumen resulting in mild to moderate upstream dilatation of the intra hepatic biliary radicals.

Discussion:

Choledocholithiasis is relatively common, seen in in 6 - 12% of patients who undergo cholecystectomy. They may present with biliary colic, ascending cholangitis, obstructive jaundice, acute pancreatitis. Stones within the bile duct may form either in situ or pass from the gallbladder, and when recurrent tend to be pigment stones, and are thought to be associated with bacterial infection.
USG: Sensitivity varies from 13 to 55%. Features include dilated duct with stones visualized within. Recently endoscopic ultrasonography (EUS) has also been used with very high sensitivity and specificity.
CT: Moderate sensitivity of 65 - 88% but have to look for very subtle findings. They are

• Target sign - Central rounded density of stone with surrounding lower attenuating bile or mucosa.
• Rim sign: Stone is outlined by thin shell of density.
• Crescent sign: Bile eccentrically outlines luminal stone, creating a low attenuation crescent.
• Calcification of the stone: unfortunately only 20% of stones are of high density

Setting window level to the mean of the bile duct and setting the window width to 150HU has been reported to improve sensitivity.
MRCP: is the gold standard investigations for biliary lithiasis replacing the ERCP. Filling defects are seen within the biliary tree on thin cross-sectional T2 weighted imaging.

Carcinoma Prostate - PET/CT

63 year old male patient operated for carcinoma prostate came for FDG PET/CT evaluation for recurrent tumor. Coronal CT and the PET/CT fused image showing non FDG avid multiple sclerotic lesions in the sacrum and right iliac bones. Multiple similar lesions also were seen in various vertebral bodies, scapulae and ribs (not shows here)

Discussion:

PET/CT in combination with PSA levels can play a significant role in detecting and staging prostate cancer. Although Prostate-specific antigen measurements are considered a useful organ-specific marker, but they are alone not necessarily an adequate tumor marker.

Localized disease within the prostate and pelvic lymph nodes can be difficult to image with PET/CT because of the proximity of bladder activity as there is will be spillover of radiotracer uptake.  

The radiotracers used in prostate PET/CT: 

1. Fluorodeoxyglucose (FDG): have a role in the detection of lymph node metastases, particularly in patients with relapsed disease after primary treatment. The sensitivity is around 50%. FDG-PET has an excellent detection rate for lytic skeletal metastases, but it has a poor detection rate for sclerotic metastases as in our case.
2. Carbon 11 (C11)–acetate and C11-choline (18F-Choline): Shown promising alternative but they are less readily available and still under assessment. Few recent studies have showed conflicting results as one study says there is relative high rate of false-negative results as prostatic disorders other than cancer may accumulate 11C-choline. Some other study shows C11-choline PET/CT can differential prostate carcinoma from benign hyperplasia, chronic prostatitis, or normal prostate tissue. The C11 choline has shows promising results in staging of the tumor; however it still needs more studies.

To conclude sextant /10 core biopsy along with PSA are the mainstay of diagnosis and FDG PET/CT and C11 Choline PET/CT are for the staging, treatment planning and response evaluation.

Cervical Carcinoma-MRI

MR Imaging of 46 Year old female with carcinoma cervix- T2 FS sagittal and axial images showing well defined homogeneously hyperintense mass lesion in the region of   cervix involving the lower segment of uterus and the upper third of the vagina and mild parametrial extension. The pelvic side walls are clear. No pelvic lymphadenopathy.

Discussion:

Cervical carcinoma is the third most common malignancy in woman and is seen in fourth to fifth decade. It often causes serious consequences and common cause of death is uremia in this condition due to involvement of the ureters. 

The International Federation of Gynecology and Obstetrics (FIGO) staging system provides worldwide epidemiologic and treatment response statistics. MR imaging is not included in the system, however it is widely accepted modality for evaluation of cervical cancer.....

What all can MRI do with cervical cancer.........

• Can quantify the volume of the tumor especially in the early stages.
• Metastatic lymphnode evaluation.
• Obviates the use of invasive procedures like cystoscopy and proctoscopy.
• Brachytherapy and external beam radiation therapy can be optimised with the MR imaging.
• Detect and confirm invasion of the adjacent organs.
• Identify fistulous tracts if any.

For more information on the MR imaging of the cervical carcinoma go through this wonderful article in the Radiographics by Viviane Nicolet et al. http://radiographics.rsna.org/content/20/6/1539.full

Bone infarct - MRI

Bone infarct is ischemic death of the cellular elements of the bone and marrow in metaphysis and diaphysis. Lesions in the epiphysis are called avascular necrosis (AVN). Presently the term osteonecrosis is accepted and used widely.

Causes: Idiopathic, Trauma, Idiopathic causes such as Legg-Calvé-Perthes disease, Renal transplantation, Increase in endogenous steroid levels, as in patients with Cushing syndrome, Collagen vascular disorders such as systemic lupus erythematosus (SLE), rheumatoid arthritis, and scleroderma, Hemoglobinopathies such as sickle cell disease and thalassemia, Hemophilia, Gaucher disease, Fabry disease, Infection, Pancreatitis, Pregnancy, Gout and hyperuricemia, Diabetes, Use of immunosuppressants and other drugs such as exogenous steroids, indomethacin, and phenylbutazone, Alcohol use, Dysbaric osteonecrosis, Radiation therapy, Arteritis.

Imaging:

Radiograph: Findings are characteristic in established case. Early stages radiograph is not of much use. In the epiphysis region, an arc like, subchondral, lucent lesion may be associated with areas of patchy loss of bone opacity intermingled with sclerotic areas and bone collapse. In the diametaphyseal region, a sheet like lucency of varying size is usually surrounded by shell-like sclerosis and/or calcification and periostitis. In flat or complex bones, patchy lucencies and sclerosis are often associated with bone collapse or fractures.

Steinberg has classified the radiologic appearance into 6 stages, as follows¹² :

• Stage 0 - Normal findings are demonstrated.
• Stage I - The appearance may vary from normal to subtle trabecular mottling, but an isotopic bone scan or MRI shows abnormal bone.
• Stage II
• Stage IIa - Focal radiopacity is associated with osteopenia.
• Stage IIb - Radiopacity is associated with osteoporosis and an early crescent sign.
• Stage III
• Stage IIIa - An established crescent sign is associated with cyst formation.
• Stage IIIb - Mild alteration in the configuration of the femoral head is caused by a subchondral fracture, but the joint space is maintained.
• Stage IV - Marked collapse of the femoral head is demonstrated with an associated acetabular abnormality.
• Stage V - Joint space narrowing is demonstrated with changes of secondary osteoarthrosis.

CT scans: Central or peripheral areas of reduced attenuation. Reformatted sagittal and coronal images show subchondral fractures and collapse of the articular surface. May show subtle trabecular irregularity associated with bone necrosis in early stages.

MRI: Ischemic bone changes become apparent in hematopoietic tissues on MRIs within 6-12 hours. MRI characteristics of bone infarction are patchy areas of low signal intensity on T1-weighted spin-echo images. Diffuse abnormal signal intensity may be present in osteonecrosis of the femoral head; these changes are reflected on both T1- and T2-weighted images.

The most characteristic appearance is the double-line sign, which consists of a hyperintense inner ring and a hypointense outer ring, on T2-weighted MRIs. This finding reflects the reactive interface between ischemic and non ischemic bone. 

Achilles Tendonitis - MRI

46 Year old male with pain in the left ankle MRI T2 FS sagittal and T2 FSE axial images showing diffuse hyperintensities in the distal Achilles tendon with mild marrow edema in the calcaneous at the insertion site and mild peritendinous inflammatory changes suggestive of Achilles Tendinitis.

DISCUSSION:

Tendinitis develops insidiously after sudden changes in activity or training level, use of inappropriate footwear, or training on poor running surfaces, especially if high-risk factors are present (Eg, age, cavus feet, tibia vara, heel and forefoot varus deformities).

Achilles tendon injuries may be classified as:

Tendonitis: Overuse of the Achilles tendon can cause inflammation that can lead to pain and swelling.

Tendinosis: Usually, this injury is an asymptomatic, noninflammatory, degenerative disease process (mucoid degeneration). The patient may complain of a sensation of fullness or a nodule in the back of the leg.

A Thompson test is performed to detect rupture of the Achilles tendon. In this test, the patient lies face downward on the examining table with bent knees and the doctor squeezes the back of the lower leg (calf). If the Achilles tendon is at least partially intact, this test causes the foot to flex.

IMAGING TESTS:

Radiographs: May detect soft tissue thickening and fractures if any associated.

Ultrasound may be usefull to detect thickening of the Achilles tendon and peritendinous collection.

MRI of tendonitis show diffuse for T2 hyperintensity within the tendon and inflammatory changes around the tendon with or without peritendinous collection. My show mild enhancement on contrast study.  Focal T2 hyperintensities seen at the tendon insertion suggestive of insertional tendinitis.

MRI helps to differentiate tendonitis from tendinosis and partial/complete tendon rupture. In tendinosis there will be only tendon degenerative changes without inflammatory changes around the tendon.

TREATMENT: Resting the tendon to allow the inflammation to settle down.

Cholesteatoma- HRCT

Non contrasted temporal bone CT reveals a soft tissue mass in the right middle ear and Prussak’s space with associated erosions of the scutum, epitympanum walls, lateral semicircular canal, tegmen tympani and middle ear ossicles. It is also extending in to the mastoid air cells.

Discussion:

• An acquired cholesteatoma is a collection of exfoliated squamous epithelium and debris.
• Cholesteatomas often begin at the pars flaccida of the tympanic membrane and grow in Prussak's space of the temporal bone and produce inflammatory reaction.
• Cholesteatomas typically occur in the setting of chronic dysfunction of the Eustachian tubes and recurrent otitis media.
• Cholesteatomas can be as small as a couple of millimeters in size or can grow to fill the entire middle ear.
• Erosions of the scutum and ossicles are commonly seen.
• The presence of bony erosions or expansion are strong support of cholesteatoma over chronic otomastoiditis.
• Acquired cholesteatomas occur in children and adults.
• Most common presenting symptoms include ear discharge, hearing loss, ear pain and vertigo.
• Without treatment cholesteatomas will progressively increase in size.
• Complications include: Hearing loss, CN 7 palsy, venous sinus thrombosis, semicircular canal fistulas, and intracranial invasion.
• Early surgical intervention usually results in complete eradication and preservation of hearing.

Differential diagnosis:

1. Acquired cholesteatoma
2. Chronic otomastoiditis
3. Middle ear cholesterol granuloma
4. Glomus tympanicum paraganglioma

Double left renal artery - CT Angiography

44 Year old female referred for CT renal angiography for transplant donor evaluation. The coronal volume rendering images showing normal bilateral kidneys with single right renal artery and two renal arteries on the left side.

Discussion:
CT angiography is the most preferred investigation for donor kidney evaluation since it gives excellent anotomical depiction of the vessels, organs and the function of kidney in urography.
Protocol - Arterial phase, Venous phase and Excretory phase.
The things to be mentioned in the radiological report are

• Size, shape and position of the kidneys.
• Number of renal arteries, any accesory artery.
• Course of left renal vein retroaortic /preaortic.
• Distance of renal artery from origin to first branching.
• Length of right renal vein.
• Any other normal varuients/renal masses.
• Collecting system - Duplication of any.

All these findings are valuable to the graft harvesting surgeon and for the transplant anastomosis.

The Azygos Lobe

55 year old male came with history of chronic cough and was reffered for CT scan to ruleout tuberculosis and any other lung disease. CT scan axial section (first image) shows a azygos vein is coursing through the apical segment of the right upper lobe (arrow). Coronal reformated image shows pleural reflection - mesoazygos (arrow) with azygos vein (arrow head) in the right apical region.

Discussion:

The azygos lobe is a rare anomaly that developmentally arises when the right posterior cardinal vein penetrates the apex of the lung, instead of passing over it, and travels inferiorly taking pleural layers with it to entrap a portion of the right upper lobe. The two folds of pleura form the mesoazygos, a fissure visible on 0.4% of chest radiographs and 1.2% of high resolution computed tomography (CT) studies. The right azygos lobe is supplied by the medial segments of the apical and anterior or posterior branches of the apical segmental bronchial artery and vein. A true left azygos lobe has also been reported.
On chest radiography, the azygos lobe is usually distinguished by the azygos fissure, which superiorly has a triangular shape and inferiorly demonstrates the azygos vein as a tear-shaped shadow. The azygos fissure typically appears as a fine, convex line that crosses the apex of the right lung. The azygos lobe can appear opaque and be incorrectly interpreted as a pathologic mediastinal finding on PA chest radiographs.
When findings on traditional imaging are not clear, CT exams can be helpful in delineating relevant anatomy. Clinically, the knowledge of azygos lobe anatomy is important during thoracic surgical approaches. Partial obstruction of the thoracoscopic view during a bilateral sympathectomy was reported during attempted mobilization of the azygos lobe. Others reported difficulty reflecting the pleura during primary repair of the esophageal atresia in a pediatric patients. There are also reports of the phrenic nerve coursing within the azygos fissure. Finally, multiple authors have reported spontaneous pneumothorax associated with the azygos lobe in both the adult and the pediatric patient.

Adrenal Myelolipoma - CT

CT scan of a 25 year old female showing well defined fat containing lesions seen in the region of right adrenal gland (arrow) suggestive of adrenal myelolipoma.

Adrenal myelolipoma is an uncommon, benign, endocrinologically inactive tumor of unknown pathogenesis composed of adipose and myeloid tissue. Majority of the lesions are detected incidentally. In most lesions, the fatty component is predominant and is recognizable on radiologic images. Such lesions are radiolucent on radiographs, hyperechoic on sonograms, have low attenuation on CT scans, and have bright signal intensity on T1 -weighted MR images and intermediate signal intensity on T2- weighted MR images.

Tumors composed primarily of myeloid tissue may be hypoechoic on sonograms and will have the imaging characteristics of red marrow on other kinds of images. In complicated cases in which infarction or hematoma is present, the margins of the lesions may be irregular and infiltrative, with blood dissecting through the retroperitoneum. The imaging findings of acute, subacute, or chronic hematoma will then be superimposed on the lesion. When lesions are fatty, well marginated, uncomplicated, and in the position of the adrenal gland, a specific radiologic diagnosis is possible. However, the mere presence of fat in an adrenal mass is insufficient for diagnosis, because a metastasis or other aggressive lesion may engulf fat as it spreads. Nonspecific calcification may sometimes present.