Intracapsular Osteoid Osteoma

T1 coronal

T2 coronal

STIR-coronal

T1FS( contrast)-coronal

PDFS-axial

T1FS(contrast)-axial

STIR-coronal

A 27 year old female patient presented with long standing severe left hip pain. Contrast enhanced MRI showed cortical thickening and a small round well-defined area of signal alteration in anteromedial cortex of neck of left femur (isointense signal to skeletal muscle on T1, target apearance on T2/ STIR/PDFS) and  intense peripheral enhancement after contrast suggestive of osteoid osteoma. There is mild effusion in left hip joint.


A non-contrast MR scan performed 6 monthes earlier ( not shown here) showed significant left hip joint effusion and synovial thickening along with a poorly marginated large area of marrow oedema in the left femoral neck. A diagnosis of infective arthritis was made ( the intracapsular osteoid osteoma was overlooked). The patient was treated with antibiotics but showed persistence of pain with mild improvement.

INTRODUCTION: 
 Osteoid osteomas are benign bone forming tumours.

DEMOGRAPHICS:

• 10-25 years of age
• M>F( 3:1)
• Relatively common being 4-10%of primary bone tumours( excluding myeloma)

CLINICAL PRESENTATION:

• Severe pain which is worse at night and is relieved by salicylates or nonsteroidal anti-inflammatory drugs in 80% patients. It is intially intermittent and becomes unremitting later.
• Intracapsular lesions present with signs of synovitis, joint pain and reduced range of movement
• Premature osteoarthritis can occur with chronic intracapsular lesions ( in 50% cases)
• Intracapsular lesions can also cause growth abnormalities
• Muscle atrophy and neurologic signs are rare

IMAGING:
LOCATION:

• Cortical diaphyseal: commonest (65-70%) with femur being the commonest site
• Intramedullary : Rare and involves carpal and tarsal bones
• Intracapsular: usually in femoral neck, calcar. Has also been reported in elbow, foot, wrist, knee and facet joints
• Subperiosteal: Usually intracapsular( common in hip and talus)
• Spine:10% and involves posterior elements( Lumbar commonest site)
• Multifocal synchronous lesions: rare

X-RAY FINDINGS


Cortical diaphyseal:

• Oval lytic lesion with surrounding cortical sclerosis which may obscure lytic nidus
• The nidus may have central calcification which is seen as a raiopaque point called the Bell

Intracapsular( intra-articular):

• Oval lytic lesion in cortex with or without surrounding sclerosis.
• Sclerotic bone may be at distant site from the lesion
• Joint effusion

CT FINDINGS:

• Accurate in specifying location: cortical vs subperiosteal/ intramedullary
• Scerotic reaction seen
• Lytic nidus better seen
• Assciated pathologic fracture may be seen
• Helpful for guidance of percutaneous RF ablation

MR FINDINGS:
Nidus:

• Low to intermediate signal on T1
• Variable intensity on T2 depending on mineralization.
• Intense and dynamic enhancement( maximum in arterial phase)
• With increased spatial resolution, a partially mineralized nidus has a target appearance with mineralized portion appearing hypointense and non-mineralized portion appearing peripherally hyperintense.Nidus may be missed however in cortical bone.

Reactive response:

• Cortical thickening and sclerosis shows low SI on all sequences
• Reactive marrow oedema is seen in 63% cases( low signal on T1, high signal on fluid sensitive sequences)
• Periosteal elevation and adjacent soft tissue reactive changes are seen in 50% cases( high signal on fluid sensitive sequences)
• Effusion is seen in intracapsular lesions

Advantages of MR: It shows not only the nidus and surrounding sclerosis, but also the marrow oedema and articular changes.

NUCLEAR MEDICINE FINDINGS:

• Technetium Bone scan shows very intense round activity at nidus and is highly sensitive
• Double density sign: Very intense central activity at nidus surrounded by less intensity of reactive bone
• Round focus helps differentiate from stress fracture which has more linear activity.

DIFFERENTIAL DIAGNOSIS :

• Arthritis:( As in the index patient)
• Osteosarcoma/ Ewing's sarcoma
• Stress fracture
• Chronic osteomyelitis

TREATMENT:

• CT Guied radiofrequency ablation is treatment of choice
• Surgical resection

REFERENCES:

• Manaster BJ: Osteoid Osteoma: Diagnostic Imaging:Musculoskeletal non-traumatic disease. Amirsys.2-26, 2010
• Chai JW et al: Radiologic Diagnosis of Osteoid Osteoma: From Simple to Challenging Findings.  Radiographics; 30(3): 737:49,2010
• emdicine. medscape. com

INTRAOCULAR CYSTICERCOSIS

T2WI of right orbit showing an intraocular cystic lesion abutting the optic nerve head

T1 W sequence showing a hypointense lesion in the posterior part of the globe

FLAIR image showing subretinal cyst with suggestion of a hyperintense scolex posteriorly

FLAIR axial image showing Co-existent cysticercosis in the brain

FLAIR axial image showing co-existent cysticercosis lesions in brain

A 22 year old young man presented with epilepsy and blurring of vision in right eye. An MRI of his brain showed neurocysticercosis with an intra-ocular cystic lesion in right globe in keeping with ocular cysticercosis.

INTRODUCTION: Cysticercosis is a parasitic infection caused by the larval form of pig tapeworm, T solium. The humans act as an intermediate host in the life cycle of the worm and contracts the disease following ingestion of eggs in contaminated water or food. After ingestion, the eggs form primary larvae which disseminate to different parts of the body( central nervous system and skeletal muscles). Once intracranial, the primary larvae develop into secondary larvae, cysticerci..
Ocular disease is reported to occur in a significant number of patients with cysticercosis.

CLINICAL PRESENTATION:
-Blurring/ loss of vision
-Distorsion of images
-Sensation of light flashes
-Periorbital pain
-Diplopia
-Ptosis

DISCUSSION:
The human eye is vulnerable to many infectious diseases. It is important to identify and timely treat these diseases to prevent loss of vision.

Most parasitic infections of the eye arise from blood borne carriage of the micro-organisms to the eye.
The extra-ocular muscles form the most common type of orbital cysticercosis.
In the ocular form, vitreous and subretinal space are the preferential sites. Anterior chamber presentation is very rare.

Diagnosis is usually by direct ophthamoscopic demonstration.
Ultrasound, CT and MRI are imaging modalities described in establishing the diagnosis.
MRI is the best imaging tool for intraocular as well as neurocysticercosis.
If not clearly identified on routine MR sequences, high resolution CISS sequence has been found to be helpful in identifying the ocular lesions.

REFERNCES:
-Nijjar IBS, Singh JP, Arora V, Abrol RA, Sandhu PS, Chopra R, Roopa. MRI in intraocular cysticercosis- A Case Report. IJRI 2005; 15:3

RIGHT ACOUSTIC NEUROMA CAUSING TRIGEMINAL NEURALGIA

Axial T1C+ MR scan showing enhancing right acoustic schwannoma with ice cream on cone appearance

 Coronal T1C+ MR showing the enhancing right acoustic schwannoma

Sagittal CISS image showing compression of the right trigeminal nerve by the acoustic schwannoma

Sagittal CISS image showing normal left trigeminal nerve for comparison.

A 54 year old lady presented with right sided deafness, vertigo and right trigeminal neuralgia.
MRI revealed a right acoustic neuroma compressing the right trigeminal nerve.

Giant cell tumour of tendon sheath

T1 and STIR images in coronal plane; T2 GRE, T1 and T2 FS images in axial plane in a 25 year old female reveal a well-defined soft tissue mass along the ulnar aspect of flexor pollicis longus tendon abutting the proximal phalanx of left thumb. It shows hypointense signal on gradient echo image suggestive of paramagnetic substance.


GIANT CELL TUMOUR OF TENDON SHEATH:


This is the second commonest tumour of hand after simple ganglion cyst.


Types: It is of two types, the common localized type and the rare diffuse variety. The diffuse variety is considered the soft tissue counterpart of diffuse PVNS and is more common in lower extermities.


Age: 30-50 years, peak at 40-50 years.
Sex:Female to male ratio is 3:2


Presentation: Commonly occurs along the volar aspect of hand/ finger and is common adjacent to a DIP joint. It presents as a firm, lobulated, non-tender and slow growing mass which is fixed to underlying structures.


Imaging: 
X-ray may show cortical erosion, calcification etc.
USG shows a soft tissue mass along a tendon sheath with vascularity on color/ power doppler.
MRI shows low to intermediate signal on T1 and T2 spin echo sequences due to the presence of hemosiderin. This effect is further exaggerated and blooms on gradient echo sequences.


References:
-Wan JM, Magarelli N, Peli WC, Guglielni G, Sheli TW. Imaging of Giant cell tumour of the tendon sheath. Radiol Med.2010 Feb; 115(1): 141-51
-Verheyden JR. Giant cell tumour of the tendon sheath. emedicine.medscape.com

DURAL SINUS THROMBOSIS IN A PATIENT OF ULCERATIVE COLITIS

Axial FLAIR MR images and MR venograms showing acute infarcts in left cerebellar / left occipital regions due to thrombosis involving left transverse, left sigmoid sinuses along with left IJV.

Case history: 55 years old female with a long history of ulcerative colitis presenting with venous infarction due to dural sinus thrombosis.

Cerebral sinus thrombosis is an uncommon complication of ulcerative colitis( UC) in approximately 7.5%patients. It is probably due to genetic predisposition in combination with hypercoagulable state during relapse of UC.
It often presents with headaches and focal/ diffuse neurological signs.
It is important to be aware of this condition as it is a serious complication of inflammatory bowel disease with the potential of being fatal.

REFERENCE:
Nudelman RJ, Rosen DG, Rouah E, Verstovsek G. Cerebral Sinus Thrombosis: A Fatal Neurological Complication of Ulcerative Colitis.Pathology Research International: Volume 2010.

Lipoma arborescens

T1 and PDFS sagittal images of the left knee of a 27 year old male with history of recurrent joint swelling for the last two years showing frond like synovial thickening in the suprapatellar and posterior parts of the knee joint. The intensity of the frond like synovial thickening is suggestive of fatty tissue.There is significant synovial effusion.

-Lipoma arborescens is a rare condition affecting synovial lining of joints and bursae.
-Usually unilateral
-Most common joint affected-knee
-Rare in other joints like hip, shoulder, wrist. elbow
-There is frond like deposition of fat in the synovial lining.
-Clinical presentation is usually of painless recurrent joint effusion
-MRI is diagnostic as it shows the fatty nature of the fat deposition most commonly in the suprapatellar region of the knee joint.
-Treatment is synovectomy. It usually does not recur after surgery.
- Differentials are: synovial chondromatosis, PVNS, synovial hemangioma, inflammatory arthritis.